CENTRALLY MEDIATED CARDIOVASCULAR :

EFFECTS OF SYSTEMCALLY - . ' >

. ADMWSTEREDECOLIENDOTQX1N\:_~‘:>II:__;E: - _

; ’ Dis’sertationforifheflégree ofPh; Du]?

* I MiCHlGAN STATE’UNIVERSW ' f '

' . "DAWDEDWARD DOBBINS
.1975; '

 

"nwhARY
Michigan State
University

"mane; ‘ .4;

This is to certify that the
thesis entitled .,

Centrally Mediated Cardiovascular Effects
of Systemically Administered E. Coli Endotoxin

presented by

David Edward Dobbins

has been accepted towards fulfillment
of the requirements for

Ph.D.

Physiology

degree in

 

Dak: April 15, 1975

0-7639

   
  

 
  

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A vascula
tion was employ
cardiovachlar
constant flow ‘
care was taken
could not be at

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that this mm

The admi
norepinephrine
experiments in

intact, elicit

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amine and HOD

PIESsme . Th

ABSTRACT

CENTRALLY MEDIATED CARDIOVASCULAR EFFECTS OF
SYSTEMICALLY ADMINISTERED E. coli ENDOTOXIN

By

David Edward Dobbins

A vascularly isolated, neurally intact canine head—trunk prepara—
tion was employed to determine if endotoxin exerts centrally mediated
cardiovascular effects. The vascularly isolated head was perfused at
constant flow with arterial blood supplied by a donor dog. Extreme
care was taken to insure that any observed cardiovascular responses
could not be attributed to leakage of the agent into the general circu—
lation. Furthermore, a number of maneuvers were performed to establish
that this technique results in a responsive experimental preparation.

The administration of histamine, acetylcholine, bradykinin,
norepinephrine and angiotensin II into the head perfusion circuit of
experiments in which the recipient dog's carotid sinus—body nerves were
intact, elicited changes in recipient trunk blood pressure consistent
with initiation of the carotid sinus baroreceptor reflex subsequent to

changes in carotid sinus pressure. Following bilateral denervation of

the recipient dog's carotid sinus—body complexes, acetylcholine, hist—
amine and norepinephrine did not alter recipient systemic arterial

pressure. This suggests that these vasoactive agents do not elicit

 

 

 

changes in bl<
actions, but c
Bradykinin ad:
ient dag's can
change or a h)
0f angiotensir
a marked vaso;
confirm the cc
indeed elicit

The infL
into the head
nerves results
within thirty
during this n
Preparation, E
Pressure, recj
thirty and cor
Substame rele
centrally medj

When enc‘
into the reci;
the respOnSe n
administratiOr
need HOt gain

ShoCk.

David Edward Dobbins

changes in blood pressure in this preparation through centrally mediated
actions, but only through the carotid sinus baroreceptor reflex.
Bradykinin administration following bilateral denervation of the recip-
ient dog's carotid sinus-body complexes resulted in a hypertensive, no
Administration

change or a hypotensive response in the recipient trunk.

of angiotensin II into the debuffered preparation uniformly resulted in

 

a marked vasopressor response in the recipient trunk. These results

confirm the conclusions of previous workers that angiotensin II does
indeed elicit a centrally mediated hypertensive effect.

The infusion of 1 mg/kg or 5 mg/kg purified E. coli endotoxin
into the head perfusion circuit of the preparation with intact buffer

nerves resulted in a marked hypotensive response in the recipient trunk

within thirty minutes. Perfusion pressure to the head was increased

during this time. When endotoxin was infused into the debuffered

preparation, eliminating the effects of alterations in carotid sinus
pressure, recipient systemic pressure again markedly fell by minute

thirty and continued to decline. This indicated that endotoxin or some

substance released by the endotoxin is capable of eliciting a marked
centrally mediated hypotensive effect.

When endotoxin 1 mg/kg or 5 mg/kg was administered intravenously
into the recipient trunk, excluding it from the central nervous system,

the response was similar to that seen following intravenous endotoxin

administration in the intact dog. These results indicate that endotoxin

need not gain access to the central nervous system in order to produce

shock.

 

 

 

The fact
endotoxin seen
administration
the early prec
endotoxin. Hc
important rolr
and/ or may cor

this often fa-

David Edward Dobbins

The fact that the centrally mediated hypotensive responses of
endotoxin seen in this study did not occur until 30 minutes after
administration of the toxin, suggests that they do not participate in
the early precipitous fall in blood pressure seen following intravenous
endotoxin. However, these centrally mediated actions may play an
important role in the maintenance of the hypotension during endotoxemia

and/or may contribute to the initiation of the irreversible phase of

this often fatal circulatory derangement.

 

CENTRALLY MEDIATED CARDIOVASCULAR EFFECTS OF

SYSTEMICALLY ADMINISTERED E. coli ENDOTOXIN

By

David Edward Dobbins

A DISSERTATION

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Physiology

1975

 

 

to my

and pa

 

DEDICATION

This dissertation is dedicated to my wife Lynn, and
to my parents. Without their encouragement, understanding

and patient support, it could not have been written.

ii

to the

this e

Dr. Fr

 

   

ACKNOWLEDGEMENTS

The author wishes to express his grateful appreciation
to the following people for their considerable assistance in
this endeavor: Dr. George J. Grega, Dr. Joe M. Dabney,

Dr. J. B. Scott, Dr. Ching-Chung Chou, Dr. Donald K. Anderson,

Dr. Francis J. Haddy and Mr. Edward Gersabeck.

"x.

 

CHAPTER

III.

IV .

V.

VI.

VII.

INTR4
SURV
STAT}
METHt
RESUl
DISCI

SUr‘L‘L

APPENDIx, _ . ‘

BIBLIOGRAPHI

TABLE OF CONTENTS

  
 

Page

CHAPTER
1

I. INTRODUCTION.......
SURVEY OF THE LITERATURE...........
. . l3

voooooooo

STATEMENT OF THE HYPOTHESIS....
- ... 14

II.

III.

 

IV. METHODS................. .
V. RESULTS .. .. .. . ..... . .. 31
VI. DISCUSSION............. .. . .. 83
VII. SUMMARY AND CONCLUSIONS...... .. . .. . . 92
APPENDIX.......................... .. . .............. . .. . . 94
.. ...... . ...... . . . . .. 97

octane.-

BIBLIOGRAPHY...........

is?

 

 

Table 1

Table 2

Table 3

Table 4

Table 5

Table 6

Table 7

Table 8

Table 9

Table 10

('5

’0

O
HQ'UO

Table 1

Table 2

Table 3

Table 4

Table 5

Table 6

Table 7

Table 8

Table 9

Table 10

LIST OF TABLES
Page
28

ol'oooooo IUIIOOOOID'

Summary of experiments..
38

Cardiovascular effects in the donor and recipient dog
of infusion of endotoxin (5 mg/kg) into the arterial
n = 7.................

perfusion circuit to the head.

Cardiovascular effects in the donor and recipient dog
of infusion of endotoxin (5 mg/kg) into the arterial
perfusion circuit to the head following bilateral
denervation of the carotid sinus-body complexes of the
.................... 4O

7............

recipient dog. n —
Cardiovascular effects in the donor and recipient dog
.................. 42

of intravenous infusion of endotoxin (5 mg/kg) in the

donor dog. n = 8.... ......
Cardiovascular effects in the donor and recipient dog

of intravenous infusion of endotoxin (1 mg/kg) in the
donor dog. n = 6 .......... .............. 44
Cardiovascular effects in the donor and recipient dog
of intravenous infusion of endotoxin (5 mg/kg) in the
recipient dog. n = 6........ ........................ 46
Cardiovascular effects in the donor and recipient dog
of intravenous infusion of endotoxin (1 mg/kg) in the
.................... 48

6.............

recipient dog. n —
Cardiovascular effects in the donor and recipient dog
of intravenous infusion of endotoxin (5 mg/kg) in the
recipient dog following bilateral cervical vagotomy.

50

7..................... ..... .......................

n =

Cardiovascular effects in the donor and recipient dog

of infusion of histamine diphosphate (15 Hg base/

minute), acetylcholine chloride (15 pg base/minute),

bradykinin (3 Ug/minute) and norepinephrine bitartrate

(6 pg base/minute into the arterial perfusion circuit
........... 52

to the head. n = 6 ........................
Control experiments prepared identically to previous
innervated experiments but without the infusion of
vasoactive agents. n = 7 ...... .... ..... .............. 54
v

Figure 1

Figure 2

Figure 3

Figure 4

n—r;

igure 5

Figure 6

Figure 7

Figure 8

Figure 9

LIST OF FIGURES
Page

Figure 1 Method of occlusion of the vertebral arteries, veins
l6

and the intraspinal venous sinuses in the recipient
dog..................................................

Figure 2 Placement of arterial inflow and venous outflow
Note arterial inflow is
19

catheters in recipient dog.

proximal to the carotid sinuses......................
Figure 3 Overview of experimental set—up depicting placement

of catheters and sites of infusion................... 21
Figure 4 Effects of infusion of acetylcholine chloride (15 pg

base/minute) into the head perfusion circuit on per—

fusion pressure, donor systemic pressure and recip—

ient systemic pressure............................... 56

Figure 5 Effects of infusion of histamine diphosphate (15 pg
base/minute) into the head perfusion circuit on per—

fusion pressure, donor systemic pressure and recip—
58

ient systemic pressure...............................

Figure 6 Effects of infusion of bradykinin (3 ug/minute) into

the head perfusion circuit on perfusion pressure,
60

donor systemic pressure and recipient systemic pres—

sure.................................................

Figure 7 Effects of infusion of norepinephrine bitartrate
(6 ug base/minute) into the head perfusion circuit on
62

perfusion pressure, donor systemic pressure and
recipient systemic pressure..........................

figure 8 Effects of bolus injection of angiotensin II (10 ug)
into the head perfusion circuit on perfusion pressure,
64

donor systemic pressure and recipient systemic pres—

sure.................................................
figure 9 Effects of bilateral cervical vagotomy of the recipe
donor systemic pres—

66

ient dog on perfusion pressure,
sure and recipient systemic pressure.................

Vi

LIST OF FIG

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

 

LIST OF FIGURES—«continued

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

10

Effects of bilateral carotid occlusion in the recip-
ient dog on perfusion pressure, donor systemic pres-
sure and recipient systemic pressure before and after
bilateral vagotomy of the recipient dog...............

Effects of bilateral carotid occlusion in the recip-
ient dog on perfusion pressure, donor systemic pres—
sure and recipient systemic pressure before and after
bilateral debuffering of the recipient dogs carotid
sinus—body complexes..................................

Effect of five minutes of cerebral ischemia in the
recipient dog on perfusion pressure and recipient
systemic pressure.....................................

Effects of bolus injection of angiotensin II (10 ug)
into the head perfusion circuit on perfusion pressure,
donor systemic pressure and recipient systemic pres—
sure following bilateral debuffering of the carotid
sinus-body complexes in the recipient dog.............

Effects of infusion of endotoxin (5 mg/kg) into the
head perfusion circuit on perfusion pressure, donor
systemic pressure and recipient systemic pressure
following bilateral debuffering of the carotid sinus—
body complexes in the recipient dog...................

Effects of infusion of bradykinin (3 ug/minute) into
the head perfusion circuit on perfusion preSSure,
donor systemic pressure and recipient systemic pres—
sure following bilateral debuffering of the carotid
sinus-body complexes in the recipient dog.............

Effects of histamine diphosphate (15 ug base/minute)
acetylcholine chloride (15 ug base/minute) and nor—
epinephrine bitartrate (6 ug base/minute) into the
head perfusion circuit on perfusion pressure, donor
systemic pressure and recipient systemic pressure
following bilateral debuffering of the carotid sinus—
body complexes in the recipient dog...................

Effects on recipient arterial pressure, donor arterial
pressure and head perfusion pressure of infusion of
endotoxin (5 mg/kg) into the head perfusion circuit
before (H ) and after (0—0) bilateral denerva—

tion of the recipient dog's carotid sinus-body complex—

es,or intravenously into the recipient trunk before

(H ) or after (H ) bilateral cervical vago—

tomy as compared to control experiments ([j—fj)......

Page

68

70

72

74

8O

82

 

 

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been eluci<
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hi’POtensior
total Peri;
Central net
has not yet

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SPinal Venc
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questiOned.
the periphe
add to, neg
Endot
in Order to
cardioVaSCU

results fro

 

CHAPTER I

INTRODUCTION

The peripheral vascular manifestations of entotoxin shock have
been elucidated by a number of investigators. In the dog, the
intravenous administration of purified endotoxin produces systemic
hypotension, decreases in cardiac output and eventually, increases in
total peripheral resistance (3,75). It has been suggested that the
central nervous system plays a role in these responses. However, this
has not yet been demonstrated with absolute certainty.

Early attempts utilizing vascularly isolated, neurally intact
head-trunk preparations failed to deal with the problem of the intra—
spinal venous sinuses (19,67,89). When these channels are not com—
pletely occluded, there is profuse venous drainage from the head to the
trunk (19,89). Therefore, the conclusions of these studies can be
questioned. Endotoxin administered to the head could gain access to
the periphery in such a preparation and exert peripheral actions which
add to, negate or obscure any central actions.

Endotoxin has also been perfused through the cerebral ventricles
in order to determine if it is capable of eliciting centrally mediated
cardiovascular effects (76,77). The difficulties in extrapolating

results from this preparation to experiments involving systemic

administrati
into the van
significant
relatively l
difficulty.
tion of endc
brain compaz
perfusion ex
Recent
which provid
and the trun
Clearly deli
peripherally
Theref
the Central
hypotensim
administratj
(Outribute t

Often fatal

administration of the toxin are twofold. First, endotoxin introduced

into the ventricular system may not reach all brain centers which are

significant to the animals responses. Secondly, endotoxin, being a

relatively large molecule, may cross the blood—brain barrier only with
difficulty. Thus, it is not certain whether the systemic administra—

tion of endotoxin would result in concentrations of the toxin in the
brain comparable to those necessary to elicit effects in ventricular
perfusion experiments.

Recently, a head cross—circulation technique has been described
which provides for absolute separation of blood flow between the head

and the trunk (7,12,83). With this technique, it should be possible to

clearly delineate centrally mediated cardiovascular effects from
peripherally mediated effects.

Therefore, it was the aim of this study to determine the role of
the central nervous system in the genesis and/or maintenance of the
hypotension associated with canine endotoxin shock following systemic

administration of the toxin. Data bearing on this question may

contribute to a better understanding of the pathophysiology of this

often fatal circulatory derangement.

 

 

 

Endot
Problem eve
i5 difficul
considerabl
Suitable ex
data has be
biochemical
the System
the manifes
review arti
(2,14,17,30,

Follo'
endotoxin i:
1y within f
markedly re.

Total
is geneIall;
is due to i}

in many Org.

CHAPTER II

SURVEY OF THE LITERATURE

Endotoxin shock has been recognized as a significant clinical
problem ever since its description by Pfeifer in 1894 (64). Since it
is difficult to obtain reliable serial data in critically ill patients,
considerable effort has therefore been applied to the development of a
suitable experimental model of this syndrome. An impressive amount of
data has been compiled, principally in the dog, characterizing the
biochemical, pathological and hemodynamic alterations attendant with
the systemic administration of endotoxin. While a brief summary of
the manifestations of endotoxin shock will be presented here, several
review articles have been published which provide more detailed data
(2,4,17,30,53,80,94).

Following the intravenous administration of lethal doses of
endotoxin in the dog, mean systemic arterial pressure falls precipitous—
ly within five minutes (56,59,66,88,9l,94). This is accompanied by a
markedly reduced cardiac output (42,45,57,9l).

Total peripheral resistance is variably changed at this time but
is generally reported to be increased (13,38,85). The rise in resistance
is due to increases in both precapillary and postcapillary resistances

in many organs. Additionally, the pressure and resistance changes

 

 

result in s:
skeletal mus
initial hypc
of large vol
return to th
43,44,45,94)
constriction
transient po
my or port
Minutes afte
returns to In
Sure Partial
resistance 13
Pressure, ca:
greSSivaly) ‘
85,94). This
marks the 0n:
sewndary de<
“but due tc
resistanCe w
PeriphEral cj

InVESti
no direct imp
force of the
late in 5h0ck

d
ue to detrea

 

result in sustained net extravascular fluid reabsorption in skin and

skeletal muscle (88). Numerous investigators have indicated that this

initial hypotension is primarily the result of hepato—splanchnic pooling

of large volumes of blood. This results in a markedly decreased venous

return to the heart and consequently diminished cardiac output (11,29,
43,44,45,94). The hepato—splanchnic pooling results from hepatic vein
constriction which inhibits venous outflow from the liver and leads to
transient portal hypertension. This pooling may be prevented by hepatec-
tomy or portal-caval anastomosis (57,59,91). Within twenty to thirty
minutes after the administration of endotoxin, portal vein pressure

returns to normal while cardiac output and mean systemic arterial pres—

sure partially recover (29,57,9l). During this period, total peripheral
resistance increases. Within the next hour, the systemic arterial
pressure, cardiac output and total peripheral resistance decline pro-
gressively, eventually culminating in the death of the animal (38,39,59,
85,94). This secondary decline in mean systemic arterial pressure
marks the onset of the irreversible phase of endotoxin shock. The
secondary decline in pressure has been attributed to decreased cardiac
Output due to fluid loss in the intestine and decreasing total peripheral
resistance which leads to progressive sequestration of blood in the
Peripheral circulation (ll,39,57,59,6l).

Investigations of cardiac function during endotoxin shock indicate

no direct impairment of myocardial function by endotoxin. Contractile
force of the ventricular myocardium is not significantly depressed until

late in shock and is probably the result of developing tissue hypoxia

due to decreased blood flow (1,8,23,31).

 

 

Renal
principally
Some renal v.-
some substax
systemic hy]
renal tissul

The rt
hypertensio:
resistances
pooling of
be due not
darily to p
subsequent
aCtion of e

The r
Intravenous
necrosis of
Veins, 51m
33,37,505:

Endot
in the blo(
inCrEased 1
bition of ‘
(14,16,18,
of a numbe

SEIotOnin

Renal dysfunction is evidenced early in endotoxin shock and is
principally the result of ischemia subsequent to systemic hypotension.
Some renal vasoconstriction, caused either directly by the endotoxin or
some substance it releases, may be seen prior to the onset of the
systemic hypotension, but no direct toxic action of endotoxin on the
renal tissues can be shown (23,40,41).

The response of the lungs to endotoxin includes moderate pulmonary
hypertension resulting from an increase in pulmonary arterial and venous
resistances, predominantly the latter, and a gain in lung weight due to
pooling of blood and pulmonary edema. These phenomena are believed to
be due not to the direct action of endotoxin on the lungs, but secon—
darily to platelet aggregation in the microcirculation of the lung and
subsequent release of the platelet amines (34,52,82). No direct toxic
action of endotoxin on pulmonary tissues has been shown.

The response of the canine intestine to endotoxin is profound.
Intravenous administration of endotoxin produces acute hemorrhagic
necrosis of the intestinal mucosa due to vasospasm of the mesenteric
veins, sloughing of Peyer's Patches and profuse blood diarrhea (6,28,
33,37,50,55,67).

Endotoxin shock is also characterized by significant alterations
in the blood which include decreased platelet counts, hyperglycemia,
increased hematocrit, acidosis and leucopenia accompanied by an inhi—
bition of diapedesis and depression of the reticulo—endothelial system
(14,16,18,35,49,70,76,77). Increases in the circulating blood levels
of a number of vasoactive agents including histamine (9,36,47,48,71,81),

serotonin (50,51,69,86), epinephrine (20,63,69,95), norepinephrine

 

 

(50,69), an:
shock.
The l

toxin shock

 

system part
I tration of
adrenal cat
central ner
adrenal gla
does not 3F
mXin shock
Systemic a:
determining
shock has 1
Separates 1
One technit
aration,
and involv.
of one dOg
0f the mo
arterieS a
Vertebral
dog is Per
dnced into
of the 0th

in the try

(50,69), and bradykinin (50,60,93) have been reported during endotoxin
shock.

The literature on the role of the central nervous system in endo—
toxin shock is conflicting. It has been shown that the central nervous
system participates in the febrile response following systemic adminis—
tration of endotoxin (5,15). Likewise, the increase in circulating
adrenal catecholamines during endotoxin shock is mediated via the
central nervous system and does not occur following denervation of the
adrenal glands (20,63,95). On the contrary, the central nervous system
does not appear responsible for the hepato—splanchnic pooling in endo—
toxin shock which is responsible for the early precipitous fall in mean
systemic arterial pressure (24,57,59). The principal difficulty in
determining the participation of the central nervous system in endotoxin
shock has been the development of an experimental preparation which
separates the central actions of endotoxin from its peripheral actions.
One technique which has been used is the head cross-circulation prep—
aration. This technique was originated by Leon Frederico in 1890 (26)
and involves the anastomosis of the cephalic end of the carotid artery
of one dog to the thoracic end of another dog. An external jugular vein
of the two dogs is anastomosed in like manner. The opposite carotid
arteries and external jugular veins of the dogs are ligated as are the
vertebral artery of both dogs. The net result is that the head of one
dog is perfused by the trunk of the other dog. Thus a substance intro-
duced into the trunk of either animal is perfused only through the head
0f the other animal. Theoretically then, alterations in hemodynamics

in the trunk of the animal whose head alone was exposed to the substance

 

 

are mediated
In 195
mine if endo
vascular eff
heat shocked
They observe
trunk of the
toxin. They
which receiv
relatiVe to
manner. The
duodemm, je
exposed to t
which reCeiV
represented
I.UI‘ther Sup}:
Prevented tli
Centratim.
Characterist
Stimulation
This x,
vertebral a1
attempt was
thin~walled
continuatioI

VeI'tEbral C;

 

are mediated through the central nervous system.

In 1952 Penner and Klein (67) utilized this preparation to deter—
mine if endotoxin was capable of eliciting centrally mediated cardio—
vascular effects. These investigators infused endotoxin, prepared from
heat shocked Shiga bacillus, intravenously into one dog of the pair.
They observed hyperglycemia, leucopenia and hemoconcentration in the
trunk of the dog whose head was perfused by the blood containing the
toxin. They noted minor changes in two experiments in the animal

which received the toxin intravenously, but these changes were small

 

relative to those seen in the opposite dog and occurred in an irregular
manner. They also noted anatomical lesions of the gall bladder,
duodenum, jejunum and adrenal glands of the dog whose brain alone was
exposed to the toxin. Because of the minimal changes seen in the dogs
which received the intravenous toxin, they concluded that these actions
represented the centrally mediated actions of Shiga endotoxin. In
further support of their theory, they noted that ganglionic blockade
prevented the tissue changes as well as the hyperglycemia and hemocon—
centration. They therefore concluded that Shiga toxin produces its
characteristic visceral lesions via the central nervous system through
stimulation of the sympathetic nerves.

This work has been criticized on two grounds. First, although the
vertebral arteries and veins were ligated in this preparation, no
attempt was made to occlude the intraspinal venous sinuses. These are
thin—walled structures which originate in the arch of the Atlas as a
continuation of the ventral occipital sinuses and travel within the

vertebral cavity to the level of the coccygeal vertebra (58). It has

been shown b
occluded, es
(19,56,92).
dog whose he
actions of t
due to leaka
intraspinal
gram negativ
neural actio
may not be r
In 195
using toxin
rePresentati
hum of e
hmrglycemi
lesions in 1‘.
Systemic art
reciPient do
tion between
Cells iTlto t
the recipien
blood activi
of Cerebral
failed to Pr
administrati

that endotOX

 

been shown by several investigators that unless these sinuses are
occluded, essentially free mixing of cerebral and corporeal blood occurs
(19,56,92). Thus, whether or not the effects seen in the trunk of the
dog whose head alone received the toxin are in fact centrally mediated
actions of the toxin are unclear. They also may be peripheral actions
due to leakage of endotoxin into the trunk of the animal through the
intraspinal venous sinuses. Secondly, although the actions of most

gram negative toxins are similar, ShigeZZa dysenteriae toxin has a

 

neural action which is not shown by most endotoxins. Thus Shiga toxin
may not be representative of endotoxins in general.

In 1956, Well et al. (92) attempted to duplicate these experiments
using toxin from Escherichia coli and BruceZZa meZitensis which are more
representative of endotoxins in general. Following the intravenous in—
jection of endotoxin into the vascularly isolated head, the authors noted
hyperglycemia, leucopenia, hemoconcentration and gastrointestinal
lesions in the trunk. Furthermore, they observed similar decreases in
systemic arterial pressure and cardiac output in both donor and
recipient dogs. In an attempt to assess the degree of vascular isola—
tion between the head and the trunk, they introduced Crsl labeled red
cells into the arterial perfusion circuit to the head. They found that
the recipient trunk blood radioactivity was 13% of the donor trunk
blood activity after only five minutes, indicating significant mixing
Of cerebral and corporeal blood. They also found that cord transection
failed to prevent the hemodynamic changes subsequent to endotoxin
administration. They interpreted this as support for their conclusion

that endotoxin does not cause its primary lesions through actions of the

 

central nen
that their 1
mediated car
been initia!
quent course
In 193
of Penner a1
following a<
observed b0‘
Whose head ;
did not We
Prufiry sit
tor of the
Preparation
sion Circui
trunk blood
of the radi
intravenous
0f the indi
of the acti
USed by the
°f bl00d £1
as 3PPOSed

Anot}

MEdiated CE

perfuSion I

central nervous system (90,92). Weil et al. (92) point out, however,
that their results do not preclude the existence of important centrally
mediated cardiovascular effects of endotoxin once the shock state has
been initiated. Such effects may play an important role in the subse—
quent course of the shock state (91,92).

In 1958, Donald, Winkler and Hare (19) repeated the experiments
of Penner and Klein in order to further study the leucopenic response
following administration of Shiga toxin. Since the leucopenia was
observed both in the dog receiving the toxin intravenously and the animal
whose head alone received the toxin and cord transection or decapitation
did not prevent the leucopenia, these authors excluded the brain as a
primary site for the leucopenic response to Shiga toxin. As an indica—
tor of the vascular isolation between the head and the trunk in their
preparation, the authors injected radiolabeled albumin into the perfu—
sion circuit to the head. They reported that the radioactivity of the
trunk blood of the animal whose head alone received the toxin was 24%
of the radioactivity of the blood from the dog that received the toxin
intravenously after only five minutes. Thirty minutes after injection
of the indicator, recipient blood radioactivity was between 65 and 85%
of the activity of the donor dog blood. Clearly then, the technique
used by these early investigators does not provide sufficient separatiOn
of blood flow between the head and the trunk to determine the central
as opposed to the peripheral actions of endotoxin.

Another technique which has been used to study the centrally
mediated cardiovascular actions of endotoxin is the cerebral ventricle

perfusion technique. Endotoxin is either injected into the lateral

" I.

 

cerebral vc
most com:
this techni
gastrointes
tion of Shi
doses (2-3
1963 (65) c
can be prev
toxin used
SYStemicall
or indirect
More
Sively to d
Vascular ef
intracister
State and d
0f the live
that Small .
were effect
lethality d.
neons SYS
Capable of ‘
leading to (
also “med,
ing intravel

they are bv

10

cerebral ventricles or perfused through the lateral and third ventricles,
most commonly in dogs or cats. In 1959 (68), Penner and Bernheim used
this technique in dogs to demonstrate that ulcerative lesions of the
gastrointestinal tract, commonly seen in response to intravenous injec—
tion of Shigella sp. toxin, occur following the introduction of small
doses (2-3 mg) of toxin into the third ventricle. Palmerio et al. in
1963 (65) confirmed these results in dogs and showed that the lesions

can be prevented by prior splanchnic denervation. Because the dose of
toxin used in these experiments is completely ineffective if given
systemically, the authors concluded that the lesions resulted from direct
or indirect actions of the toxin on the central nervous system.

More recently, Simmons et al. (76,77) used this technique exten—
sively to determine if endotoxin exhibits centrally mediated cardio—
vascular effects. They found that small doses of intraventricular or
intracisternal E. coli endotoxin were capable of producing a shock—like
state and death. They also reported massive pulmonary edema, congestion
of the liver, and cardiac damage, especially to the valves. The fact
that small doses of endotoxin, which would be ineffective systemically,
were effective centrally, coupled with the fact that the degree of
lethality depended on the location of the toxin within the central
nervous system, led these investigators to conclude that endotoxin is
capable of inducing significant systemic pathophysiological alterations
leading to death by its presence in the central nervous system. They
also noted,however, that while the pathologic changes that occur follow—
ing intraventricular and intravenous endotoxin are similar in some ways,

they are by no means identical. The gross lesions of the

p.
l

 

 

 

gastrointer
not present
venous end:
heart weigl
monary eden
Whether the
difference
although 3:
caused pat}
Primary cer
{OXin coulc
0f endotoxj
nervous SYS

In a
decreased (
ChangeS We]
after intrz
declined 33
Value unti:
reSPOIlSeg (
istration (
This SuPPO]
Central he]
this mechaI

Ratio“ of

 

ll

gastrointestinal tract, seen with intravenous endotoxin in dogs, were
not present with intraventricular endotoxin. Likewise, while intra—
venous endotoxin resulted in small nonsignificant increases in lung/
heart weight ratios, intraventricular endotoxin produced massive pul—
monary edema and significant increases in lung/heart weight ratios.
Whether these differences represented separate pathogenesis or merely a
difference in degree, was not clear. Thus, they concluded that,
although administration of endotoxin to the central nervous system
caused pathologic changes leading to death, a convincing case for the
primary central nervous system action of systemically administered endo—
toxin could not be made. It was unclear whether systemic administration
of endotoxin results in concentrations of the toxin in the central
nervous system sufficient to elicit these changes.

In a companion hemodynamic study, Simmons et al. reported that
decreased cardiac output was the most consistent finding. No significant
changes were found in total peripheral resistance until several hours
after intraventricular administration of the toxin. Arterial pressure
declined slowly but was not significantly different from the control
value until two hours after administration of the endotoxin. These
responses differ significantly from those seen following systemic admin—
istration of endotoxin where arterial pressure falls within two minutes.
This supports their conclusion that, while endotoxin can act in the
central nervous system to produce peripheral cardiovascular effects,
this mechanism is not necessarily operative following systemic adminis—

tration of endotoxin.

 

Thu
ventricle
tered and
brain to
circulati
adequate
allow sep.
actions.

In .
tion teclu
With a sp(
blood flor
Small amor
mdined f0]
Circulatic
OCCluded t
inJetted 1'
trunk. ind
that time,
further an
Vascular e
confines a
fore New
free from
This is th
centrally I

i. 30% en

 

12

Thus both techniques have disadvantages. With regard to the
ventricle perfusion technique, it is unclear if systemically adminis—
tered endotoxin results in sufficient concentration of toxin in the
brain to elicit the effects shown. With regard to the cerebral cross—
circulation experiments, this technique clearly does not provide
adequate separation of blood flow between the head and the trunk to
allow separation of central actions of endotoxin from its peripheral
actions.

In 1935, Nowak and Samaan (61,62) described a new cross-circula—
tion technique in which the intraspinal venous sinuses are occluded
with a specially—formed ”U" clamp. This technique provides for better
blood flow separation than previous techniques, but there is still
small amounts of venous drainage between the head and the trunk. It re—
mained for Taylor and Page in 1951 (83) to devise the first cross—
circulation preparation with complete separation of blood flow. They
occluded the intraspinal venous sinuses with a tonsil snare. T—l824 dye
injected into the perfusion circuit to the head did not appear in the
trunk, indicating complete occlusion of all vascular channels. Since
that time, Buckly and co—workers (12,32,72,74,78) improved the technique
further and used it extensively to study the centrally mediated cardio-
vascular effects of a number of vasoactive agents. This technique then
confines a substance to the cerebral circulation of an animal and there—
fore provides the means to study the pure central action of an agent,
free from contamination by any peripheral actions the agent may have.
This is the technique we have utilized in this study to determine the

centrally mediated cardiovascular effects of systemically administered

E. coli endotoxin.

 

The c
that E. 002
Participate
tion of enc
any Central

irreversibj

 

CHAPTER III

STATEMENT OF THE HYPOTHESIS

The objectives of this study were: 1) to test the hypothesis
that E. coli endotoxin, by its presence in the central nervous system,
participates in the hypotension which follows the systemic administra—
tion of endotoxin, and 2) to attempt to determine the significance of
any centrally mediated cardiovascular effects in relationship to the

irreversible phase of endotoxin shock.

 

l3

 

 

Mongr
kilograms y
hated, and
neck was cj
arteries in
and eSOpha,
Sarted. T1
”38 of ele‘
column bet:
A dorsal 1
CM was e
A Suitable
a Sponge 3
Passed 11nd
The Sponge
Wire was t
Schiffrin
armies,

“We. t}

CHAPTER IV

METHODS

Mongrel dogs of either sex, ranging in weight from seven to eleven

kilograms were anesthetized with sodium pentobarbital (30 mg/kg), intu—

bated, and placed on positive pressure ventilation. The skin of the

 

neck was circumferentially sectioned. The jugular veins and carotid
arteries were isolated and wrapped with saline soaked gauze. The trachea
and esophagus were tied and sectioned and the tracheal tube was rein—
serted. The neck muscles were isolated and removed in layers with the
use of electrocautery. The remaining muscle was removed from the spinal
column between C—3 and C-4 and the head was placed in a rigid holder.

A dorsal laminectomy was performed and the dorsal surface of the spinal
cord was exposed. Care was taken to keep the spinal cord moist.

A suitable length of 21 gauge steel wire was passed lengthwise through i
a sponge approximately 60 by 10 by 5 mm and the wire and sponge were
passed under the spinal cord with the use of specially curved hemostats.
The sponge was positioned beneath the spinal cord (Figure 1) and the
wire was tightened around the intravertebral disc with the use of a
Schiffrin wire tightener. This successfully occluded the vertebral
arteries, veins and the intraspinal venous sinuses. A moistened gauze

Sponge, the approximate size of the neck muscle mass removed, was

14

 

 

 

 

 

15

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placed around
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were exposed.
of the donor (1
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Carotid arterj
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17

placed around the column to provide support and to keep the spinal cord
moist.

Mongrel dogs of 18 to 30 kilograms, which served as donors, were
anesthetized with sodium pentobarbital (30 mg/kg), intubated, and placed
on positive pressure ventilation. The right femoral artery and vein
were exposed. Circulation was established between the femoral artery
of the donor dog and the two common carotid arteries of the recipient
dog with the use of a Y—tube cannula. A pressure independent pump was

interposed in this circuit to provide a constant blood flow through the

 

arterial perfusion circuit to the head. Circulation was established
between the two jugular veins of the recipient and the femoral vein of
the donor dog with the use of a Y-tube cannula (Figure 2). Thus the
recipient's head received arterial blood only through the cannulated
carotid arteries and was drained only through the cannulated jugular
veins. The right femoral artery of the recipient dog was cannulated

(PE 240) for the measurement of systemic arterial pressure. Systemic
arterial pressure of the donor dog was measured via a cannulated carotid
artery (PE 240). Perfusion pressure to the head was measured via a
needle tipped catheter inserted into the arterial perfusion circuit to
the head immediately distal to the Y—tube (Figure 3). Both dogs
received intravenous injections of sodium heparin (10,000 units) prior
to the beginning of the experiment, to prevent intravascular coagula—
tion.

The donor dog was transfused with 6% dextran in normal saline if

it was considered hypotensive upon catheterization. The recipient

animals were likewise transfused if significant blood loss occurred

 

 

 

18

Figure 2. Placement of arterial inflow and venous outflow catheters
in recipient dog. Note arterial inflow is proximal to
the carotid sinuses.

Carotid A.
JWUIor Vs

l9

figure 2

Recipient Dog

flow catheters
proximal to

  
 

Carotid Artery
Jugular Vein

Vogus Nerve

NI? Head Perfusion

I Circuit
Venous Return '
Circuit I

Blood flo "'

Blood flow .—

 

 

 

 

20

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during surg
cc) did not
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To e1
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arterial pi
blood samp
wavelength
0f the dye
from the h
0f flow fr
ing inject
displayed
0f the spj
ing the re
bl°0d flon
flow afte]
V3g0tomy,
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Period an
minutes a
hemateri

nique, dU

22

during surgery. If transfusion of moderate amounts of dextran (50—300
cc) did not result in rapid improvement and stabilization of pressures,
the experiment was discarded.

To evaluate the degree of venous drainage from the head to the
trunk of the recipient, 180 mg of Evans blue dye was injected into the
arterial perfusion circuit to the head. Control and post—dye arterial
blood samples were analyzed on a double—beam spectrophotometer at a
wavelength of 608 millimicrons for the presence of the dye. An absence

of the dye in the recipient's trunk blood indicated that all channels

 

from the head to the trunk had been successfully occluded. The presence
of flow from the trunk to the head was ascertained in like manner follow—
ing injection of dye into the recipient's trunk. Only experiments which
displayed no mixing of cerebral and trunk blood were used. The integrity
of the spinal cord and vagus nerves was ascertained by routinely observ—
ing the recipient's blood pressure response to interruption of carotid
blood flow and frequently to vagotomy, interruption of carotid blood
flow after vagotomy, hypoxia, vasoactive drugs both before and after
vagotomy, and the central nervous system ischemic reflex.

Once it had been determined that complete circulatory separation
existed between the head and the trunk of the recipient, donor and
recipient systemic arterial pressure, pulse pressure, heart rate and
cerebral perfusion pressure were measured during a five minute control
period and two, five, ten, fifteen, thirty, forty~five and sixty
minutes after the infusion of endotoxin. Both donor and recipient
hematocrit were measured, in triplicate using the microcapillary tech—

nique, during the control period and at the end of the sixty minute

experimental
at a rate 01
sion pump.
nent transdi
oscillograp]
existence at
E. 001i and
below and a‘
A. In
E. 3011' end
the arteria
and carotid
was used to
the toxin,
atti0n en t
B- Ir
HdEbufferec‘
0f the dam
resPonse u
0chUsion t
obtained b}
intact. F;
in nofinal ;
head. The
Series A t

the reSPOn

23

experimental period. E. coli endotoxin (Difco Laboratories) was infused
at a rate of 2 cc/minute for ten minutes with the use of a Harvard infu—
sion pump. All pressures were measured with Statham low-volume displace—
ment transducers (PZBG-B) and recorded on a Sanborn direct writing
oscillograph. Ten series of experiments were performed to determine the
existence and importance of centrally mediated cardiovascular effects of
E. coli endotoxin. These experiments, labeled A through J, are described
below and are summarized in Table l.

A. In these experiments 5 mg/kg (based on donor weight) purified
E. coli endotoxin suspended in 20 ml. of normal saline was infused into
the arterial perfusion circuit to the head. The recipient dogs vagi
and carotid sinus nerves were left intact. This large dose of endotoxin
was used to indicate if the toxin itself, or some substance released by
the toxin, was capable of eliciting cardiovascular effects by a direct
action on the central nervous system.

B. In these experiments the recipient dogs were bilaterally
"debuffered” by sectioning the sinus (Hering) nerves. The effectiveness
of the denervation was confirmed by the failure of a blood pressure
response to occur in the recipient subsequent to bilateral carotid
occlusion (Figure 11) or alterations in cerebral perfusion pressure
obtained by altering the pump speed. The recipient dogs vagi were left
intact. Five mg/kg (donor weight) purified E. coli endotoxin suspended
in normal saline, was infused into the arterial perfusion circuit to the
head. The results of these experiments were compared with those of
series A to determine if the carotid sinus—body complexes contributed to

the responses seen.

 

 

C. In t
purified E. c
intravenousl)
sinus nerves
the natural 5
aperipheral
mine if the (
dependent upt

D. This
except that t
weight). The
the Central (
adElirtistratic

E» In I
W 5- colt"
Venously int<
Carotid Sinus
to determine
CardiWaSculg
reach the Cei

F' Thi:
in SIOUp E e:
(recipient w.
cardiOVaSCuL

toxin Could I

24

C. In this series of experiments, 5 mg/kg (based on donor weight)
purified E. coli endotoxin, suspended in normal saline, was infused
intravenously into the donor dog. The recipientdogfinvagi and carotid
sinus nerves were left intact. These experiments more closely resembled
the natural situation where endotoxin gains access to the circulation at
a peripheral site. The results of these experiments were used to deter-
mine if the centrally mediated cardiovascular effects of endotoxin were
dependent upon the site of access of the toxin into the circulation.

D. This group of experiments were identical to those in group C

 

except that the intravenous dose of endotoxin used was 1 mg/kg (donor
weight). The results of these experiments were used to determine whether
the central cardiovascular effects of endotoxin following intravenous
administration, were dose dependent over these two doses.

E. In this series of experiments, 5 mg/kg (recipient weight) puri—
fied E. coli endotoxin, suspended in normal saline, was infused intra—
venously into the trunk of the recipient dog. The recipient's vagi and
carotid sinus nerves were left intact. These experiments were employed
to determine the effect of intravenously administered endotoxin on the
cardiovascular system under conditions in which the toxin could not
reach the central nervous system.

F. This group of experiments were prepared identically to those
in group E except that the intravenous dose of endotoxin was 1 mg/kg
(recipient weight). These experiments were used to determine if the
cardiovascular effects of endotoxin, under conditions in which the

toxin could not reach the central nervous system, were dose dependent.

G.
fied E. 01
venously
bilateral.
nerves re]
determine
effects 0.
the centr.

H.
drugs wer.
Periods o,
acetylcho
histamine
6 ug has
likewise
COntrol v.
infused i‘
recipient
determine
the indirt

I.
"debuffere
Sim Ciro
acEtchhov
haSe/mimJ

base/“lion

 

25

G. In this group of experiments, 5 mg/kg (recipient weight) puri—
fied E. coli endotoxin, suspended in normal saline, was infused intra—
venously into the trunk of the recipient animals. The recipients were
bilaterally vagotimized prior to the infusion but the carotid sinus
nerves remained intact. The results of these experiments were used to
determine the participation of the vagal afferents in the cardiovascular
effects of endotoxin under conditions in which the toxin could not reach

the central nervous system.

 

H. In these experiments endotoxin was not used. The following
drugs were infused into the arterial perfusion circuit to the head for
periods of five minutes; serotonin creatine sulfate 45 pg base/minute,
acetylcholine chloride 15 pg base/minute, bradykinin 3 ug/minute,
histamine diphosphate 15 pg base/minute and norepinephrine bitartrate
6 pg base/minute. A bolus injection of 10 pg of angiotensin II was
likewise introduced into the arterial perfusion circuit to the head.
Control values were obtained prior to each infusion and the drugs were
infused in a random sequence. The vagi and carotid sinus nerves of the
recipient dogs remained intact. These experiments were employed to
determine if any of these vasoactive substances could be responsible for
the indirectly mediated cardiovascular effects of endotoxin.

I. In these experiments, the recipient dogs were again bilaterally
"debufferedfl The following drugs were infused into the arterial perfu—
sion circuit to the head; serotonin creatine sulfate 45 11g base/minute,
acetylcholine chloride 15 11g base/minute, histamine diphosphate 15 rig
base/minute, bradykinin 3 rig/minute and norepinephrine bitartrate 6 llg

base/minute. A bolus injection of 10 14g of angiotensin II was likewise

introduced
values were
were left i
contributio
vasoactive

J. T11
recipient a
previous ex
sinus nerve

All c‘
rePlicates.
value at mj
WU control

Commonly 0(

26

introduced into the arterial perfusion circuit to the head. Control
values were obtained prior to each infusion. The vagi of the recipients
were left intact. These experiments were utilized to determine the
contribution of the carotid sinus—body complex to the response of these
vasoactive substances.

J. This set of experiments served as controls. The donor and
recipient animals were surgically prepared in a manner identical to the
previous experiments in which the buffer nerves were intact. The carotid
sinus nerves and vagi of the recipient dogs were left intact.

All data were analyzed with Students t test as adapted for paired
replicates. This test compares an experimental value with its control
value at minute zero. Thus each experiment within a series serves as its

own control. This eliminates the inherent hemodynamic variations which

commonly occur in mongrel dogs.

 

 

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In
jected in
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ient. Cc
were not
were ther
series 01
into the
Venously
Channels
Sorbance
were not
in the h
the head

that the
blood f]
Ti

eXperime

 

CHAPTER V

RESULTS

In each series of experiments 180 mg of Evans Blue dye was in—

jected into the arterial perfusion circuit to the head to indicate the

presence of vascular channels from the head to the trunk of the recip-

 

ient. Control and post—dye recipient trunk blood absorbance values
were not different, all vascular channels from the head to the trunk
were therefore successfully occluded in these experiments. In the three
series of experiments involving the intravenous infusion of endotoxin
into the recipient trunk, 240 mg of Evans Blue dye was injected intra-
venously in the recipient trunk to indicate the presence of vascular
channels from the trunk to the head of the recipient. Donor blood ab—
sorbance values after intravenous dye administration in the recipient
were not different from the absorbance values following dye injection
in the head perfusion circuit all vascular channels from the trunk to
the head had therefore been successfully occluded. These results show
that the experimental technique utilized does indeed provide complete
blood flow separation between the head and trunk of the recipient dog.
The data presented herein were obtained from 66 successful

experiments which are divided into ten experimental groups.

31

 

 

A. 1
into the :
recipient
trol valui
experimen
elevated
the remai
donor or
sions in

B.
into the
tion of 1
mean sysi
and rema
Was mark
P9rfusio
and rema
and Puls
lllinute 6

C.
the dOnc
two and
Signifi(
Pressm
eleVate.

meot.

32

A. Following the infusion of 5 mg/kg purified E. coli endotoxin
into the arterial perfusion circuit to the head (Table 2), the donor and
recipient mean systemic arterial pressures fell significantly below con—
trol values by minute thirty and remained depressed throughout the
experimental period. Perfusion pressure to the head was significantly
elevated by minute thirty and remained above control values throughout
the remainder of the experiment. There were no significant changes in
donor or recipient heart rates and only transiently significant depres—

sions in donor and recipient pulse pressures.

 

B. Following the infusion of 5 mg/kg purified E. coli endotoxin
into the arterial perfusion circuit to the head with bilateral denerva—
tion of the carotid sinus-body complexes (Table 3, Figure 14), donor
mean systemic arterial pressure fell markedly below control by minute 10
and remained at hypotensive levels. Recipient systemic arterial pressure
was markedly depressed by minute 30 and remained below control whereas
perfusion pressure to the head was significantly increased at this time
and remained elevated. Only transient changes were seen in heart rates
and pulse pressures. Donor hematocrit was significantly increased at
minute 60 whereas recipient hematocrit was decreased.

C. Following the intravenous infusion of 5 mg/kg of endotoxin into
the donor dog (Table 4), donor systemic arterial pressure fell by minute

two and remained depressed. Recipient systemic arterial pressure fell

 

significantly by minute thirty and continued to fall markedly. Perfusion
pressure to the head fell below control by minute two, was significantly
elevated by minute five and continued to increase throughout the experi—

ment. Donor pulse pressure and heart rate were depressed from minute

 

 

 

two throu
Recipient
experimen
significa
increased
D.
donor do:
hypotens:
30, inert
donor he.
pulse pr
tocrit w
E.
the reci
reCipien
SiVe 1ev
“mained
this PEI
minute 3
measUm
F
recipiej
Series
minUte
ORWal-d_

minute

 

33

two through fifteen but then recovered and remained near control values.
Recipient pulse pressure was significantly depressed by the end of the
experiment while recipient heart rate remained unchanged. There was no
significant change in recipient hematocrit whereas donor hematocrit was
increased by minute sixty.

D. The infusion of 1 mg/kg of endotoxin intravenously into the
donor dog (Table 5), resulted in changes identical to those in series C;
hypotension in the donor by minute two and in the recipient by minute

30, increased perfusion pressure by minute ten, transient depression of

 

donor heart rates and pulse pressure, late depression of recipient
pulse pressure and no change in recipient heart rate. Again donor hema—
tocrit was increased while recipient hematocrit remained unchanged.

E. Following the intravenous infusion of 5 mg/kg of endotoxin into
the recipient trunk (Table 6), the systemic arterial pressure of the
recipient was markedly depressed by minute five and remained at hypoten-
sive levels. Recipient pulse pressure was depressed by minute five and
remained below control whereas recipient heart rate was increased during
this period. The recipient hematocrit was significantly decreased by
minute sixty. No changes were seen in any of the dOnor parameters
measured.

F. The infusion of 1 mg/kg of endotoxin intravenously into the
recipient trunk (Table l) yielded results quite similar to those in
series F; recipient systemic arterial pressure fell significantly by
minute two while recipient pulse pressure was depressed from minute five
onward. Perfusion pressure to the head was significantly increased by

minute 15. No change was seen in recipient heart rate, hematocrit or

 

any of th
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Recipient
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fusion 0
Th
Perfusio
in a Vas
increaSe

artErial

 

34

any of the donor parameters measured.

G. Following the intravenous infusion of 5 mg/kg of endotoxin in
the recipient trunk after bilateral cervical vagotomy (Table 8), systemic
arterial pressure was depressed by minute five and continued to fall.
Recipient pulse pressure was depressed by minute ten and remained below
control values. Recipient heart rate was transiently increased from
minute two through fifteen while recipient hematocrit did not change.
Perfusion pressure to the head was increased by the end of the experi-

ment whereas no significant changes occurred in any of the donor para-

 

meters measured.

H. Drug infusions into the arterial perfusion circuit to the head
are summarized in Table 9. The infusion of acetylcholine, histamine and
bradykinin resulted in significantly increased recipient systemic
arterial pressure subsequent to a decrease in head perfusion pressure.
Typical response patterns to acetylcholine, histamine and bradykinin
may be seen in Figures 4, 5 and 6 respectively. The infusion of nor—
epinephrine resulted in a decrease in the recipient systemic arterial
pressure subsequent to increases in perfusion pressure to the head.

A typical response pattern to norepinephrine may be seen in Figure 7.
Donor systemic arterial pressure did not change as a result of the in—
fusion of any of the above drugs.

The response to 10 ug bolus injections of angiotensin II into the
perfusion circuit to the head Were less consistent but usually resulted
in a vasodepressor response in the recipient trunk subsequent to an
increase in perfusion pressure to the head (Appendix). Donor systemic

arterial pressure also increased significantly following angiotensin II

fifiectic
in Figui

I.
followir
body con
resultec
did not
of note;
sure to
Pressure
debuffei

T1
the hea<
unchangg
Drassuri
and milr
and hyp(

B(
fusion (
and rec:
A tYPic;

J
Cally t<
remains
Daramet

Derqui‘

35

injection. A hypotensive response pattern to angiotensin II may be seen
in Figure 8.

1. Drug infusions into the arterial perfusion circuit to the head
following the bilateral denervation of the recipient dogs carotid sinus-
body complexes (Appendix). The infusion of acetylcholine and histamine
resulted in a significant decrease in perfusion pressure to the head but
did not change donor or recipient systemic arterial pressure. Infusion
of norepinephrine resulted in a significantly increased perfusion pres—
sure to the head but did not alter donor or recipient systemic arterial
pressure. Typical response patterns to these three drugs following the
debuffering of the recipient may be seen in Figure 16.

The infusion of bradykinin into the arterial perfusion circuit to
the head resulted in a significantly decreased perfusion pressure and an
unchanged donor systemic arterial pressure. Recipient systemic arterial
pressure was markedly increased in some experiments, unchanged in others
and mildly decreased in still other experiments. Typical hypertensive
and hypotensive responses to bradykinin infusion can be seen in Figure 15.

Bolus injections of 10 pg of angiotensin II into the arterial per—
fusion circuit to the head resulted in significant increases in donor
and recipient systemic arterial pressures and perfusion pressure.

A typical response pattern to angiotensin II may be seen in Figure 13.

J. In control experiments (Table 10), which were prepared identi—
cally to previous experiments in which the recipient dogs buffer nerves
remained intact, there were no changes in any of the experimental
parameters measured with the exception of a significant increase in

perfusion pressure at minute 60.

 

 

 

The

both befo

Bef
Control I

121: AJ

Se<
increase
Pattern .
in 1Tiguri

A
and afte

Fi‘
in Strik
Cerebral

A
the head
into the

trol exp

36

The responses to sixty second interruption of carotid blood flow

both before and after vagotomy were likewise tested and are as follows:

60 second interruption of flow

Before Vegotomy After Vagotomy

Control Par Experimental Par Control Par Experimental Par
121 i 4.4 174 r 6.0* 126 i 5.9 220 i 4.0*

* = significance paired T P< .01

Par = recipient mean arterial pressure i standard errors.

Sectioning of the recipientdogssvagi resulted in a significant
increase in recipient systemic arterial pressure. A typical response
pattern to bilateral cervical vagotomy in the recipient dog may be seen
in Figure 9.

A typical response pattern to bilateral carotid occlusion before
and after vagotomy may be seen in Figure 10.

Five minutes of cerebral ischemia in the recipient dog resulted

 

in striking increases in recipient systemic arterial pressure. A typical

cerebral ischemic reflex may be seen in Figure 12.

A summary slide comparing the effects of endotoxin infusion into

the head perfusion circuit before and after debuffering, or intravenously

into the recipient trunk before and after vagotomy, as compared to con—

trol experiments, may be seen in Figure 17.

 

 

37

 

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38

 

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n.0 H 00H 0.0 H 0HH 0.0 H 00 0.0 H 00 +0.0H H 00H Hm.¢H H 00 «H.H H NH 00
0.0 H HHH 0.0 H 0NH +0.0 H H0 0.0 H H0 0.0 H 0HH 0.0H H 00 0.0 H 00 0H
0.5 H 00H 0.N H 0HH 0.0 H 00 0.0 H N0 N.H H 00H «.0H H 00 H.0 H N0 0H
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um um Heads Howie mm ems H3 959

 

 

 

 

 

 

39

 

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0.0H H HOH 5.0 H 00H 0.0 H 50 +H.5 H H0 *0.0H H 05H «0.0 H 50 «0.5 H 05 0c
H.0H H 00H 0.0 H 00H 0.0 H 50 0.0 H 00 *0.0H H 00H s0.0 H 50 +0.5 H NOH 00
0.5 H ¢0H 0.5 H 00H 0.0 H 00 «.5 + H0 +5.0H H 00H «5.0 H 00 0.0a H 00H 0H
0.0 H «0H 0.0 H qu 0.0 H 00 5.0 H H0 0.0H H 00H «0.0 H 00 H.0H H HmH 0H
0.0 H 00H 0.0 H 00H 0.0 H 00 0.0 H 00 0.0 H 00H *0.0 H 00 0.0H H HOH 0
0.0 H HOH 0.0 H q0H 0.0 H 50 0.5 H 00 5.0 H HOH 0.0 H 00 0.0 H 00H m
0.0 H 50H «.5 H HOH 0.0 H 00 5.0 H 00 0.0 H 00H «.0 H 00H 0.0 H 00H 0
0.0 H 50H «.5 H HOH 0.0 + 00 5.0 H 00 «.0 H 00H «.0 H 0NH 0.0 H 00H 0|
um um womHzm Howasm mm 0mm Hum oaHH

 

 

 

 

 

 

41

 

 

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stouowam Ho GOHwDHnH msooo>muucH Ho wow usmHmHooH 0cm

0 n a .000 Hocov mzu 5H wa\ma 0v
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42

 

 

 

 

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0 ouosHa u< can ouowom Hocov I oHsmmoHH HMHHouHm UHEoumHm n NH
wuHHooumamm mmmmmmqum uamHHHooH I endomeH HmHHmuHm UHBoume u HmH
0.0 H ova 0.NH H 00H 0.0 H 00 «0.0 H 00 «H.0H H 00H «0.5 H 50 «0.0 H 50 00
0.0 H 00H 5.NH H 00H 0.0 H 00 H0.q H N0 «0.0H H 00H «0.0 H 00 «5.0 H 00 0a
0.5 H 00H 0.0H H 00H 5.0 H 00 0.0 H OH sq.0 H 00H «5.0H H 50 +0.0H H 55 00
«0.0 H 00H 0.NH H 00H «0.0 H 00 0.0 H NH +5.0H H 0NH «0.0 H 00 0.NH H H0 0H
*N.0 H 00H 0.0H H 00H «0.0 H 00 0.0 H 50 +q.m H HOH «0.0 H 00 0.0H H 00 0H
«0.0 H 00H N.¢H H 00H H0.0 H 00 0.5 H 50 0.0 H 50H «5.0 H Hq 5.0H H 00H 0
+5.5 H HOH 0.HH H 00H +0.0 H H0 0.5 H 5w +0.0 H 00 H5.¢H H 00 H.NH H 00H N
0.0 H qu N.HH H 00H H.q H 00 H.0 H 00 0.0 H 00 0.5 H 00H 0.0 H 00H 0
0.0 H 00H 0.0H H 00H H.¢ H 00 0.0 H 00 0.0 H 00 «.5 H 00H 0.0 H 00H 0I
em as @345 H83 3 ems com me:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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43

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aonuo0nm Ho GOHmDHcH msoao>muucH 00 000 unoHHHooH 0cm

0 u 0 .000 H0000 030 CH Amx\0a H0
H0000 can 0H muooHHo H0H0000>0H0Hmo

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00. v H H 00HHmH .00000HHH00H0 n +
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+u0.H H H0 H0000 «00.0 H 00.H H0000 H0000 I 0H0000HH omHsH u omHDH
00 0000HE H0 000 Houw0 u0oHHH00H I oHsmmMHH omHsH u omHDH
”mum H mm unoHMMMMM “WNW M ”WNW H00HMWMMM mHsmmoHH 00H00HH0H 0000 u mH
0 0000HE 00 0H0 mHOHmm H0000 I oHSmonH HmHHouHm oHaoumHm u 0MH
muHHooumamm mmmwMMIMNm 000HHH00H I oHsmonH HmHHouHm 0Hamume n HmH
0.0 H 00H ¢.HH H 0HH 0.0 H 50 «0.0 H Hm «0.0H H 00H *0.0 H 00 «5.0 H 00 00
0.5 H 00H 0.0 ”H 0NH 0.0 H 50 «0.0 H 00 «0.0H H 00H H0.0H H 00 «0.0 H 00 00
0.0 H NOH 0.0H H 00H 0.0 H 00 H.N H 00 0.0H H 05H *0.0 H 00 x0.0 H 55 00
«0.0 H 00H 0.0 H 00H 0.0 H 00 0.0 H «q 0.0H H 00H «0.0 H N0 0.0H H 00H 0H
0.0H H 00H 0.5 H 00H 0.0 H 00 0.0 H «q 0.0H H 00H «0.5 H 50 N.0H H 00H 0H
0.0H H 00H 0.0 H 00H 0.0 H «N 0.0 H 00 0.0a H 00H sq.0H H 00 H.0H H 00H 0
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0.0 H 00H 0.0 H OHH 0.0 H 00 0.0 H 00 0.0 H 0HH 0.0 H 5HH 0.0 H 0HH 0
0.0 H 00H 0.0 H OHH 0.0 H 00 0.0 H 00 «.0 H 0HH 0.0 H 5HH 0.0 H 0HH 0I
em He 0300 0300 mm emm Mme we:

 

 

 

,

45

 

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0onuo00o H0 00H0000H mso0o>mHH0H 00 000 H00HHH00H 0

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46

 

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000HHH00H >\H .000 H00H0 H0000 I 000H HH000 u 0H
NH.H H 00 H0000 0HO0HHO H0000 I 0H0000HH 0mHsH u 000H0H
00 0000HE 00 00H00HH0H 000: .0H0 H0uw¢ 000HHH00H I 0H0000HH 00H0H u HowHDH
mm... mm ....me M: M E ....me it- e
0 0000HE 00 0H0 0H0H00 H0000 I 0H0000HH HMHHouHm 0Hs0uwhw u 0mH
muHHUOHMEom mmmflMNIMNm 000HHH00H I 0H0000HH HmHHmuHm 0HE0HmHm u HWH
5.0 H 50H +0.5 H 00H 0.H H 0N «5.0 H.mN «5.5 H 00H H.0 H HHH «0.0 H 00 00
0.5 H 00H +0.5 H 00H 0.H H 0N «0.0 H N0 «0.0 H 00H 0.0 H 0HH «0.0 H 50 00
H.0 H NOH +0.5 H NOH 5.H H 0N 0.0 H 0N «H.HH H 00H 0.0 H 5HH «0.0 H N0 00
0.0H H 0NH +0.5 H NOH 0.H H 0N «0.0 H 5N +0.0 H «NH 0.5 H NNH «0.0 H 00 0H
0.5 H NOH +0.0 H NOH 0.H H 0N HN.0 H 0N 0.0 H 0HH N.5 H 0NH «0.0 H 00 0H
0.0. H 00H +0.0 H 0NH H.H H 5N «N.q H 0N 0.0H H HHH N.0 H 5HH «0.0 H 00 0
0.0 H 00H N.0 H 0NH N.N H 0N 0.0 H 00 0.0 H NOH 0.0 H 0HH 0.5 H 00 N
0.0 H 00H 0.5 H 0HH H.N H 0N 5.N H 00 0.0 H 00H 0.0 H 0HH H.0 H 0HH 0
0.0 H 00H 0.5 H 0HH H.N H 0N 5.N H 00 0.0 H 00H 0.0 H HHH N.0 H 0HH 0|
0 H 0 H 0 H

H H 00H0H omHSH HH 0H 0H 0EHH

 

 

 

 

 

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00 000 000H0H00H 000 H0000 000 0H 0000000 H0H0000>0H0H00 .5 0Han

47

0onuo000 mo 00H0000H 00000>0H00H

 

48

 

 

 

 

 

 

000.0 H 50.0 H00H0H000 H0. v m H 00HH00 0o0monH00Hm n 0
26 H 34 Hosea mo. v m H 030:0 8:83?me u ..H
u00H0H00H >\H .0%0 H0uw< H0000 I 0umH uH000 n 00
NH.N H 50 H0000 uHDOHHu H0000 I 0H0000H0 00H50 n 00mH50
00 0000HE 00 00H000H00 0000 .000 H0000 000H0H00H I 0Hsmw0H0 00H00 n H00H00
H WW 30” 0 m 0 £0 a: 0
0 0u=0HE 00 0%0 0How00 H0000 I 0H0000H0 HmHH0uHm 0008 H mm
muHH00u0800 mmmflMNIwNm 000H0H00H I 0H0000H0 HmHH0uHm 0008 u HWm
N.N H 00H N.HH H 00H 0.H H 00 «5.N H 5H «N.HH H 00H 0.0 H 5NH 0.0 H mm 00
H.0 H 5NH 0.0 H 00H 0.H H H0 00.0 H Hm «0.0H H 00H H.0 H mNH 00.0 H 00 mq
0.5 H NNH H.0H H NMH 0.N H 00 «0.0 H 0N «0.HH + HmH «.0 H 0NH 00.0 H mm 00
5.0 H 5HH «.5 H mNH 0.0 H mm +0.0 H 00 +H.m H HNH 0.5 H NMH 00.0 H N0 mH
H.0 H 00H 0.0 H 0NH 0.0 H 00 +0.0 H mm 0.5 H 0HH N.5 H 00H «0.0H H 00 0H
0.0 H 00H «.5 H mNH 0.0 H 00 +N.m H N0 0.0 H «OH 0.5 H 0NH +H.mH H 05 m
0.0 H 00H 0.0 H mNH 0.0 H 00 0.0 H 00 0.0 H 00 5.5 H 5mH +0.0H H mm N
0.0 H 00H 0.0 H MNH 0.0 H mm 0.0 H Hm 0.0 H 00H 0.0 H 0NH H.5 H NHH 0
0.0 H 00H 0.0 H mNH 0.0 H mm 0.0 H Hm 0.0 H 00H 0.0 H 00H H.5 H NHH ml
00 H0 003:0 0305 mm 0mm 0mm 0&3.

 

 

 

49

.m.m H 0002 5 u
0onuo000 mo 00H0000H m:o00>0Hu0H

0 .0800000> H00H>H00 H0H0H0HH0 00H30HH00 000 H00H0H00H 000 0H A0x\ma 00

00 000 u00H0H00H 000 H0000 000 0H 0000000 H0H0000>0H0H00

.w mHQMH

 

 

 

50

 

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HH.0 H «0.H H0000 00. v m H 00HH00 00000H0H00Hm u +

H00H0H00H >\H “0%0 H0000 H0000 .0H0H HH000 u 00

Nm.H H Hm uaonHowm *mw.m m MW.” “aonwmmm “coHQHumH .oumH “H000 u H0

N0.H H 00 H0000 HHSUHHU 0H=mm0H0 00H00 H0000 u 0 0mHsm

00 0H00HE 00 00H000H00 0000 “0%0 H0000 0H0000H0 00H00 000H0H00H u H00H00

MM.M M MN HO0HMMHWM MW.W m Mm.w HO0HMWMMM 0H0000H0 00H000H00 0000 n 0mm

0 0u00HE 00 000 0H000m 0H0000H0 H0HH0HH0 H0000 H mm

muHHooumfi0m mmmMMNIMNm 0H0000H0 H0HH0HH0 000H0H00H n Hmm

0.0 H 00H 0.5 H 00H 0.N H H0 «N.0 H 0H «0.0 H 00H 0.0 H 00H «0.0 H mm 00
0.0 H HmH 0.0 H 00H m.N H Hm «0.N H mm «q.m H 00H N.5 H 00H *0.N H 00 00
0.5 H 00H 0.0 H 00H 0.H H 0N 00.0 H mm 0.H H 00 0.0 H 0HH «0.0 H 00 00
0.0 H 00H +0.0 H 00H 0.H H 0N 0H.q H «N 0.0 H 50 0.0 H 0HH «5.0 H 50 0H
0.0 H HMH +0.0 H 00H H.N H 0N «H.0 H «N N.0 H 00 0.0 H 0HH «0.0 H 00 0H
0.5 H 00H +0.5 H 00H H.N H 50 0.0 H 50 0.0 H 00 0.0 H 0HH +0.NH H 00 0
5.0 H 00H +5.0 H 00H H.N H 00 0.0 H 00 0.0 H 00 0.0 H 00H 0.0H H 00 N
0.5 H 50H 0.0 H 50H H.0 H 00 5.0 H 00 0.0 H 00 0.0H H 00H 0.0H H 0HH 0
0.5 H 50H 0.0 H 50H 0.0 H 00 5.0 H mm 0.0 H 00 0.0H H 00H 0.NH H 5HH 0|

0 H 0

H 0 H
H 0 mesm mmHsm mm mm mm maHH

 

.0.0 H

000 00 HH00HH0 00H000H00 H0HH00H0 000 000H A0000HB\01 0V 000H0H0HH

A0HD0HE\01 my 0H0H0000H0 .A0000HS\0000 01 0H0 00HH0H00 00HH000H00000
000000000H0 00HE000H0 00 00Hmd00H 00 000 H00H0H00H 000 H0000 000 0

0002 0 n 0 .0000
0 00HH0000H00H00 000
.A0000HE\0000 01 0H0

H 0000000 H0H0000>0H0H00

.0 0H00H

52

 

H0. v 0 H 00HH00 00000H0H00Hm n 0
0H0000H0 00H000H00 0000 0005 u 00

H0000 I 0H0000H0 H0HH0uH0 0000 u 000

 

 

 

 

 

H00H0H00H I 0H=wm0H0 H0HH0HH0 0008 u HMm
00.0H H 00H 0.0 H 0NH 00.0 H N0 00.N H 00 0.0 H 5HH 0N.0 H 00H 0
05.0H H HOH N.¢ H 0NH 00.5 H N0 00.N H 00 0.0 H 0NH 00.0H H 05H N
0.0 H 0HH N.q H 0HH 0.0 H 00H N.HH H 00H 0.0 H 0NH 0.N H HNH 0
0.0 H 0HH N.0 H 0HH 0.0 H 00H 0.HH H 00H H.0 H HNH 0.N H HNH 0t
.0HE\0000 01 0 .0HB\0000 0: 0H
0H0HHH0HH0 00HH0000H00Hoz 000000000H0 00Ha0umH0
00.5 H 05 0.0 H NHH 0N.0 H 00H 00.5 H 00 0.5 H 0NH 00.0H H 55H 0
00.HH H 05 0.0 H NHH 00.0 H 05H 00.0 H 05 0.0 H 0NH 00.0H H 00H N
0.5 H 50H 0.0 H 0HH 5.0 H 0NH 0.HH H 00H N.0 H 0NH 0.5 H 0NH 0
0.0 H 00H H.0 H 0HH 0.0 H 0NH 0.HH H 00H 0.0 H 0NH N.5 H HNH 0|
.0HE\01 0 .0HE\0000 0: 0H
0HOH0000H0 00HH0H00 00HH000H0000¢
00 000 H00 00 000 H00 maHH

 

 

 

 

53

 

.m.m H 0002 5 n 0 .000000 0>Huo0om0> 00 00H0000H
000 unocqu 0:0 mu00EHH0mx0 00H0>H000H 000H>0H0 ou 0HH00HH000H 00H000H0 mu00EHH0000 H0Hu000

.OH 0H00H

54

 

 

II
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00. v 0 H 00HH00 00000H0H00Hm u +
H0000 I 0u0H uH000 u 0m
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“5.H H 00 H0000 0qN.0 H 00.H H0000 H0000 I 0H0000H0 00H00 u 000H00
00 0000HE u< 000 H0000 H00H0H00H I 0H0000H0 00H00 u H00000
WMHN M WM u00HMMMMM WWWHW M ”WNW 000HMMMMM 0H0000H0 00H000H00 0000 n 0mm
0 0u=0HE H0 000 0H000m H0000 I 0H0000H0 H0HH0HH0 oHamumzw H mm
HHHooumfi0m mmmwmmlmwm u00H0H00H I 0H0000H0 H0HH0HH0 oHa0umkw u Hmm
0.NH H 5NH 5.0H H 0NH H.N H 0N 0.0 H 00 +0.0H H 0HH 0.0 H 0NH 0H.HH H 00H 00
0.0H H 5NH 0.0H H 0HH 0.H H N0 0.N H 50 «.0 H 00H 0.0 H 0NH 0q.NH H 00H 00
H.0H H 00H 0.0H H 5HH 0.N H 00 5.0 H 00 0.5 H HOH 0.0 H 0NH 00.HH H HHH 00
0.0H H 00H 0.0H H 0NH 0.0 H 0N N.0 H 50 0.0 H 00 0.0 H 0HH H0.0H H 50H 0H
H.0H H 00H 0.0H H 5NH 5.0 H H0 0.0 H 00 N.0 H 00 0.0 H 5HH 05.5 H 00H 0H
0.0H H 50H 0.0H H 0NH H.0 H N0 0.0 H 00 0.0 H 50 0.0 H 0HH HN.0 H 00H 0
0.0H H 00H 5.HH H 5HH N.N H N0 0.0 H 00 0.0 H 00H 5.0 H 0HH 00.0 H HOH N
0.0H H 00H N.0H H 5HH 0.0 H H0 0.0 H Nq 0.0 H 50 0.0 H 0HH 00.0 H HOH 0
0.NH H 0NH H.0H H 0HH 0.N H 00 0.0 H H0 0.0 H 50 0.0 H 0HH 05.0 H 00H 0|
00 H.H. 003:0 H035 mm 000 H00 200

 

 

 

 

Figure 4.

55

Effects of infusion of acetylcholine chloride (15 pg base/
minute) into the head perfusion circuit on perfusion
pressure, donor systemic pressure and recipient systemic
pressure.

---- 1"

plant. Dunno-n—A

.56

 

 

 

 

FIGURE 4
‘31)
E Donor
E
E
loride (15 ug base/
on perfusion O)
ecipient systemic S
m D
8 Perfusmn
i-I
9-:
”U
Q
2
m . .
Reelplent

 

 

 

 

 

 

 

 

 

 

 

 

 

 

57

m HHHDHVHH

.0H0000H0

0Hfimum%m 000H0H00H 000 0H0000H0 0Hamummm H0000 .0H0000H0
00H00wH00 0o HHDUHHU 00H000H00 0000 000 ou0H A0000HE
\0mmn w: mav 000000000H0 00H0000H0 m0 00H0000H mo mHommmm

.m 0stHm

FIGURE 5

 

58

*- " .10; 3551503031..
aaIIImuIIIInuIIuIIIIIIIIIIIIm

0010:5510 Ham
IIEEES ifiiifiir’réfisfiififi
00033003 @503

I:

Donor
Perfusion

(3H mu!) amssaJd

 

E
.2
.9
8
I:

P0018

 

 

 

Figure 6.

59

Effects of infusion of bradykinin (3 ug/minute) into
the head perfusion circuit on perfusion pressure,
donor systemic pressure and recipient systemic
pressure.

Blood Pressure ( mm Hg)

;/minute) into
1 pressure,
Iystemic

Blood _ Pressure ( mm Hg)

60

FIGURE 6

Donor

 

 

Perfusion

Recipient

 

 

 

.... ...I fl.-

 

Figure 7.

61

Effects of infusion of norepinephrine bitartrate (6 pg base/
minute) into the head perfusion circuit on perfusion
pressure, donor systemic pressure and recipient systemic
pressure.

Pressure ( mm Hg)

Blood

62

 

FIGURE 7
’\
i”
E Donor
5
Q)
:artrate (6 Mg base/ is
)n perfusion U) .
:ipient systemic E PerquIon
'U
8
_ O .
m Reelplent

 

 

 

    
 

Figure 8.

63

Effects of bolus injection of angiotensin II (10 pg) into
the head perfusion circuit on perfusion pressure, donor
systemic pressure and recipient systemic pressure.

Blood Pressure (mm Hm)

64

FIGURE 8

   

A
m“
E Donor
v
g
11 (10 pg) int°
ressure, donor % .
preSSUTe' e Perfusmn
0..
'8
D
N
m

Recipient

 

 

 

  

Figure 9.

65

Effects of bilateral cervical vagotomy of the recipient
dog on perfusion pressure, donor systemic pressure and
recipient systemic pressure.

7'

D‘oa and- ‘91-

.l?1,‘,‘rl

66

FIGURE 9

 

 

\
é”
Donor
E
the recipient V
pressure and
3:2
8 Perfus10n
E
9..
0 . .
0 ReapIc-nt
.9.
m

 

 

 

 

 

 

 

67

r! ‘5 '(hrlv

.w00 000H0H00H
00H mo hfiouom0> H0H000HHQ Hmumm 00m 0How0p 0Hnmm0H0 oHamumzm
H00H0H00H 00m 0H0000H0 0HE0um>m H0000 .0H0000H0 00HmSMH00 00

mo0 u00H0H00H 0:» 0H 00HmSH000 0H00H00 HmHmumaHn Ho 0000mmm

.00 muamHH

68

FIGURE 10

 

t

Q

.Q Q
H ‘63 -9
O 0%
5 ‘E a
Q Q. 0

(5H HHH) QJIISSQJJ poolg

 

 

 

Figure 11.

69

Effects of bilateral carotid occlusion in the recipient
dog on perfusion pressure, donor systemic pressure and
recipient systemic pressure before and after bilateral
debuffering of the recipient dogs carotid sinus—body
complexes.

PRESSURE (mm Hg)

BLOOD

in the reciiJient
ic pressure and
after bilateral
id sinus-body

PRESSURE (mm Hg)

BLOOD

70

FIGURE 1 1

Control
Bilateral
Carotid
Occlusion

 

Effects
of
Debuffering

Bilateral
Carotid
Occlusion
After
Debuffering

 

 

 

 

 

Figure 12.

71

Effects of five minutes of cerebral ischemia in the
recipient dog on perfusion pressure and recipient
systemic pressure.

BLOOD PRESSURE (mm Hg)

hemia in the
recipient

BLOOD PRESSURE (mm Hg)

72

FIGURE 12

 
 

Perfusion

 
 

1

off on

Recipient

 

off on

I—5———I
minutes

 

 

 

Figure 13.

73

Effects of bolus injection of angiotensin II (10 ug)
into the head perfusion circuit on perfusion pressure,
donor systemic pressure and recipient systemic pressure
following bilateral debuffering of the carotid sinus-
body complexes in the recipient dog.

 

.IEIKIEESESIEIEKIE (ltlrrllLIc-l

BLOOD

in 11 (10118)
usion pressure,
ystemic pressure
carotid sinus-

PRESSURE (mm Hg)

BLOOD

74

FIGURE 13

Donor

Perfusion

  
 

 

 

75

V—w m-mhwmyfim

.wo0 HO0HOHO0H

00H 0H m0x0HQEoo m0oau000Hm 0HO0Hmo 000 mo w0HH0wm0900
H0H000HHQ w0H30HHow 0H0000H0 0Ha0uwmm H00H0H00H 000 0H0000H0
0Ha0umzm H0000 .0stm0H0 00H000H00 00 uHsoHHu 00H000H0m

0000 0:0 000H wa\wa mv 0H0000000 we 00Hmsw0H Ho 0000Hmm

.qH mHsmHH

76

 

co 5E m0

 

0 22080

000355

 

.555

 

    

u
..0

. 0:00:81
TOON

505:5

Seen

3 HKDGE

HHHSSCEIHJ ([0018

(SH mu!)

 

 

 

 

Figure 15.

77

Effects of infusion of bradykinin (3 ug/minute) into
the head perfusion circuit on perfusion pressure, donor
systemic pressure and recipient systemic pressure
following bilateral debuffering of the carotid sinus—
body complexes in the recipient dog.

PRESSURE (mm Hg)

I31;()()I)

’minute) into
pressure, donor
: pressure
:arotid sinus-

PRESSURE (mm Hg)

BLOOD

Perfusion

Recipient

Perfusion

Recipient

78

FIGURE

15

 

 

 

 

 

Figure 16.

79

Effects of histamine diphosphate (15 pg base/minute),
acetylcholine chloride (15 ug base/minute) and nor-
epinephrine bitartrate (6 pg base/minute) into the head
perfusion circuit on perfusion pressure, donor systemic
pressure and recipient systemic pressure following bilateral
debuffering of the carotid sinus—body complexes in the
recipient dog.

; base/minute),
Ite) and nor-

:e) into the head

a, donor systemic

"a following bilateral
:omplexes in the

PRESSURE (mm Hg)

BLOOD

Recipient

Perfusion

Recipient

Perfusion

Recipient

Perfusion

80

FIGURE 16

ACETYLCHOL I NE

   

HISTAMINE

 

 

 

 

 

 

 

Figure 17.

81

Effects on recipient arterial pressure, donor arterial
pressure and head perfusion pressure of infusion of
endotoxin (5 mg/kg) into the head perfusion circuit
before (H) and after ( W) bilateral denerva—
tion of the recipient dog's carotid sinus—body complexes,
or intravenously into the recipient trunk before (

or after ( H) bilateral cervical vagotomy as com-
pared to control experiments ( [3-{3 ).

PRESSURE (mm Hg)

l3IJ()()I)

82
Figure 17

140? Donor Arterial Pressure

 

 

 

 

 

 

120' M
100- '
804
601
40‘
, donor arterial ‘3) 1801 Head Perfussion Pressure
E infusion of :
usion circuit E 160‘1
ilateral denerva- E
nus-body complexes, v 1401
unk before (
vagotomy as com— a 120—
m /
D 100‘
E
a 80—
9* 155. Recipient Arterial Pressure
130—
Q
E; 105_ :::k —_AE_——““-———i}—______.‘.‘fl
I4
” 80-
55
30'-T4I I 1”
- 0 2 5 1'0 1'5 3'0 4'5 ‘60

TIME IN MINUTES

 

 

of EI
the 1
tion
Thus,
exclu
perip

head,

norma
arter;
an aC(
Secon(
in ma:
barore
the re
in SYS
interr

tienal

 

CHAPTER VI

DISCUSSION

Spectrophotometric examination of blood following the injection
of Evans Blue dye into the head perfusion circuit or into the trunk of
the recipient indicates that this preparation provides complete separa-
tion of blood flow between the head and trunk of the recipient dog.

Thus, the endotoxin can be confined to the head of the recipient while
excluding it from the peripheral circulation. Any modifications in the
peripheral circulation following administration of endotoxin to the
head, must then be mediated through the central nervous system.

A number of criteria indicate that this technique results in
normally responsive experimental preparation. First, the mean systemic
arterial pressures obtained in both the donor and recipient dogs are in
an acceptable range for pentobarbital anesthetized dogs and are steady.
Secondly, interruption of carotid blood flow in the recipient dog results
in marked hypertensive responses indicating functional carotid sinus
baroreceptor reflex afferents and efferents. Bilateral denervation of
the recipient dog's carotid sinus—body complexes resulted in increases
in systemic pressure to levels approximating those obtained following
interruption of carotid blood flow. This further substantiates the func-

tional ability of the carotid sinus—body reflexes. Likewise, the

83

pressure rt
dog increa:
aortic arcl
integrity I;
increase it.
vagotomy.
also tested
bilateral d
Under these
an impressi
animal, the
exceeded 35
ischemia ha
interruptim
reflex resu;
0n the Othei
the Carotid
90 Seconds 5
Severe
Circuit in (
any, and to
ing this m
releaSed by
agents mimic
The De

 

84

pressure response to interruption of carotid blood flow in the recipient
dog increased after bilateral cervical vagotomy suggesting that the
aortic arch pressoreceptor afferents and efferents are functional. The
integrity of the aortic arch pressoreceptors is further evidenced by the
increase in recipient systemic pressure subsequent to bilateral cervical
vagotomy. Thirdly, the functional state of the sympathetic nerves was
also tested by eliciting the cerebral ischemic response following the
bilateral denervation of the recipient dog's carotid sinus-body complexes.
Under these circumstances, five minutes of cerebral ischemia resulted in
an impressive hypertensive response in the recipient trunk. In one
animal, the peak mean systemic arterial pressure as a result of ischemia
exceeded 350 mm Hg. The typical response pattern as a result of cerebral
rischemia had a different time course than the pressor response following
interruption of carotid blood flow. Initiation of the carotid-sinus
reflex resulted in an increase in systemic pressure within ten seconds.
0n the other hand, the cerebral ischemic reflex following denervation of
the carotid sinuses does not result in increases in pressure until 30 to
90 seconds after occlusion of the carotid arteries.

Several vasoactive agents were introduced into the head perfusion
circuit in order to study their effects on trunk arterial pressure, if
any, and to provide a basis for comparison with previous studies utiliz-
ing this technique. Additionally, the vasoactive agents studied are all
released by endotoxin and it is of interest to determine if any of these
agents mimic the effects of endotoxin.

The peripheral vasodilators, histamine, acetylcholine and brady-

kinin all elicit a hypertensive response in the recipient trunk

subsequent
pheral vas
in the rec
to the hea
perfusion
pressure.
F011
sinus-body
tonin and
blood pres
ePinephrin
Preparatio
not throug
are not in
reported t
recipient
ing the bi
complexes.
methaniSmS
epinephrin
drug Was 1
different
the Cthra
with the r
Page of th

POSsible e

85

subsequent to a decrease in perfusion pressure to the head. The peri-

pheral vasoconstrictor, norepinephrine elicited a hypotensive response

in the recipient trunk subsequent to an increase in perfusion pressure

to the head. Serotonin usually produced small but variable effects on

perfusion pressure but failed to consistently affect recipient systemic
pressure.

Following the bilateral denervation of the recipient dog's carotid
sinus-body complexes, the infusion of acetylcholine, histamine, sero—
tonin and norepinephrine had no significant effect on the recipient
blood pressure. This indicates that acetylcholine, histamine and nor-
epinephrine cause alterations in recipient systemic pressure in this
preparation solely by their ability to alter carotid sinus pressure and
not through any direct central cardiovascular effects. These results
are not in agreement with those of Taylor and Page (83). These authors
reported that norepinephrine produces a hypotensive response in the
recipient trunk while histamine elicits a hypertensive response follow—
ing the bilateral denervation of the recipient dog's carotid sinus-body
complexes. The reason for this disparity of results is unclear but two
mechanisms are possible. First, in the work by Taylor and Page, nor-
epinephrine was injected as a bolus of 10 ug whereas in this study the
drug was infused at a rate of 6 ug/minute. Thus it is possible that the
different concentration used in this study were insufficient to elicit
the central responses seen by Taylor and Page. The same may be true
with the results of histamine although no mention is made by Taylor and
Page of the concentration of histamine used in their study. A second

possible explanation for this divergence in reSults stems from a

difference
study, the
carotid art
the present
utilized in
bility exit
may also cc
mine and I
The
denervatio
In some ex
the recipi
in the rec
Pressure c
Obtained t
015 bradyk;
In
into the 1
elicited
abrupt in
with the
tiOns of
Preparati
retipient
ient deg'

hypertens

86

difference in the two experimental techniques. In the Taylor and Page
study, the head of the recipient dog was perfused only through one
carotid artery and drained through only one external jugular vein. In
the present study, both carotid arteries and both jugular veins were
utilized in the recipient head perfusion circuit. Therefore, the possi—
bility exists that differences in the circulatory dynamics in the head
may also contribute to the differences in results obtained with hista-
mine and. norepinephrine in these two preparations.

The responses to the infusion of bradykinin following bilateral
denervation of the recipients carotid sinus—body complexes were varied.
In some experiments bradykinin produced a striking pressor response in
the recipient trunk. In others it produced a mild depressor response
in the recipient trunk and still in others, it did not alter the systemic
pressure of the recipient. These results are in agreement with those
obtained by Buckley et al. (12) following the injection of 0.5—4 pg/kg
of bradykinin into the cerebral cross-circulation preparation.

In the present study, 10 pg bolus injections of angiotensin II
into the head perfusion circuit with intact carotid sinus—body nerves,
elicited either no change or a fall in trunk pressure subsequent to an
abrupt increase in carotid sinus pressure. These results do not agree
with the results obtained by Buckley et al. (7,72) following the injec—
tions of 0.5-4 pg/kg angiotensin II into the cerebral cross—circulation
preparation. These authors reported a hypertensive response in the
recipient trunk ranging from 11—50% in experiments in which the recip—
ient dog's buffer nerves were intact. The average duration of the

hypertensive response in the recipient trunk was 1.2 minutes.

The reason
ity exists
were more a
the increas
have elicit
obscured at
is a possil
trunk occul
escape to 1

The l
debufferin;
response i1
Buckley et
centrally 1
0n the (zen
rasponse 1
Centers (3
ranged bet
tenSiVe re
abOVe Cont

The
0r 5 Ing/ kg
0”le into
the reCipi
thirty and

perquiOn

87

The reason for these differences in results is uncertain. The possibil—
ity exists that, in the present study, the carotid sinus baroreceptors
were more sensitive to alterations in perfusion pressure. Therefore,
the increase in perfusion pressure produced by the angiotensin II could
have elicited a reflex vasodilation in the peripheral circulation which
obscured any central hypertensive actions of angiotensin II. Also, it
is a possibility that minute amounts of leakage from the head to the

trunk occurred in the Buckley preparation, allowing angiotensin II to

 

escape to the peripheral circulation and cause a hypertensive response.
The bolus injection of 10 ug of angiotensin II following bilateral
debuffering of the recipient dog uniformly resulted in a hypertensive
response in the recipient trunk. These findings concur with those of
Buckley et al. (7,12,72,73) that angiotensin II does indeed elicit a
centrally mediated hypertensive effect. Further study by these authors
on the central hypertensive effects of angiotensin suggest that this
response is mediated through stimulation of the central sympathetic
centers (32,74,78). The hypertensive response seen by Buckley et al.
ranged between 10 and 50% with a duration of thirty seconds. The hyper—
tensive response seen in the present studies ranged from 40 to 60%
above control and the duration of the response was four to five minutes.
The infusion of purified Escherichia coli endotoxin, either 1 mg/kg
or 5 mg/kg, into the arterial perfusion circuit to the head or intraven—
ously into the donor dog resulted in a marked hypotensive response in
the recipient trunk. Systemic pressure was markedly depressed by minute
thirty and continued to fall further with time. However, since the

perfusion pressure to the recipient head was also increasing, the

 

“mun

crease 1

 

1) naturl

supporte(
COntrol e
donor dog
circuit 0
0f the va
afferents
ing hypot
to the he
ized dogs
Th
those in
were bil
the resp
was made
complica
carotid
resulted

ten seco

pressure

would be

   

88

hypotensive response in the recipient dog could have resulted either
from a centrally mediated hypotensive action of endotoxin, or reflexly
through initiation of the carotid sinus baroreceptor reflex. The in—
crease in perfusion pressure appears to arise from three sources;

1) natural liberation of vasoconstrictor substances from the donor dog,
supported by the increase in perfusion pressure at minute 60 in the
control experiments, 2) release of vasoconstrictor substances from the
donor dog following administration of endotoxin into the head perfusion
circuit or intravenously into the donor dog, 3) reflex vasoconstriction
of the vasculature of the head as a result of decreased activity in the
afferents from the aortic arch baroreceptors as a result of the develop—
ing hypotension. This is supported by the fact that perfusion pressure
to the head only increased half as much and 30 minutes later in vagotim—
ized dogs as compared to those with intact vagi.

Therefore, the critical series of experiments in this study were
those in which the carotid sinus—body complexes of the recipient dog
were bilaterally denervated. This denervation was verified by noting
the response to bilateral carotid occlusion in the recipient. The test
was made while the vertebral arteries were still patent to avoid any
complicating vasopressor response due to cerebral ischemia. With the
carotid sinus—body nerves intact, occlusion of the carotid arteries
resulted in a marked vasopressor response in the recipient trunk within
ten seconds (Figure ll). When the buffer nerves were sectioned, the
pressure in the recipient trunk rose to a new steady state value as

would be expected following the denervation of the carotid sinus—body

 

 

elicit
the cal

alteratj

acetchh,
head per!
51- 0017: e]
carotid sj
sure was a
further th
carotid six
sinus baro
the recipi
centrally
liberated i
that marked
thirty minu
ventricles,
(76,77). 1
in the press

early precip

istration of

3Muse is du

 

 

89

complexes. Following the denervation, occlusion of the carotid arteries,
usually for sixty seconds but sometimes for up to five minutes, did not
elicit a pressor response in the recipient trunk. This indicated that
the carotid sinus«body complexes of the recipient dog had indeed been
successfully denervated. This was further verified by the fact that
alterations in perfusion pressure elicited by the administration of
acetylcholine, histamine, norepinephrine and angiotensin II into the
head perfusion circuit, did not result in predicted compensatory changes
in the recipient systemic arterial pressure. When 5 mg/kg purified

E. coli endotoxin was infused into the head perfusion circuit of this
carotid sinus—body denervated preparation, the recipient systemic pres—
sure was again markedly decreased by minute thirty and continued to fall
further thereafter. Since any increase in perfusion pressure in this
carotid sinus—body denervated preparation could not initiate a carotid
sinus baroreceptor peripheral vasodepressor response, the decrease in
the recipient mean systemic arterial pressure must arise as a result of
centrally mediated hypotensive actions of the endotoxin or substance(s)
liberated in the donor dog by the endotoxin. It is interesting to note
that marked centrally mediated endotoxin hypotension occurs within
thirty minutes whereas when endotoxin in injected into the cerebral
ventricles, no significant hypotension occurs for at least two hours
(76,77). The time course of the centrally mediated hypotensive actions
in the present study would suggest that they do not participate in the
early precipitous fall in blood pressure following the systemic admin—
istration of endotoxin. The literature is in agreement that this re—

sponse is due to a non—neurogenic hepato—splanchnic pooling of blood

 

°f the h

tesPOHSQE

 

a. tration o

‘ S“Pport t
need not:

a conditi(
s actions 01
impact in
tension fc
irreversil

the centr:

mately th:

 
  
    
  
  
   

pressure
the intra
decline '

phase of

through

tensive

 

 

90

(21,22,42,45,94). It is also of interest to note that when either

1 mg/kg or 5 mg/kg of endotoxin was infused intravenously into the trunk
of the recipient, excluding it from the central nervous system, the
responses seen were similar to those seen following intravenous adminis-
tration of endotoxin in intact animals (56,66,88,94). These results
support the conclusions of previous authors (89,90,92) that endotoxin
need not gain access to the central nervous system in order to produce

a condition of shock. However, the centrally mediated hypotensive
actions of E. coli endotoxin observed in this study may have an important
impact in the intact animal in regards to the maintenance of the hypo-
tension following intravenous endotoxin and/or the initiation of the
irreversible phase of endotoxin shock. It is interesting to note that
the central hypotensive actions of endotoxin are manifest at approxi—
mately the same time as the secondary decline in cardiac output, blood
pressure and total peripheral resistance in the intact animal following
the intravenous administration of endotoxin. It is this secondary
decline in hemodynamics that marks the beginning of the irreversible
phase of endotoxin shock. Hinshaw (35) has suggested that this secondary
decline may be due to a progressive fall in total peripheral resistance
and subsequent peripheral pooling of blood. He also questioned whether
or not this decline in total peripheral resistance may be mediated
through the central nervous system. Whether the centrally mediated hypo—
tensive actions of E. coli endotoxin found in this study are a result

of decreased sympathetic activity on blood vessels and/or heart, or are

the result of stimulation of a vasodilator system cannot be determined

from these data.

 

Wher
struck wit
tration of
levels, b]
tion, circ
central bl
resistance
and renal
combinatic
immense.
and prover
sults of 1
eluded in
shows that
hypotensix
C08 in ths

death of 1

 

91

When one surveys the literature on endotoxin shock, one is rapidly
struck with the complexities of this syndrome. The intravenous adminis~
tration of endotoxin leads to changes in acid—base balance, blood glucose
levels, blood viscosity, cellular defense mechanisms, temperature regula—
tion, circulating levels of vasodilator and vasoconstrictor substances,
central blood volume and venous capacity, precapillary and postcapillary
resistances, lysozyme levels in the blood, cardiac output, respiratory
and renal function and many other alterations. The number of possible
combinations of actions as a result of these alterations are surely
immense. Clearly, no one effect has been isolated from the others
and proven to be the primary determinant of irreversibility. The re-
sults of these experiments indicate that yet another factor must be in—
cluded in this list of deleterious effects of endotoxin. This study
shows that endotoxin is capable of eliciting a marked centrally mediated
hypotensive response and it is likely that this response is yet another
cog in the vicious cycle of endotoxin shock which leads to the eventual

death of the animal.

The
and vario
vascularl
head was
donor ani
trunk blo
there was
recipient
denervatj
and effez
functionj

Inf
arterial
hypertens
and injec
a hypOter
denerVatj
sion of E

ient trur

 

CHAPTER VII

SUMMARY AND CONCLUSIONS

The centrally mediated cardiovascular effects of E. coli endotoxin
and various vasoactive agents were studied utilizing a neurally intact,
vascularly isolated head—trunk preparation. The vascularly isolated
head was perfused at constant flow with arterial blood supplied by a
donor animal. Spectrophotometric examination of the donor and recipient
trunk blood following administration of Evans Blue dye indicated that
there was no circulatory leakage between the head and trunk of the.
recipient dog. The responses to various physiological maneuvers and
denervations indicated that the central nervous system and all afferents
and efferents involved in the control of the cardiovascular system were
functioning normally.

Infusion of acetylcholine, histamine and bradykinin into the
arterial perfusion circuit to the vascularly isolated head elicited a
hypertensive response in the recipient trunk. Infusion of norepinephrine
and injection of angiotensin II into the head perfusion circuit elicited
a hypotensive response in the recipient trunk. Following bilateral
denervation of the recipient dog's carotid sinus—body complexes, infu—
sion of acetylcholine, histamine and norepinephrine did not alter recip—

ient trunk pressure. This indicates these drugs elicited changes in

92

 

recipient
barorecep
mediated
debuffere
crease in
bradykini
mediated
the debuf
the recip
mediated
The
circuit t
marked by
toxin Was
ing bilat
Systemic
These fin
eliciting
0f Endoto
the Centr
The
mediated
preSSure

it may Co

 

93

recipient systemic pressure through stimulation of the carotid sinus—
baroreceptor compensatory reflexes and not through any direct centrally
mediated cardiovascular actions. Administration of bradykinin to the
debuffered preparation caused either no change, an increase or a de—
crease in recipient systemic pressure. These results indicate that
bradykinin is capable of eliciting varied, inconsistent centrally
mediated cardiovascular effects. The injection of angiotensin II into
the debuffered preparation uniformly produced a hypertensive response in
the recipient trunk, indicating it is capable of eliciting a centrally
mediated hypertensive response.

The infusion of endotoxin, either into the arterial perfusion
circuit to the head or intravenously into the donor dog, resulted in
marked hypotension within 30 minutes in the recipient trunk. When endo-
toxin was infused into the arterial perfusion circuit to the head follow-
ing bilateral denervation of the carotid sinus—body complexes, recipient
systemic pressure was again markedly depressed within thirty minutes.
These findings indicate that purified E. coli endotoxin is capable of
eliciting marked centrally mediated hypotensive responses. The infusion
of endotoxin into the trunk of the recipient, excluding the toxin from
the central nervous system, produced marked hypotension within 5 minutes.

The time course of these responses suggest that the centrally
mediated hypotension does not participate in the initial fall in blood
pressure following systemically administered endotoxin, but rather that

it may contribute significantly to the maintenance of the hypotension.

 

 

APPENDIX

 

 

 

Th
II into

sinus-b0

Recipiem
D0nor Art

Head Per 1

The
perquiOD
Acetchho

P5
gr
Pa

_d
Pp

Histamine
P31
P7
id

Pp

 

APPENDIX

DRUG INFUSION DATA

The data obtained following 10 ug bolus injections of angiotensin
II into the head perfusion circuit in which the recipient's carotid
sinus—body nerves were intact is as follows:

Means 1 Standard Errors

Control Peak Response
Recipient Arterial Pressure 127 i 3.4 108 i 4.4+
Donor Arterial Pressure 120 i 3.2 206 i 2.5*
Head Perfusion Pressure 120 i 3.1 210 i 2.4*

T = statistical significance paired T P < .05
* = statistical significance paired T P < .01
n = 9

Duration of response 4—6 minutes.

The data obtained following drug administrations into the head

perfusion circuit in the debuffered preparations is as follows:

Acetylcholine (n = 7) Control Peak Response

Par 177 i 5.3 175 i 6.4

Pad 126 t 4.4 125 a 3.8

P5 120 i 2.8 70 i 2.5*
Histamine (n = 7) Control Peak Response

Par 180 i 6.1 181 i 5.8

Pad 122 1 3.8 122 i 3.3

P5 125 i 4.2 63 i 2.0*

94

Norepine
Pa
P5
P5
Bradykin
P5
P5
P13
Angioten
Pa
P5
P13

It
Prelimin
Sible to
manner 0
0f the h
and cone
ficulty
head_

It

is very

95

Norepinephrine (n = 7) Control Peak Response
Par 187 i 3.9 188 i 4.0
Pad 120 i 4.1 120 i 2.3
Pp 120 i 3.2 163 i 5.1*
Bradykinin (n = 10) Control Peak Response
Par 165 i 4.1 165 i 3.7
Pa' 119 i 3.5 119 i 3.8
P13 128 e 2.2 78 i 2.1*
Angiotensin II (n - 7) Control Peak Response
P5 163 i 3.6 207 i 3.1*
Paid 125 i 3.3 184 i 2.2*
P5 123 i 3.0 221 f 3.1*

ALL DATA ARE MEANS 1 STANDARD ERRORS

Pa = systemic arterial pressure — recipient
Pad = systemic arterial pressure — donor
Pp = head perfusion pressure
* = statistical significance paired T P < .01
PROCEDURAL OBSERVATIONS
It is interesting to note that when venous leakage did occur in
preliminary experiments, it was usually very large. It was in fact pos—

sible to hemorrhage the donor dog into the recipient trunk within a

manner of minutes.
of the head,

and concomitant decreases in donor arterial pressure.

This was evidenced upon beginning of the perfusion
by very noticeable increases in recipient arterial pressure

There was no dif—

ficulty in any experiment with arterial leakage from the trunk to the

head.

It is

is very important.

also important to note that the size of the recipient dog

With the wire and sponge device used to occlude the

intraspina
to assure
the recipi

device wi]

96

intraspinal venous sinuses, recipient weight must be kept under 15 kg
to assure occlusion of the sinuses. Indeed, the ideal weight range for
the recipient dogs is 7-10 kg. With larger dogs, the wire and sponge

device will not properly occlude the intraspinal venous sinuses.

 

 

BIBLIOGRAPHY

  
 

 

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