3&5 WW“WWW"WWWWHHWWIHH
THESII
IBIRAR IES
NIH II
8923
This is to certify that the
thesis entitled
Projections from the Pontomesencephalic Tegmentum
to the Cranial Nerve Nuclei in the Rat
presented by
Sheila Keane
has been accepted towards fulï¬llment
of the requirements for
Masteï¬s—degree in Anatomy
WWW: 0†Wm
Major piéfessér
Irena Grofova, PhD
Date 5/18/90
0-7639 MS U is an Affirmative Action/Equal Opportunity Institution
‘ LXBMRY
Michigan State
University
L _,l
*—
PLACE IN RETURN BOX to remove this checkout from your record.
TO AVOID FINES return on or before date due.
DATE DUE DATE DUE DATE DUE
—7
MSU Is An Affirmative Action/Equal Opportunity Institution
c:\c|rc\d¢odtnpm3-p.'
PROJECTIONS FROM THE PONTOMESENCEPHALIC TEGMENTUM TO THE
CRANIAL NERVE NUCLEI IN THE RAT
BY
Sheila Keane
A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE
Department of Anatomy
1990
we 51:7
ABSTRACT
PROJECTIONS FROM THE PONTOMESENCEPHALIC TEGMENTUM TO THE
CRANIAL NERVE NUCLEI IN THE RAT
BY
Sheila Keane
The purpose of this study was to determine whether the
nucleus tegmenti pedunculopontinus (PPN) links the output
nuclei of the basal ganglia to the cranial motor nuclei.
Unilateral injections of an anterograde tracer Phaseolus
vulgaris-leucoagglutinin (PHA-L) were placed in the PPN and
the distribution of labeled fibers in the pontomedullary
cranial nerve nuclei was charted. Results of these
experiments demonstrated distinct crossed and uncrossed
projections from the PPN to the facial nucleus, but only
modest bilateral projections to the hypoglossal, ambiguus,
dorsal motor vagus, and solitary nuclei. Since the PPN-facial
projection exhibited two different distribution patterns in
the facial nucleus, additional experiments utilizing
retrograde transport of lectin-conjugated horseradish
peroxidase (HRP-WGA) from the lateral or medial portions of
the facial nucleus were carried out. ‘Ehese latter experiments
did not substantiate the existence of PPN-facial projection
and demonstrated that facial afferents actually originated
from several structures surrounding the PPN.
ACKNOWLEDGMENTS
I would like to express my sincere appreciation and
thanks to my advisor, Dr. Irena Grofova, whose support,
advice, encouragement, and occasional sharp prodding greatly
facilitated the completion of this research project. I also
appreciate the assistance of my graduate committee members:
Drs. Jack Johnson, Gerry Gebber, Duke Tanaka, and Charlie
Tweedle.
I also wish to express my deep appreciation of and
gratitude for the technical advise and assistance of our
laboratory technician, Ms. Kathy Bruce. Thanks also go to my
fellow graduate students for their support and encouragement.
iii
TABLE OF CONTENTS
List of Tables ............ . ........................... v
List of Figures ........ . ..... . ........................ vi
Abbreviations ............. ... ......................... vii
Introduction .......................................... 1
Material and Methods .................................. 4
Results ................................... ............ 8
PHA-L Experiments .............. .................... 10
Projections to the Brainstem ..... ................ 13
Projections to the Facial Nucleus ................ 17
Projections to Medullary Cranial Nerve Nuclei .... 17
HRP Experiments ....... . .......................... 22
Lateral Facial Injections ................... 27
Medial Facial Injections .................... 38
Summary of Results ..... .......................... 47
Discussion ....... ...... .... ........................... 49
PPN Projections to the Facial Nucleus ............ 49
PPN Projections to Medullary Cranial Nerve Nuclei 51
Mesopontine Efferents to the Facial Nucleus ...... 53
Descending PPN Efferents . ........................ 57
Functional Considerations ........................ 59
Bibliography ...................... ....... ...... ....... 63
iv
LIST OF TABLES
Table 1: Retrogradely Labeled Cells Following Lateral
Facial HRP-WGA Injections ............ ......... 33
Table 2: Retrogradely Labeled Cells Following Medial
Facial HRP-WGA Injections ..... ..... .. ......... 39
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
l:
2:
3:
10:
11:
LIST OF FIGURES
PHA-L Injection Sites . .......................
Bright-field Photomicrographs of PHA-L
Deposits in the PPN .................. ........
Distribution of Labeled Fibers in the
Facial Nucleus in Case PHA-L #28 .. ...... .....
Bright-field Photomicrographs Illustrating
the Two Distribution Patterns of PHA-L Labeled
Fibers in the Facial Nucleus .................
Distribution of Labeled Fibers in the
Facial Nucleus in Case PHA-L #25 .............
Photomicrographs Showing PHA-L Labeled Fibers
in the Medullary Cranial Nerve Nuclei ........
Distribution of Labeled Fibers in the
Medullary Cranial Nerve Nuclei ........ .......
Lateral Facial HRP-WGA Injection Sites .......
Photomicrographs Showing Center of Injection
Sites in Cases CN7 #17 and CN7 #13 ...........
Distribution of HRP Labeled Cells in
case CN7 #17 ooooooooooooooooooooooo oooooo oo
Photomicrographs of HRP Labeled Cells
in the Ipsilateral Parabrachial Region
in Case CN7 #17 ................. ............
Medial Facial HRP-WGA Injection Sites .......
Photomicrographs of HRP Labeled Cells
in the Contralateral Retrorubral Region
incaseCN7 #13 00000000009000.0000. oooooooooo
Distribution of HRP Labeled Cells in
case CN7 #13 ......OOOOOOOOOOOOOOOOOO .......
Circuit Diagram - Orienting Reflex ..........
vi
12
16
19
21
24
26
29
31
35
37
41
43
46
6O
ABBREVIATIONS
Am
AP
CG
Cnf
CP
g7
GiA
IC
icp
IO
IRt
KF
LC
11
LPB
LPGi
LRt
LSO
LVe
Me5
mes
ml
M05
MPB
MVe
PCRt
PN
PPNc
PPNd
Pr5
PY
Rmes
RPC
RPO
RRF
rs
SC
scp
SNc
SNr
SO
Sol
ambiguus nucleus
area postrema
central gray
cuneiform nucleus
cerebral peduncle
genu facial nerve
gigantocellular reticular nucleus, pars alpha
inferior colliculus
inferior cerebellar peduncle
inferior olive
intermediate reticular nucleus
Kolliker-Fuse nucleus
locus coeruleus
lateral lemniscus
lateral parabrachial nucleus
lateral paragigantocellular reticular nucleus
lateral reticular nucleus
lateral superior olive
lateral vestibular nucleus
mesencephalic trigeminal nucleus
mesencephalic trigeminal tract
medial lemniscus
motor trigeminal nucleus
medial parabrachial nucleus
medial vestibular nucleus
parvicellular reticular nucleus
pontine nucleus
pedunculopontine tegmental nucleus, pars compactus
pedunculopontine tegmental nucleus, pars dissipatus
principal sensory trigeminal nucleus
pyramidal tract
mesencephalic reticular nucleus
red nucleus
reticularis pontis caudalis nucleus
reticularis pontis oralis nucleus
retrorubral nucleus
retrorubral field
rubrospinal tract
superior colliculus
superior cerebellar peduncle
substantia nigra, pars compacta
substantia nigra, pars reticulata
superior olive
nucleus of the solitary tract
vii
ABBREVIATIONS (continued)
sol
sp5
Sp50
SPTg
SpVe
Tz
tz
VLL
vsc
xscp
3
4
6
5n
7
7n
10
12
solitary tract
spinal trigeminal tract
spinal trigeminal nucleus, pars oralis
subpeduncular tegmental nucleus
spinal vestibular nucleus
nucleus of the trapezoid body
trapezoid body
ventral nucleus of the lateral lemniscus
ventral spinocerebellar tract
decussation of superior cerebellar peduncle
oculomotor nucleus
trochlear nucleus
abducens nucleus
trigeminal nerve
facial nucleus
facial nerve
dorsal motor nucleus of vagus
hypoglossal nucleus
viii
INTRODUCTION
The nucleus tegmenti pedunculopontinus (PPN) was first
described in the human caudal mesencephalic tegmentum as being
"bounded medially by the superior cerebellar peduncle (scp),
laterally by fibers of the medial lemniscus, and dorsally by
the nucleus cuneiformis and subcuneiformis (Olszewski & Baxter
'54). These authors further identified two subdivisions of
the nucleus on the basis of cellular density. The smaller
pars compacta "occupies the dorsolateral portion of the caudal
half of the nucleus" and the "remainder of the nucleus
constitutes the pars dissipata". In subprimate species, the
nucleus is less clearly defined. Delineation of the PPN and
its subdivisions has been variously made on the basis of
cytoarchitectural features (Spann & Grofova '89),
cytochemistry (Rye et.al '88, Woolf & Butcher '86), and basal
ganglia input (Moon-Edley & Graybiel '83, Nauta & Mehler '66).
The functions and connections of the PPN have not been fully
established.
The PPN has widespread connections with the basal
ganglia, thalamus, and limbic structures and has been
implicated in a wide variety of functions including motor
control, sleep-wake cycles, respiration, locomotion, chewing,
and other rhythmic behaviors (Garcia-R111 & Skinner '88) and
sensory modulation (Hylden et.al. '85, Katayama et.al. '84,
Basbaum & Fields '80, Carstens et.a1. '80).
2
The role of the PPN in the control of movement is well
supported by both anatomical and physiological data.
Convincing evidence exists that the PPN receives substantial
input from.several nuclei of the basal ganglia (Grofova et.al.
in press, Spann & Grofova '89, Jackson & Crossman '83, Gerfen
et.al. '82, Beckstead et.al. '79, Granata & Kitai '89, Carter
& Fibiger '78, Nakamura et.al. '89, Noda & Oka '86, Garcia-
Rill et.al. '83, Moon-Edley & Graybiel '83, Larsen & McBride
'79, Nauta & Cole '78, Parent & DeBellefeuille '82, Beckstead
& Frankfurter '82, Kim et.al. '76) and ascending efferents of
the PPN return these basal ganglia projections (Woolf &
Butcher '86, Jackson.&iCrossman '83, Saper & Loewy '82, Gerfen
et.al. '82, VanDerKooy & Carter '81, Garcia-Rill et.al. '83,
Moon-Edley & Graybiel '83, Gonya—Magee & Anderson '83, DeVito
& Anderson '82). In addition, physiological experiments have
identified a "midbrain locomotor region" in the decorticate
cat (Mori et.al. '80) and rat (Garcia-Rill '87) which is
located in the pedunculopontine region and includes the PPN
(Garcia-Rill '86). Furthermore, lesions of the PPN in the rat
have been associated with impaired motor function (Kilpatrick
& Starr '81), and clinical studies have shown an association
between PPN cell loss in humans and.movement.disorders related
to progressive supranuclear palsy (Zweig et.al. '85, '87) and
Parkinson's disease (Zweig, et.al. '89, Jellinger '88).
The pathways by which the PPN affects motor behavior are
currently under investigation. Descending PPN efferents
3
include projections to the ventromedial pontomedullary
reticular formation (Grofova et.al. in press, Nakamura et.al
'89, Mitani et.al. '88, Rye et.al. '88, Moon-Edley & Graybiel
'83, Jackson & Crossman '83). This reticular region contains
neurons projecting to the ventral horn and cranial motor
nuclei (Vertes et.al. '86, Jones & Yang '85, Zemlan et.al.
'84, Travers & Norgren '83, Holstege & Kuypers '82, Martin
et.al. '81, Peterson '80). In addition, sparse projections
from PPN to the spinal cord have been reported in the rat
(Spann & Grofova '89, Rye et.al. '88, Goldsmith & VanDerKooy
'88). Considering its many connections with the nuclei of the
basal ganglia, the PPN is well situated to function as a relay
nucleus for descending basal ganglia influence on lower motor
structures.
While PPN efferents to the reticular formation and
spinal cord have been documented by several authors,
investigations of PPN projections to the cranial motor nuclei
are lacking. The purpose of the present study is to determine
the projections from PPN to the pontomedullary cranial motor
nuclei.
MATERIAL AND METHODS
A total of 15 male Sprague-Dawley albino rats weighing
300-350 g were utilized for this study. Eight animals
received unilateral injections of Phaseolus vulgaris-
leucoagglutinin (PHA-L) in ‘the nucleus tegmenti
pedunculopontinus (PPN), while seven received unilateral
injections of wheat-germ-agglutinin conjugated horseradish
peroxidase (HRP-WGA) in the facial nucleus. Both surgeries
and perfusion were performed under deep anesthesia (sodium
pentobarbital, 50-100 ‘mg/kg, i.p.), and, atropine sulfate
solution (0.7 mg/kg) was administered i.m. prior to the
surgery in order to prevent brain edema. Injections of both
tracers were made iontophoretically using glass micropipettes
with an inside tip diameter of 15-35 pm, and a positive 75
pulsed 5 MA current. The stereotaxic coordinates were derived
from the atlas of Paxinos and Watson ('86).
PHA-L Experiments
Micropipettes filled with a 2.5% solution of PHA-L
(Vector Labs) in 10mM Tris buffer (pH 8.0) were inserted
vertically through the ipsilateral hemisphere and tectum of
the midbrain. Single iontophoretic depositions of PHA-L were
made for 30-40 minutes. Following a survival period of 10 to
14 days, deeply anesthetized animals were perfused through the
heart with a sodium phosphate buffered saline solution
5
followed by a fixative consisting of 4% paraformaldehyde and
0.2% glutaraldehyde in 0.15M sodium phosphate buffer. The
brains were immediately removed and stored overnight at 4°C
in fixative. The following day, the brains were divided into
a caudal block containing the caudal pons and medulla, and a
left and right rostral block including the forebrain,
midbrain, and rostral pons. Serial sectioning was done at 30
um on a vibratome in the coronal (caudal block) or sagittal
(rostral block) plane. Sections were collected in Tris
buffered saline and processed for PHA-L immunohistochemistry
using a biotin-avidin (Vector Labs) protocol by Gerfen &
Sawchenko ('84). Immuno-reacted sections were mounted onto
gelatin-chrom-alum-coated slides, air-dried, dehydrated, and
lightly stained with cresyl violet. The sections were
examined on a Leitz Orthoplan microscope, using bright-field
illumination for the localization of PHA-L injections and the
presence of labeled nerve fibers and terminal fields. The
localization of the PHA-L deposit in the PPN was charted on
a standard map of sagittal sections through the
pontomesencephalic region containing the lateral and medial
halves of the PPN} The distribution of the labeled fibers and
plexuses in the cranial nerve nuclei was documented on
projection drawings and photomicrographs of selected sections.
HRP-WGA Experiments
Single unilateral injections were made in the medial or
lateral portions of the facial nucleus using a 2% HRP-WGA
solution in Tris buffer delivered iontophoretically for 15 to
25 minutes according to Graybiel & Devor ('74). In order to
minimize leakage of HRP-WGA along the needle track, the
micropipette remained in situ for’ 10 minutes after the
injection, and reversed. polarity' was applied. during its
withdrawal.
After a 24—48 hour survival period, deeply anesthetized
animals were perfused intracardially with a fixative
consisting of 1% paraformaldehyde and 1.25% glutaraldehyde in
0.15M sodium phosphate buffer. The brains were blocked into
right and left halves, and serial sections were cut sagittally
at 30-50 pm on a freezing microtome or vibratome. HRP-WGA
histochemistry using the chromogen tetramethyl benzidine (TMB)
was performed according to Mesulam ('82) . Some of the
sections were additionally stabilized with ammonium.molybdate
(Olucha et.al. '85). Reacted sections were :mounted on
gelatin-chrom-alum—coated slides and lightly counterstained
with neutral red.
Sections were analyzed in bright-field illumination for
the presence of retrogradely labeled cells in the PPN and
surrounding regions. The distribution of labeled cells was
documented on projection drawings in representative cases
using major'blood vessels and fiber tracts as landmarks. Cell
7
counts for all retrogradely labeled mesopontine nuclei were
taken from alternating sections, and the numbers of labeled
cells contained in a specific nucleus was pooled from all
inspected sections.
The borders of the PPN and its subnuclei were identified
according to previously established criteria (Spann & Grofova
'89). For clarity, the delineation of all other relevant
structures was taken fromtthe atlas of Paxinos & Watson ('86).
RESULTS
Before describing the experimental results, the normal
morphology of the pedunculopontine region will be considered
briefly. The PPN represents a portion of a continuous cell
column surrounding the ascending limb of the superior
cerebellar peduncle (scp) at the pontomesencephalic junction.
It consists of two subdivisions: 1) the pars compacta (PPNc)
composed primarily of larger cholinergic neurons; and 2) the
pars dissipata (PPNd) containing a considerable portion of
smaller non-cholinergic cells. While the boundaries of the
PPN and its subdivisions are well-defined in primates, the
outlines of the PPN in carnivores and rodents are less clear.
Consequently, there is little consistency in the literature
regarding the delineation of this nucleus or its subdivisions
in the rat brain. In the present report, we adhere to the
definition of PPN based on cytoarchitectural features
described in a previous study (Spann & Grofova '89).
The rat PPN is located medial to the nuclei of the
lateral lemniscus and lateral to the decussation of the scp.
It is caudally contiguous with the lateral and medial
parabrachial nuclei (LPB and MPB) and is rostrally adjacent
to the retrorubral field (RRF) and retrorubral nucleus (RR)
as defined by Paxinos & Watson (1986). The PPN borders
ventrally on the nucleus reticularis pontis oralis (RPo), and
dorsally on the cuneiform (Cnf) and mesencephalic reticular
SC ' SC
PHA-L # 24
Rmes ' LPB 774?? PHA-L # 25
/( K R
' W; .. __ mes
/’< a; PHA'L # 27
@319" \
u m . / \\\ \\\-\‘ PHA-L # 28 §\
SNR \ / / \D \\
u (33$ i"? l/ PHA-L # 31 SNC
1mm \\
I>
’2
?@
T
l
9
/
;{//
Figure 1: PHA-L Injection Sites
Schematic representation of PHA-L injection sites
involving the lateral (A) and medial (B) halves of the PPN in
cases in which labeled fibers could be traced to the facial
nucleus and to the medullary cranial nerve nuclei
10
(Rmes) nuclei. While both divisions of PPN can be
distinguished in the rat, the PPNd comprises the bulk of the
nucleus. The PPNd is particularly prominent medially and
appears to receive a substantial input from the substantia
nigra pars reticulata (Spann & Grofova '88).
PHA-L Experiments
PHA-L injections were directed toward the PPN region
receiving afferents from the substantia nigra (i.e. the medial
two thirds of the PPNd). Out of eight cases, five showed
excellent anterograde labeling as well as precise localization
of the injection in the PPNd. These five cases represent the
core material for the present report. The remaining three
cases yielded less intense labeling and provided.complementary
data.
While centered in the medial portions of PPNd, all PHA-
L injections involved the entire mediolateral extent of the
PPN (Fig. 1). Two zones of different labeling intensity were
observed at the injection sites; a central zone in which the
DAB reaction product obscured the cytoarchitecture, and a
peripheral zone in which single neurons exhibiting Golgi-like
labeling could be discerned. In all animals, a variable
number of labeled neurons were observed in the surrounding
nuclei. However, fiber tracts passing through the injection
site were always free of label (Fig.2). The absence of
labeling was particularly striking with regard to the scp
11
Figure 2: Bright-field Photomicrographs of PHA-L Deposits
in the PPN.
A-C: Illustrate the extent of PHA-L injection in case PHA-L
#25. The injection extended somewhat beyond the
lateralmost border of PPN (C) and the tracer was taken
up by a few cells (arrowheads) in the RR. More medially,
single labeled cells can be seen in the RRF and in the
rostral MPB (arrowheads in B). Unstained fibers of the
scp traverse the medial (A) and middle (B) regions of the
PPN (arrows).
D: The center of PHA—L injection in case PHA-L #28. A few
Golgi-like labeled cells are present in the MPB
(arrowheads).
Scale bar: 0.5mm
rips -
I V ~ .\ I.
an; . ..
Figure 2
13
which was inevitably included in the central zone of all PHA-
L injections.
In case PHA-L #25, there was a dense deposit of PHA-L
throughout the entire extent of the PPN. Some cells in the
Cnf were also labeled along the course of the needle track.
In.addition, a feW'PHArI.labeled cells were observed rostrally
in the RR and RRF, ventrally in the RFC, caudally in the MPB,
and laterally in the nuclei of the lateral lemniscus (Fig. 2).
The inclusion of rostrally adjacent structures in the
peripheral zone of PHA-I.uptake'was also observed in case PHA-
L #31, where the rostroventral half of PPN was labeled in
addition to individual neurons in the surrounding'RR, RRF, and
RPo. In cases PHA-L #28, PHA-L #27, and PHA-L #24, injections
were also centered in PPN but extended somewhat caudally to
include neighboring regions of the MPB and LPB. The PHA-L
injection in case PHA-L #28 was the most laterally placed of
these, involving the caudoventral PPN and labeling several
cells caudal to PPN in the MPB and ventrally in the RFC (Fig.
2).
Projections to the Brainstem
The bulk of PPN descending projections were distributed
within the reticular nuclei of the brainstem. Labeled fibers
were seen descending through the pontine reticular nuclei to
the ventromedial portions of the nucleus gigantocellularis
(GiA and GiV). Although many fibers appeared to cross the
l4
midline in the caudal pons and rostral medulla, terminal
arborizations were somewhat more numerous ipsilaterally. In
the pons, numerous varicose branches of the labeled fibers
were seen to terminate around large reticular neurons,
especially in the reticularis pontis caudalis (RPc).
Projections to the medulla and spinal cord were relatively
sparseu The course and.distribution of these projections have
been described and illustrated elsewhere (Grofova et.al. in
press).
In addition to the fibers distributing to the reticular
formation, PHA-L labeled fibers were also seen in several
cranial nerve nuclei in the pons and medulla. No labeled
fibers were found in the motor trigeminal (M05) nucleus.
However, two distinct distribution patterns were observed in
the facial nucleus. One pattern, present in all cases,
consisted. of diffuse labeling in ‘the ipsilateral facial
nucleus, while two cases (PHA-L #25 and PHA-L #31)
additionally demonstrated a dense contralateral projection to
the rostromedial two thirds of the facial nucleus.
Projections to the cranial nerve nuclei of the lower brainstem
were relatively sparse and were bilaterally distributed.
15
Figure 3: Distribution of Labeled Fibers in the Facial Nucleus
in Case PHA-L #28
Projection drawings of coronal sections through three
pontomedullary levels showing the distribution of labeled
fibers in the facial nucleus and ventral reticular nuclei in
experiment PHA-L #28. labeled varicose fibers are present
throughout the ipsilateral facial nucleus with greater
concentration caudally.
- ~-_ :I’Yier _'_~_. ' ' T ’
l6
' PHA—L #28
Rostral
Middle
Caudal
Contralateral
nnm
Ipsilateral
Figure 3
17
Projections to the Facial Nucleus
Results presented from cases PHA-L #28 and PHA-L #25 are
representative of the two patterns of distribution found in
the facial nucleus. In case PHA-L #28, labeled varicose
fibers were dispersed diffusely throughout the ipsilateral
facial nucleus with somewhat greater concentration in its
lateral half (Fig; 3). Thick.labeled fibers typically divided
into smaller branches exhibiting multiple terminal and
preterminal varicosities both in the neuropil and near the
somata of lateral facial motoneurons (Fig. 4 A & B).
In case PHA-L #25, in addition to the diffuse
ipsilateral facial projection which was present in all cases,
a dense plexus of anterogradely labeled fibers was observed
in the rostromedial two thirds of the contralateral facial
nucleus (Fig. 5). Numerous varicose arborizations formed a
dense terminal plexus surrounding the medial groups of facial
motoneurons (Fig. 4 C & D). This contralateral projection to
the medial facial nucleus was also seen in case PHA-L #31, but
was not present in other cases.
Projections to Medullary Cranial Nerve Nuclei
All cases demonstrated a sparse bilateral distribution
to the solitary (Sol), dorsal motor vagus (10), and
hypoglossal (12) nuclei. In addition, a few thin varicose
fibers in the proximity of the large motoneurons of the
nucleus
18
Figure 4: Bright-field Photomicrographs Illustrating the Two
Distribution Patterns of PHA-L Labeled Fibers in the Facial
Nucleus.
A&B:
C&D:
Diffuse ipsilateral projection to the lateral half of the
facial nucleus in case PHA-L #28. Figure A illustrates
a modest number of labeled fibers (arrows) within the
dorsolateral group of facial.motor neurons. 'Fhese fibers
are shown at higher magnification in Figure B. Arrows
indicate a thick fiber of an even diameter dividing in
several thin branches exhibiting multiple varicosities.
Contralateral projection to the medial groups of facial
motoneurons in case PHA-L #25. A dense terminal plexus
of labeled fibers within the ventromedial group of facial
motoneurons and LPGi is shown in Figure CL Figure D
represents a higher magnification of the region outlined
by a rectangle in Figure C, and illustrates numerous
preterminal and terminal varicosities surrounding the
cell bodies of the medial facial motoneurons (arrowheads)
as well as distributing in the neuropil (arrow).
Scale bar: 0.1mm
..., 1 ..Im ..
3&5 ...wvmry .ï¬ 1".
W.“ 0‘!
9.3.9
a
..I
20
Figure 5: Distribution.of Labeled Fibers in the Facial Nucleus
in Case PHA-L #25
Projection drawings of coronal sections through three
pontomedullary levels illustrating a dense plexus of labeled
varicose fibers in the rostral two thirds of the medial
portion of the contralateral facial nucleus in experiment PHA-
L #25.
21
PHA—L #25
Ipsilateral Contralateral
Figure 5
22
nucleus ambiguus (Am) were occasionally seen bilaterally (Fig.
6A).
The distribution of PHA-L labeled fibers to the caudal
medullary cranial nerve nuclei are illustrated in Figure 7.
Varicose fibers descended bilaterally in the hypoglossal
nuclei near midline, subsequently turning and passing to the
reticular formation ventrolateral to 12. Similarly, thin
varicose fibers were seen coursing from midline along the
borders of Sol, branching and terminating in the lateral
portions of Sol and 10. While present bilaterally, varicose
arborizations were somewhat more numerous ipsilaterally in the
lateral regions of Sol and 10, and in the reticular formation
ventral to this region (Fig. 6).
HRP EXPERIMENTS
Results of PHA-L experiments suggested a topographical
organization of PPN projections to the facial nucleus, with
rostral portions of PPN projecting to the contralateral groups
of medial facial neurons, and caudal portions of PPN
projecting ipsilaterally primarily to the lateral half of the
facial nucleus. To verify this hypothesis, experiments
utilizing the retrograde transport of HRP-WGA from medial
(N=4) or lateral (N=3) portions of the facial nucleus were
carried out.
23
Figure 6: Photomicrographs Showing PHA-L Labeled Fibers in
the Medullary Cranial Nerve Nuclei.
A: Arrows indicate labeled fibers in the ipsilateral Am in
case PHA-L #24.
B: Labeled fibers (arrows) in the ipsilateral 12 in case
PHA-L #25.
C&D: A discrete plexus of fine varicose fibers in the lateral
portion of the 801 ipsilateral to the PHA-L injection in
case PHA-L #25.
Scale bar: 0.1mm
____1
.--?!A. "r_‘.' .’_ 11..
Figure 6
25
Figure 7: Distribution of Labeled Fibers in the Medullary
Cranial Nerve Nuclei
Projection drawings of coronal sections through the
dorsal portion of the lower medulla showing a relatively
modest number of varicose fibers in the 12, 10, and Sol in
experiment PHA-L #25.
26
PHA—L #25
Rostral
Ipsilateral < T > Contralateral
Caudal
$4
.5.
P.
... __ _\_ _
Figure 7
27
Lateral Facial Injections
The HRP-WGA injection sites involving the lateral
portions of the facial nucleus are shown in Figure 8. Dense
deposits of HRP-WGA.were observed in the lateral third.to half
of the facial nucleus in all three lateral injections.
Despite all precautionary measures, HRP-WGA reaction product
was also consistently present along the needle track and in
portions of surrounding structures.
In case CN7 #17, the dense deposit of HRP-WGA was nearly
completely confined to the lateral two thirds of the facial
nucleus in its middle antero-posterior extent. A "halo" of
diffused reaction product extended ventrally into the
trapezoid (tz) and rubrospinal (rs) fiber tracts, and into the
reticular formation caudolateral to the facial nucleus (Fig.
9A).
No retrogradely labeled cells were observed in the PPN.
Labeled neurons were identified primarily in the ipsilateral
principal trigeminal (Pr5), medial parabrachial (MPB), and
Kolliker-Fuse (KF) nuclei (Fig. 11». Retrogradely labeled
cells of the MPB were concentrated rostrally, near the caudal
border of the PPN (Fig. 11 C & D). A substantial number of
labeled cells in the ipsilateral Pr5 and KF were also present
at levels lateral to the PPN (Fig. 11 A & B). Fewer neurons
were labeled in the ipsilateral lateral parabrachial and
reticularis pontis oralis nuclei. Several labeled neurons
were observed in the contralateral red nucleus (RN). In
28
Figure 8: Lateral Facial HRP-WGA Injection Sites
Projection drawings of sagittal sections through the
center of HRP-WGA injections involving the lateral portion of
the facial nucleus in three cases described in the text. The
position of dense reaction product around the pipette is
indicated by cross-hatching. Hatching indicates a surrounding
area of lighter diffusion which may be somewhat overestimated
because of use of the sensitive chromogen, TMB.
29
\\ mos .
‘0‘. o. ‘0... 0‘0
\ m °.o\::.;:;:;:o;;:;.,.
7 .0 $55.30.. 0
/ / rs Afï¬wo. :.;.;.;.;.;.;..
H. , o o .o.o‘:.o.o.o.o.o /
5 n / we .a
O %‘0. mt
CN7 #14
VL VSC / 1mm
W ‘ “(7/ l
/5‘ .5/ PCRt
/ .
CN7 #17
Figure 8
30
Figure 9: Photomicrographs Showing Center of Injection Sites
in Cases CN7 #17 and CN7 #13
Bright-field photomicrographs illustrate the center of
HRP-WGA injection sites in two representative cases CN7 #17
(A) and CN7 #13 (B) . The distributions of retrogradely
labeled cells in the pontomesencephalic tegmentum of these two
cases are shown in Figures 10 and 14 respectively.
Scale bar: 0.5mm
31
a uuzmflh
Lmuua
32
addition, a few scattered retrogradely labeled cells were
found in the ipsilateral nucleus reticularis pontis caudalis
(RPc) and contralaterally in the deep layers of the superior
colliculus (SC). Results are summarized in Table 1.
Other injections of HRP—WGA in the lateral half of the
facial nucleus exhibited larger diffusion of the reaction
product into the surrounding tissue. In animal CN7 #16, the
injection was centered at the caudolateral edge of the facial
nucleus and exhibited diffuse HRP-WGA reaction product with
Golgi-like labeling of neurons in the caudolateral two thirds
of the facial nucleus as well as the parvicellular reticular
nucleus (PCRt) dorsolateral to the facial nucleus. In case
CN7 #14, the injection was centered caudal to the facial
nucleus and included only the caudal half of the lateral
portions of the facial nucleus. HRP-WGA reaction product in
animal CN7 #14 was seen as far caudally as the rostral Am and
extended dorsally into the reticular formation as well.
In these additional cases, the PPN exhibited only a few
retrogradely labeled neurons. The larger and more caudally
placed injection in case CN7 #14 resulted in ten labeled PPN
neurons ipsilaterally, while five PPN neurons were labeled
contralaterally. Case CN7 #16 demonstrated only one labeled
cell in the ipsilateral PPN. Confirming the results of case
CN7 #17, other lateral facial experiments also resulted in
heavy HRP labeling ipsilaterally in several nuclei caudal to
the PPN (including the MPB, KF, and Pr5) while the core of the
33
.flmaos: Amnmv Hmcflammwuu Hmmflocï¬um can .Ame mwsmiumxflaaom .Ammqv acwnomuncumm
annoyed .3sz Haï¬nomunwumm H369: on» 939593 zmm new: uwumooa ..aoaosc acum>wm a“
haamnmumaflmmfl uoamnma one mcousoc .um>msom .Hwflucmumnsmcfl ma 2mm may no maï¬amnwa mumumouumm
A.mmmm£ucouwm ca mum “mans: Hmnwumamuucoo may Eoum mucsoo Hamuv .mCOAuoom guanu couowe
om mcflumcuouam Eoum Umucsoo mums mamaosc deï¬es“ may mo mcoï¬uuoa Hmuwpca may CH mcofluommcfl
«UBIQmm maï¬soaaom Hoaosc oflamnmmocmmmEoucom may :a mHHwo cmaonma maouwuoonumm ï¬n wanna
o
we a .mmem a
omma .m>:mOH
.oqnsmmm no
mzm H .mos a Amamv u “owe me on mm Lady «ma AVHC ma Ame son Ame 0H was
.mmemm .m>:me
ucoa .oansmw "H
m>sm H "o
o "H “Hat 0 Loy a on 0 Any m on a on mm on a one
magma .ooa
.mma .ome no AHHV o on ma on mm Ame mad on mm “my and Loy 0 has
0mm m "H
nonuo zm 0mm man mm: as mum 2mm #520
wme
mcofluomncH «wzimmm deflomm Hmumumq mcfl3oHHom maamo Umamhmq Samccuoouumm "u wanna
34
Figure 10: Distribution of HRP Labeled Cells in Case CN7 #17
Projection drawing of lateromedially arranged sagittal
sections through the pontomesencephalic region showing the
distribution of HRP labeled cells in the contralateral (A-C)
and ipsilateral (D-F) nuclei surrounding the PPN in case CN7
#17. Sections illustrated in A and D are lateral to the PPN.
Each dot represents one labeled cell.
35
Figure 10
Fig.
36
11: Photomicrographs of HRP Labeled Cells in the
Ipsilateral Parabrachial Region in Case CN7 #17.
A&B:
C&D:
Show the position (A) and morphology (B) of retrogradely
labeled neurons in the pontomesencephalic tegmentum
lateral to the PPN. Labeled neurons in the ipsilateral
KF (open arrows in B) exhibit round somata located
ventral to the superior cerebellar peduncle while the
smaller fusiform cells of the Pr5 (small arrows in B) lie
more ventrally, immediately caudal to the lateral
lemniscus. In addition, several larger multipolar
neurons within the Pr5 (large arrowheads) also contain
HRP granules.
Show HRP labeled cells in a more medial region of the
pontomesencephalic tegmentum. Most of these cells lie
well within the confines of the MPB (small arrows in D).
Two neurons in a border zone between the MPB and PPN are
indicated by open arrows. A few labeled cells are
intermingled with the fibers of the scp (large arrows).
Scale bar: 0.1mm
37
38
PPN nucleus was remarkably free of labeled cells.
Medial Facial Injections
In four animals, HRP-WGA injections were centered in the
medial half of the facial nucleus (Fig. 12). In case CN7 #13,
dense HRP-WGA reaction product was almost totally confined to
the medial half of the facial nucleus. However, slight
encroachment of the underlying fibers of the trapezoid body
and faint HRP-WGA reaction product was also evident in a small
region of the GiA medial to the facial nucleus (Fig. 9B).
Results are presented in Table 2.
Similar to the observations following HRP-WGA injections
in the lateral portions of the facial nucleus, there were no
labeled cells well within the confines of the PPN. In case
CN7 #13, only one PPN’ cell, located. at 'the rostralmost
boundary of the contralateral PPNd, was labeled (Fig. 13).
Immediately rostral to the PPN, the contralateral R was
heavily labeled. This projection was exclusively
contralateral. Labeled. RR. cells 'were located caudally,
abutting the rostral pole of PPN and often occupying the
border region between these two nuclei. In addition, a more
moderate number of labeled neurons were observed in the
ipsilateral MPB in case CN7 #13 (Fig. 14). Similar to the
pattern observed following lateral HRP-WGA injections,
retrogradely labeled.MPB cells were found primarily along the
rostral and dorsal borders of MPB in a zone bordering
39
.HmHosc HmmHv HmHnomHnmumm HmumumH new .Hmmv mmsmuumxHHHox .Hmmzv
Hwflnowunmuwm HMHUmE .Amumv HmcHEmmHHu Hmmflocflum on» CH maacumumaflmmfl Umaonma mHHwo mu Hams
mm Ammv mstosc kuhsuouumu Honoumamupcoo one :H mHHmo pmamnma mo mumnesc mmHmH may muoz
A.mmmmnucmuwm :H mum HmHosc Hmuwuwacuucoo on» Eoum mucsoo HHmUv
om wcflpccumuam Eoum cmpcsoo muo3 msmHosc HmHomu on» yo mcoHuHom HchmE on» :H mcoflpomncï¬
.mcofluomm xoflnu COHUHE
dozimmm mcflsoHHom HmHosc oHHmcmmocwmeoucom map :a mHHmo umHoan hamuwumouuom "a canes
oo H .zm H no
00 H "H Hoe o Hoe o Hoe m Hoe o Hoe o HHHV o e*
mac: Hoe o Hoe o on o Hoe o Hov o AHV o ma
wo H â€o
m>sm m .omm m .Zm s .mwz m "H Hoe a Hoe H Hoe mm Hov oH Loy H AHNV o HHH
0mm m .zm m .mmm NH .mmsm he no
2m m .mmam s .oo 0H .omm sH "H Hoe m Lav m Hoe mm Ame HH “He 0 HHmHv o HH¢
umnuo mmH as mas mum 2mm mm * szo
Ommo
m:0HuommcH auzummm HmHomm
Hcflpoz mcHsoHHom mHHmU cmHmnmq Samumumouumm "
CHQGB
40
Figure 12: Medial Facial HRP—WGA Injection Sites
Projection drawing of sagittal sections through the
center of HRP-WGA injections involving the medial half of the
facial nucleus in four representative cases described in the
results. See legend to Figure 8 for further explanation.
41
SCD/ /
MVB " 22
Me5 \._i:
m 1“" '—
RPo 7n "
5 31%;. l
c3339
\ Mo / /
N2 80 Wï¬â€˜Ã©f/é-P‘fl. fl;
/
,1 PCRt I
â€226;-
CN7 #11
CN7 #13 1mm
Figure 12
~¢ ‘ “n
#1
n! - -
42
Figure 13: Photomicrographs of HRP Labeled Cells in the
Contralateral Retrorubral Region in Case CN7 #13.
A&B: The location (A) and morphology (B) of retrogradely
labeled cells in the contralateral RRF. Most of these
cells lie well within the caudal half of the RRF (B). An
arrow (B) indicates one labeled cell in the border zone
between the PPNd (**) and the RRF; The PPNc is indicated
by a single asterisk.
C&D: Show HRP reactive neurons in a more lateral region of
the pontomesencephalic tegmentum. Labeled cells (arrows
in D) are observed along the caudal border of the RR.
Scale bar: 0.1mm
44
the caudal PPN. The other mesopontine nuclei exhibiting HRP—
labeled.neurons in.case CN7 #13 included, in decreasing order:
the bilateral Rmes (more contralaterally); bilateral RPo
(more ipsilaterally); contralateral RRF; ipsilateral Pr5;
ipsilateral CG (in clusters along the ventral border);
bilateral KF; bilateral RN; and the ipsilateral LPB.
In the other three animals with injections in medial
portions of the facial nucleus, moderately dense HRP-WGA
reaction product was observed in neighboring regions of the
adjacent reticular nuclei. GiA was labeled medial to the
facial nucleus in cases CN7 #11, CN7 #4, and CN7 #9, while
the reticular formation caudodorsal to the facial nucleus was
labeled only in cases CN7 #11, and CN7 #4.
Results from these animals confirmed those of animal CN7
#13. There were essentially no labeled cells in the PPN
following HRP-WGA injections into medial portions of the
facial nucleus. Diffusely labeled neurons were observed in
nuclei surrounding (but not including) the ipsilateral PPN,
particularly the MPB and Pr5. Distinct labeling in the
contralateral RR was present in all medial cases, even in one
case (CN7 #9) with an extremely small injection site.
45
Figure 14: Distribution of HRP Labeled Cells in Case CN7 #13
Projections drawings of sagittal sections illustrating
the distribution.of HRP labeled cells in the contralateral (A-
C) and ipsilateral (D-F) pedunculopontine region following
HRP-WGA injection involving the medial part of the facial
nucleus in case CN7 #13. Each dot represents one labeled
cell.
46
O
p.
. a R
O I
, ..O/
I s N
I P
D. .
s It udsolll
9 “sun
m 2.. Cr.
R ’ od%
0..
o N
O. 8
1mm
Figure 14
47
Summapy of Results
In summary, results of unilateral FHA-L injections
centered in the PPN showed anterograde labeling primarily in
the ventromedial pontomedullary reticular nuclei, but also in
several nuclei of the cranial nerves. Labeled fibers were
most dense in the facial nucleus, and relatively sparse in the
caudal cranial nerve nuclei (12, Sol, 10, and Am). PmmrL
projections to the facial nucleus exhibited two distinct
patterns: 1) a diffuse ipsilateral projection present in all
cases, and 2) a punctate contralateral projection to the
rostromedial two thirds of the facial nucleus in two cases.
The HRP-WGA experiments which were designed to clarify
the organization of this PPN-facial pathway failed to confirm
the existence of such projections. Retrograde labeling of
cells located well within the PPN was not observed after
injections of HRP-WGA.in either the lateral or medial portions
of the facial nucleus. The exception was case CN7 #14, in
which HRP-WGA was also deposited in the reticular formation
caudal to the facial nucleus. Similarly, retrograde labeling
in the PPN (136 cells ipsilaterally, 54 contralaterally) was
observed in one additional case (CN7 #18) in which the core
area of the HRP-WGA injection included the entire extent of
the facial nucleus and substantial portions of the surrounding
reticular nuclei.
In contrast to the absence of labeled cells in PPN,
retrograde. experiments showed labeling' of several nuclei
48
surrounding the PPN. HRP-WGA injections into the medial
facial nucleus resulted in distinct labeling of cells in the
contralateral RR. Furthermore, both medial and lateral facial
injections resulted in a primarily ipsilateral pattern of HRP-
labeled neurons in the MPB, KF, LPB, and Pr5. These nuclei
were labeled most distinctly in lateral facial injections.
DISCUSSION
PPN Projections to the Facial Nucleps
The anterograde and retrograde labeling experiments
yielded contradictory results. While PHA-L injections in the
PPN clearly demonstrated two distribution patterns of labeled
fibers in the facial nucleus, the HRP-WGA experiments failed
to retrogradely label cells located in the core of the PPN.
Particularly significant. was. a complete absence of
retrogradely labeled cells in the medial two thirds of the
PPNd which appear to receive the bulk of nigral afferents
(Spann & Grofova '88). It may be argued that the negative
results obtained from the HRP experiments were due to
technical failure. However, this seems unlikely since
retrogradely labeled cells were consistently present in the
areas surrounding the PPN. Furthermore, the PPN cells did
exhibit distinct labeling in one of the experimental animals
in whidh the HRP-WGA injection involved mostly the ventral
part of the reticular formation adjacent to the medial aspect
of the facial nucleus. Taken together, these observations
indicate that the PPN does not give rise to the facial
projections demonstrated in the experiments utilizing
anterograde transport of PHA-L. Although there exist
occasional reports (Cliffer & Giesler '88, Schofield '89) that
the PHA-L can be taken up by fibers passing through the
injection site, most authors agree with the original
49
50
observations of Gerfen & Sawchenko ('84) that PHA-L does not
appear to be taken up and transported effectively by fibers
of passage. Our own observations fully support the latter
notion. The PPN is traversed by several prominent fiber
systems including the superior cerebellar peduncle and the
central tegmental tract.which were unavoidably involved.in.all
PHA-L injections. However, there was no evidence of PHA-L
uptake and transport by these fiber systems. In fact, the
fiber bundles of the scp traversing the center of PHA-L
deposits were clearly discernable by the absence of reaction
product (Fig.2), and no labeled fibers could be traced to the
red nucleus. Thus labeling of fibers "en passage" does not
provide a reasonable explanation. of the results of the
anterograde tracing experiments.
Most likely, the labeled fibers in the facial nucleus
originated from scattered PHA-L labeled cells located within
the nuclei surrounding the lateral aspect of the PPN. This
conclusion is substantiated by careful comparisons between the
distributions of HRP labeled cells following medial and/or
lateral facial injections, and the distribution of single PHA-
I.labeled.cells surrounding the:dense center of PHA-I.deposit.
The HRP-WGA injections into the medial groups of facial motor
neurons resulted in labeling of a discrete group of cells in
the contralateral RR and lateral RRF. Correspondingly, single
Golgi-like labeled cells were seen.in these regions in the two
PHA-L experiments (#25 and #31) which demonstrated a
51
contralateral projection to the medial portion of the facial
nucleus. 0n the other hand, retrogradely labeled neurons were
most numerous in the ipsilateral MPB, KF, LPB and Pr5
following HRP-WGA injections centered laterally in the facial
nucleus, and uptake of PHA-L by isolated cells within these
regions was more prominent in cases PHA-L #28, #27 and #24
which demonstrated a diffuse projection terminating
predominantly ipsilaterally in the lateral division of the
facial nucleus.
PPN Projections to Medullary Cranial Nerve Nuclei
While retrograde experiments were not carried out to
clarify our findings of labeled fibers in the caudal cranial
nerve nuclei (12, 10, Sol, and Am) following PHA-L injections
centered in PPN, the literature supports the impression that
these projections may also originate in nuclei surrounding the
PPN. Several authors have shown retrogradely labeled KF, and
to a lesser extent MPB and LPB neurons following HRP-WGA
injections in several regions of the Sol in the rat (Herbert
et.al. '90, Fulwiler & Saper '84, Rye et.al. '88). The
largest proportion of these cells have been reported in the
KF, with the remaining retrogradely labeled cells surrounding
the ventrolateral scp in the MPB and LPB nuclei. Rye and
colleagues ('88) have additionally shown that while many cells
were retrogradely labeled in the parabrachial nuclei following
injections of HRP-WGA in the ventrolateral Sol region, only
52
a few cells in the PPN were so labeled. In the present
experiment, PHA-L injections sites did not include cells in
the KF but did include several cells of the rostral and middle
regions of the LPB and MPB. This may explain the sparse
distribution of PHA-L labeled fibers to Sol in our results.
Parabrachial projections to the ventrolateral medulla
(including Am) and the hypoglossal nucleus have also been
reported in the rat (Rye, et.al. '88; Saper & Loewy, '80;
Fulwiler & Saper, '84; Herbert, et.al '90) and in the pigeon
(Wild, et.al. '90). The ‘Ventrolateral medulla is widely
thought to be involved in respiratory control (Ellenberger
et.al. '90, Feldman & Grillner '83), and it has been suggested
that the ventrolateral portion of the Sol also contributes to
the control of respiration (Herbert et.al., '90). Moreover,
the muscles controlling the patency of the upper airway are
innervated by the hypoglossal (Krammer, et.al. '79; Lewis,
et.al. '71; Odutola, '76) and dorsal motor vagus (Lewis,
et.al. '70) nuclei and receive parabrachial input (Saper &
Loewy '80). On the basis of their connections with these
respiratory and oral motor nuclei, it has been proposed that
the parabrachial nuclei (particularly the KF) may contribute
to the control of respiration (Herbert, et.al. '90) and
vocalization (Wild, et.al. '90). While it seems unlikely that
the PPN contributes directly to these functions, the present
study can not rule out this possibility.
53
Mesopontine Efferents to the Facial Nucleus:
1) Parabrachial Nuclei
An ipsilateral projection from the KF, MPB, and LPB to
intermediate and lateral portions of the facial nucleus has
been reported previously in the rat (Isokawa-Akesson &
Komisaruk '87, Hinrichsen & Watson '83, Travers & Norgren
'83, Saper & Loewy '80), cat (Fort et.al. '89, Holstege
et.al. '86, Takeuchi et.al. '80), and opossum (Panneton &
Martin '83). Our findings confirm these results. In many
species, the lateral facial subnuclei contain motoneurons
innervating the buccolabial musculature (Watson et.al. '82,
Komiyama et.al. '84, Dom et.al. '73). Our data implicates
the MPB to a greater degree than other parabrachial nuclei in
projecting to lateral portions of the ipsilateral facial
nucleus, and these results are supported in the literature by
autoradiographic studies (Saper & Loewy '80). The MPB has
been identified as having gustatory functions (Saper & Lowey
'80, Hill '87, Herbert et.al. '90) and, as was previously
discussed, the ventrolateral parabrachial region has been
associated with respiratory function. It follows that
projections from parabrachial nuclei to the lateral facial
subnuclei may contribute to the control of oral musculature
in respiratory and feeding behaviors.
54
2) Retrorubral Nucleus
In addition to parabrachial facial afferents, our data
confirm a contralateral projection from RR to medial
subdivisions of the facial nucleus which was first reported
in the rat by Isokawa-Akesson & Komisaruk ('87). The rat RR
is a compact group of small to medium sized cells located
rostral to the ventral nucleus of the lateral lemniscus and
rostromedial to the fibers of the lateral lemniscus (Paxinos
& Watson '86). In other retrograde tracing studies in the
rat, the contralateral "midbrain reticular fermation"
(Hinrichsen & Watson '83) or the "paralemniscal zone" (Travers
& Norgren '83) have been identified as sources of afferents
to the medial groups of facial motoneurons. Similar
observations have also been reported in the cat (May et.al.
'89, Fort et.al. '89, Takeuchi et.al. '79, Henkel & Edwards
'78) and opossum (Panneton & Martin '83). Since all these
regions are rather vaguely defined, it is possible that the
discrepancies are more semantic than factual.
The cat "paralemniscal zone" has been. described in
coronal sections as a narrow, vertical region consisting of
darkly staining“ clusters, of :medium-sized, densely' packed
neurons extending from the nuclei of the lateral lemniscus to
the caudal pole of the RR (Henkel & Edwards '78). The cat
retrorubral nucleus represents a distinct entity which is
characterized by the presence of catecholaminergic cells
projecting to the striatum (Vandermaelen et.al. '78) and
55
having similar morphological and functional properties as the
nigral cells in the pars compacta (Preston et.al. '81). No
similar information is available for the rat RR delineated by
Paxinos and Watson ('86) . In fact, the cytoarchitectural
features of the rat RR resemble more those described for the
cat paralemniscal zone. This zone appears to receive
projections from the superior colliculus and other structures
known to be involved in visual and auditory orienting
responses (Henkel '81), and it has been suggested that the
connection from.this zone:to the medial facial motoneurons:may
play a role in the pinnae orienting response. Although no
such function has been previously proposed for the rodent RR,
it is interesting that the projection from the rat RR to the
contralateral facial nucleus is restricted only to medial
facial motoneurons which innervate the pinnae (Watson et.al.
'82). Thus, the rodent RR is clearly in a position to affect
pinnae movements during the orienting response. It would be
of interest to further explore the functional connectivity of
the rat RR, particularly with regard to its involvement in
the orienting reflexes.
3) Red Nucleus
Our experiments confirm a crossed rubro-facial pathway
terminating in the lateral and intermediate facial subnuclei
as described in the literature (Travers & INorgren '83,
Hinrichsen & watson '83, Isokawa-Akessan & Komisaruk '87,
56
Edwards '72, Dom et.al. '73, Panneton & Martin '83). Our
data shows this to be a sparse projection. The large number
of RN cells labeled in case CN7 #14 is very likely due to
uptake of HRP-WGA by damaged fibers of the rubrospinal tract
passing caudolateral to the facial nucleus.
4) Principal Sensopy Trigeminal Nucleus
Finally, we have demonstrated a rather substantial
projection from Pr5 to the lateral and intermediate facial
subnuclei. Many neurons located just caudal to the ventral
spinocerebellar tract (rostrolateral to M05) were labeled
following HRP-WGA injections in both the medial and lateral
portions of the facial nucleus. These were more numerous
after lateral facial injections. Physiological studies
demonstrating disynaptic responses of facial motoneurons to
stimulation of the trigeminal nerve seem to support these
findings (Tanaka et.al., '71). In contrast to our results,
previous investigators have described Pr5 innervation of the
facial nucleus to be rather sparse in the rat (Travers &
Norgren.'83, Erzurumlu.& Killackey '79) and opossum (Panneton
& Martin '83).
The discrepancy with respect to the abundance of facial-
projecting Pr5 cells may be due to the difficulties in the
delineation of the Pr5 from the KF. In the sagittal plane,
the KF and Pr5 nuclei intermix and the exact borders are
difficult to distinguish. We defined KF cells as round or
57
pyramidal, darkly staining cells with a distinct nucleolus and
a cell diameter exceeding 16pm (Fulwiler & Saper '84). Pr5
cells were smaller and more lightly stained than KF cells
(Fukushima & Kerr '79). It is also possible that some of the
retrogradely labeled cells in this transitional region
represent neurons of the catecholaminergic A7 cell group. A7
cells are dispersed throughout the subcoeruleus, KF, and Pr5
nuclei and are known to project to the facial nucleus in the
rat (Grzanna et.al. '87) and cat (Fort, et.al. '89). Cells
labeled in the ipsilateral Pr5 may have also resulted from
uptake onHRP-WGA.in.reticular regions lateral to the targeted
facial nucleus. However, this can not entirely explain our
results since several Pr5 cells were also labeled
ipsilaterally with injections of HRP-WGA in the medial
portions of the facial nucleus which completely avoided this
reticular region.
Since the Pr5 receives primary facial sensory input, a
projection from Pr5 to the lateral subdivisions of the facial
nucleus may provide a pathway mediating the tactual guidance
of oromotor behavior.
Descending PPN Efferents
Our data suggests there does not exist a direct
projection from the PPN to the cranial nerve nuclei, but
descending PPN efferents clearly project to the ventromedial
pontomedullary reticular nuclei. The majority of PPN
58
efferents to the reticular formation are concentrated
ventromedially in the RFC, GiA, and Giv (Grofova et.al. in
press, Nakamura et.al. '89, Mitani et.al. '88, Rye et.al. '88,
Jackson & Crossman '83, Moon-Edley & Graybiel '83) , and these
nuclei have been shown to project to somatic and autonomic
motor columns in the medulla and spinal cord (Vertes et.al.
'86, Jones & Yang '85, Travers & Norgren '83, Zemlan et.al.
'82, Holstege & Kuypers '82, Martin.et.al. '81, Peterson '80),
thus establishing a potential pathway by which PPN may affect
motor behavior. The existence of a PPN-reticulo-spinal
pathway has been proposed by Garcia-Rill & Skinner ('87) on
the basis of electrophysiological experiments. Extracellular
recordings of‘singletmedioventral.medullary'neurons.in the.cat
showed. short latency' orthodromic .responses following
stimulation of the mesencephalic locomotor region (MLR)
coexistent with the ability to antidromically activate these
same neurons from stimulation of the spinal cord. Since the
reticular nuclei receiving input from the PPN project not only
to the spinal cord but also to several motor and autonomic
nuclei of the cranial nerves, it is possible that the PPN may
influence both the spinal and cranial motor systems
indirectly, through a relay in the brainstem reticular
formation. Clinical syndromes associated with neuronal loss
in the PPN in humans seem to support this suggestion since
they invariably include disorders related to dysfunctions of
the cranial nerves.
59
In progressive supranuclear palsy (PSP) , symptoms include
unsteady gait, dysarthric or dysphonic speech, and impaired
ocular movements, particularly in the vertical plane
(Jellinger '88, Maher & Lees '86). Another syndrome
associated with PPN cell loss is Meige syndrome, a rare
disorder involving involuntary head turning, blepharospasm,
and grimacing movements of the orofacial musculature (Tolosa
& Marti '88, Zweig et.al. '88).
Functional Considerations
The PPN has been implicated in motor control by virtue
of its abundant connections with the basal ganglia and spinal
cord projecting reticular nuclei, and by its co-localization
within the physiologically identified.mesencephalic locomotor
region. However, it became increasingly obvious that it would
be an oversimplification to consider PPN functions only in
terms of locomotion.or motor control in general. In.the light
of various lines of evidence, it is tempting to speculate that
the PPN may represent.a part.of a complex substrate underlying
orienting reflexes.
While the precise pathways involved in the orienting
reflex are far from clear, several contributing nuclei have
been identified (Fig. 15). In particular, the deep layers of
the SC are necessary to elicit orienting behaviors (Peterson
'80). It is possible that.the orienting reflex, characterized
by turning of the head, pinnae and eyes toward a novel
6O
ISNrF
PPN ,. SC
RPc
Gi
cervical cord
CN 7 CN 3, 4, 6
Figure 15: Circuit Diagram - Orienting Reflex
Circuit diagram illustrates the connections of some of
the structures thought to be involved in the orienting reflex.
Abbreviations: intermediate and deep layers of the superior
colliculus (SC), substantia nigra pars reticulata (SNr) ,
pedunculopontine nucleus (PPN), nucleus reticularis pontis
caudalis (RPc) , nucleus gigantocellularis (Gi) , cranial nerves
(CN) 3, 4, 6, and 7.
61
stimulus, may be executed via deep tectal efferents projecting
directly to appropriate motor structures.
Intermediate and deep layers of the SC project to the
upper cervical segments, innervating axial musculature
required for head turning (Huerta & Harting '82), to the
cranial motor nuclei involved in extraocular and pinnae
movements (Vidal et.al. '88, Keller '79, Graham '77) and to
the pontomedullary reticular formation projecting to these
cranial motor nuclei (Vertes et.al. '86, Kawamura & Hashikawa
'78, Edwards '80, Isokawa—Akesson & Komisaruk '87, Panneton
& Martin '83, Takeuchi et.al. '79, Fort et.al. '89). Since
the PPN sends descending projections to these same reticular
nuclei (i.e. the medioventral RPc, GiA, and Giv) (Grofova
et.al. in press, Mitani et.al. '88, Rye et.al. '88, Moon-Edley
& Graybiel '83, Jackson & Crossman '83, Zemlan '84) it is well
situated to modulate neural activity occurring during the
orienting response.
On the other hand, the SNr is in a position to influence
these two structures (i.e. the SC and PPN) which both project
either directly or indirectly to the motor nuclei required for
execution of the orienting response. The SNr projects
substantially to the ipsilateral deep layers of the SC
(Grofova et.al. in press, Williams & Faull '88, Beckstead &
Frankfurter '82, Gerfen et.al. '82) as well as extensively to
the ipsilateral PPN (Spann & Grofova '88, Noda & Oka '84,
Garcia-Rill et.al. '83, Gerfen et.al. '82, Beckstead et.al.
62
'82). Physiological experiments have also confirmed a SNr-
PPN-reticular pathway (Kelland & Asdourian '89, Nakamura
et.al. '89, Garcia-Rill.& Skinner '87), and monosynaptic input
from SNr to tectospinal neurons has been described (Williams
& Faull '88). There seem to be considerable interconnections
within this circuitry. In this regard, it is of interest to
note that the PPN also sends input to the SC (Hall et.al. '89,
Woolf & Butcher '86, Beninato & Spencer '86). Thus, nigral
efferents may assist in coordinating the influence of the SC
and PPN on the medial RPc, GiA, and Giv reticular nuclei.
Physiological observations of directionally specific
behavioral abnormalities following unilateral lesions of the
rat PPN (Kilpatrick & Starr '81) also support a possible role
of the PPN in the orienting reflex. Because of the
multiplicity of nuclei involved in control of the orienting
response, and the complexity of interconnections among them,
further detailed studies will be required to elucidate the
role of the PPN in the orienting reflex as well as other
functions.
BIBLIOGRAPHY
BIBLIOGRAPHY
Basbaum, A.A. & Fields, H.L. (1980) Pain Control: A New
Role for the Medullary Reticular Formation. In THE
RETICULAR FORMATION REVISITED, edited by J .A. Hobson
& M.A.B. Brazier, Raven Press, New York, pp. 329-
348.
Beckstead, R.M. & Frankfurter, A. (1982) The
Distribution and Some Morphological Features of
Substantia Nigra Neurons That Project to the
Thalamus, Superior Colliculus and Pedunculopontine
Nucleus in the Monkey. NEUROSCIENCE 7(10): 2377-
2388.
Beckstead, R.M., Domesick, V.B., & Nauta, W. (1979)
Efferent Connections of the Substantia Nigra and
Ventral Tegmental Area in the Rat. BRAIN RES 175:
191-217.
Beninato, M. & Spencer, R.F. (1986) A Cholinergic
Projection to the Rat Superior Colliculus
Demonstrated by Retrograde Transport of Horseradish
Peroxidase and Choline Acetyltransferase
Immunohistochemistry. J COMP NEUROL 253: 525-538.
Carstens, E., Klump, D. & Zimmerman, M. (1980)
Differential Inhibitory Effects of Medial and
Lateral Midbrain Stimulation on Spinal Neuronal
Discharges to Noxious Skin Heating in the Rat.
J NEUROPHYSIOL 43: 332-342.
Carter, D.A. & Fibiger, H.C. (1978) The Projections of
the Entopeduncular Nucleus and Globus Pallidus in
Rat. as Demonstrated. by’ .Autoradiography' and
Horseradish Peroxidase Histochemistry. J COMP
NEUROL 177: 113-124.
Cliffer, K.D. & Giesler, G.J. (1988) PHA-L Can Be
Transported Anterogradely Through Fibers of Passage.
BRAIN RES 458: 185-191.
63
64
DeVito, J.L. & Anderson, M.E. (1982) An Autoradiographic
Study of Efferent Connections of the Globus Pallidus
in Macaca Mulatta. EXP BRAIN RES 46: 107-117.
Dom, R., Falls, W., & Martin, G. F. (1973) The Motor
Nucleus of the Facial Nerve. In the Opossum
(Didelphis marsupialis virginiana). Its
Organizations and Connections. J COMP NEUROL 152:
373-402.
Edwards, S.B. (1980) The Deep Cell Layers of the
Superior Colliculus in THE RETICULAR FORMATION
REVISITED, edited by J.A. Hobson & M. Brazier.
Raven Press, New York, pp. 193-209.
Edwards, S.B. (1972) The Ascending and Descending
Projections of the Red Nucleus in the Cat: An
Experimental Study Using an Autoradiographic Tracing
Method. BRAIN RES 48: 45-63.
Ellenberger, H.H., Feldman, J.L. & Zhan, W.Z. (1990)
Subnuclear Organization of the Lateral Tegmental
Field of the Rat. II: Catecholamine Neurons and
Ventral Respiratory Group. J COMP NEUROL 294: 212-
222.
Erzurumlu, R.S. & Killackey, H.P. (1979) Efferent
Connections of the Brainstem Trigeminal Complex with
the Facial Nucleus of the Rat. J COMP NEUROL 188:
75-86.
Feldman, J.L & Grillner, S. (1983) Control of Vertebrate
Respiration and Locomotion: A Brief Account.
PHYSIOL 26: 310-316.
Fort, P., Sakai, K., Luppi, P., Salvert, D. & Jouvet, M.
(1989) Monoaminergic, Peptidergic, and Cholinergic
Afferents to the Cat Facial Nucleus as Evidenced by
a Double Immunostaining Method with Unconjugated
Cholera Toxin as a Retrograde Tracer. J COMP NEUROL
283: 285-302.
Fukushima, T. & Kerr, F.L. (1979) Organization of
Trigeminothalamic Tracts and Other Thalamic Afferent
Systems of the Brainstem in the Rat. J COMP NEUROL
183: 169-184.
Fulwiler, C.E. & Saper, C.B. (1984) Subnuclear
Organization of the Efferent Connections of the
Parabrachial Nucleus in the Rat. BRAIN RES REV 7:
229-259.
65
Garcia-Rill, E., Skinner, R.D., Jackson, M.B. & Smith,
M.M. (1983) Connections of the Mesencephalic
Locomotor Region (MLR): I. Substantia Nigra
Afferents. BRAIN RES BULLETIN 10: 57-62.
Garcia-Rill, E., Skinner, R.D., Gilmore, S.A. & Owings,
R. ( 1983) Connections of the Mesencephalic
Locomotor Region (MLR) : II. Afferents and Efferents.
BRAIN RES BULLETIN 10: 63-71.
Garcia-Rill, E. ( 1983) Connections of the Mesencephalic
Locomotor Region (MLR): III. Intracellular
Recordings. BRAIN RES BULLETIN 10: 73-81.
Garcia-Rill, E. (1986) The Basal Ganglia and the
Locomotor Regions. BRAIN RES REV 11: 47-63.
Garcia-Rill, E., Houser, C.R., Skinner, R.D., Smith, W.,
& Woodward, D.J. (1987) Locomotion-Inducing Sites
in the Vicinity of the Pedunculopontine Nucleus.
BRAIN RES BULLETIN 18: 731-738.
Garcia-Rill, E. & Skinner, R.D. (1987) The Mesencephalic
Locomotor Region. II. Projections to Reticulospinal
Neurons. BRAIN RES 411: 13-20.
Garcia-Rill, E. & Skinner, R.D. (1988) Modulation of
Rhythmic Function in the Posterior Midbrain.
NEUROSCIENCE 27(2): 639-654.
Gerfen, C.R. & Sawchenko, P.E. (1984) An Anterograde
Neuroanatomical Tracing Method that Shows the
Detailed Morphology of Neurons, Their Axons and
Terminals: Immunohistochemical Localization of an
Axonally Transported Plant Lectin, Phaseolus
vulgaris Leucoagglutinin (PHA-L). BRAIN RES 290:
219-238.
Gerfen, C.R., Staines, W.A., Arbuthnott, G.W., & Fibiger,
H.C. (1982) Crossed Connections of the Substantia
Nigra in the Rat. J COMP NEUROL 207: 283-303.
Goldsmith, M. & Vanderkooy, D. (1988) Separate Non-
Cholinergic Descending Projections and Cholinergic
Ascending Projections from the Nucleus Tegmenti
Pedunculopontinus. BRAIN RES 445: 386-391.
Gonya-Magee, T. & Anderson, M.E. (1983) An
Electrophysiological Characterization of Projections
from the Pedunculopontine Area to Entopeduncular
Nucleus and Globus Pallidus in the Cat. EXP BRAIN
RES 49: 269-279.
66
Graham, J. (1977) An Autoradiographic Study of the
Efferent Connections of the Superior Colliculus in
the Cat. J COMP NEUROL 173: 629-654.
Granata, A.R. & Kitai, S.T. (1989) Intracellular
Analysis of Excitatory Subthalamic Inputs to the
Pedunculopontine Neurons. BRAIN RES 488: 57-72.
Graybiel , A. M. & Devor , M. (1974) A Micro-
electrophoretic Del ivery Technique for Use with
Horseradish Peroxidase. BRAIN RES 68: 167-173.
Grofova, I., Spann, B.M., & Bruce, K. (in press)
Involvement of the Nucleus Tegmenti
Pedunculopontinus in the Descending Pathways of the
Basal Ganglia in the Rat. In BASAL GANGLIA III:
PROCEEDINGS OF THE INTERNATIONAL BASAL GANGLIA
SOCIETY'S THIRD TRIENNIAL MEETING, edited by G.
Bernardi, Plenum Press, New York.
Grzanna, R., Chee, W.K. & Akeyson, E.W. (1987)
Noradrenergic projections to Brainstem Nuclei:
Evidence for Differential Projections From
Noradrenergic Subgroups. J COMP NEUROL 263: 76—91.
Hall, W.C., Fitzpatrick, D., Klatt, L.L & Raczkowski, D.
( 1989) Cholinergic Innervation of the Superior
Colliculus in the Cat. J COMP NEUROL 287: 495-514.
Henkel, C.K. & Edwards, S.B. (1978) The Superior
Colliculus Control of Pinna Movements in the Cat:
Possible Anatomical Connections. J COMP NEUROL 182:
763-776.
Henkel, C. (1981) Afferent Sources of a Lateral Midbrain
Tegmental Zone Associated with the Pinnae in the Cat
as Mapped by Retrograde Transport of Horseradish
Peroxidase. J COMP NEUROL 203: 213-226.
Herbert, H., Moga, M.M., & Saper, C.B. (1990)
Connections of the Parabrachial Nucleus with the
Nucleus of the Solitary Tract and the Medullary
Reticular Formation in the Rat. J COMP NEUROL 293:
540-580.
Hill, D.L. (1987) Development of Taste Responses in the
Rat Parabrachial Nucleus. J NEUROPHYSIOL 57(2) :481.
Hinrichsen, C.F.L. & Watson, C.D. (1983) Brain Stem
Projections to the Facial Nucleus of the Rat. BRAIN
BEHAV EVOL 22: 153-163.
67
Holstege, G., Van Ham, J., Joeptan (1986) Afferent
Projections to the Orbicularis Oculi Motoneuronal
Cell Group. An Autoradiographical Tracing Study in
the Cat. BRAIN RES 374: 306-320.
Holstege, J.C. & Kuypers, H.G.J.M. (1982) Brain Stem
Projections to Spinal Motoneuronal Cell Groups in
Rat Studied by Means of Electron Microscopy
Autoradiography. In PROG BRAIN RES vol. 57,
DESCENDING PATHWAYS TO THE SPINAL CORD, edited by
H. Kuypers & G.F. Martin, Elsevier, New York, pp.
177-183.
Huerta, F.M. & Harting, J.K (1982) Tectal Control of
Spinal CordMActivity: Neuroanatomical Demonstration
of Pathways Connecting the Superior Colliculus with
the Spinal Cord Grey. PROG BRAIN RES 57: 293-328.
Hylden, J.K., Hayashi, H., Bennett, G.J., & Dubner, R.
(1985) Spinal Lamina I Neurons Projecting to the
Parabrachial Area of the Cat Midbrain. BRAIN RES
336: 195-198.
Isokawa-Akesson, M. & Komisaruk, B.R. (1987) Difference
in Projections to the Lateral and Medial Facial
Nucleus: Anatomically Separate Pathways for
Rhythmical Vibrissa Movements in Rats. EXP BRAIN
RES 65: 385-398.
Jackson, A. & Crossman, A.R. (1983) Nucleus Tegmenti
Pedunculopontinus:EfferentConnectionswithSpecial
Reference to the Basal Ganglia, Studied in the Rat
by Anterograde and Retrograde Transport of
Horseradish Peroxidase. NEUROSCIENCE 10(3): 725-
765.
Jellinger, K. (1988) The Pedunculopontine Nucleus in
Parkinson's Disease, Progressive Supranuclear Palsy
and Alzheimer's Disease. J NEUROL NEUROSURG
PSYCHIATRY 51:540-543.
Jones, B.E. & Yang T-Z (1985) The Efferent Projections
From the Reticular Formation and the Locus Coeruleus
Studied by Anterograde and Retrograde Axonal
Transport in the Rat. J COMP NEUROL 242: 56-92.
68
Katayama, Y., DeWitt, D.S., Becker, D.P., & Hayes, R.L.
(1984) Behavioral Evidence for a Cholinoceptive
Pontine Inhibitory .Area: Descending Control of
Spinal Motor Output and Sensory Input. BRAIN RES
269: 241-262.
Kawamura, K. & Hashikawa, T. (1978) Cell Bodies of
Origin of Reticular Projections from the Superior
Colliculus in the Cat: An Experimental Study with
the Use of Horseradish Peroxidase as a Tracer. J
COMP NEUROL 182: 1-16.
Kelland, M.D. & Asdourian, D. (1989) Pedunculopontine
Tegmental Nucleus-induced Inhibition of Muscle
Activity in the Rat. BEH BRAIN RES 34: 213-234.
Keller, E.L. (1979) Colliculoreticular Organization in
the Oculomotor System. PROG BRAIN RES 50: 725-734.
Kilpatrick, I.C. & Starr, M.S. (1981) The Nucleus
Tegmenti Pedunculopontinus and Circling Behavior in
the Rat. NEUROSCI LETTR 26: 11-16.
Kim, R., Nakano, K., Jayaraman, A., & Carpenter, M.B.
(1976) Projections of the Globus Pallidus and
Adjacent Structures: An Autoradiographic Study in
the Monkey. J COMP NEUROL 169: 263-290.
Komiyama, M., Shibata, H., & Takashi, S. (1984)
Somatotopic Representation of Facial Muscles within
the Facial Nucleus of the Mouse. BR BEHAV EVOL 24:
144-151.
Krammer, E.B., Rath, T., & Lischka, M.F. (1979)
Somatotopic Organization of the Hypoglossal Nucleus:
a HRP Study in the Rat. BRAIN RES 170: 533-537.
Larsen, K.D. & McBride, R.L. (1979) The Organization of
Feline Entopeduncular Nucleus Projections. J COMP
NEUROL 184: 293-308.
Lewis, P.R., Flumerfelt, B.A., & Shute, C.C.D. (1971)
The Use of Cholinesterase Techniques to Study
Topographical Localization in the Hypoglossal
Nucleus of the Rat. J ANAT 110(2): 203-213.
Lewis, P.R., Scott, J.A. & Navaratnam V. (1970)
Localization in the Dorsal Motor Nucleus of the
Vagus in the Rat. J ANAT 107: 197-208.
69
Maher, E.R. & Lees, A.J. (1986) The Clinical Features
and a Natural History of the Steele-Richardson-
Olszewskisyndrome(ProgressiveSupranuclearPalsy).
NEUROLOGY 36: 1005-1008.
Martin, G.F., Cabana, T., Humbertson, A.O., Laxson, L.C.,
& Panneton, W.M. (1981) Spinal Projections from the
Medullary Reticular Formation of the North American
Opossum: Evidence for Connectional Heterogeneity.
J COMP NEUROL 196: 663-682.
May, P.J., Vidal, P—Pn & Baker, R. (1989) Synaptic
Organization of the Tecto-Facial Pathways in the
Cat: II. Synaptic Potentials Following Midbrain
Tegmentum Stimulation. J NEUROPHYSIOL (submitted).
Mesulam, M. (1982) TRACING NEURAL CONNECTIONS WITH
HORSERADISH PEROXIDASE. Wiley & Sons, New York.
Mitani, A., Ito, K., Hallanger, A.E., Wainer, B.H.,
Kataoka, K. & McCarley, R.W. (1988) Cholinergic
Projections from the Laterodorsal and
Pedunculopontine Tegmental Nuclei to the Pontine
Gigantocellular Tegmental Field in the Cat. BRAIN
RES 451: 397-402.
Moon Edley, S. & Graybiel, A. (1983) The Afferent and
Efferent Connections of the Feline Nucleus Tegmenti
Pedunculopontinus, Pars Compacta. J COMP NEUROL
217: 187-215.
Mori, S., Nishimura, H., & Aoki, M. (1980) Brain Stem
Activation of the Spinal Stepping Generator. In THE
RETICULAR FORMATION REVISITED, edited by’J.A. Hobson
& M. Brazier. Raven Press, New York, pp.171-192.
Nakamura, Y., Tokuno, H., Moriizumi, T., Kitao, Y., &
Kudo, M. (1989) Monosynaptic Nigral Inputs to the
Pedunculopontine Tegmental Nucleus Neurons Which
Send Their Axons to the Medial Reticular Formation
in the Medulla Oblongata. An Electron Microscopic
Study in the Cat. NEUROSCI LETTR 103: 145-150.
Nauta, H.J.W. & Cole, M. (1978) Efferent Projections of
the Subthalamic Nucleus: An Autoradiographic Study
in Monkey and Cat. J COMP NEUROL 180: 1-16.
70
Nauta, H.J.W. & Mehler, W.R. (1966) Projections of the
Lentiform Nucleus in the Monkey. BRAIN RES 1: 3-
42.
Noda, T. & Oka, H. (1986) Distribution and Morphology
of Tegmental Neurons Receiving Nigral Inhibitory
Inputs in the Cat: An Intracellular HRP Study. J
COMP NEUROL 244: 254-266.
Odutola, A.B. (1976) Cell Grouping and Golgi
Architecture of the Hypoglossal Nucleus of the Rat.
EXP NEUROL 52: 356-371.
Olucha, F., Martinez-Garcia, F. & Lopez-Garcia, C. (1985)
A New Stabilizing Agent for the Tetramethyl
Benzidine (TMB) Reaction Product in the
Histochemical Detection of Horseradish Peroxidase
(HRP). J NEUROSCI METHODS 13: 131-138.
Olszewski, J. & Baxter, D. (1954) CYTOARCHITECTURE OF
THE HUMAN BRAIN STEM. J .P. Lippincott & Co.,
Philadelphia.
Panneton, W. M. & Martin, G. F. (1983) Brainstem
Projections to the Facial Nucleus of the Opossum:
A Study Using Axonal Transport Techniques. BRAIN
RESEARCH 267: 19-33.
Parent, A. & DeBellefeuille, L. (1982) Organization of
Efferent Projections from the Internal Segment of
Globus Pallidus in Primate as Revealed by
Fluorescent Retrograde Labeling Method. BRAIN RES
245: 201-213.
Paxinos, G. & Watson, C. (1986) THE RAT BRAIN IN
STEREOTAXIC COORDINATES, SECOND EDITION. Academic
Press, New York.
Peterson, B.W. (1980) Participation of Pontomedullary
Reticular Neurons in Specific Motor Activity in THE
RETICULAR FORMATION REVISITED, edited by J.A. Hobson
& M. Brazier. Raven Press, New York, pp.171-192.
Preston, R.J., McCrea, R.A., Chang, H.T., & Kitai, S.T.
(1981) Anatomy and Physiology of Substantia Nigra
and Retrorubral Neurons Studied by Extra- and
Intracellular Recording and by Horseradish
Peroxidase Labeling. NEUROSCIENCE 6(3): 331-344.
71
Rye, D.B., Lee, H.J., Saper, C.B., & Wainer, B.H. (1988)
Medullary' and. Spinal Efferents of ‘the
Pedunculopontine: Tegmental Nucleus and .Adjacent
Mesopontine Tegmentum in the Rat. J COMP NEUROL
269: 315-341.
Saper, C.B. & Loewy, A.D. (1982) Projections of the
Pedunculopontine Tegmental Nucleus in the Rat:
Evidence for Additional Extrapyramidal Circuitry.
BRAIN RES 252: 367-372.
Saper, C.B. & Loewy, A.D. (1980) Efferent Connections
of the Parabrachial Nucleus in the Rat. BRAIN RES
197: 291-317.
Schofield, P.R. (1989) Labeling of Axons of Passage by
Phaseolus Vulgaris Leucoagglutinin (PHA-L).
NEUROSCI ABSTR 15: 306.
Spann, B.M. & Grofova, I. (1988) Substantia Nigra
Afferents of the Nucleus Tegmenti Pedunculopontinus.
NEUROSCI ABSTR 14: 1027.
Spann, B.Mg & Grofova, I. (1989) The Origin of Ascending
and Spinal Pathways from the Nucleus Tegmenti
Pedunculopontinus in the Rat. J COMP NEUROL 283:
13-27
Takeuchi, Y., Uemura, M., Matsuda, K., Matsushima, R. &
Mizuno, N. (1980) Parabrachial Nucleus Neurons
Projecting to the Lower Brain Stem and the Spinal
Cord. A Study in the Cat by the Fink-Heimer and
the Horseradish Peroxidase Methods. EXP NEUROL 70:
403-413.
Tanaka, T., Yu, H., & Kitai, S.T. (1971) Trigeminal and
Spinal Inputs to the Facial Nucleus. BRAIN RES 33:
504-508.
Tolosa, E. & Marti, M.J. (1988) Blepharospasm-
Oromandibular Dystonia.Syndrome (Meige's Syndrome):
Clinical Aspects. In ADVANCES IN NEUROLOGY vol.49:
FACIAL DYSKINESIAS, edited by J. Jankovic & E.
Tolosa, Raven Press, New York, pp. 73-84.
Travers, J.B. & Norgren, R. (1983) Afferent Projections
to the Oral Motor Nuclei in the Rat. J COMP NEUROL
220: 280-298.
72
VanDerKooy, D. & Carter, D.A. (1981) The Organization
of the Efferent Projections and Striatal Afferents
of the Entopeduncular Nucleus and Adjacent Areas in
the Rat. BRAIN RES 211: 15-36.
Vandermaelen, C.P., Kocsis, J.D., & Kitai, S.T. (1978)
Caudate Afferents From the Retrorubral Nucleus and
Other Midbrain Areas in the Cat. BRAIN RES BULLETIN
3: 639-644.
Vertes, R.P., Martin, G.F., & Waltzer, R. (1986) An
Autoradiographic Analysis of Ascending Projections
from the Medullary Reticular Formation in the Rat.
NEUROSCIENCE 19(3): 873-898.
Vidal, P—P, May, P.J., & Baker, R. (1988) Synaptic
Organization of the Tecto-Facial Pathways in the
Cat: I. Synaptic Potentials Following Collicular
Stimulation. J NEUROPHYSIOL 60 (2): 769-797.
Watson, C.R.R., Sakai, 8., Armstrong, W. (1982)
Organization of the Facial Nucleus in the Rat.
BRAIN BEHAV EVOL 20: 19-28.
Wild, J.M., Arends, J., & Zeigler, H.P. (1990)
Projections of the Parabrachial Nucleus in the
Pigeon. J COMP NEUROL 292: 499-523.
Williams, M.N. & Faull, R.L.M. (1988) The Nigrotectal
Projections and Tectospinal Neurons in the Rat: A
Light and Electron Microscopic Study Demonstrating
a Monosynaptic Nigral Input to Identified
Tectospinal Neurons. NEUROSCIENCE 25(2): 533-562.
Woolf, N.J. & Butcher, L.L. (1986) Cholinergic Systems
in the Rat Brain: III. Projections from the
Pontomesencephalic Tegmentum to the Thalamus,
Tectum, Basal Ganglia, and Basal Forebrain. BRAIN
RES BULL 16(5): 603-37.
Zemlan, F.P., Behbehani, M.M., & Beckstead, R.M. (1984)
Ascending and Descending Projections from Nucleus
Reticularis Magnocellularis and Nucleus Reticularis
Gigantocellularis: An Autoradiographic and
Horseradish Peroxidase Study in the Rat. BRAIN RES
292: 207-220.
Zweig, R.M., Jankel, W.R., Hedreen, J.C., Mayeux, R., &
Price, D.L. (1989) The Pedunculopontine Nucleus in
Parkinson's Disease. ANN NEUROL 26: 41-46.
73
Zweig, R.M., Whitehouse, P.J., Casanova, M.F., Walker,
L.C., Jankel, W.R., & Price, D.L. (1985) Loss of
Putative Cholinergiereurons of the Pedunculopontine
Nucleus in Progressive Supranuclear Palsy. ANN
NEUROL 18(1): 144.
Zweig, R.M., Hedreen, J.C., Jankel, W.R., Casanova, M.F.,
Whitehouse, P.J., & Price, D.L. (1988) Pathology
in Brainstem Regions of Individuals with Primary
Dystonia. NEUROLOGY 38: 702-706.
Zweig, R.M., Whitehouse, P.J., Casanova, M.F., Walker,
L.C., Jankel, W.R., & Price, D.L. (1987) Loss of
PedunculopontineNeuronsinIuegressiveSupranuclear
Palsy. ANN NEUROL 22: 18-25.
\IHIMilli\llilllilllllliNWâ€WillilllmlllllHl