Mesenteric vascular-projecting neurons in the celiac and splanchnic ganglia project widely and contribute to the regulation of systemic arterial pressure

The splanchnic circulation holds one third of the body’s total blood volume, making it a critical target for the regulation of systemic hemodynamics by sympathetic neurons in prevertebral ganglia. Mesenteric arteries and veins are innervated by separate subpopulations of neurons in prevertebral ganglia. The studies described in this dissertation examine the effects of a selective lesion of artery-projecting and vein-projecting neurons on the hemodynamic response to activating sympathetic fibers innervating the splanchnic circulation. The presence of artery-projecting and vein-projecting neurons in both the celiac ganglion and the splanchnic ganglion was demonstrated with retrograde tracers that were applied to the surface of mesenteric arteries and veins. Nicotine application to the celiac ganglion elevated systemic arterial pressure 7.89 ± 1.53 mmHg via activation of postganglionic neurons in the celiac ganglion. Electrical stimulation of the greater splanchnic nerve elevated systemic arterial pressure 7.36 ± 1.07 mmHg via activation of postganglionic nerve fibers of neurons residing in the splanchnic ganglion. Application of a neurotoxin, saporin, conjugated to an antibody against dopamine beta hydroxylase (DH-sap) onto two small 7 mm segments of mesenteric arteries and veins ablated 94% of neurons in prevertebral ganglia. Three weeks after application of DH-sap to the mesenteric vasculature, electrical stimulation of the greater splanchnic nerve elicited a -1.59 ± 1.53 mmHg change in systemic arterial pressure. Lesions generated by DH-sap indicate prevertebral vascular-projecting neurons have wide fields of innervation and play a role in the regulation of systemic hemodynamics.