Identification of Rat Inferior Mesenteric Ganglion Neurons Differentially Innervating Splanchnic Veins and Arteries

Abstract

The splanchnic circulation contains approximately 70% of the total body blood volume and the majority of this resides in the splanchnic veins. Splanchnic vascular resistance and capacitance can be differentially regulated by the sympathetic nervous system and in some species this is associated with separate arterial and venous innervation. We examined the innervation of mesenteric arteries and veins by neurons in the inferior mesenteric ganglion (IMG). An ex vivo preparation of the IMG attached to mesenteric vessels was placed in organotypic culture. After removing the endothelium fluorescent beads of different colors were injected separately into the arteries and veins of the mesentery. The preparation was cultured for 7 days. After 5 days a solution of fast blue was instilled around the ganglion to mark sympathetic ganglion neuron cell bodies. In 3 ganglia 90% of all neurons were filled when a single tracer was placed in both vessels. Of the neurons that innervate blood vessels 95% of them innervated either artery or vein and 5% innervated both artery and vein. These studies suggest that a majority of neurons in the IMG regulate mesenteric vascular tone and that there are separate neuronal pathways innervating artery or vein. Support:HL70687.