The overall objectives of this proposal are to delineate the role of nerve pathways involving the abdominal prevertebral ganglia in controlling mesenteric blood vessels and to determine the organization of the abdominal nerve-vessel system. Experiments have been designed to determine: 1) the organization of the sympathetic outflow to branches of the inferior mesenteric and celiac arteries and the inferior mesenteric and portal veins; 2) whether or not there are afferent pathways from the mesenteric vasculature to neurons in the prevertebral ganglia; 3) whether there are reflexes between different vascular regions in the mesentery and/or between the mesenteric vasculature and the musculature of the gastrointestinal tract; 4) the nature of neuroeffector transmission from the postganlionic fibers of the prevertebral ganglia to mesenteric vascular smooth muscle cells. In vitro preparations from guinea pigs and cats that consist of the celiac plexus and inferior mesenteric ganglion attached to selected abdominal organs will be used. Electrophysiologic techniques will be used to determine the intracellular responses of prevertebral ganglia neurons and vascular smooth muscle cells. Pressure recording techniques will be used to distend and record the contractile responses of mesenteric vascular and gastrointestinal segments.