Nerve pathways in celiac plexus of the guinea pig.

In vitro preparations consisted of the right and left celiac, superior mesenteric and inferior mesenteric ganglia with attached extrinsic nerves, vasculature, mesentery, and colon. There were no systematic differences in membrane electrical properties (recorded intracellularly) between neurons in the different ganglia. Stimulation of associated nerve trunks produced graded synaptic responses in plexus neurons. Presynaptic fibers were found in splanchnic and mesenteric nerves. Input from celiac nerves dominated in the celiac galglia; input from the intermesenteric fibers dominated in the superior mesenteric ganglion. When the ganglia were attached to the entire colon, 33% of the neurons in the celiac and 54% in the superior mesenteric ganglion received a continuous excitatory synaptic input that was increased by distending the colon. This input was interrupted irreversibly by transsection of the mesenteric nerves. These results show that both the afferent and efferent pathways of a peripheral reflex arc are located in the mesenteric nerves and may mediate visceral reflexes between mechanoreceptors and sympathetic neurons in the colon.