Reflex pathways in the abdominal prevertebral ganglia: evidence for a colo‐colonic inhibitory reflex.

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Abstract
In vitro experiments were performed on preparations consisting of prevertebral ganglia attached to the entire colon of guinea-pigs. The colon was divided into an orad and a caudad segment and intraluminal pressure was recorded from the terminal end of each segment. Intracellular recordings were simultaneously obtained from neurons in the celiac plexus. The source of mechanosensory input from the colon paralleled the responses to mesenteric nerve stimulation. Section of the mesenteric nerve that contributed the strongest synaptic input to a neuron eliminated most of the mechanosensory input to that neuron. The origin of the mechanosensory input to some neurons was localized as coming from either the orad or caudad segment of the colon. In the celiac ganglia 68% of the neurons tested responded primarily to orad distension and 37% to caudad distension. In the superior mesenteric ganglion 57% responded to orad distension and 43% to caudad distension. Repetitive stimulation of the mesenteric nerve trunks arising from the prevertebral ganglia inhibited contractions differentially in the orad and caudad segments. The inferior celiac nerves inhibited primarily the orad segments of colon and the lumbar colonic nerves inhibited primarily the caudad segments of colon. Stimulation of the superior celiac nerves did not alter the motility of either segment. When 1 of the colonic segments was distended, contractions in the other colonic segment were inhibited in 71% of the distensions. This inhibition operated in both directions: either orad inhibiting caudad or vice versa. Cutting the intermesenteric nerve which communicates between the orad and caudad prevertebral ganglia eliminated the inhibitory reflex. A colo-colonic inhibitory reflex may be mediated through pathways in the prevertebral ganglia.