THE ORIGIN AND DISTRIBUTION OF NEURONS WITH PROJECTIONS PASSING THROUGH THE INFERIOR MESENTERIC GANGLION OF THE GUINEA-PIG

Retrograde tracing with the fluorescent dye, Fast Blue, was used to ex amine the origin and distribution of neurons whose axons project throu gh the inferior mesenteric ganglion (IMG) of the guinea-pig. These stu dies were performed by applying the tracer to (a) the rostral cut-end of the hypogastric nerves and (b) the caudal cut-end of the intermesen teric nerve (IMN). After application of tracer to the hypogastric nerv es retrogradely labelled cell profiles were observed in the IMG and th e superior mesenteric ganglion (SMG). The number of labelled cell prof iles in the SMG was consistently about 15% of the number in the IMG. I n only one of seven animals tested were labelled cells seen in the wal l of the colon. Application of tracer to the IMN labelled cells in the IMG and in the wall of the colon. The distribution of the labelled en teric neurons was skewed towards the anal end of the colon. These resu lts confirm that postganglionic sympathetic neurons in the SMG project axons through the guinea-pig IMG and describe the colonic distributio n of enteric neurons that project through the IMG and into the IMN.