A study of the extrinsic innervation of the guinea pig pylorus with the horseradish peroxidase tracing technique.

The extrinsic innervation of the guinea pig pylorus was studied by the use of the horseradish peroxidase (HRP) tracing technique. Forty-eight hours after injection of HRP into the pyloric sphincter labeled neurons of varying sizes were found throughout the rostrocaudal extent of the dorsal motor nuclei of the vagus. No HRP positive cells were seen in the medial solitary nuclei or the ambiguous nuclei. Many HRP-positive cells were observed in the celiac-superior mesenteric ganglion complex. Occasional cells in the superior cervical and stellate ganglia were also labeled. When the vagal ganglia were analyzed many enzyme-containing cells were found in the nodose ganglia and some cells in the jugular ganglia. Furthermore, about 15-20% of the labeled afferent neurons were located in dorsal root ganglia on both sides, with the majority of cells at the T5--T10 levels. The results are discussed in relation to recent transmitter histochemical findings as well as possible functional roles of the neurons.