Use of horseradish peroxidase to identify hindbrain sites that influence gastric motility in the cat.

To identify hindbrain sites that influence gastric motility, we administered multiple injections of horseradish peroxidase into the anterior surface of the antrum near the lesser curvature in 3 cats, and used light microscopy to identify horseradish peroxidase-positive neurons in the hindbrain. Retrogradely labeled neurons were found evenly distributed on both sides in the dorsal motor nucleus of the vagus. Labeling extended from 2.5 mm rostral to 2.0 mm caudal to the obex. Labeled neurons were not localized to a specific region of the dorsal motor nucleus of the vagus: no labeling was observed in the nucleus ambiguus or in the nuclei of the solitary tract. Electrical stimulation of the dorsal motor nucleus of the vagus in the area with the greatest number of labeled cell bodies was performed in 4 cats while monitoring antral motility, arterial pressure, and heart rate. Stimulation elicited pronounced antral contractions but no changes in arterial pressure or heart rate. These data demonstrate that the retrograde neuronal tracing technique permits localization of central nervous system sites that specifically influence gastric function.