Medullary parasympathetic projections innervate specific sites in the feline stomach

The purpose of our study was to determine the site of origin of vagal neurons that innervate specific parts of the stomach (the fundus, corpus, and antrum/pylorus). This was done by injecting the retrograde fluorescent tracer Fast Blue into these parts of the cat stomach and examining the hindbrain for cells labeled with retrograde tracer. We found that vagal preganglionic innervation to the stomach originates from two medullary nuclei, namely, the dorsal motor nucleus of the vagus (bilateral) and the nucleus retroambiguus (left). All parts of the stomach receive innervation from the dorsal motor nucleus of the vagus (primarily from the area ranging from 0.5 to 1.8 mm rostral to the obex), but only the fundus and corpus receive innervation from the nucleus retroambiguus. Injection of tracer into the fundus labeled cells within the lateral half of the dorsal motor nucleus of the vagus and injection of tracer into the antrum/pylorus labeled cells within the medial portion. Finally, injection of tracer into the corpus labeled cells throughout the mediolateral axis of the dorsal motor nucleus of the vagus. The finding of a columnar organization of the dorsal motor nucleus of the vagus implies some type of functional organization of gastrointestinal control. The fact that vagal inputs to the stomach arise from the dorsal motor nucleus of the vagus and nucleus retroambiguus suggests a separation of vagal pathways controlling different gastric functions (e.g., pacemaker activity, motility, and secretion).