Vagal regulation of gastric function involves thyrotropin-releasing hormone in the medullary raphe nuclei and dorsal vagal complex.

There is convincing electrophysiological, neuroanatomical and functional data in support of an excitatory action of thyrotropin-releasing hormone (TRH) on the dorsal motor nucleus of the vagus neurons leading to stimulation of vagal outflow to the stomach and to a vagal cholinergic-dependent stimulation of gastric secretory and motor function and alterations of mucosal integrity in rats and cats. The raphe pallidus and obscurus have become important medullary nuclei regulating vagal function through their TRH and serotonin projections to the dorsal vagal complex. However, still little is known about the transmitters and conditions which influence the activity of these TRH-containing medullary raphe neurons. Existing knowledge points out a possible physiological role of TRH in mediating vagal reflex and the cephalic phase of digestion.