GRP mediates an inhibitory response of gut-related vagal motor neurons to PVN stimulation

We previously characterized neurons in the dorsal motor nucleus of the vagus (DMNV) that were modulated by electrical stimulation of the PVN and by gastrointestinal distention. Bombesin has been identified in a subset of PVN neurons projecting to the DMNV. It is currently unknown whether this neurotransmitter is involved in descending communication from PVN to DMNV neurons. In this study we determined whether the specific bombesin antagonist, N-acetyl-GRP(20-26), influenced (1) the basal firing rate of DMNV neurons and (2) the response to electrical current stimulation of the PVN. Our results indicate that N-acetyl-GRP(20-26), significantly attenuated the inhibitory response of DMNV neurons to PVN stimulation. These results provide a possible mechanism by which bombesin regulates gastrointestinal function, body temperature homeostasis, and feeding behaviors.