Lateral hypothalamus modulates gut-sensitive neurons in the dorsal vagal complex

The lateral hypothalamus (LH) regulates metabolic, behavioral and autonomic functions. The influence of the LH on gastrointestinal function and feeding behavior may be mediated by the dorsal vagal complex (DVC). In the present experiment, we used tract tracing and neurophysiologic techniques to evaluate the interrelationship between the LH and DVC. Using the tracer DiI, we demonstrated that the LH projects to both the nucleus of the solitary tract (NST) and the dorsal motor nucleus of the vagus (DMNV). We determined the effects of electrical stimulation of the LH and/or distention of the gastrointestinal tract on the firing rates of 107 DMNV neurons and 68 NST neurons. As previously reported, the majority of the DMNV neurons were inhibited and the majority of the NST neurons were excited by gastrointestinal distention. Electrical stimulation of the LH significantly changed the spontaneous activities of 71% of the DMNV neurons (46 excited and 30 inhibited). Of the 68 NST neurons characterized, 25 neurons were inhibited and 8 were excited by LH stimulation. In a separate experiment, we characterized the effects of both electrical and chemical stimulation of the LH on 36 DMNV and 14 NST neurons. Glutamate (0.8 nM) induced similar responses in the DVC neurons as electrical stimulation of the LH. The results indicate that the LH influences the electrical activity of DVC neurons. This effect may be the mechanism by which the LH modulates gastrointestinal function and feeding behavior.