Ghrelin in the lateral parabrachial nucleus influences the excitability of glucosensing neurons, increases food intake and body weight

Ghrelin plays a pivotal role in the regulation of food intake, body weight and energy metabolism. However, these effects of ghrelin in the lateral parabrachial nucleus (LPBN) are unexplored. C57BL/6J mice and GHSR−/− mice were implanted with cannula above the right LPBN and ghrelin was microinjected via the cannula to investigate effect of ghrelin in the LPBN. In vivo electrophysiological technique was used to record LPBN glucose-sensitive neurons to explore potential udnderlying mechanisms. Microinjection of ghrelin in LPBN significantly increased food intake in the first 3 h, while such effect was blocked by [D-Lys3]-GHRP-6 and abolished in GHSR−/− mice. LPBN ghrelin microinjection also significantly increased the firing rate of glucose-excited (GE) neurons and decreased the firing rate of glucose-inhibited (GI) neurons. Additionally, LPBN ghrelin microinjection also significantly increased c-fos expression. Chronic ghrelin administration in the LPBN resulted in significantly increased body weight gain. Meanwhile, no significant changes were observed in both mRNA and protein expression levels of UCP-1 in BAT. These results demonstrated that microinjection of ghrelin in LPBN could increase food intake through the interaction with growth hormone secretagogue receptor (GHSR) in C57BL/6J mice, and its chronic administration could also increase body weight gain. These effects might be associated with altered firing rate in the GE and GI neurons.