Ghrelin fibers from lateral hypothalamus project to nucleus tractus solitaries and are involved in gastric motility regulation in cisplatin-treated rats

Abstract

Ghrelin can alleviate cancer chemotherapy-induced dyspepsia in rodents, though the neural mechanisms involved are not known. Therefore, ghrelin projections from the lateral hypothalamus (LH) and its involvement in the regulation of gastric motility in cisplatin-treated rats were investigated with a multi-disciplined approach. Retrograde tracing combined with fluoro-immunohistochemical staining were used to investigate ghrelin fiber projections arising from LH and projecting to nucleus tractus solitaries (NTS). Results revealed that ghrelin fibers originating in LH project to NTS. Expression of ghrelin and its receptor growth hormone secretagogue receptor (GHS-R1a) in LH and NTS were detected by Western Blot. 2days after cisplatin dosing, expression of ghrelin in LH decreased while GHS-R1a in both LH and NTS increased. In electrophysiological experiments, the effects of N-methyl-d-aspartate (NMDA) microinjection in LH on neuronal discharge of gastric distension-responsive neurons in NTS and gastric motility were assessed. NMDA in LH excited most of ghrelin-responsive gastric distension (GD)-sensitive neurons in NTS and promoted gastric motility. This effect was partially blocked by ghrelin antibody in NTS. Furthermore, the excitatory effects of NMDA in cisplatin-treated rats were weaker than those in saline-treated rats. Behaviorally, cisplatin induced a significant increase of kaolin consumption and decrease of food intake. These studies reveal a decreased expression of ghrelin in LH and up-regulation of GHS-R1a in LH and NTS, which are involved in the regulation of GD neuronal discharge in NTS and gastric motility.