Effect of ghrelin on the exitatory synaptic inputs to the magnocelluer neurosecretory neurons in the supraoptic nucleus of rat

Abstract

Ghrelin is an orexigenic peptide discovered from stomach as a ligand of orphan G protein coupled receptor and participates in the regulation of growth hormone release. Previous studies have demonstrated that ghrelin suppressed water intake and stimulated the secretion of arginine vasopressin (AVP) in rats. The magnocellular neurosecretory cells (MNCs) in the supraoptic nucleus (SON) terminate their axons in the posterior pituitary and secrete AVP into the systemic circulation. In the present study, we examined the effect of ghrelin on the excitatory synaptic inputs to the MNCs in in vitro rat brain slice preparations, using whole-cell patch-clamp recordings. Application of ghrelin (0.1-1 μM) caused a significant increase in the frequency of the spontaneous excitatory postsynaptic currents (sEPSCs) without affecting the amplitude in a dose-related manner. The increased frequency of sEPSCs persisted in the presence of tetrodtoxin (1 μM). Ghrelin-induced potentiation of sEPSCs was significantly suppressed by previous exposure to transient receptor potential vanilloid (TRPV) blocker, ruthenium red (10 μM). These results suggest that ghrelin participates in the regulation of synaptic inputs to the MNCs in the SON and TRPV family may be involved in peptidergic modulation of sEPSCs to the MNCs in the SON. [J Physiol Sci. 2008;58 Suppl:S130]