Abstract
Ghrelin is an gut-brain peptide and its endocrine activities are mediated by GH secretagogue receptor (GHSR)-1a. Des-acyl ghrelin does not activate GHSR-1a and is devoid of endocrine activities. While the microinjection of ghrelin into rat nucleus tractus solitarius (NTS) elicited hypotensive effects, this was not the case upon injection into GHSR-expressing caudal ventrolateral medulla or rostral ventrolateral medulla. To make clear the reason of the discrepancy between receptor distribution and neuronal responses, we examined the cardiovascular response of rats microinjected with des-acyl ghrelin into NTS. Intra-NTS injection of des-acyl ghrelin significantly reduced mean arterial pressure and heart rate (80pmol, -13±2 mmHg and -34±6 bpm, p<0.05). The hypotensive and bradycardic activity evoked by des-acyl ghrelin was not significantly different from that of native ghrelin (80 pmol, -13±2 mmHg and -23±4 bpm). These results suggest that des-acyl ghrelin contribute to the regulation of cardiovascular control and that a receptor other than GHSR-1a exists in NTS. [Jpn J Physiol 55 Suppl:S205 (2005)]
