Abstract
Ghrelin is a gut-brain peptide, which was identified from the rat stomach as the first endogenous ligand for the growth-hormone secretagogue receptors. Ghrelin has been known to increase food intake and body weight by intravenous (IV) injection and intracerebroventricular (ICV) administration. In addition, ghrelin also elicits a decrease in mean arterial pressure (MAP) and heart rate (HR) by IV and ICV administration. However, little is known about central effects of ghrelin on cardiovascular regulation. In order to investigate whether ghrelin has effect on cardiovascular actions in the restricted region of the CNS, we examined cardiovascular response to microinjection of ghrelin into the nucleus tractus solitarius (NTS) of rat. After administration of vehicle solution into the NTS, no significant changes in MAP (-3 ± 0 mmHg) and HR (-4 ± 3 beats/min) were observed. In contrast, intra-NTS injection of 40 pmol/100 nl of ghrelin reduced 12 ± 3 mmHg of MAP and 22 ± 4 beats/min of HR, respectively (n=5). These reductions were significant (p<0.05) against the changes in vehicle control. The intra-NTS injection of ghrelin evoked hypotension and bradycardic responses. These results suggest that ghrelin may contribute to regulation of the cardiovascular control. [Jpn J Physiol 54 Suppl:S216 (2004)]
