INTRACEREBROVENTRICULAR GROWTH-HORMONE-RELEASING PEPTIDE-6 STIMULATESEATING WITHOUT AFFECTING PLASMA GROWTH-HORMONE RESPONSES IN RATS

The purpose of this study was to determine the effect of intracerebrov entricular (icy) injections of a synthetic, opioid-related hexapeptide , growth-hormone-releasing peptide-6 (GHRP-6), on stimulation of eatin g by rats and to correlate this aspect of feeding behavior with the pe ripheral plasma growth hormone (GH) response to the administered pepti de. GHRP-6 dissolved in 5 mu L of saline was injected into the lateral ventricles of sated, adult, male, Sprague-Dawley rats in doses from 0 pmol (saline only) to 1000 pmol. For 1 hour after injection, the occu rrence of eating was noted, and specimens of arterial blood were colle cted at 0, 15, 30, and 60 minutes. The plasma was assayed for GH. A ne arly linear, statistically significant (p<0.01) dose-response relation ship between the dose of GHRP-6 and the incidence of eating was noted. The mean change from baseline of plasma GH during the 60 minutes afte r injection was not dose-related (p>0.2, p>0.1, and p>0.1 at 15, 30, a nd 60 minutes, respectively). We conclude that GHRP-6 given intracereb roventricularly to sated, adult, male, Sprague-Dawley rats stimulates eating and suggest that it does so by some mechanism that is independe nt of its GH-releasing property.