Prolongation of the postprandial intermeal interval by gastrin-releasing peptide1-27 in spontaneously feeding rats.

The present study explored the effects of intravenous gastrin-releasing peptide1-27 (GRP) on the postprandial intermeal interval (IMI) when delivered shortly after termination of the first spontaneous nocturnal meal in freely-feeding rats. Undisturbed, ad lib-fed (milk), male rats (n = 11) with chronic inferior vena caval catheters were infused with saline and each of three doses (2.5, 5 and 10 nmol/kg) of GRP in counterbalanced order. Infusions began 5 min after the last lick of the first nocturnal meal and continued for 2 min (60 microliters/min), with delivery of the peptide during the first minute. Infusions and recording of meal data (licks) were fully automated and computer-controlled. Both 5 and 10 nmol/kg of GRP significantly prolonged the IMI by over 50%, but had no effect on the size of the following meal. This is the first demonstration of the prolongation of the IMI by intravenous GRP in undisturbed, freely-feeding rats, and the result suggests that endogenous GRP may play a role in the control of the postprandial intermeal interval.