Nociceptin, an endogenous ligand for the ORL1 receptor, decreases cardiac output and total peripheral resistance in the rat

The heptadecapeptide nociceptin, also known as Orphanin FQ, is a newly discovered endogenous ligand for the opioid-like G-protein coupled receptor, ORL1. In the present study, responses to intravenous injections of nociceptin were investigated in the systemic vascular bed of the rat. Nociceptin induced dose-related decreases in systemic arterial pressure and total peripheral resistance when injected in doses of 1-30 nmol/kg IV. Nociceptin decreased heart rate and in doses of 10 and 30 nmol/kg IV, significantly decreased cardiac output. In terms of relative vasodilator activity, nociceptin was approximately 10-fold less potent than the beta adrenergic receptor agonist isoproterenol. These data show that nociceptin has novel vasodilator activity in the systemic vascular bed of the rat. (C) 1997 Elsevier Science Inc.