Nociceptin, an endogenous ligand for the ORL1 receptor, has novel hypotensive activity 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 administration of nociceptin were investigated in the systemic vascular bed of the rat. Nociceptin induced dose-related decreases in systemic arterial pressure when injected in doses of 1-30 nmol/kg i.v. In terms of relative vasodepressor activity, nociceptin was approximately 10-fold more potent than the nitric oxide donor, DEA/NO, and 10-fold less potent than adrenomedullin. The duration of the vasodepressor response to nociceptin was shorter than adrenomedullin but longer than DEA/NO. These results show that nociceptin has significant vasodepressor activity in the rat.