DECREASES IN SYSTEMIC ARTERIAL AND HINDQUARTERS PERFUSION-PRESSURE INRESPONSE TO NOCICEPTIN ARE NOT INHIBITED BY NALOXONE IN THE RAT

Nociceptin, the endogenous ligand for the ORL1 receptor, has been show n to decrease systemic arterial and hindquarters perfusion pressures i n the rat. The present study was undertaken to determine if decreases in systemic arterial and hindquarters perfusion pressures, in response to nociceptin, are mediated by a naloxone-sensitive mechanism. Inject ions of nociceptin decreased systemic arterial and hindquarters perfus ion pressures in a dose-related manner. The decreases in systemic arte rial and hindquarters perfusion pressure in response to nociceptin wer e not altered by the administration of naloxone in a dose of 2 mg/kg I V. Met-enkephalin decreased systemic arterial and hindquarters perfusi on pressures and responses to the opioid receptor agonist were signifi cantly reduced by naloxone, whereas decreases in systemic arterial pre ssure in response to the nitric oxide donor, DEA/NO, were not altered. The results of the present study show that decreases in systemic arte rial and hindquarters perfusion pressure in response to nociceptin are not mediated by a naloxone-sensitive mechanism in the rat. (C) 1997 E lsevier Science Inc.