Effect of nociceptin/orphanin FQ on venous tone in conscious rats.
Nociceptin (orphanin FQ) is an endogenous agonist for the opioid receptor-like1 (ORL1) receptor. We investigated the effects of nociceptin on mean circulatory filling pressure, an index of venous tone. The effects of nociceptin (10, 30 nmol/kg, i.v.) and the vehicle (0.9% NaCl) on mean arterial pressure, heart rate and mean circulatory filling pressure were examined in two groups each of conscious rats: rats with, or without, ganglionic blockade through pretreatment with mecamylamine (1 mg/kg, i.v.) and noradrenaline (2 microg/kg min, i.v.). In the unblocked rats, both doses of nociceptin decreased mean arterial pressure and heart rate, and the high dose also decreased mean circulatory filling pressure. In the ganglionic-blocked rats, nociceptin did not alter heart rate but caused greater reductions of mean arterial pressure and mean circulatory filling pressure. The vehicle had no effects in any group. Therefore, nociceptin is a depressor agent with prominent direct venodilator and bradycardic action.
Abdelrahman
Aly M
AM
Department of Pharmacology and Therapeutics, Faculty of Medicine, The University of British Columbia, 2176 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3.
Pang
Catherine C Y
CC
D000818:Animals; D001775:Blood Circulation / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D003243:Consciousness; D005730:Ganglionic Blockers / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D008464:Mecamylamine / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D018847:Opioid Peptides / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*; D014690:Venous Pressure / Q000187:drug effects; D000097629:Nociceptin
D005730:Ganglionic Blockers; D008464:Mecamylamine; D009638:Norepinephrine; D018847:Opioid Peptides; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D000097629:Nociceptin