THI Jouanc. or PHARMACOLOGY AND EXPERIMENTAL TRERAPEUTIC8 CopyrightO issa by The American Society for Pharmacology and Experimental Therapeutics Central Opiold Receptors and Baroreflex Control of Sympathetic and Cardiovascular Function

The effect of central opioid receptor activation and blockade on arterlel baroreflex regulation of cardiovascular function was stud-led. Baroreceptor reflexes were ted in urethane-anesthetized rats by graded electrical stimulation of the aortic nerve while mean arterial pressure, heart rate and sympathetic nerve activity were recorded simultaneously. Barorefiex response curves were constructed after intradstemal administration of saline vehicle, after kitradstemai infusion of the relatively selective mu and delta opiold receptor agonists D-Ala2-MePhe4-GIy(ol) enkephalin (DAGO), or AIa2--Leu enkephalin (DADLE) respectively, and again after i.v. naloxone. Reflex reductions in mean arterial pressure, heart rate and sympathetic nerve activity elicited by aortic nerve stimulation were attenuated in a dose-related fashion by intracistemal DAGO. Opiold effects were greatest at lo