The Journal of pharmacology and experimental therapeutics
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J. Pharmacol. Exp. Ther. · May 1986
Central opioid receptors and baroreflex control of sympathetic and cardiovascular function.
The effect of central opioid receptor activation and blockade on arterial baroreflex regulation of cardiovascular function was studied. Baroreceptor reflexes were elicited 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. Baroreflex response curves were constructed after intracisternal administration of saline vehicle, after intracisternal infusion of the relatively selective mu and delta opioid receptor agonists D-Ala2-MePhe4-Gly(ol)5 enkephalin (DAGO), or D-Ala2-D-Leu5 enkephalin (DADLE) respectively, and again after i.v. naloxone. ⋯ These results suggest that the effect of DADLE on baroreflexes was mediated by activation of mu rather than delta opioid receptors. No evidence was obtained to suggest a role for endogenous opioid modulation of baroreflexes because i.v. naloxone was without effect. These results demonstrate that activation of central mu opioid receptors significantly impairs baroreflex control of sympathetic and cardiovascular function.