ENDOGENOUS OPIOIDS INHIBIT AMBULATORY BLOOD-PRESSURE DURING NATURALLY-OCCURRING STRESS

Objective: Laboratory experiments suggest that endogenous opioids inhi bit blood pressure responses during psychological stress. Moreover, th ere seem to be considerable individual differences in the efficacy of opioid blood pressure inhibition, and these differences may be involve d in the expression of risk for cardiovascular disease. To further eva luate the possible role of opioid mechanisms in cardiovascular control , the present study sought to document the effects of the long-lasting oral opioid antagonist naltrexone (ReVia, DuPont, Wilmington, DE) on ambulatory blood pressure responses during naturally occurring stress. Method: Thirty male volunteers participated in a laboratory stress st udy using naltrexone followed by ambulatory blood pressure monitoring during the subsequent 24-hour period. Within-subject analyses were per formed on ambulatory blood pressures under placebo and naltrexone cond itions. Results: Laboratory results indicate no significant group effe cts of naltrexone on blood pressure levels or reactivity. Ambulatory r esults indicate that during periods of low self-reported stress, no ef fect of opioid blockade was apparent. In contrast, during periods of h igh stress, opioid blockade increased ambulatory blood pressure. Concl usions: These findings suggest that naltrexone-sensitive opioid mechan isms inhibit ambulatory blood pressure responses during naturally occu rring stress.