Opioid dysfunction and risk for hypertension: naloxone and blood pressure responses during different types of stress

Opioidergic inhibition of sympathetic nervous system responses may be deficient in persons at risk for essential hypertension (McCubbin et al: Hypertension 7:808, 1985). The opiate antagonist naloxone increases blood pressure responses during psychological stress in young adults with low causal blood pressure, but has no pressor effect in subjects with high casual blood pressure. The purpose of the present study was to determine the role of altered baroreflex function in the abnormal pressor effect of naloxone in persons at risk for hypertension development. We tested this by comparison of the effects of naloxone on responses to psychological stress with responses to orthostatic stress in persons with high and low casual blood pressure. The results suggest that abnormal opioidergic control of systolic blood pressure responses to psychological stress is not likely a result of altered baroreflex function. Persons at risk for hypertension show evidence of an opioid peptide lesion that can probably be localized either at the adrenal medullae or at levels of central autonomic control that are parallel with or rostral to baroreflex circuits.