sensitivity and exaggerated adrenocortical stress reactivity have been documented in individuals at high risk for hypertension. The endogenous opioid system may play a role in these response alterations. We compared adrenocortical and nociceptive responses to opioid blockade
in hypertension-prone men and women.
Ninety-nine participants completed two sessions during which a placebo or 50 mg naltrexone
was administered using a double-blind, counterbalanced design. Participants rated their pain
and completed the McGill Pain
Questionnaire (MPQ) after three assessments of the nociceptive flexion reflex and after assessment of nociceptive pain
threshold and tolerance. Saliva samples were obtained throughout the sessions.
levels increased after pain
assessment after the ingestion of naltrexone
, but not after placebo, with the low-risk group exhibiting an earlier peak of cortisol
response. Participants reported greater pain
ratings and higher MPQ scores in the naltrexone
versus placebo condition, and these effects were more pronounced in women. Pain
threshold and tolerance were higher among high-risk men relative to low-risk men.
The results are consistent with the inhibitory effects of the endogenous opioids on cortisol
response and suggest an altered response timeline among hypertension-prone individuals. The results demonstrate that hypoalgesia may be a marker of hypertension risk
in men but not in women.
ACTH = adrenocorticotropin; BP = blood pressure; CPT = cold pressor test; CRF = corticotrophin-releasing factor; HPA = hypothalamic-pituitary-adrenocortical axis; MPQ = McGill Pain Questionnaire; NFR = nociceptive flexion reflex; EMG = electromyographic activity.