Naloxone decreases the inhibitory effect of alprazolam on the release of adrenocorticotropin/cortisol induced by physical exercise in man

AIMS To establish the possible involvement of alprazolam (ALP) and/or opiates in the mechanism underlying the ACTH/cortisol response to physical exercise. METHODS Tests were carried out under basal conditions (exercise control test), exercise plus ALP (50 mu g at time -90 min), naloxone (10 mg at time 0) or ALP plus naloxone. Plasma ACTH and serum cortisol concentrations were evaluated in blood samples taken before, during and after the bicycle ergometer tests. RESULTS ACTH and cortisol concentrations rose significantly after physical exercise. Maximum peak at time 15 min (P < 0.01 vs. baseline) for ACTH and at time 30 min (P < 0.01 vs. baseline) for cortisol. In the presence of naloxone, the ACTH and cortisol responses were significantly increased (maximum peak at time 20 min, P < 0.02 vs. control test for ACTH, and at time 30 min (P < 0.01 vs. baseline) for cortisol) whereas they were abolished by ALP. When ALP and naloxone were given together, the inhibitory effect of ALP was partial. CONCLUSIONS These data demonstrate an inhibitory effect of ALP in the regulation of the ACTH/cortisol response to physical exercise in man and suggest that GABAergic receptor activating benzodiazepines and opioids interact in the neuroendocrine secretion of ACTH/cortisol.