Effect of naloxone on the hormone response to CRF in normal man

Ovine corticotropin releasing factor (CRF) was administered to six normal men and the plasma ACTH and cortisol responses compared with those following the same dose of CRF (200 micrograms) plus the opiate receptor blocker naloxone (20mg). The addition of naloxone was associated with a significant increase in plasma ACTH, cortisol and aldosterone responses. No change was observed in peripheral plasma levels of epinephrine, norepinephrine, arginine vasopressin, angiotensin II or renin activity in response to CRF plus naloxone. It is concluded that endogenous opioid peptides may inhibit the ACTH response to CRF. However the addition of naloxone does not increase the ACTH response to CRF sufficiently to constitute a useful test of pituitary function.