Headache patients: different responses induced by naloxone during work-test.

The responses to work-test in ischemia (tourniquet technique), before and after I.V. injection of naloxone (2 mg) or saline, were investigated in healthy volunteers and patients suffering from various types of headache. The patients were examined during both painful and painless periods. We found that only the subjects suffering from migraine showed a significantly shortened pain tolerance at work-test in ischemia, after injection of naloxone, and only during painful periods. Psychogenic headache patients and migraine patients in painless periods showed responses during work-test similar to those in healthy volunteers, even after injection of naloxone. We believe that hyperalgesic effect of naloxone is due to involvement of beta-endorphin systems only during organic pain.