Increased reactivity to a met-enkephalin analogue in the control of autonomic responses in migraine patients.

The effects of naloxone and a met-enkephalin analogue on head pain, vascular responses, and autonomic-associated symptoms were studied in 24 migraine patients, 12 patients suffering from tension-type headache, and 24 normal subjects in whom headache was induced by intravenous injections of increasing doses of histamine (histamine test). A hypersensitivity to histamine was found in migraine patients. Naloxone slightly increased the intensity of pain in migraine and tension-type headache sufferers. The met-enkephalin analogue did not affect the intensity of pain in migraine patients, tension-type headache patients, and normal subjects, but it reduced the intensity and duration of facial flushing (p less than 0.001) and the autonomic symptoms (p less than 0.001) in migraine patients when the pretreatment was not given shortly before histamine. In migraine patients, there seems to be an increased reactivity (receptor supersensitivity?) to the met-enkephalin analogue at the level of systems that inhibit facial vasodilatation and autonomic symptoms.