Morphine abstinence and serotonin supersensitivity in man: analogies with the mechanism of migraine?

Supersensitivity to serotonin during migraine attack has been previously observed. Since the attack has been attributed to a critical lowering of morphine-like factors, we can expect serotonin supersensitivity during morphine abstinence. Slight signs of morphine abstinence have also been induced in volunteers after mild (10-24 mg/day) and limited (3 days) treatment. To evaluate the sensitivity to serotonin, dopamine, noradrenaline, and tyramine in the smooth muscle of the hand dorsal vein, in vivo, the computerized venotest was applied before, during, and 24 h after withdrawal of morphine. Venous sensitivity to serotonin and dopamine (but not to noradrenaline and tyramine) increased 10- to 20-fold after morphine withdrawal. Venous monoamine supersensitivity in morphine abstinence, similar to that observed during migraine attacks, could be indirect evidence of an analogous mechanism in both conditions.