Serotonin metabolism in migraine.

To investigate systemic serotonin (5-HT) metabolism in migraine, we determined platelet and platelet-free plasma concentrations of 5-HT, its precursors tryptophan and 5-hydroxytryptophan, and its main metabolite 5-hydroxyindoleacetic acid (5-HIAA), as well as the activities of the platelet enzymes monoamine oxidase and phenolsulfotransferase in classic and common migraineurs. Between attacks, migraineurs had lower plasma 5-HT and higher 5-HIAA levels than did healthy controls and patients with tension headache. During migraine attacks, plasma 5-HT levels were substantially higher than during attack-free periods, while 5-HIAA concentrations and platelet enzyme activities were lower. Platelet 5-HT was reduced only during common, but not classic, migraine attacks. We hypothesize that systemic 5-HT metabolism is enhanced in migraineurs during headache-free periods and transiently decreases during attacks, presumably due to a fall in enzymatic degradation. Furthermore, platelet behavior differs during migraine attacks with and without aura, and release of platelet 5-HT cannot (exclusively) be held accountable for the rise of plasma 5-HT during migraine attacks.