Platelet Met-Enkephalin Immunoreactivity and 5–Hydroxytryptamine Concentrations in Migraine Patients: Effects of 5–Hydroxytryptophan, Amitriptyline and Chlorimipramine Treatment

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Abstract
In thirty patients with common migraine the platelet concentrations of met-enkephalin immunoreactivity (ME) (76 9 pg/mg protein) were similar to those in 23 healthy volunteers (77 5), suggesting that there is no alteration in the ME pool in this biochemical compartment in migraine. Chronic treatment (4 weeks) with drugs that interfere with 5–hydroxytryptamine (5–HT) synthesis or uptake induced the expected changes in platelet 5–HT levels, i.e. a rise following administration of the 5–HT precursor 5–hydroxytryptophan (daily dose: 300–500 mg, n = 9) and a decrease after amine uptake inhibition by amitryptyline (30–75 mg, n = 7) and even more by chlorimipramine (30–50 mg, n = 9). Platelet ME concentrations rose by up to ∼90% over the basal values after either 5–hydroxytryptophan (significantly from week 2) or amitriptyline (at week 2) and were unchanged after chlorimipramine, indicating that 5–HT and ME concentrations in platelets can vary independently. The high platelet ME levels following 5–hydroxytryptophan and amitriptyline cannot be explained at present. They might be due either to increased ME synthesis, possibly in the megakaryocyte, or to decreased utilization by platelets or both.