Platelets in migraine

Modification in platelet activation and aggregation has been demonstrated in migraine patients both during and between attacks. A different pattern in the secretion of platelet products has also been observed in patients affected by migraine compared with controls. The most important variation concerns a hyposecretion of dense body products. Platelets share structural and functional analogies with monoaminergic neurons, in particular serotoninergic neurons, and have been used as a peripheral model to study monaminergic function in migraine patients. A reduced turnover of serotonin has been shown in migraine patients in the interictal period, whereas a reduced content of this monoamine was detected in patients with chronic daily headache (CDH), particularly in those with analgesic abuse. Nitric oxide metabolism was also studied in platelets of migraine patients between and during attacks. An increased activity of nitric oxide synthase (NOS), which was more accentuated during attacks, was found in these patients compared to healthy individuals. The increase in platelet NOS activity was also confirmed in CDH patients in association with a reduction of serotonin content and increased calcium levels. Variations in aggregation to different agents and secretion may not, at the moment, be indicative of similar changes in cerebral circulation of migraine patients. Its occurrence should be confirmed in samples of jugular venous blood during attacks to establish a definite link with migraine pathogenesis. Moreover changes in serotonin and NO metabolism observed in platelets of migraine patients may only indirectly suggest similar modifications in the neuronal pathways involved in inducing and maintaining head pain in migraineurs.