Serotonin metabolism in cluster headache

Despite some evidence of the involvement of the serotonergic system in cluster headache (CH) pathophysiology, the serotonin (5HT) metabolism has so far been poorly studied. The aim of this study was to investigate plasma and platelet levels of 5HT and 5-hydroxyindoleacetic acid (5HIAA) in CH patients in the active period of the disease. Nineteen CH sufferers and 17 sex- and age-matched healthy controls were studied. CH patients showed significantly higher plasma levels of 5HT and 5HIAA compared to controls (5HT: 5.7+/-6.1 ng/ml vs 0.2+/-0.2 ng/ml; p=0.02; 5HIAA: 34.7+/-46.1 ng/ml vs 0.6+/-0.7 ng/ml; p=0.004). In platelet 5HT levels were slightly reduced in CH patients in comparison with those of control subjects (662.4+/-522.3 ng/10(-8) platelets vs 832.4+/-587.9 ng/10(-8) platelets; n.s.) and 5HIAA levels resulted significantly lower in CH sufferers than in control subjects (3.2+/-2.6 ng/10(-8) platelets vs 6.7+/-4.8 ng/10(-8) platelets; p=0.04). Our data suggest that CH is characterized by an increase of plasma serotonergic metabolism that could reflect an involvement of the central serotonergic system in the pathogenesis of CH.