SPONTANEOUS AND 5HT-INDUCED CYCLIC CONTRACTIONS IN SUPERFICIAL TEMPORAL ARTERIES FROM CHRONIC AND EPISODIC CLUSTER HEADACHE PATIENTS

Superficial temporal arteries (STAs) are abnormally dilated in the pai nful side during cluster headache (CH) attacks. We have assessed the p ossible dysfunction of these arteries by comparing in vitro the reacti vity of STAs removed from the painful side of CH patients during a clu ster of attacks with that of STAs from patients free of CH. The respon ses to KCl and norepinephrine (NE) of both types of arteries were simi lar. Serotonin (5HT) induced a classical dose-dependent constriction i n arteries from non-CH patients, but systematically triggered rhythmic contractions in arteries from episodic CH patients. Arteries from chr onic CH patients also showed spontaneous rhythmic contractions. In bot h cases, this activity was stopped by calcitonin gene-related peptide (CGRP) but, even in the presence of CGRP, it could be restored by low concentrations of 5HT. Thus, 5HT, unlike NA, can trigger rythmic activ ity in STAs of CH patients and may play a major role in CH through abn ormal smooth muscle cell reactivity.