Is the 5-HT(7) receptor involved in the pathogenesis and prophylactic treatment of migraine?

The mechanisms underlying the pathogenesis of migraine and their possible association with serotonin (5-hydroxytryptamine; 5-HT) have not yet been elucidated. One of the major obstacles in achieving this goal is the lack of information on the mechanisms by which the monoamine could possibly trigger and/or modulate the basic pathophysiological features of the condition, that is, cranial vasodilatation and neurogenic inflammation. This information should provide a useful theoretical framework to insight the nature of the postulated fundamental triggering mechanism in the brain that ultimately results in head pain. Novel avenues for research and drug development may be envisaged upon the recent observations showing that 5-HT is actually able to produce vasodilatation of intra- and extra-cranial blood vessels through a mechanism pharmacologically resembling the 5-HT(7) receptor type, and that the messenger RNA (mRNA) encoding for this receptor is highly expressed in cranial vessels. Other lines of evidence have suggested that the 5-HT(7) receptor may play an excitatory role in neuronal systems and that it may be involved in hyperalgesic pain and neurogenic inflammation. On the basis of these observations, it is proposed that the 5-HT(7) receptor may well represent a link between the abnormal phenomena of 5-HT processing and neurotransmission that are observed in migraine patients, and the vascular and neurogenic alterations that account for migraine headache. This view is supported by the fact that most of the migraine prophylactic 5-HT receptor antagonists display relatively high affinity for the 5-HT(7) receptor, which significantly correlates with their pharmaceutically active oral doses.