[Mechanism of action of zolmitriptan]

Zolmitriptan is a new serotonergic agonist with excellent oral bioavailability exhibiting a potent symptomatic antimigraine effect. Zolmitriptan is a selective agonist of 5-HT1B/D receptors. 5-HT1B receptors are concentrated in the wall of the cranial extracerebral arteries. 5-HT1D receptors are located on the trigeminal terminals which receive pain from the leptomeningeal vessels. Migraine pain has its origin on cranial vessels. In fact, during a migraine attack the trigeminovascular system, which is composed by the cranial vessels and its trigeminal terminals, is activated. The activation of this system induces both dilatation and aseptic inflammation of cranial vessels. Zolmitriptan blocks both vascular phenomena. Its agonist action upon the 5-HT1D receptor ends the aseptic inflammation by inhibiting the release of vasoactive peptides. The dilatation of meningeal vessels disappears due to the stimulation of zolmitriptan of 5-HT1B receptors. As this drug crosses the blood brain barrier, zolmitriptan has both peripheral and central actions over the espinal trigeminal nucleus, which is rich in 5-HT1B/D receptors. Thus, the mechanism of action of zolmitriptan is double. On the one hand, zolmitriptan acts peripherally inhibiting dilatation and inflammation of cranial vessels. On the other, zolmitriptan exhibits a central nociceptive action in the brainstem nuclei. This dual action of zolmitriptan on migraine pain is completed with its beneficial effects on nausea and vomiting, due to its binding to the nucleus of the tractus solitarius, the center for control of vomiting.