The trigemino-vascular system and migraine.

Neurogenic inflammation has been proposed as a possible pathogenetic mechanism for migraine and cluster headache. Antidromic stimulation of trigeminal fibers causes plasma protein extravasation, mast cell activation and degranulation, vacuolation and increase in endothelial vesicle number within post capillary venules in rat dura mater. The antimigraine drugs sumatriptan and dihydroergotamine block the development of plasma extravasation and ultrastructural changes, as well as plasma calcitonin gene-related peptide (CGRP) increase in the superior sagittal sinus following electrical trigeminal ganglion stimulation. Sumatriptan and dihydroergotamine bind with high affinity to the 5-HT1D/1B receptors, thus suggesting that their neurogenic antiinflammatory activity is mediated by activation of 5-HT autoreceptors present on sensory fibers innervating blood vessels in dura mater.