Effect of antimigraine drugs on dural blood flows and resistances and the responses to trigeminal stimulation.

The effects of 2 antimigraine drugs sumatriptan and dihydroergotamine on dilatation of the middle meningeal artery elicited by stimulation of the trigeminal ganglion at the entry point of the first and second divisions was investigated in cats. Carotid and middle meningeal arterial blood flows and resistances were measured in 9 cats anesthetised with chloralose. Electrical stimulation of either trigeminal ganglion produced a frequency-dependent decrease in resistance of the carotid artery ipsilaterally and the middle meningeal artery bilaterally. The intravenous injection of sumatriptan increased carotid and meningeal vascular resistance, but this response was not prolonged. The intravenous injection of dihydroergotamine produced a larger and more prolonged vasoconstriction in these 2 beds than did sumatriptan. Dihydroergotamine, but not sumatriptan, blocked some components of the vascular response induced by stimulation of the trigeminal ganglion. Dihydroergotamine and sumatriptan have a different spectrum of activity on cranial circulatory beds and neither of them is able to reduce trigeminal-induced vasodilatation by blocking antidromic activation of trigeminal nerve fibres in cats at the doses used in these experiments.