REACTIONS OF THE MIDDLE MENINGEAL ARTERY OF THE CAT TO NEURAL AND HUMORAL STIMULATION

The physiology and pharmacology of the middle meningeal artery was inv estigated in cats in order to determine whether this artery was subjec t to normal neural and humoral control mechanisms. Carotid and middle meningeal arterial blood flows and resistances were measured in 16 cat s anaesthetized with chloralose. The cervical sympathetic nerves were stimulated electrically. Stimulation of the cervical sympathetic nerve s pre-ganglionically reduced blood now in the middle meningeal artery by producing vasoconstriction in its resistance bed. The vasoconstrict ion was mediated via catecholamine-containing nerves, as it was abolis hed by prior intravenous administration of bretylium. Intravenous inje ctions of noradrenaline or adrenaline also produced vasoconstriction i n the middle meningeal arterial bed. 5-Hydroxytryptamine (5HT), on the other hand, produced a dilatation in the middle meningeal artery. We conclude that neurally or humorally released catecholamines can provid e a plausible mechanism for vasoconstriction in the middle meningeal a rtery. The dilator effect of 5HT contrasts with the constrictor effect of the 5HT(1)-like receptor agonist sumatriptan and suggests a comple x 5HT receptor pharmacology for the artery.