Effect of changes in magnesium ion concentration on cat cerebral arterioles

Abstract

The effect of changes in cerebrospinal fluid (CSF) concentration of magnesium ion ([Mg2+]) on pial arterioles was investigated in anesthetized cats equipped with acutely implanted cranial windows for the observation of the pial microcirculation. Increased [Mg2+] caused vasodilation, whereas decreased [Mg2+] caused vasoconstriction. The effect of [Mg2+] was dose dependent and was the same in small and larger arterioles. There was an interaction between CSF [Mg2+] and calcium ion concentration ([Ca2+]), such that the vasodilator effect of Mg2+ was greater when the [Ca2+] was lower, especially in larger vessels. The vasodilator effect of Mg2+ on pial arterioles was enhanced in the presence of the calcium antagonist verapamil (0.5 micrograms/ml), despite the fact that verapamil by itself caused a 12-13% arteriolar dilation. These results show that the vasodilator effect of Mg2+ is probably related to an interaction at the cell membrane resulting in reduction in the influx of Ca2+ into vascular smooth muscle.

Initial Clinical Experience of Vasodilatory Effect of Intra-cisternal Infusion of Magnesium Sulfate for the Treatment of Cerebral Vasospasm After Aneurysmal Subarachnoid Hemorrhage

“…19) Our preclinical study demonstrated that intra-cisternal infusion of 10 mmol/l magnesium sulfate solution improved the CBF reduced by experimental SAH in the rat. 13,21) The optimal concentration may be 10 mmol/l magnesium sulfate solution. The vasodilatory effect of magnesium infusion therapy may depend on maintaining the CSF Mg 2＋ concentration at 3 mEq/l more than the concentration of the infusate.…”

“…21) In contrast, in vitro studies clearly show that increased extracellular Mg 2＋ concentration definitely causes vasodilation of both normal and contracted cerebral vessels in the presence of vasospasm-inducing agents. 11,17) Therefore, intra-cisternal administration of Mg 2＋ is expected to reverse delayed cerebral vasospasm.…”

Reduction of Infarct Volume by Magnesium after Middle Cerebral Artery Occlusion in Rats

“…Vol. 11, No.6, 1991 pial arterioles in situ, magnesium causes a dose dependent vasodilatation that is probably due to a reduction in the influx of Ca 2 + into vascular smooth muscle cells (Seelig et al , 1983;Altura and Altura, 1984). Intravenously injected, magnesium induces dilatation of the basilar artery in cats after the ves sel has undergone spasm (Kapp et al , 1970).…”

Regulation of intracellular free magnesium in central nervous system injury

“…On the other hand, magnesium deficiency has been found to sensitize the vascular epithelium to prostanoids and induces rapid calcium-mediated vasospastic responses in cerebral blood vessels (91). Administration of magnesium decreases vascular resistance and causes vascular dilation (92). Furthermore, recent experimental data have demonstrated that magnesium sulfate injection reverses pressor effects and cerebral vasoconstriction previously induced by noradrenaline (93).…”