Effect of changes in magnesium ion concentration on cat cerebral arterioles.
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.
D000818:Animals; D001158:Arteries / Q000502:physiology*; D001160:Arterioles / Q000502:physiology*; D002415:Cats; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D007700:Kinetics; D008274:Magnesium / Q000134:cerebrospinal fluid / Q000494:pharmacology*; D008833:Microcirculation / Q000187:drug effects; D009928:Organ Specificity; D010296:Parietal Lobe / Q000098:blood supply*
D008274:Magnesium