Magnesium protection against in vitro cerebral vasospasm after subarachnoid haemorrhage.

Mg2+ has recently been proposed for the treatment of cerebral vasospasm and is known to dilate vessels. In this study, we examine the effects of Mg2+ on in vitro vasospasm using CSF from vasospastic subarachnoid haemorrhage patients with vasospasm (CSFv). Oxygen consumption and isometric force measurements in the porcine carotid artery were used to assess the contractile and metabolic status of the vessels' responses to CSFv and the effect of Mg2+. Mg2+ caused a dose dependant decrease in tension following contraction by CSFv. Mg2+ (12 mM) caused a normalization of relaxation rate in tissue exposed to CSFv, caused a significant decrease in basal oxygen consumption, as well as significantly decreasing the rate of oxygen consumption of the porcine carotid artery when stimulated by CSF (0.70 +/- 0.12 versus. 0.46 +/- 0.1 micromol O2 min(-1) g(-1)). Acute Mg2+ addition demonstrated the most effective protection using an assay based on CSFv contraction. These results suggest that Mg2+ can protect vascular smooth muscle exposed to CSFv by benefiting contractile behaviour and metabolism of the arteries.