Low-dose magnesium protects brain tissue against focal ischemia in the rat

Abstract

The endogenous cation, magnesium, is a natural competitor of calcium and inhibits calcium entry into cells via the voltage-dependent Ca channel and the NMDA receptor-associated channel. We reported previously that systemic administration of MgC1₂ is neuroprotective, and reduces the ischemic damage in middle cerebral artery (MCA) occluded rats. However, the induced hyperglycemia appeared to affect the infarct undesirably. We therefore investigated the effect of low-dose magnesium in normoglycemia so as to minimize any systemic influence of magnesium. The MCA was occluded under halothane anesthesia employing the method of Tamura et al. Body temperature was regulated during the whole surgical procedure. At 48 hours after the MCA occlusion, TTC was infused via the heart to stain the healthy tissue. Systemic variables and body temperature were measured in an additional group of rats (N = 11). The magnesium-treated group (N = 13) was given MgCl₂ (0. 2 mmol/kg) just after the MCA occlusion and again at 1. 5 and 3 hours later. The control group (N = 13) was given saline instead of MgC1₂. The MgCl₂ treatment did not alter any systemic parameter including the blood glucose content, as compared to those of the control group. The total volume of ischemic damage was smaller in the magnesium-treated group (65 ± 9 mm³) than in the control group (111 ± 12 mm³). MgCl₂significantly reduced the volume of cortical infarction by 34%, but had no significant effect on the striatum. We conclude that low-dose magnesium can exert a beneficial effect on focal cerebral ischemia without any systemic influence.