Quinolinate and kainate facilitate magnesium penetration into brain tissue.

To study the penetration of magnesium ions from blood into brain tissue, magnesium content in serum and hippocampus of normal and of excitotoxically affected rats was estimated after a single subcutaneous injection of magnesium sulphate (600 mg kg-1). In normal rats Mg2+ levels in serum rose from 1 to 6 mM, while that of the hippocampus remained constant, provided the brains were perfused before magnesium measurement. Following unilateral intracerebroventricular injection of the excitotoxic glutamate analogues, quinolinate or kainate acid, Mg2+ levels increased up to 38% on the (unaffected) contralateral side. Since magnesium is known to prevent glutamate-mediated neurodegeneration, our findings on the accessibility of exogenously applied magnesium may justify further investigations on the utility of magnesium for a therapeutic approach to limiting excitotoxic brain injury in human patients.