Central anticonvulsant effects of magnesium sulfate on N-methyl-D-aspartate-induced seizures

OBJECTIVE: The objective of this study was to determine if magnesium sulfate's central anticonvulsant activity is effective against N-methyl-D-aspartate-induced seizures. STUDY DESIGN: In two separate experiments we investigated magnesium sulfate's ability to inhibit N-methyl-D-aspartate-induced hippocampal seizures in rats. In the first experiment magnesium sulfate was administered peripherally before an intracranial injection of 20 µg of N-methyl-D-aspartate. In the second experiment magnesium sulfate was injected intracranially concurrently with N-methyl-D-aspartate. The ability of magnesium sulfate to suppress N-methyl-D-aspartate-induced seizure activity under both conditions was assessed. RESULTS: Peripherally administered magnesium sulfate significantly increased the latency from the time of an N-methyl-D-aspartate injection to the first seizure both by acute injection and after 2 hours of sustained elevation of serum magnesium levels when compared with saline solution-injected controls (p<0.01). The duration of the first seizure was also significantly reduced. Intracranially administered magnesium sulfate significantly (p<0.01) increased the seizure latency period by 120%. Overall, central magnesium sulfate prevented seizure activity in 40% of the animals (p<0.01). CONCLUSION: Magnesium sulfate has a central anticonvulsant action on N-methyl-D-aspartate-induced seizures in this rat model of hippocampal seizures.