The role of nitric oxide in the kainate-induced seizures in mice.

The effect of L-arginine (L-Arg), D-arginine (D-Arg), N-nitro-L-arginine methyl ester (L-NAME) and N-monomethyl-L-arginine (L-NMMA) on the kainate-induced seizures was studied in mice. It was found that the precursor of nitric oxide (NO) L-Arg (150-600 mg/kg i.p.) increased dose-dependently the dose of kinate necessary to produce clonic convulsions in 50% of the animals (CD50). Such an anticonvulsant effect was not observed in mice pretreated with D-Arg (150-600 mg/kg i.p.), the latter drug not being a substrate for NO formation. The inhibitors of NO synthase L-NAME and L-NMMA, both administered in doses of 30-30 mg/kg i.p., reduced the convulsive threshold by decreasing the CD50 of kainate. Moreover, L-NAME (3 mg/kg) antagonized the anticonvulsant effect of L-Arg (300 mg/kg). These results indicate that NO may play a role of an endogenous anticonvulsant substance in mice.