THE ROLE OF NITRIC-OXIDE IN CHEMICALLY-INDUCED AND ELECTRICALLY-INDUCED SEIZURES IN MICE

The effect of the nitric oxide synthase (NOS) inhibitors N-nitro-L-arg inine methyl ester (L-NAME) and 7-nitroindazole (7-NI) on seizures ind uced by N-methyl-D-aspartate (NMDA), pilocarpine (PTZ) and pentylenete trazol (PTZ), as well as on the electroconvulsive threshold was studie d in mice. It was found that L-NAME and 7-NI decreased the dose of NMD A necessary to produce clonic convulsions in 50% of animals (CD50). Su ch a proconvulsant effect was not observed in mice pretreated with N-n itro-D-arginine methyl eater (D-NAME), an inactive isomer of L-NAME. N either L-NAME nor 7-NI affected the convulsions induced by PIL (clonic seizures) or PTZ (clonic and tonic seizures), having no effect on the ir CD50 values. Similarly, neither NOS inhibitor affected the electros hock threshold. These results, together with some literature data, ind icate that nitric oxide (NO) may be regarded as an anticonvulsant subs tance in relation to seizures induced by NMDA and other excitatory ami no acids, but not by other agents, in mice.