EVIDENCE THAT SODIUM-NITROPRUSSIDE POSSESSES ANTICONVULSANT EFFECTS MEDIATED THROUGH NITRIC-OXIDE

THE effect of sodium nitroprusside (SNP) on epileptiform activity elic ited by administration of penicillin (500 units) into the somatomotor cortex was studied in anaesthetized rats. No epileptiform activity was observed after intracortical microinjection of SNP (5 and 20 nM). Mic roinjection of penicillin into the somatomotor cortex induced epilepti form activity in electrocorticograms (ECoG). Epileptiform discharges e licited by penicillin were significantly decreased by SNP. The effect of SNP appeared within 1 min of application and lasted for 2-5 min. Th e inhibitory effect of SNP on epileptiform activity could be prevented by pretreatment with methylene blue (20 nM), a soluble guanylate cycl ase inhibitor. Prior injection of haemoglobin (5 mu 1), a nitric oxide (NO) scavenger, prevented the anticonvulsant effect of SNP. These res ults suggest that NO may be an endogenous anticonvulsant substance.