Homocysteine, well-known risk factor for cardiovascular disease, displays neuroexcitatory effects and acts as convulsant agent by still unclear mechanisms. Reported results on the role of nitric oxide (NO) in epileptogenesis are highly contradictor. NO levels could be decreased by N-nitro-L-arginine methyl ester (L-NAME), an inhibitor of enzyme NO synthase (NOS).

The aim of the current study was to examine the effects of L-NAME on seizure susceptibility induced by subconvulsive dose of D,L homocysteine–thiolactone (HcyT) in rats.

Adult male Wistar albino rats were intraperitoneally (i.p.) treated with HcyT 5.5 mmol/kg and observed for convulsive behavioral manifestations during next 90 min. Increasing doses of L-NAME (200, 500 and 700 mg/kg, i.p.,) or saline were injected 30 min prior to HcyT administration. Convulsive behavior was assessed by incidence of convulsions and latency period (time from administration of HcyT to the first convulsion). L-NAME in dose of 700 mg/kg significantly decreased latency period to homocysteine convulsions (p<0.05) and increased incidence of convulsions (p<0.05) when compared with saline –injected rats. Other two applied doses of L – NAME (200 and 500 mg/kg,) had no statistically significant effect on latency period and incidence of convulsions (p>0.05).

Based on these results it cold be concluded that NOS inhibitor, L – NAME, potentiates convulsive properties of HcyT.