Phenytoin (PHT) and Valproate (VPA) are known to induce
cognitive dysfunction, in terms of long term memory loss. Nitric oxide
(NO) on the other hand is said to help in long term potentiation and hence
enhance memory. The effects of nitric oxide donor L-arginine (L-Arg) and
nitric oxide synthase inhibitor N-W-L-Nitroarginine (L-NOARG) were
studied on the cognitive dysfunction, induced by PHT and VPA in normal
healthy rats, using the step-through passive avoidance test (PAT). It was
observed that combining L-Arg with PHT significantly enhanced long term
memory while, combining PHT with L-NOARG decreased it, as compared
to PHT alone. When combined with VPA, L-Arg and L-NOARG increased
the retention latency as compared to PVA alone but this was not
statistically significant. We conclude that the No donor L-Arg is able to
increase the difference in LTE in acquisition and retention trials with
both PHT and VPA, but with VPA the increase is not statistically
significan t.