Protective effect of NG-nitro-L-arginine (N5-[imino(nitroamino)methyl]-L-ornithine) against cyanide-induced convulsions in mice.

The effects of NG-nitro-L-arginine (NNA; an inhibitor of the oxidative L-arginine pathway) on convulsions induced by cyanide were investigated in mice. NNA prevented cyanide-induced convulsions in a dose-dependent manner. Furthermore, the inhibitory effect against convulsions induced by cyanide with NNA was abolished by pretreatment of L-arginine. However, NNA did not change blood cyanide levels in mice 5 min after injection of potassium cyanide. Since NNA prevents against oxidative L-arginine pathway-dependent guanylate cyclase activation in intact cells, it was suggested that the protection against cyanide-induced convulsions with NNA may be due to the inhibition of guanylate cyclase. In support, methylene blue, an inhibitor of guanylate cyclase, elicited a similar inhibition against convulsions induced by cyanide.