Studies on the antinociceptive effects of sodium nitroprusside and molsidomine in mice

The participation of nitric oxide (NO) in antinociceptive activity of molsidomine and sodium nitroprusside (SNP) was studied in mice using the writhing test. Molsidomine (300 and 150 mg/kg) and SNP (1.52-0.38 mg/kg) induced antinociception that was antagonized by naloxone. L-arginine (500-62.5 mg/kg) did not produce antinociceptive effects, whereas N omega-nitro-L-arginine methyl ester (L-NAME) (37.5-150 mg/kg) induced antinociception which was suppressed by naloxone. Methylene blue did not change the molsidomine- and SNP-induced antinociception, but significantly intensified that produced by L-NAME. L-arginine increased antinociceptive effect of molsidomine but not that of SNP. Antinociceptive activity of L-NAME was partially reversed by L-arginine. D-arginine failed to influence these effects. The present findings suggest that the NO-cGMP pathway is not involved in the mechanism of molsidomine- and SNP-induced antinociception in the writhing test in mice.