Prophylactic effect of methylene blue against neurotoxicity of sodium nitroprusside

AIM: To examine the effect of methylene blue (MB) on cytotoxicities of sodi um nitroprusside (SNP) and cyclic guanosine monophosphate (cGMP) in cultiva ted cerebellar neurons. METHODS: The cytotoxicities of xenobiotic SNP and c GMP on cultivated murine cerebellar neurons were examined according to Dess i's method. Toxicity of SNP icy to mice and the prophylactic effect of icy MB were investigated with respect to the incidence of seizure and the morta lity of mice within 24 h. RESULTS: Ten min treatment of SNP 1 mmol.L-1 decr eased the survival rate of murine cerebellar nerve cells from 92 % of norma l control to 35 %. Incubation with cGMP 0.1 mmol.L-1 for 1 h declined the s urvival rate from 94 % of normal to 40 %. Injection icy SNP 20 nmol killed one tenth of the mice in 24 h, and SNP 30 nmol killed 11/13 of the mice. MB (100 nmol) icy injection protected 11/13 of the mice against seizure and d eath caused by SNP (30 nmol, icy), and completely eliminated the toxicity o f SNP 20 nmol. CONCLUSION: SNP and cGMP inhibit the vitality of murine neur ons in vitro. MB injection icy markedly antagonizes the dose-dependent neur on-toxic effect of SNP in respect of convulsion and mortality of mice.