Neuromuscular blocking action of sodium nitroprusside alone and with d-tubocurarine

The effect of sodium nitroprusside (SNP) per se on neuromuscular transmission and its effect on the action of d-tubocurarine (d-Tc) was studied in rabbits and rats. SNP produced a dose-dependent neuromuscular block which was not significantly antagonized by physostigmine. The tetanic response to nerve stimulation was not affected. Pretreatment with SNP significantly increased the intensity and the duration of action of d-Tc. The probable mechanism involved in SNP-induced neuromuscular blockade is discussed.