The effect of sodium nitroprusside on tracheal smooth muscle of rabbit

excitation and contraction of the smooth muscles in the airways lead to the constriction which causes abnormal airflow. Nitric oxide is considered as one of the most important factors which causes smooth muscles relaxation. Since Sodium Nitroprusside (S.N.P) is used in emergency services as a potent NO donor and many reports have indicated that this agent causes the smooth muscles relaxation, so this study was designed to determine the effect of S.N.P on tracheal smooth muscle of rabbit. in this study intratracheal pressure (I.T.P) was recorded as an index of contraction of tracheal smooth muscle. Control groups were exposed to the electrical stimulation with various voltages and frequencies. Treatment groups were first exposed to various concentrations of S.N.P along with the same electrical stimulation as the control groups. Our results showed that in the treatment groups, different concentrations of S.N.P significantly increased ITP (p<0.05). when they were exposed to various concentrations of S.N.P along with electrical stimulation, the lowest concentration of S.N.P (0.5 10 M), decreased the ITP in response to electrical stimulation with different voltages and frequencies (p=0.00). Application of medium and high concentrations of S.N.P led to the increase of ITP in response to electrical stimulation. ITP was significantly increased following administration of the medium concentration of S.N.P. (1.66 10 M) SNP (p=0.00). SNP, 5 10 M, also led to a significant increase of ITP in all voltages and frequencies (p<0.05). According to our findings, S.N.P had an excitatory concentration-dependant effect on the tracheal smooth muscle and only the minimum concentrations induced relaxation of the muscles.