Inhibitory effect of lidocaine on isolated trachea in rats

Objective: To study the effect of lidocaine on tracheal smooth muscles and its mechanism.Methods:The effect of lidocaine on the precontraction induced by acetylcholine(ACh) and potassium chloride (KCl) was observed in isolated trachea of rats.The effect of lidocaine on the dose-response curves of the contraction of tracheal smooth muscles induced by ACh,KCl,and CaCl_2 was observed and was compared with that of verapamil.Results: Administration of lidocaine caused relaxation of the isolated tracheal smooth muscles pre-contracted by ACh and KCl in rats,and the effect of lidocaine was not affected by Nomega-nitro-L-arginine methyl ester(L-NAME)and propranolol.Lidocaine shifted the dose-response curves of ACh,KCl,and CaCl_2 to the right and inhibited the maximum response.Lidocaine inhibited the contraction caused by ACh-induced intracellular Ca~(2+) release,and the difference in the inhibitive rats of lidocaine of 0.69 and(3.45) mmol/L was signigicant [(41.7±(12.8))% vs.(98.9±1.4)%,P0.01].Lidocaine inhibited the contraction depending on extracellular Ca~(2+),and the difference in the inhibitive rates of lidocaine of 0.69 and 3.45 mmol/L was significant [(6.1±6.6)% vs.(60.9±7.8)%,P0.01].Conclusion: Lidocaine can obviously relax the isolated tracheal smooth muscles of rats.