Effects of the selective muscarinic receptor antagonist penehyclidine hydrochloride on the respiratory tract.

We investigated the effects and mechanisms of penehyclidine hydrochloride (PHC), a novel selective anticholinergic drug on respiratory tract. The methods of isolated guinea-pig tracheas, and isolated bronchoalveoar lavage fluid were employed to estimate PHC's anti-spasm mechanisms in smooth muscle. The results indicated relaxing effect of penehyclidine hydrochloride was obviously stronger than that of atropine sulfate in two assays according to PA 2 values and maximal reducing mount index. The method of radio-immunity assay was furtherly employed to determine cAMP levels in isolated guinea-pig tracheal and lung smooth muscle for comparing with selective effect on muscarinic receptor subtypes. In the assay, PHC could increase the content of cAMP in isolated guinea-pig lung smooth muscle, while decrease the content of cAMP in isolated guinea-pig tracheal smooth muscle, but the difference was no statistical significant at dose of 10 μmol · L ―1 . In conclusion, our results suggested that PHC has little or no effect on M 2 receptor subtypes in isolated guinea-pig tracheal and lung smooth muscle and could be used in asthma and COPD therapy.