Relaxation Effect of Schisandra Chinensis Lignans on the Isolated Tracheal Smooth Muscle in Rats and Its Mechanism

Schisandra chinensis (S. chinensis) is one of the core drugs used for relieving cough and asthma in traditional Chinese medicine. However, there are few basic studies on the treatment of respiratory diseases with S. chinensis in modern pharmacology, and the material basis and mechanism of its antiasthmatic effect are still unclear. Lignans are the main active components of S. chinensis. The aim of this study was to observe the relaxation effect of S. chinensis lignans (SCL) on the tracheal smooth muscle of rats by in vitro tracheal perfusion experiments, and to explore the mechanism by preincubation with L-type calcium channel blocker verapamil, four potassium channel blockers glibenclamide, tetraethylamine, 4-aminopyridine and barium chloride (BaCl₂), β-adrenoceptor blocker propranolol, nitric oxide synthase inhibitor Nω-nitro-L-arginine methyl ester (L-NAME), and the cyclooxygenase inhibitor indomethacin, respectively. The results showed that SCL (0.25-1.75 mg/mL) reduced the contraction of isolated tracheal smooth muscle induced by acetylcholine, the preincubation with verapamil and glibenclamide could attenuate the relaxation effect, whereas propranolol, 4-aminopyridine, BaCl₂, tetraethylamine, L-NAME, and indomethacin had no such effect. These results suggest that SCL has a significant relaxation effect on the isolated tracheal smooth muscle of rats, and the mechanism may be related to the inhibition of extracellular calcium influx and intracellular calcium release from the sarcoplasmic reticulum, as well as the activation of ATP-sensitive potassium channels. These findings may provide a pharmacological basis for the traditional use of S. chinensis to treat asthma.