Schisandrol A Relaxes the Rat Trachea Via L-Type Ca²⁺ Channels and K_V Channels

Background Schisandra chinensis is widely applied in the prevention and treatment of asthma in China, but the material basis for the antiasthmatic effect of S. chinensis is unclear. Our previous studies found that the lignans from S. chinensis can relax tracheal smooth muscle in rats. Schisandrol A (SCA) is a representative monomer of S. chinensis lignans with high content and activity. Purpose This study was aimed at further exploring the relaxation effect of SCA and its mechanism on the isolated tracheal smooth muscle of rats through tracheal perfusion experiments. Methods The isolated rat tracheal ring was precontracted with acetylcholine (ACh). Then, the impact of SCA on the tension of precontracted tracheal ring was studied. Verapamil (L-type calcium channel blocker) and four potassium channel blockers, including glibenclamide, tetraethylamine, 4-aminopyridine (4-AP), and barium chloride (BaCl2), as well as propranolol (β-adrenergic receptor antagonist), were respectively used to precontract the tracheal ring for investigation. Results SCA could dose-dependently reduce the ACh-induced contraction of the tracheal ring, and the verapamil and 4-AP could weaken this effect, while BaCl2, glibenclamide, tetraethylamine, and propranolol did not show this effect. Conclusion SCA can significantly relax the effect of tracheal smooth muscle of rats, and the underlying mechanism might be involved in the blocking of L-type Ca2+ channels and activating the voltage-dependent potassium channels (KV).