Steroidal muscle relaxants attenuate the contractile and phosphatidylinositol responses of rat trachea.

Interaction of the steroidal muscle relaxants, pancuronium, vecuronium and rocuronium with airway muscarinic receptors of rat trachea was investigated in vitro concerning the contractile and phosphatidylinositol (PI) responses. Pancuronium and vecuronium attenuated, while rocuronium did not affect carbachol (CCh)-induced contraction and CCh-induced IP1 accumulation. Pancuronium could inhibit completely CCh-induced contraction at a dose of 30 microM, while it could not inhibit completely CCh-induced IP1 accumulation at the same dose. These drugs attenuated KCl-induced contraction. These results suggest that pancuronium and vecuronium would attenuate airway smooth muscle contraction through the inhibition of muscarinic receptor-mediated PI response, and that the inhibition of voltage-operated Ca++ channel might be involved, in part, in the attenuation by pancuronium of the contraction.