Effects of paeoniflorin (PF) and glycyrrhizin (GLR), contained in paeony and licorice roots, respectively, on contractile and non-contractile Ca2+ mobilization were examined by measuring the Ca(2+)-aequorin luminescence (Ca2+ transients) of the nerve-stimulated skeletal muscle of mice in the presence of neostigmine (0.3 microM). PF (0.1-1 mM) prolonged the duration of non-contractile Ca2+ transients, which may induce the desensitization of nicotinic acetylcholine receptor, but did not affect contractile Ca2+ transients. GLR (0.3-1 mM) depressed contractile Ca2+ transients without affecting non-contractile transients. These results suggest that PF and GLR may have complementary effects on intracellular Ca2+ mobilization to block the neuromuscular transmission.