Effects of thioproline on disturbance of action potentials of papillary muscles caused by large dose of lidocaine

Thioproline (T) 938 micromol/L had no significant effect on maximum velocity of the phase 0 of action potential (Vmax), height of action potential (APH) and action potential duration (APD), but prolonged the functional refractory period (FRP) of guinea pig papillary muscles. Lidocaine (68.3, 136.6 and 273.2 micromol/L) depressed Vmax in dose-dependent manner and this process was evidently antagonized by T. The regression coefficients of dose-dependent effect on Vmax of lidocaine and T plus lidocaine did not differ significantly from each other. Concentrations of lidocaine higher than 136.6 micromol/L showed a frequency-dependent block action, which was partially antagonized by T.