Fig. 5. (A ) Effect of 1 mm methylmethacrylate (MMA) on voltage-sensitive Ca2+current (ICa) evoked from isolated guinea pig ventricular myocytes at room temperature. L-type ICa(ICa, L) triggered by a voltage step to 0 mV from a holding potential of −40 mV was obtained. (B ) Concentration-dependent depressant effect of MMA on ICa. Current amplitude of the ICameasured in the presence of MMA is normalized to the respective baseline amplitude in the absence of MMA, and thus normalized current amplitudes of the ICaare plotted as a function of MMA concentration (n = 5 at each concentration except 0.1 mm [n = 1]). The apparent dissociation constant and slope factor were 1.33 mm and 1.93, respectively.