Figure 5. Steady-state inactivation (f [infinity]). The schematic depicts the stimulus protocol, which was repeated every 5 s. Variable amplitude conditioning potentials (C) were followed by a test potential (T). Amplitudes of C (shown only to -10 mV) were extended to +10 mV. As C was increased, the amplitude of I^Ca,L evoked by T decreased. The fraction of maximum I^Ca,L evoked by T was plotted against the amplitude of C. Estimates of V⁰.5 and slope factor (k) were obtained using the Boltzmann function (inset), and are given in Table 3. Data are from six myocytes. R²for fits were not less than 0.998.