FIGURE 7.

Separation of snail cardiac LCa_v3-12a (T-type) and LCav1 (L-type) currents using holding potentials and drugs (isradipine, mibefradil, and nickel) in whole cell patch clamp recording. A, fast T-type currents (red color) isolated by difference current in 2 mm [Ba²⁺]_ex and 100 mm [Na⁺]_ex with a holding potential (HP) of −110 mV versus −60 mV in whole cell recording of native LCav3/LCav1 channel currents in snail cardiomyocytes. B, ramp protocols (−110 to +100 mV in 800 ms) carried out in the presence of external solutions 2 mm [Ba²⁺]_ex and 100 mm [Na⁺]_ex and differing doses of drug perfused on cardiomyocytes. Isradipine at 1 μm is a specific blocker of L-type currents, whereas mibefradil and nickel are nonspecific blockers of L-type and T-type currents. C, dose-response curves ± S.E. for isradipine (n = 6), mibefradil (n = 8), and nickel (n = 8); sample data are shown in B.