Figure 3. Pharmacology of calcium influx and exocytosis.

A and B, calcium currents (I_Ca; A) and capacitance changes (ΔC_m; B) evoked by depolarizations to -21 mV are shown for two different cells before, during, and after substitution of 5 mm Co²⁺ for Ca²⁺ in the external medium. C, summary data for cells reversibly exposed to 5 mm Co²⁺. D and E, calcium currents (I_Ca; D) and capacitance changes (ΔC_m; E) evoked by depolarizations to -21 mV are shown for another two cells before and after exchanging the bath solution for one containing either nimodipine (Nimo) or Bay K 8644. (Note as in B the capacitance trace in E has been abridged during the 1 s control and 3 s test depolarizing pulses when measurements are not interpretable.) I_Ca was elicited with 15 ms depolarizations to -21 mV. Residual I_Ca following nimodipine exposure was blocked by the addition of 200 μm Cd²⁺. F, summary data for cells exposed to either nimodipine, nimodipine + Cd²⁺ or Bay K 8644. In both C and F, the magnitude of ΔC_m (□) and I_Ca (▪) is expressed as a fraction of the control value ±s.e.m. Calibration bars: A: 40 pA, 5 ms; B: 40 fF, 500 ms; D: left trace 20 pA, right trace 50 pA, 2 ms; E: 40 fF, 300 ms.