Figure 9.

Effect of blocking VGCCs on Ca²⁺ responses elicited by symmetrical bipolar pulses. Averaged cell responses ± s.e.m for cells exposed to a 150 ns unipolar pulse vs a ↑150 + ↓150 ns symmetrical bipolar pulse with all pulse phases set to 3.1 kV/cm. Ca²⁺ responses were monitored in cells in the absence of VGCC blockers (A) Control (n = 8–6), or in the presence of a (B) cocktail of VGCC blockers containing 100 nM ω-agatoxin, 20 nM ω-conotoxin and 20 µM nitrendipine (n = 18–25) or (C) 20 µM nitrendipine (n = 32–34). The arrow indicates when the pulse was delivered to the cells. (D) Bar graph showing the mean ± s.e.m. for the maximal increase in [Ca²⁺]_i elicited by a 150 ns unipolar pulse vs a ↑150 + ↓150 ns symmetrical bipolar pulse in the absence or presence of the VGCC blocker cocktail, 20 µM nitrendipine (Nitren) or 20 μM (n = 13–10) or 40 μM (n = 9–9) nimodipine (Nimo). Cells were pre-treated with the blockers for 1 hr at room temperature. ^*p < 0.05, significantly different from the corresponding unipolar pulse.