Figure 7. ‘Silent’ L- and T-voltage-gated Ca²⁺ channels in NAc can be unmasked.

A, D and G, mean profiles of [DA]_o ± SEM vs. time evoked by one or five electrical pulses (5–100 Hz) in NAc in 3.6 mm extracellular Ca²⁺ (control, black) or the presence (grey) of P/Q block (A), L-block (D) or T-block (G). Data are normalized to 1p peak [DA]_o. B, E and H, mean peak [DA]_o ± SEM vs. frequency (5p) in NAc in 3.6 mm extracellular Ca²⁺, in control conditions (filled) or block (unfilled). Bonferroni post-tests vs. control: *P < 0.05 **P < 0.01. C, F and I, mean peak [DA]_o ± SEM in NAc after P/Q block (C), L-block (F) or T-block (I) expressed as percentage of control at each frequency compared for 2.4 mm [Ca²⁺]_o (filled) and 3.6 mm [Ca²⁺]_o (unfilled) shows a significantly greater effect of each voltage-gated Ca²⁺ channel blocker at higher [Ca²⁺]_o. Bonferroni post-tests, *P < 0.05 **P < 0.01, n = 5–6 animals. Data for 2.4 mm [Ca²⁺]_o in (C), (F) and (I) is taken from Figs 2, 4 and 5. DA, dopamine; NAc, nucleus accumbens.