Figure 4.

 Cav1 channel deletion compensated by the increased expression of other Ca²⁺ channel types. Contribution of Cav channels to the exocytosis of neurotransmitters in mouse chromaffin cells from WT and Cav1.3^−/− mice. (a and b) C _m traces recorded simultaneously to the Ca²⁺ currents of Fig. 2(c and d) in WT and Cav1.3^−/− cells, respectively. (c) Percentage of total secretion attributed to each Ca²⁺ channel type in WT (black columns) and Cav1.3^−/− cells (white columns). (d) Total secretion attained under control conditions for WT (black column) and Cav1.3^−/− cells (white column). Experiments were performed on seven paired cultures of WT (n = 15 cells) and Cav1.3^−/− cells (n = 11 cells), using 1–2 mice from each strain. Bars represent means ± SEM. *p < 0.05; **p < 0.01, versus the percentage of the same channel in the other mouse strain.