Figure 1. Delayed in vitro maturation of Cav1.2KO OPCs. A, After 3 d of 4-OH-tamoxifen treatment, semiquantitative RT-PCR and Western blot analysis of Cav1.2 expression in OPCs was performed using GAPDH and β-actin, respectively, as internal standards. In addition, the expression of Cav1.2 was analyzed by immunocytochemistry. Scale bar, 80 μm. B, VOCC activity was examined in OPCs from control and Cav1.2KO mice using high K+ (50 mm). Fura-2 images were obtained with specific filters at 2 s intervals for a total of 4 min. Each frame represents a single section of a fura-2 time-lapse experiment. An increased fura-2 fluorescence ratio is indicated by warmer colors. Time is denoted in minutes in the bottom right corner. Scale bar, 80 μm. C, Ca2+ uptake was stimulated in control and Cav1.2KO cells using high K+ (50 mm) in the presence of nifedipine (5 μm), verapamil (5 μm), and zero Ca2+ medium (−Ca2+). The bar graph shows the average amplitude of the Ca2+ response, calculated from the responding cells expressed as a percentage of change of the emission intensities. D, Fura-2 imaging of Ca2+ responses to 50 mm K+ in control and Cav1.2KO OPCs. Note that each trace corresponds to a single cell and the horizontal bar indicates the time of high K+ addition. E, F, Two days after mitogen withdrawal, OPCs were stained with antibodies against PDGFr, Olig1, NG2, CC1, and MBP and the percentage of positive cells in each experimental condition was examined by confocal microscopy. Scale bar, 80 μm. G, Morphological complexity of MBP-positive cells was scored in four categories. Values are expressed as mean ± SEM of at least five independent experiments. *p < 0.05, **p < 0.01, ***p < 0.001 versus control.