Figure 4

APα-induced [Ca²⁺]_i increases result from influx of extracellular calcium and are mediated by the L-type calcium channel. (A) Neurons (3–4 DIV) were exposed to 500 nM APα or vehicle control in Ca²⁺-free medium at the time-point indicated by the arrow. In the medium without calcium, APα showed no effect on intracellular calcium concentration. A representative graph of four independent experiments is shown (N = 36 neurons/condition/experiment). (B) La³⁺ diminished APα-induced [Ca²⁺]_i rises. Neurons (3–4 DIV) were incubated with or without 10 μM La³⁺ (a calcium channel blocker) for 30 minutes prior to and continuously throughout imaging, and 500 nM APα or vehicle was added at the time-point indicated by the arrow. (B1) Representative graph of three different experiments (N = 36 neurons/condition/experiment). (B2) Bar graph represents the summary of [Ca²⁺]_i rise in response to control, 10 μM La³⁺, 500 nM APα, and APα + La³⁺. Data are mean ± SEM, *p < 0.05 compared to APα treated neurons; N = 3 experiments with 36 neurons/condition/experiment. (C) Nifedipine blocked APα induced [Ca²⁺]_i rises. Neurons were incubated with or without 10 μM nifedipine (an L-type calcium channel blocker) for 30 minutes prior to and continuously throughout imaging, and 250 nM APα or vehicle was added at the time-point indicated by the arrow. (C1) The graph is representative of three different experiments (N = 36 neurons/condition/experiment). (C2) The bar graph represents quantitative changes in [Ca²⁺]_i in response to control, 10 μM nifedipine, APα, and APα + 10 μM nifedipine. Data are mean ± SEM (**p < 0.01 compared to APα treated neurons; N = 36 neurons/condition/experiment).