CaMKIα mediates VDCC-dependent mitochondrial changes after high K⁺. (A) Neurons (10 DIV) were cotransfected with pDsRed2-Mito and GFP (negative control; top) or GFP–CaMKIα-DN. Neurons (at 11 DIV) were treated with 45 mM K⁺ for 15 min. GFP fluorescence is shown in the left panels, and mitochondrial fluorescence is shown before (Pre-K⁺) and after high K⁺ treatment in the middle and right panels. Bars, 20 μm. (B) Neurons were transfected with GFP–CaMKIα-CA and pDsRed2-Mito. GFP fluorescence is shown in the left panel, and mitochondrial fluorescence is shown in the right panel. Bar, 20 μm. (C) Mitochondrial movement or length was measured for neurons that were either untreated (no stimulation) or treated with 45 mM K⁺ as shown in A. The movement events after high K⁺ stimulation were normalized to the value obtained before stimulation. The elongation index after 15 min of high K⁺ stimulation was also normalized to the value obtained before stimulation. Data were obtained from >150 mitochondria in three to five independent experiments for each condition. Error bars indicate SEM in each group. *, P < 0.001. (D) Mitochondrial movement or elongation index was measured for neurons that were either untreated (Control; transfected with GFP) or after transfection with GFP–CaMKI-CA as in B. Mitochondrial movement was measured by time-lapse fluorescence microscopy. Mitochondrial length was measured through analysis of the elongation index. Data were obtained from at least 350 mitochondria in 7–10 neurons for each condition. Error bars indicate SEM in each group. *, P < 0.001.