(A) Representative images showing the effects of FCCP on mitochondrial morphology. FCCP (12.5 μM) for 24 hours induced fragmentation of dendritic mitochondria compared to DMSO treatment. Scale bar, 20 μm. (B to E) Mitochondrial morphology of DMSO- and FCCP-treated neurons. Frequency distribution of the area occupied by individual dendritic (B) and axonal (C) mitochondria. FCCP treatment reduced the average area of dendritic mitochondria (meanDMSO = 1.44 μm2, meanFCCP = 1.06 μm2) and decreased the number of dendritic mitochondria (nDMSO = 28,718, nFCCP = 3713). FCCP increased the number of axonal mitochondria (nDMSO = 33,457, nFCCP = 51,767), while it did not change the average area of axonal mitochondria (meanDMSO = 0.39 μm2, meanFCCP = 0.39 μm2). Average well CA differed significantly between DMSO and FCCP treatment for dendritic (meanDMSO,Dend CA = 1292 ± 213, meanFCCP,Dend CA = 123 ± 44) (B, right) and axonal mitochondria (meanDMSO,Ax CA = 404 ± 79, meanFCCP,Ax CA = 629 ± 83 (C, right). FCCP treatment produced a significant decrease in dendritic length (D), with average medianFCCP = 2.77 ± 0.07 μm compared to medianDMSO = 3.35 ± 0.08 μm (D, right). FCCP treatment also produced a significant increase in the median axonal mitochondrial circularity compared to DMSO treatment (average medianDMSO = 0.83 ± 0.007 and medianFCCP = 0.94 ± 0.004; E, right), also illustrated by their frequency distribution (E, left). Bar graphs represent mean ± SD, nwells = 8 per treatment. Unpaired t tests, ****P < 0.0001, nDMSO,axonal = 33,457 and nFCCP, axonal = 51,767, nDMSO, dendritic = 28,718 and nFCCP, dendritic = 3713, 32 fields, eight wells.