OCRs of acute STR slices (150 μm*1.5 mm) from both the young (A, B, and C) and the old group (D, E, and F) mice, exposed to successive additions of respiratory modulators (showed in arrows). OCR of the young group was not significantly different between different genotype (B), while the coupling efficiency was decreased in PINK1 KO slices (C). In the old group, the PINK1 KO slices showed significantly decrease of basal respiration level (E) and the coupling efficiency (F). With 10 mM pyruvate (P), 20 μM Oligomycin (O), 10 μM FCCP (F), and 20 μM Antimycin A (A) injected sequentially. N = 4 for each genotype and age.