Fig. 6. The depolarisations reflected transient openings of the mitochondrial permeability transition pore. (A) Treatment of cells with N-methyl 4-valine cyclosporin (400 nM) reduced the incidence of transient depolarisations. Line images illustrate that mitochondrial flickering was almost completely prevented in cells treated with meth-v-Cs, which reduced the integrated activity from control values of 12.0±2.6 (n=122) to 9.8±2.5 (n=82) (mean±s.d., P<0.0001, two-tailed, unpaired t test), suggesting that the transient depolarisations were transient openings of the mPTP. (B) 10 µM Trifluoperazine, another inhibitor of mPTP formation, slowed the rate of global mitochondrial depolarisation, reducing the slope from a control of 0.041±0.018 (n=27 cells) to 0.008±0.006 (n=60 cells; P<0.0001).