Reactive oxygen species production in synaptosomes is independent of ΔΨm

This study addressed whether dissipation of ΔΨ m had any influence on ROS generation of in situ neuronal mitochondria. The ROS formation was measured as a release of H 2 O 2 by Amplex Red assay. Complete blockage of Complex I by rotenone or Complex III by antimycin caused enhanced H 2 O 2 release. Dissipation of ΔΨ m by FCCP or DNP had no effect on the H 2 O 2 production induced by rotenone or antimycin. Antimycin substantially diminishes the ΔΨ m , but part of the membrane potential still maintained by the reverse function of mitochondrial ATP synthase. When antimycin was applied together with oligomycin, ΔΨ m was totally dissipated, but the ROS production decreased only by 15%. Rotenone inhibited the antimycin‐induced H 2 O 2 release by 55%, but not eliminated completely. These experiments suggest that in in situ mitochondria of synaptosomes (i) ROS generation because of inhibition of Complex I or III is not dependent on ΔΨ m and (ii) when Complex I is completely inhibited electrons entering the respiratory chain distal from rotenone site could fuel the ROS formation.