Abstract The effect of electrical pulses on the oxidation-reduction states of the respiratory intermediates in isolated rat brain tissue was studied. The results indicate that each of the electron transport intermediates undergoes a transition from a relatively more oxidized to a reduced state. A pulse response spectrum reveals reduced peaks corresponding to NAD(P)H, ubiquinone and cytochromes c, b, and a− a 3. The amount of cytochrome c reduced after 10 sec of electrical pulses is 13% of the cytochrome c reduced by dithionite. These results indicate that the rate of electron transport is dependent on and coupled to adenine nucleotides.