Partial inhibition of complexes III and IV depletes ATP levels in synaptosomes. Synaptosomes (0.5 mg/mL) were divided into groups and incubated at 37°C with 10 mM glucose and inhibitors as indicated. ATP from polarized synaptosomes was PCA extracted after 15 min incubation. In the depolarised groups 4-AP and KCl were added following 5 min incubation with inhibitors. Results are expressed as a percentage of the initial [ATP] at zero time (439.4 ± 42.6 pmol/mg protein) and represent the mean ± SEM for experiments carried out on three separate synaptosomal preparations. *p < 0.05.