Accumulated evidence suggests that hydrogen peroxide (H₂O₂) generated in cells during insulin stimulation plays an integral role in insulin receptor signal transduction. The role of insulin-induced H₂O₂ in neuronal insulin receptor activation and the origin of insulin-induced H₂O₂ in neurons remain unclear. The aim of the present study is to test the following hypotheses (1) whether insulin-induced H₂O₂ is required for insulin receptor autophosphorylation in neurons, and (2) whether mitochondrial respiratory chain is involved in insulin-stimulated H₂O₂ production, thus playing an integral role in insulin receptor autophosphorylation in neurons.

Insulin stimulation elicited rapid insulin receptor autophosphorylation accompanied by an increase in H₂O₂ release from cultured cerebellar granule neurons (CGN). N-acetylcysteine (NAC), a H₂O₂ scavenger, inhibited both insulin-stimulated H₂O₂ release and insulin-stimulated autophosphorylation of insulin receptor. Inhibitors of respiratory chain-mediated H₂O₂ production, malonate and carbonyl cyanide-4-(trifluoromethoxy)-phenylhydrazone (FCCP), inhibited both insulin-stimulated H₂O₂ release from neurons and insulin-stimulated autophosphorylation of insulin receptor. Dicholine salt of succinic acid, a respiratory substrate, significantly enhanced the effect of suboptimal insulin concentration on the insulin receptor autophosphorylation in CGN.

Results of the present study suggest that insulin-induced H₂O₂ is required for the enhancement of insulin receptor autophosphorylation in neurons. The mitochondrial respiratory chain is involved in insulin-stimulated H₂O₂ production, thus playing an integral role in the insulin receptor autophosphorylation in neurons.