Repeated electroconvulsive shock (ECS) alters the phosphorylation of glutamate receptor subunits in the rat hippocampus

Glutamate and its receptors are involved in the pathophysiology of mood disorders and have recently emerged as potential targets for the pharmacotherapy of depression. In rats, we investigated plasticity changes of the glutamatergic system evoked by electroconvulsive shock (ECS), which represents the most effective therapy for patients who are refractory to antidepressants. Chronic ECS produced a marked increase in the phosphorylation of the regulatory NMDA receptor subunit NR2B (Ser(1303)) and the AMPA receptor subunit GluR-A (Ser(831)) in the hippocampus, with no effects on the obligatory subunit NR1. No effects were found on total receptor subunit expression levels. We suggest that, at least in part, ECS exerts its clinical activity through the modulation of the glutamatergic synapses, via potentiation of AMPA currents mediated by GluR-A (Ser(831)) phosphorylation, and a reduction of NMDA receptor activity through the phosphorylation of NR2B (Ser(1303)), presumably uncoupling NR2B from its signalling partner CaMKII. These effects functionally resemble the recently described antidepressant effects of ketamine.