The activity of rat brain nitric oxide synthase following chronic antidepressant treatment.

Nitric oxide synthase (NOS) is an enzyme involved in the activation of the glutamate/NMDA receptor-induced cascade of events. In this study we investigated the NOS activity in different rat brain regions after chronic electroconvulsive, imipramine and citalopram treatments. Chronic electroconvulsive treatment significantly increased the NOS activity (by 49%) in the cerebral cortex. However, chronic treatment with imipramine or citalopram did not alter the activity of NOS in all examined brain regions (cortex, hippocampus or cerebellum). The increased NOS activity after electroconvulsive but not pharmacologic (imipramine or citalopram) treatment may well reflect the differences between the adaptive changes of the NMDA receptor complex induced by these treatments.