Electrical stimulation of rat medial prefrontal cortex enhances forebrain serotonin output: Implications for electroconvulsive therapy and transcranial magnetic stimulation in depression

Decreased activity of the prefrontal cortex (PFC), as well as reduced serot onergic neurotransmission, is considered as a characteristic feature of maj or depression. The mechanism by which electroconvulsive therapy (ECT) and t ranscranial magnetic stimulation (TMS) achieve their antidepressant effects may involve changes in PFC activity. It is, however, still unclear whether these changes are accompanied by increased synaptic availability of seroto nin (5-HT). In the present study, 5-HT efflux in the rat ventral hippocampu s and amygdala was analyzed using in vivo microdialysis during low-current electrical stimulation of PFC and other cortical regions. Electrical stimul ation of the medial PFC produced current-dependent increases in limbic 5-HT output in both urethane-anesthetized and behaving rats. No effects on 5-HT levels were seen after comparable stimulation of either the lateral parts of the PFC, the medial precentral area, the primary motor cortex or the par ietal cortex. This pronounced regional specificity of the effect of medial PFC stimulation on limbic 5-HT output suggests that activation of this part icular area might play a crucial role in such antidepressant treatments Its ECT and TMS. (C) 1999 American College of Neuropsychopharmacology. Publish ed by Elsevier Science Inc.