Transcranial magnetic stimulation and antidepressive drugs share similar cellular effects in rat hippocampus

Transcranial magnetic stimulation (TMS) has been proposed as a safe and eff icient treatment of human clinical depression. Although its antidepressive mechanism of action remained unknown, our previous studies indicate that TM S has a long-lasting effect on neuronal excitability in the hippocampus. We now compare the effects of chronic TMS with those of the antidepressant dr ugs desipramine and mianserin. The three treatments did not effect basal co nduction in the perforant path to the dentate gyrus, but markedly suppresse d paired-pulse and frequency-dependent inhibition, resulting from a reducti on in local circuit inhibition in the dentate gyrus. Concomitantly, these t reatments enhanced the expression of long-term potentiation in the perforan t path synapse in the dentate gyrus. Finally, chronic TMS as well as mianse rin suppressed the serotonin-dependent, potentiating action of fenfluramine on population spike in the dentate gyrus. Thus, TMS, mianserin, and desipr amine are likely to affect the same neuronal populations, which may be rele vant to their antidepressant action. (C) 2001 American College of Neuropsyc hopharmacology. Published by Elsevier Science Inc.