Chronic repetitive transcranial magnetic stimulation enhances c-fos in theparietal cortex and hippocampus

Repetitive transcranial magnetic stimulation (rTMS) is a novel non-invasive method with anti-depressant properties. However, the mechanism of activati on on the cellular level is unknown. Twelve hours after the last chronic rT MS treatment (14 days, once per day, 20 Hz, 10 s, 75% machine output, the t ranscription factor c-fos was markedly increased in neurons in layers I-IV and VI of the parietal cortex and in few scattered neurons in the hippocamp us of Sprague-Dawley rats. The cortical activation was not blocked by the N MDA antagonist MK-801. The increase of c-fos was not paralleled by an incre ased glial response and activation of cortical growth factors. Thus, it is concluded that chronic rTMS differentially activates parietal cortical laye rs and this might be involved in mediating anti-depressant activity in othe r brain areas. (C) 2000 Elsevier Science B.V. All rights reserved.