Repetitive transcranial magnetic stimulation induces active coping strategies and attenuates the neuroendocrine stress response in rats

The effects of repetitive transcranial magnetic stimulation (rTMS) on Vario us brain functions were investigated in adult male Wistar rats. The stimula tion parameters were adjusted according to the results of accurate computer -assisted, magnetic resonance imaging-based reconstructions of the current density distributions induced by rTMS in the rat and human brain, ensuring comparable stimulation patterns in both cases. The animals were subjected t o daily rTMS-treatment (three trains of 20 Hz; 2.5 s) for 8 weeks from the age of 4 weeks on. In the forced swim test these rats showed a more active stress coping strategy than the control rats. This was accompanied by a sig nificantly attenuated stress-induced elevation of plasma ACTH concentration s. Pituitary changes accounting for the attenuation were ruled out by the c orticotropin-releasing hormone test. Baseline concentrations of ACTH and co rticosterone were indistinguishable in the two groups. No changes were foun d in the anxiety-related behavior of the rats on the elevated plus-maze or in behavior during the social interaction test. Accordingly, the binding ch aracteristics of the benzodiazepine agonist [H-3]flunitrazepam at the benzo diazepine/gamma -aminobutyric acid type A receptor complex were similar in the rTMS and control groups. In summary, chronic rTMS treatment of frontal brain regions in rats resulted in a change in coping strategy that was acco mpanied by an attenuated neuroendocrine response to stress, thus revealing parallels to the effects of antidepressant drug treatment. (C) 2000 Elsevie r Science Ltd. All rights reserved.