Repetitive transcranial magnetic stimulation increases the release of dopamine in the mesolimbic and mesostriatal system

Repetitive transcranial magnetic stimulation (rTMS) is suggested to be a potentially useful treatment in major depression. In order to optimize rTMS for therapeutic use, it is necessary to understand the neurobiological mechanisms involved, particularly the nature of the neurochemical changes induced. Using intracerebral microdialysis in urethane-anesthetized and conscious adult male Wistar rats, we monitored the effects of acute rTMS (20 Hz) on the intrahippocampal, intraaccumbal and intrastriatal release patterns of dopamine and its metabolites (homovanillic acid, 3,4-dihydroxyphenylacetic acid). The stimulation parameters were adjusted according to the results of accurate MRI-based computer-assisted reconstructions of the current density distributions induced by rTMS in the rat brain, ensuring stimulation of frontal brain regions. In the dorsal hippocampus, the shell of the nucleus accumbens and the dorsal striatum the extracellular concentration of dopamine was significantly elevated in response to rTMS. Taken together, these data provide the first in vivo evidence that acute rTMS of frontal brain regions has a modulatory effect on both the mesolimbic and the mesostriatal dopaminergic systems. This increase in dopaminergic neurotransmission may contribute to the beneficial effects of rTMS in the treatment of affective disorders and Parkinson's disease.