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Neurobiological effects of TMS: Functional neuroimaging of dopaminergic neurotransmission using SPECT and [123I] IBZM
Transcranial magnetic stimulation (TMS) is effective in the treatment of moderate to severe depression. To elucidate acute TMS effects on dopaminergic neurotrans-mission, we investigated depressed patients under TMS using a dynamic nuclear medicine technique (1–3).
Patients underwent a SPECT study using a [123I]IBZM bolus followed by a continuous infusion. In equilibrium two SPECT scans were performed, before and after TMS challenge. The change in striatal IBZM binding between pre- and post-TMS scans was used as a measure of endogenous dopamine release triggered by TMS.
Five complete data sets are available. Four studies showed a mean 2% (range: 1.2 to 4.2) reduction in IBZM binding to striatal D2 receptors, in one patient binding was unchanged (p<0.05, one-sided Wilcoxon).
The reduction of IBZM binding is suggestive of an increase in endogenous dopaminergic stimulation. Our preliminary data provide in vivo evidence of a dopaminergic mechanism of the acute TMS effects in depressed patients.
1. Padberg, F. et al. Neuropsychopharmacology 27 (2002):638–645.
2. Keck, M. et al. Neuropharmacology 43 (2002):101–109.
3. Laruelle, M. et al. J Nucl Med 36 (1995):1182–1190.