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The Journal of Neuroscience, February 25, 2009, 29(8):2648-2653; doi:10.1523/JNEUROSCI.5366-08.2009

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Behavioral/Systems/Cognitive
D₁-Receptor Impact on Neuroplasticity in Humans

Michael A. Nitsche, ^* Min-Fang Kuo, ^* Jan Grosch, Christin Bergner, Katia Monte-Silva, and Walter Paulus

Department of Clinical Neurophysiology, Georg August University, 37099 Göttingen, Germany

Correspondence should be addressed to Michael A. Nitsche, Department of Clinical Neurophysiology, Robert-Koch-Strasse 40, 37099 Göttingen, Germany. Email: mnitsch1{at}gwdg.de

Dopamine improves learning and memory formation. The neurophysiological basis for these effects might be a focusing effect of dopamine on neuroplasticity: Accordingly, in humans L-dopa prolongs focal facilitatory plasticity, but turns nonfocal facilitatory plasticity into inhibition. Here we explore the impact of D₁ receptors on plasticity. Nonfocal plasticity was induced by transcranial direct current stimulation (tDCS), and focal plasticity by paired associative stimulation (PAS). Subjects received sulpiride, a D₂ antagonist, to increase the relative contribution of D₁ receptors to dopaminergic activity, combined sulpiride and L-dopa, to increase the relation of D₁/D₂ activity further, or placebo medication. Under placebo, anodal tDCS and excitatory PAS (ePAS) increased motor cortex excitability. Cathodal tDCS and inhibitory PAS (iPAS) reduced it. Sulpiride abolished iPAS-induced inhibition, but not ePAS-generated facilitation, underlining the importance of D₁-receptor activity for focal facilitatory neuroplasticity. Combining sulpiride with L-dopa reestablished iPAS-induced inhibition, but did not affect ePAS-induced plasticity. tDCS-induced plasticity, which was abolished by sulpiride in a former study, also recovered. Thus enhancing D₁ activity further relative to D₂ activity is relevant for facilitatory and inhibitory plasticity. However, comparison with former results show that an appropriate balance of D₁ and D₂ activity seems necessary to (1) consolidate the respective excitability modifications and (2) to elicit a focusing effect.

Key words: dopamine; human; motor cortex; neuroplasticity; paired associative stimulation; transcranial direct current stimulation

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Received Nov. 7, 2008; revised Jan. 6, 2009; accepted Jan. 31, 2009.

Correspondence should be addressed to Michael A. Nitsche, Department of Clinical Neurophysiology, Robert-Koch-Strasse 40, 37099 Göttingen, Germany. Email: mnitsch1{at}gwdg.de

This article has been cited by other articles:

				K. Monte-Silva, M.-F. Kuo, N. Thirugnanasambandam, D. Liebetanz, W. Paulus, and M. A. Nitsche Dose-Dependent Inverted U-Shaped Effect of Dopamine (D2-Like) Receptor Activation on Focal and Nonfocal Plasticity in Humans J. Neurosci., May 13, 2009; 29(19): 6124 - 6131. [Abstract] [Full Text] [PDF]

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