title: Cathodal transcranial direct current stimulation induces regional, long-lasting reductions of cortical blood flow in rats.
abstract: OBJECTIVE
  Transcranial direct current stimulation (tDCS) induces polarity-specific changes of cerebral blood flow (CBF). To determine whether these changes are focally limited or if they incorporate large cortical regions and thus have the potential for a therapeutic application, we investigated the effects of cathodal tDCS on CBF in an established tDCS rat model with particular attention to the spatial extension in CBF changes using laser Doppler blood perfusion imaging (LDI).
  
  
  METHODS
  Twenty-one Sprague Dawley rats received a single 15-minute session of cathodal tDCS at current intensities of 200, 400, 600, or 700 μA applied over electrode contact areas (ECA) of 3·5, 7·0, 10·5, or 14·0 mm(2). One animal died prior to the stimulation. Cerebral blood flow was measured prior and after tDCS with LDI in three defined regions of interest (ROI) over the stimulated left hemisphere (region anterior to ECA - ROI 1, ECA - ROI 2, region posterior to ECA - ROI 3).
  
  
  RESULTS
  A regional decrease in CBF was measured after cathodal tDCS, the extent of the decrease depending on the current density applied. The most effective and spatially limited reduction in CBF (up to 50%, lasting as long as 90 minutes) was found after the application of 600 μA over an ECA of 10·5 mm(2). This significant reduction in CBF even lasted up to 90 minutes in distant cortical areas (ROI 1 and 3) that were not directly related to the ECA (ROI 2).
  
  
  CONCLUSIONS
  Cathodal tDCS induces a regional, long-lasting, reversible decrease in CBF that is not limited to the region to which tDCS is applied.
authors.affiliation: University Medical Center Göttingen, Germany.
authors.forename: Dorothee
authors.initials: D
authors.lastname: Mielke
authors.forename: Arne
authors.initials: A
authors.lastname: Wrede
authors.forename: Walter
authors.initials: W
authors.lastname: Schulz-Schaeffer
authors.forename: Ali
authors.initials: A
authors.lastname: Taghizadeh-Waghefi
authors.forename: Michael A
authors.initials: MA
authors.lastname: Nitsche
authors.forename: Veit
authors.initials: V
authors.lastname: Rohde
authors.forename: David
authors.initials: D
authors.lastname: Liebetanz
mesh_terms: D000818:Animals; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods; D004566:Electrodes; D019054:Evoked Potentials, Motor / Q000502:physiology*; D017078:Laser-Doppler Flowmetry / Q000379:methods; D008297:Male; D009044:Motor Cortex / Q000098:blood supply* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley