Transcranial direct current stimulation induces polarity-specific changes of cortical blood perfusion in the rat

Objective: Transcranial direct current stimulation (tDCS) induces changes in cortical excitability and improves hand-motor function in chronic stroke. These effects depend on polarity, duration of stimulation and current intensity applied. Towards evaluating the therapeutic potential of tDCS in acute stroke, we investigated tDCS-effects on cerebral blood flow (CBF) in a tDCS rat model adapted for this purpose. Methods: In a randomised crossover design eight Sprague-Dawley rats received three single cathodal and anodal tDCS for 15 min every other day. At each polarity, current intensities of 25,50 and 100 mu A were applied. CBF was measured prior and after tDCS for at least 30 min with laser Doppler flowmetry (LDF). Results: At higher intensities (50 and 100 mu A) anodal tDCS increased CBF up to 30 min. At 100 mu A CBF was increased by about 25%, at 50 mu A by about 18%. In contrast, cathodal tDCS led to a decrease of CBF, likewise depending on the current intensity applied. At 100 mu A the effects were about 25% of baseline levels and persisted for at least 30 min. At 25 and 50 mu A, baseline-levels were mostly re-established within 30 min. Conclusions: tDCS modulates CBF in a polarity specific way, the extent of modulation depending on the stimulation parameters applied. Because of its polarity-specificity, we assume that CBF-alterations are causally related to tDCS-induced alterations in cortical excitability via neuro-vascular coupling. tDCS may constitute a therapeutic option in acute stroke patients or in patients at risk for vasospasm-induced ischemia after subarachnoid hemorrhage. (C) 2010 Elsevier Inc. All rights reserved.