gms | German Medical Science

Objective: First experiments indicate that transcranial direct current stimulation (tDCS) might have a sustained effect on the activity of the brain by affecting the membrane potentials of the neurons. The application of a positive current (anodal stimulation) increases the activity of neurons, whereas the application of a negative current (cathodal stimulation) decreases it. We assumed that the change of the activity of neurons results in changes of the cortical perfusion depending on variables such as polarity and duration of the direct current stimulation, as well as on the applied current strength. Sustained changes of cortical perfusion might be of clinical significance in situations of ischemia, which stimulated us to investigate if cortical perfusion could be influenced by tDCS.

Methods: Forty-eight measurements were performed on eight Sprague Dawley rats. Each rat received three single cathodal and anodal DC stimulations at 25, 50 and 100 mA each for 15 minutes every other day through a probe holder that was fixed onto the skull in a surgical procedure. Cerebral blood flow velocity (CBF) was measured prior and after stimulation for at least 30 minutes with Laser Doppler flowmetry. Statistical analysis was performed to calculate the impact of tDCS on CBF depending on current intensity, polarity and time. Histological evaluation was performed 48 h after the last DC stimulation.

Results: Multivariate analysis was significant for time; polarity and intensity regarding the effect of tDCS on CBF (p=0,013). The application of negative current lead to a decrease of CBF, whereas the application of positive current produced an increase of CBF. The CBF changes persisted for at least 30 minutes. Histological analysis did not reveal abnormalities or currency-induced changes.

Conclusions: TDCS leads to reproducible and significant changes of CBF depending on the stimulation parameters applied. It can be assumed that decreased CBF after cathodal stimulation is an indicator of reduced neuronal activity. Possibly, neurons in the state of reduced activity are more resistant to ischemic damage, which would offer the possibility to influence the ischemic tolerance by tDCS.