Anodal tDCS applied to the left frontal cortex abrogates scopolamine-induced fear memory deficit via the dopaminergic system

Evidence suggests that transcranial direct current stimulation (tDCS) modulates conditioned fear memories and has effects on cognitive flexibility via the dopaminergic system. This study examines whether modulation of scopolamine-induced fear memory deficit by anodal tDCS could be mediated by the dopaminergic system. The male NMRI mice received scopolamine, 30 min before fear conditioning, and showed impaired contextual memory retention. Mice subjected to left frontal anodal stimulation for 20 or 30 min, before fear conditioning, impaired fear memory retrieval. Anodal application for 20 min significantly decreased scopolamine response on fear retention, while the one applied for 30 min did not alter. Moreover, anodal stimulation for 30 min abolished scopolamine-induced fear memory deficit. Dopaminergic antagonists SCH23390 and sulpiride, alone or in combination, prevented the abolishment effect of anodal stimulation on scopolamine-induced fear memory deficit, whereas they did not alter the impairing effect of scopolamine at the dose of 2 mg/kg. Our data suggest that anodal stimulation for 30 min abrogates the impairing effect of scopolamine on fear memory retention. This influence could be prevented by dopaminergic antagonists, indicating the involvement of the dopaminergic system in the effect of anodal stimulation on scopolamine-induced fear memory deficit.