Intensity-dependent effects of repetitive anodal transcranial direct current stimulation on learning and memory in a rat model of Alzheimer's disease

Single-session anodal transcranial direct current stimulation (tDCS) can improve the learning-memory function of patients with Alzheimer's disease (AD). After-effects of tDCS can be more significant if the stimulation is repeated regularly in a period. Here the behavioral and the histologic effects of the repetitive anodal tDCS on a rat model of AD were investigated. Sprague-Dawley rats were divided into 6 groups, the sham group, the beta-amyloid (A beta) group, the A beta + 20 mu A tDCS group, the A beta + 60 mu A tDCS group, the A beta + 100 mu A tDCS group and the A beta + 200 mu A tDCS group. Bilateral hippocampus of the rats in the A beta group and the A beta + tDCS groups were lesioned by A beta(1-40) to produce AD models. One day after drug injection, repetitive anodal tDCS (10 sessions in two weeks, 20 min per session) was applied to the frontal cortex of the rats in the tDCS groups, while sham stimulation was applied to the AD group and the sham group. The spatial learning and memory capability of the rats were tested by Morris water maze. Bielschowsky's silver staining, Nissl's staining, choline acetyltransferase (ChAT) and glial-fibrillary-acidic protein (GFAP) immunohistochemistry of the hippocampus were conducted for histologic analysis. Results show in the Morris water maze task, rats in the A beta + 100 mu A and the A beta + 200 mu A tDCS groups had shorter escape latency and larger number of crossings on the platform. Significant histologic differences were observed in the A beta + 100 mu A and the A beta + 200 mu A tDCS groups compared to the AD group. The behavioral and the histological experiments indicate that the proposed repetitive anodal tDCS treatment can protect spatial learning and memory dysfunction of A beta(1-40)-lesioned AD rats. (C) 2015 Elsevier Inc. All rights reserved.