Transcranial direct current stimulation (tDCS) in conscious mice: a refined method for repetitive applications without restraint

Transcranial direct current stimulation (tDCS) for painless, non-invasive brain stimulation is a promising approach to enhance recovery after stroke. However, the precise molecular and cellular mechanisms underlying the effects of tDCS remain unclear, impeding its use in humans and necessitating research in experimental animals. Unlike humans, who receive tDCS fully awake, experimental models of tDCS have so far been conducted under anaesthesia to ensure the immobility required by currently available experimental setups. The use of anaesthesia may, however, confound results, decreasing their translational value. To address this problem, we developed a refined method enabling tDCS in awake and freely moving mice. A tube attached to the skull contains the stimulation electrode, whose position can be adapted flexibly to the target brain region; the reference electrode is implanted subcutaneously at the contralateral chest. Here, we report <i>n</i> = 135 awake mice that underwent tDCS in their home cage for up to 15 minutes per session over 10 consecutive days. None of those animals showed any adverse effects, neither regarding their general wellbeing, body weight, and behavioural activity, nor in ex vivo histology and immunohistochemistry. We suggest using this refined approach in future experimental studies of neuropsychological disorders.