Transcranial direct current stimulation improves motor function in rats with 6-hydroxydopamine-induced Parkinsonism

Area of Science:

• Neuroscience
• Neurology
• Biomedical Engineering

Background:

• Parkinson's disease (PD) presents complex motor deficits.
• Evaluating transcranial direct current stimulation (tDCS) efficacy in PD is challenging due to patient and treatment variability.
• A unilateral 6-hydroxydopamine-induced PD rat model was employed to standardize assessment.

Purpose of the Study:

• To investigate the effects of anodal tDCS applied to the primary motor cortex (M1) on motor deficits in a PD rat model.
• To assess the impact of tDCS on forelimb use asymmetry, locomotor activity, and gait abnormalities.
• To determine the duration of therapeutic effects after tDCS cessation.

Main Methods:

• Induction of unilateral PD in rats using 6-hydroxydopamine.
• Application of anodal tDCS to the primary motor cortex (M1) for 5 days.
• Behavioral assessments including cylinder test, open field test, and treadmill walking analyzed with DeepLabCut.
• Histological analysis of dopamine neuron and fiber preservation.

Main Results:

• tDCS treatment gradually ameliorated forelimb-use asymmetry and increased locomotor activity to pre-lesion levels.
• PD-related abnormal forelimb movements during walking were normalized, and gait balance was restored.
• Therapeutic effects diminished rapidly or gradually after tDCS treatment termination.
• Histology confirmed moderately advanced PD with 40-50% dopamine neuron/fiber preservation on the injured side.

Conclusions:

• Anodal tDCS of M1 demonstrates positive behavioral outcomes in a PD rat model, alleviating motor deficits.
• The motor improvements induced by tDCS are transient, highlighting the need for further research into neural mechanisms.
• These findings support further clinical investigation of tDCS for Parkinson's disease treatment.