Levodopa Rescues Retinal Function in the Transgenic A53T Alpha-Synuclein Model of Parkinson's Disease

Area of Science:

• Neuroscience
• Ophthalmology
• Pharmacology

Background:

• Parkinson's disease (PD) is characterized by dopaminergic cell loss and alpha-synuclein (α-syn) deposits.
• Levodopa (L-DOPA) is the primary treatment for PD symptoms.
• Retinal changes in PD models and L-DOPA's effects are not fully understood.

Purpose of the Study:

• To investigate in vivo retinal structural and functional changes in a transgenic PD mouse model.
• To evaluate the impact of acute levodopa (L-DOPA) treatment on retinal function and structure in this PD model.

Main Methods:

• Used A53T alpha-synuclein overexpressing (HOM) and wildtype (WT) mice.
• Administered L-DOPA or vehicle intraperitoneally.
• Assessed retinal function via electroretinography (ERG) and structure via optical coherence tomography (OCT).
• Quantified tyrosine hydroxylase (TH)-positive cells using immunohistochemistry (IHC).

Main Results:

• L-DOPA significantly enhanced ERG a-wave and b-wave amplitudes in A53T HOM mice compared to WT mice.
• Outer retinal thinning (ONL, OPL) was observed in A53T HOM mice.
• L-DOPA did not ameliorate the observed retinal thinning.
• No significant changes in TH-positive amacrine cells were noted.

Conclusions:

• Acute L-DOPA treatment offers transient improvement in visual dysfunction associated with alpha-synuclein accumulation.
• Findings enhance understanding of dopamine-alpha-synuclein interactions in the retina.
• Establishes a preclinical framework for screening PD therapeutics.