Abstract
Pathological intracellular aggregation of alpha-synuclein (a-syn) plays a key role in the neurodegenerative process of Parkinson's disease (PD). The spread of a-syn pathology from the lower brainstem to the cortex lead to variable motor and non-motor symptoms clinically. Here, we aimed to recapitulate these symptoms together in one model.
200-250 g female Sprague-Dawley rats were used (Permission:2014/51-08). AAV-carrying either a-syn (n=11) or green fluorescent protein (GFP; n=11) gene, or saline (n=8) injections were performed bilaterally into substantia nigra (SN) and hippocampus. All animals, including naive controls (n=7), were tested for memory, spatial learning, anxiety and motor activity by novel object recognition (NOR), Morris water maze (MWM), elevated plus maze (EPM), rotarod and locomotor activity tests respectively, between 16-18 weeks following injection. Brain samples were analyzed by Western blotting for a-syn and GFP overexpression, NeuN and tyrosine hydroxylase (TH) for neuronal loss and synaptophysin for synaptic loss.
A-syn group spent shorter time with the novel object in NOR test, longer time to find the platform in MWM and longer time on open arm in EPM compared to naive controls (p<0.05). In rotarod test, a-syn group displayed worse motor performance and in locomotor activity test, they showed significant increase in horizontal activity after apomorphine injection compared to controls (p<0.05). A-syn and GFP overexpression in striatum and hippocampus was confirmed by Western blotting. There was a mild decrease in TH and NeuN expression levels in the a-syn group but not statistically significant. However, synaptophysin expression levels both in striatum and hippocampus, significantly decreased in the a-syn group compared to all control groups (p<0.05).
Viral vector mediated a-syn overexpression in SN and hippocampus together, led to memory impairment, spatial learning deficits and motor dysfunction. Synaptic loss together with mild neuronal loss in hippocampus and SN might be responsible from the cognitive and motor impairments. This model can be successfully used to study further details of neurodegenerative process underlying motor and non-motor symptoms of PD.
Alpha-synuclein and GFP viral vectors were kindly obtained from Michael J Fox Foundation.
Supported by Hacettepe University Scientific Research Projects Coordination Unit (ID:5291).
