PT - JOURNAL ARTICLE AU - Østergaard, Freja Gam AU - Skoven, Christian Stald AU - Wade, Alex R. AU - Siebner, Hartwig R. AU - Laursen, Bettina AU - Christensen, Kenneth Vielsted AU - Dyrby, Tim B. TI - No Detectable Effect on Visual Responses Using Functional MRI in a Rodent Model of α-Synuclein Expression AID - 10.1523/ENEURO.0516-20.2021 DP - 2021 May 01 TA - eneuro PG - ENEURO.0516-20.2021 VI - 8 IP - 3 4099 - http://www.eneuro.org/content/8/3/ENEURO.0516-20.2021.short 4100 - http://www.eneuro.org/content/8/3/ENEURO.0516-20.2021.full SO - eNeuro2021 May 01; 8 AB - Parkinson’s disease (PD) is a progressive neurodegenerative disease that is typically diagnosed late in its progression. There is a need for biomarkers suitable for monitoring the disease progression at earlier stages to guide the development of novel neuroprotective therapies. One potential biomarker, α-synuclein, has been found in both the familial cases of PD, as well as the sporadic cases and is considered a key feature of PD. α-synuclein is naturally present in the retina, and it has been suggested that early symptoms of the visual system may be used as a biomarker for PD. Here, we use a viral vector to induce a unilateral expression of human wild-type α-synuclein in rats as a mechanistic model of protein aggregation in PD. We employed functional magnetic resonance imaging (fMRI) to investigate whether adeno-associated virus (AAV) mediated expression of human wild-type α-synuclein alter functional activity in the visual system. A total of 16 rats were injected with either AAV-α-synuclein (n = 7) or AAV-null (n = 9) in the substantia nigra pars compacta (SNc) of the left hemisphere. The expression of α-synuclein was validated by a motor assay and postmortem immunohistochemistry. Five months after the introduction of the AAV-vector, fMRI showed robust blood oxygen level-dependent (BOLD) responses to light stimulation in the visual systems of both control and AAV-α-synuclein animals. However, our results demonstrate that the expression of AAV-α-synuclein does not affect functional activation of the visual system. This negative finding suggests that fMRI-based read-outs of visual responses may not be a sensitive biomarker for PD.