Alpha synuclein associated neurotoxicity in the SN. Unbiased stereological analysis of TH immunopositive cells in coronal sections across the SN was performed using DAB. Cytotoxicity is determined by extent of TH lesion as measured by the ratio of TH positive cells ipsilateral (right, asterisk) vs. contralateral (left) (a). A 43% lesion was measured in rats injected with both AAV-V1S and AAV-SV2 (n = 8, p < 0.0001) and a 51% lesion was measured in rats injected only with SV2 (n = 7, p < 0.0001), both significantly lower than a non-lesion value of one (b). The lesion, measured in the SNpc, was also noticeable in the striatum (c). In the control group injected with full-length venusYFP a non-significant 15% lesion was measured (n = 4) (b). Representative image are displayed. Scale bar 500 μm and 100 μm (zoomed-in images) in a and 500 μm in c.