Stereotactic surgery

We performed all surgical procedures under general anesthesia using an isoflurane/oxygen mixture. Mice were placed in a stereotaxic frame (Kopf) and vector solutions were injected using a 10-μL Hamilton syringe fitted with a glass capillary (outer diameter of 100–200 nm). We injected 1 μL of AAV2/5-huα-syn virus at the following coordinates for the substantia nigra (SN, flat skull position, coordinates relative to bregma and dural surface): antero-posterior: − 2.8 mm, medio-lateral: − 1.1 mm, dorso-ventral: − 4.3 mm). The AAV2/5-huα-syn particles were infused unilaterally at a rate of 0.2 μL/min and the needle was left in place for an additional 3 min before it was slowly retracted at a rate of 1 mm/min. Three weeks following virus injection, 2 μL of either sterile PBS (control animals), LPS (1 μg), or IL-4 (10 ng) was injected unilaterally into the right striatum at the following coordinates (flat skull position, coordinates relative to bregma and dural surface): antero-posterior: + 1.0 mm, medio-lateral: − 2.0 mm, dorso-ventral: − 2.5, 3.0 mm). Two dorso-ventral sites were used to spread the 2 μL volume evenly throughout the mouse striatum.