Intracerebral injection of α-synuclein is taken up by microglia and induces galectin-3 expression. Injections of fluorescent labeled α-synuclein (tagged with ATTO-550) into the olfactory bulbs were performed to study if α-synuclein can be taken up by microglia and induce microglial activation with galectin-3 expression. α-synuclein in the form of monomers, oligomers and fibrils were injected. Sections were stained for galectin-3 and Iba-1 (microglial markers). At 12 h post-injection, monomers and oligomers of α-synuclein were taken up by microglia and showed low expression of galectin-3 (A). No microglia with galectin-3 expression was detected at 12 h after injection of fibrils. At 72 h post-injection, galectin-3 expression was clearly detected after injection of oligomers and fibrils, but had disappeared for monomers (B) (n = 3).