Background: Alpha - synuclein (ASN) is the principal component of Lewy pathology and strongly influences on the pathogenesis of Parkinson's disease (PD). The increased level of ASN protein causes microglial response. The reactive microglial cells may actively participate in the damaging of dopaminergic neurons. The data suggests that ASN accumulation in astrocytes might damage these cells in the substantia nigra pars compacta (SN) and promotes degeneration of dopaminergic neurons in SN. We examined the potential role of recombinant ASN monomers as a major pathogenic factor causing the inflammatory response in the central nervous system. Methods: Mice were bilaterally infused by human ASN monomers into the striatum (ST) or SN (single treatment was 4 mg/structure, 8 mg per brain) and decapitated after 1, 4 or 12 weeks post injection. The changes in the level of inflammatory factors in ST were evaluated using Real-Time PCR and Western Blot method. The analysis of morphological changes of glial cells was performed by immunohistochemical staining. Results: We observed a strong activation of microglia cells in ST and increased expression of striatal interleukin 1 alpha, tumor necrosis factor alpha and interferon gamma after ASN injection into the ST. We noticed an increase in striatal glial fibrillary acidic protein mRNA level 4 weeks after ASN injection into the ST. Injection of ASN into the SN led to an increase of striatal transforming growth factor beta mRNA level and has no influence on striatal glial fibrillary acidic protein mRNA level. Conclusion: Our results suggest that both the microglia activation and supressing astrocytes play a crucial role in ASN-related dopaminergic neurotoxicity. (C) 2016 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Sp. z o.o. All rights reserved.