Keywords: a-syn; alpha synuclein; GI; gastrointestinal; ENS; enteric nervous system; PD; Parkinson׳s disease; GDNF; glial cell line-derived neurotrophic factor; TGF-Ã; transforming growth factor-Ã; SMP; submucosal plexus; MP; myenteric plexus; P; postnatal day;