This FOA invites new applications to participate in the Gut-Brain Communication in Parkinsons Disease (PD) Consortium (GBPDC). The goals of this initiative are 1) to establish a network of individual research projects and a Coordinating Center focused on clinical research; 2) recruitment of sufficient patients and use of standardized protocols to collect data and biospecimens relevant to both neurology and gastroenterology research on PD; 3) share data, biomaterials, models, reagents, resources and methods among projects in the GBPD; and 4) make these publicly available through the Coordinating Center. The objective of this consortium is to accelerate research on the role gastrointestinal (GI) symptoms and changes in gut-brain communication in the initiation and pathogenesis of Parkinsons disease in order to facilitate development and validation of innovative early-phase GI-based diagnostic tools and biomarkers for PD. The research centers of the GBPDC will serve as sites for enrollment of PD patients with and without GI symptoms, patients with GI symptoms considered to be at risk for PD, and healthy age-matched controls for laboratory-based studies on biological samples obtained from these patients. The NIDDK strongly encourages Research on Sex/Gender Differences, Sexual and Gender Minority-Related Research and Race/Ethnic Diversity (see NOT-DK-22-003).