SLC6A3 and Parkinson disease: Indeed, the possibility to elucidate the role of DAT in the gut as well as its influence on neurotransmitter pathways within the ENS, may strengthen the causal relationship between development of brain disorders associated to gastrointestinal comorbidities, such as addictive disorders, attention-deficit/hyperactivity disorder, schizophrenia, Parkinson’s disease and dopaminergic system dysregulation.