The "core" of the neuronal lesions in Parkinson's disease (PD) is the progressive degeneration of dopamine neurons in the substantia nigra. A significant loss of dopamine neurons and the presence of Lewy bodies (a pathological hallmark in PD) in enteric neurons have also been reported in that disease. These lesions may explain the frequent gastro-intestinal dysfunction observed in PD patients. Alterations of other neuronal populations within the enteric nervous system (ENS) as well as the mechanisms responsible for these lesions (type of cell death, alteration of neuromediators gene expression) remain to be identified. The aim of the study is to demonstrate that alterations of the human ENS in PD can be evidenced by bowel biopsies and to determine whether they are correlated to the severity of motor disability and to gastrointestinal dysfunction.