SERPING1 and Parkinson disease: In this study, based on the report that the MPTP (1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine) is a representative dopamine neuron toxin in the ENS inducing gastrointestinal (GI) dysfunction4, the association between serping1, a major controller of the kinin system, and α-syn in PD colon was investigated in an MPTP-induced chronic PD model.