Colonic electrical stimulation improves colonic transit in rotenone-induced Parkinson's disease model through affecting enteric neurons

Aims: The aims of this study were to investigate the effect of colonic electrical stimulation (CES) on delayed colonic transit in Parkinson's disease (PD) model induced by rotenone and its possible mechanisms. Main methods: Sprague-Dawley male rats were implanted with a pair of electrodes on the serosa at the proximal colon and rotenone was subcutaneously injected for 6 weeks to induce the PD model. Behavior activity, stool volume and open-field test were recorded during the injection. Colonic propulsion rate was measured 6 weeks after rotenone injection. Colon samples of all rats were collected for the measurement of phosphorylated alpha-synuclein, choline acetyltransferase (CHAT), neuronal nitric oxide synthase (nNOS), and tyrosine hydroxylase (TH). The protocols of control rats were the same as the PD rats except that no electrodes were implanted and no rotenone was injected. Key findings: (1) Rotenone-induced PD rats demonstrated weight loss, significant decrease of the dopaminergic neurons in substantia nigra, and impairment of colon movement (2) CES significantly accelerated the delayed colonic transmit (91.67 +/- 5.58% vs 51.33 +/- 4.18%), superior to Macrogol-4000. (3) CES significantly upregulated the expression of CHAT, nNOS and TH protein in colon of PD rats. (4) In colon of PD rats, the phosphorylated alpha-synuclein was significantly upregulated, but CES had no significant effect on phosphorylated alpha-synuclein. Significance: Our data show that CES can normalize the delayed colonic transit and this normalization may attribute to affecting enteric excitatory and inhibitory neurons.