Physiological and pathological changes in the enteric nervous system of rotenone-exposed mice as potential early biomarkers for Parkinson's disease

Parkinsons disease (PD) is known to involve the peripheral nervous system (PNS) and the enteric nervous system (ENS). Functional changes in PNS and ENS appear early in the course of the disease and are responsible for some of the non-motor symptoms observed in PD patients like constipation, that can precede the appearance of motor symptoms by years. We have shown that environmental toxins can trigger the disease by acting on the ENS and on the autonomic nervous system. Oral exposure to the pesticide rotenone, a mitochondrial Complex I inhibitor, leads to decreased stool depositions in mice. Here we analyzed the effect of rotenone on the function and structure of the ENS by measuring intestinal contractility in a tissue bath and by analyzing related protein expression. Our results show that rotenone changes the normal physiological response of the intestine to carbachol, dopamine and electric field stimulation. The magnitude and direction of these alterations varies between intestinal regions and exposure times and is associated with an early up-regulation of dopaminergic, cholinergic and adrenergic receptors and an irregular reduction in the amount of enteric neurons in rotenone-exposed mice. The early appearance of these alterations makes them ideal candidates to be used as biomarkers for the detection of Parkinsons disease in its early stages.