Characterization of the Basic Membrane Properties of Neurons of the Rat Dorsal Motor Nucleus of the Vagus in Paraquat-Induced Models of Parkinsonism.

Most of Parkinson's disease (PD) patients experience gastrointestinal dysfunctions, including gastric hypomotility. The dorsal motor nucleus of the vagus (DMV) modulates the motility of the upper gastrointestinal (GI) tract. Paraquat (P) administration induces Parkinsonism in experimental models, and we have developed recently an environmental model of Parkinsonism in which rats are treated with subthreshold doses of P and lectins (P + L), in both models rats develop reduced gastric motility prodromal to the full extent of motor deficits. The aim of the present study was to examine whether the membrane properties of DMV neurons in these two experimental models of Parkinsonism were altered. Whole cell recordings in slices containing DMV neurons were conducted in male Sprague Dawley rats which received either injections of paraquat (10 mg/kg i.p.; 10P), or oral administration of paraquat (1 mg/kg) and lectin (0.05% w/v; P + L). Morphological reconstructions of DMV neurons were conducted at the end of the recordings. The repolarization kinetics of the afterhyperpolarization phase of the action potential was accelerated in 10P neurons vs control, while the phase plot revealed a slower depolarizing slope. At baseline, the amplitude of miniature excitatory postsynaptic currents was increased in P + L neurons. No differences in the morphology of DMV neurons were observed. These data indicate that the membrane and synaptic properties of DMV neurons are altered in rodent models of Parkinsonism, in which neurons of 10P and P + L rats demonstrate an increased excitatory transmission, perhaps in an attempt to counteract the paraquat-induced gastric hypomotility.