Motor function is not impaired in all components of the oral phase of feeding in a rat rotenone model of Parkinson’s disease

Abstract

Parkinson’s disease results in pathological swallowing, or dysphagia, in up to 90% of cases. Severity and extent of functional impairment of feeding is highly variable in this disease. Feeding is a multi step neuromuscular process of tightly coordinated orofacial behaviors -transport, food reduction, pharyngeal swallowing- involving multiple musculoskeletal systems — tongue, jaw muscles, hyolaryngeal muscles — innervated by multiple cranial and cervical spinal nerves. The type of food being ingested further affects this sequence. The pesticide rotenone, a type II mitochondrial inhibitor, has been epidemiologically linked to Parkinson’s disease. The goal of this project is to identify how parkinsonian neurodegeneration affects this sequence in an animal model. We hypothesize that not all elements of the sequence will be equally affected. Twelve young adult male Lewis rats received daily intraperitoneal injections of either 2.75 mg/kg of rotenone or vehicle control for 8 days. The rats were trained to eat breakfast cereal and drink water mixed with barium in front of a high speed (200 fps) videofluoroscope. From the high speed video recording duration of intraoral transport and chewing of solid food as well as lick duration for liquid drinking were measured for multiple swallows per individual on day 0 (before injection), day 1, day 4, and day 7. On day 8 animals were perfused and brains harvested, sliced, stained with immunofluorescent markers for striatal tyrosine hydroxylase to confirm effectiveness of the model. Mixed model ANOVA was used to test the hypothesis that duration of the phases varied over the course of treatment. Duration of intra oral transport changed in neither control nor rotenone treated animals (p=0.1136), but duration of chewing increased in rotenone treated rats only by day 4 (p<0.001). Duration of licks increased in liquid drinking rats from day 0. Different components of the oral feeding process vary in degree and timing of impairment in the rat rotenone model of Parkinson’s disease, with coordinated rhythmic tongue and jaw movements (licking and chewing) being most sensitive. The neurological basis for this differential sensitivity remains unclear. Internal Rowan funds to Dr. Gould supported this work. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.