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Parkinson’s disease (PD) is a common neurodegenerative disorder with a variety of motor and non-motor features. Non-motor symptoms, such as gastrointestinal dysfunction, usually set in 5 to 15 years earlier than motor manifestations. Cytoplasmic aggregates of phosphorylated α-synuclein are a typical marker of PD. They are observed not only in cerebral neurons but also in intramural plexuses of the intestine. Therefore, it is essential to investigate the peripheral component of the molecular pathogenesis of the disease using PD models, including those involving the use of parkinsonian neurotoxins, such as the well-known herbicide paraquat. The aim of this study was to identify a complex of early α-synuclein-related changes induced by long-term systemic administration of paraquat to rats at doses of 6 mg/kg. The open-field test revealed a decline in the motor activity of the experimental animals; the tapered beam walking test demonstrated a two-fold increase (р = 0.044) in the number of left paw slips. Besides, the intensity of staining for tyrosine hydroxylase (TH) in the substantia nigra and myenteric plexus fibers was 50% (р = 0.033) and 20% (р = 0.01) lower, respectively, in the main group than in the controls. Phosphorylated α-synuclein content was increased in the cell bodies of myenteric neurons and in TH-positive nervous fibers of the experimental animals. Changes indicating the development of peripheral α-synuclein pathology in the early stage of induced PD are similar to the changes observed in patients with PD at the onset of the disease. The proposed paraquat regimen could be very promising for PD modeling.

Studies of dietary preferences of migratory species are of great importance as these species connect food webs of habitats across the migration route and thus represent trophic relationships between the spatially disjointed communities. Here we describe dietary preferences of threespine stickleback G. aculeatus in the White Sea during the spawning season using stable isotope and stomach content analyses. Both analyses indicated that during the spawning season, when sticklebacks spend most of the time in the inshore, their diet significantly consist of benthic species in contrast to the start of the spawning season when fishes migrating from the offshore are feeding on zooplankton. Also, we show that stickleback eggs contribute greatly to the diet of both male and female fishes. Using Bayesian mixing modelling we show that dietary preferences in females were broader than in males, and more variable during the spawning season. Males fed on eggs almost while guarding their nests. Both stomach contents and isotope signatures demonstrate that by the end of the spawning season sticklebacks again increase consumption of plankton, and isotope analysis proved to be more reliable tool to trace this change than stomach content analysis. Our results show that stable isotope and stomach content analyses well supplement each other in understanding of seasonal changes in dietary composition of stickleback.

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