ОЦЕНКА ИЗМЕНЕНИЙ ПОВЕДЕНЧЕСКИХ РЕАКЦИЙ ЛАБОРАТОРНЫХ ЖИВОТНЫХ ПРИ НАХОЖДЕНИИ В МОДЕЛЬНЫХ УСЛОВИЯХ С ПОВЫШЕННЫМ СОДЕРЖАНИЕМ ДИОКСИДА УГЛЕРОДА В УСЛОВИЯХ СУБХРОНИЧЕСКОГО ЭКСПЕРИМЕНТА

Abstract

The study of behavioral responses of Wistar rats under a 56-day exposure to carbon dioxide (CO₂) concentrations ranging from <500 ppm to >1500 ppm is relevant due to the issue of its accumulation in indoor air, an imperfect regulatory framework, and the lack of sufficient experimental evidence on the mechanisms of neurological disorders. A model experiment allows the establishment of pathogenic patterns of hypercapnia's effects on the CNS and the development of criteria for assessing human health risk.
The aim of the study is to assess the dynamics of changes in the behavioral responses of Wistar laboratory rats under conditions of subchronic exposure to elevated concentrations of carbon dioxide.
Materials and methods. The study involved 40 mature male Wistar rats weighing 250-300 g. The animals were randomized into 4 groups of 10 animals each. Group 1 (experimental, 1st shift): exposure to gradually increasing CO₂ concentrations (<500 ppm – 1-2 weeks; 500-1000 ppm – 3-4 weeks; 1000-1500 ppm – 5-6 weeks; >1500 ppm – 7-8 weeks) for 5.5 hours a day (from 8:00 to 13:30). Group 2 (experimental, 2nd shift): similar exposure to CO₂ at a different time of day (from 14:00 to 19:30). Groups 3 and 4 (control): intact animals maintained under identical conditions without additional CO₂ exposure (<500 ppm – 0-8 weeks), with observation during the first and second shifts, respectively. CO₂ exposure was conducted in sealed 400-liter chambers. The following parameters were assessed: functional activity of the nervous system.
Statistical analysis was performed using the Statistica 10.0 software. Data are presented as median (Me) and percentile range. The critical significance level for testing statistical hypotheses was considered to be differences at p ≤ 0.05. Animal experiments were conducted in accordance with the rules of the European Convention for the Protection of Animals used for Scientific Purposes, after approval by the Ethics Committee of the FSBI «Novosibirsk Research Institute of Hygiene» of Rospotrebnadzor. The study employed generally accepted and standardized methods.
Results and their discussion. During a 56-day experiment, statistically significant (p ≤ 0.05) dose-dependent impairments in behavioral responses were observed, manifested as progressive suppression of motor, exploratory, and emotional activity. The obtained data reveal the pathogenetic patterns of the effects of chronic hypercapnia on the central nervous system and confirm the need to revise the criteria for assessing health risks for humans during prolonged exposure in rooms with elevated CO₂ levels.
Conclusion. As a result of a 56-day subchronic experiment, it was found that exposure to CO₂ at concentrations ≥1000 ppm causes dose-dependent progressive suppression of motor, exploratory, and emotional activity in laboratory rats. The pronounced neurotropic effect of chronic hypercapnia did not depend on the time of day of exposure. The obtained data, particularly the observed similarity with age-related declines in CNS functions, justify the need to revise existing hygiene standards for CO₂ levels in indoor air.