Impact of seasonality on certain parameters of behavioral testing in rats

Introduction. Effects of the daytime period (circadian photoperiod) and seasonality on behavioral reactions and physiology of humans and animals remains one of the important issues of modern science. Material and methods. We have summarized our own data on control animals collected in experimental studies conducted in all seasons of the year. The hole-board test and summation threshold index were chosen to assess the behavior of rats. The data analysis was performed in Microsoft Excel 2016 using Student’s t-test, p<0.05. In addition, we estimated a percent deviation of the indicators under study from their annual averages. Results. We established that, as assessed by the number of head dips in the hole-board test, male rats kept at natural lighting demonstrated the most active exploratory behavior in spring and autumn while in summer, on the opposite, their exploration was statistically reduced. Values of the summation threshold index were the highest in winter and summer but lower in spring and especially in autumn. In springtime, the summation threshold index in male rats was statistically different from that observed in autumn and winter. In female rats, the index of the the hole-board test in spring was statistically significantly increased compared to data for all seasons of the year. Limitations of the study. An analysis was carried out of the data obtained at the experimental animal clinic of the Yekaterinburg Medical Research Center for Prophylaxis and Health Protection in Industrial Workers for 7 years (2015–2022). Conclusion. Our findings show that duration of the daytime period and seasonality can affect the results of some behavioral tests measuring lability of the central nervous system and exploratory activity of animals. They can contribute to the methodological basis for planning toxicity testing with account for seasonal fluctuations in physiological parameters of laboratory rodents.