Book of Abstracts - New Frontiers 2022

Abstracts of poster presentations

CARDIOVASCULAR RESPONSE OF RATS TO BEHAVIOURAL STRESS MEASURED IN PHENOTYPER

L. Molcan , H. Sutovska, L. Olexová, M. Morová, L. Kršková, M. Zeman

Department of Animal Physiology and Ethology, Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia

Psychosocial factors play a significant role in developing hypertension, and underlying causal connections are relatively complex. Therefore, defined experiments in animal models are necessary. In animals, the effects of psychosocial factors are usually studied through conditioned, pain-evoked tests. We took an alternative approach and measured the cardiovascular and behavioural parameters remotely and applied the weak stimuli randomly at different times of the day. Our aim was to test the cardiovascular response in telemetrically measured rats to weak, repeated and unconditional stress stimuli in rats kept in phenotypers. Adult male Wistar rats (n = 8; 444 ± 12 g) were include d in the experiment. Relative humidity (50 – 70 %), air temperature (20 – 22 ℃), and light regime (12L/12D; ZT0 = 8:00, beginning of the light phase) were controlled in the experimental room. We measured blood pressure (BP) and heart rate (HR) by telemetry (DSI, USA), a continuous 5 min recording with a sampling frequency of 500 Hz every 15 minutes. From beat-to-beat measurements, we analysed the number of normal-to-normal beats > 9 ms (NN9), the percentage of NN9 (pNN9) and the standard deviation of RR intervals (SDNN), which are presumably related to parasympathetic regulation. Before testing, the animals were tested and housed in PhenoTyper (Noldus, NL) for two days (habituation to the environment). After habituation, we exposed rats for 5 min to acoustic stress (scream typical for fights or pain; 0.2 – 20 kHz; http://ratbehavior.org) during both the light (ZT4.5 and 6.5) and dark (16.5 and 18.5) phases of the day. In ZT5.5 and 17.5, we exposed the animals to 5 min of air-jet stress. We compared the data by paired T-test or two-factor ANOVA (factors: stimulus vs phase or time vs phase). We found higher HR (p < 0.001) and BP (p < 0.001) in rats during the dark compared to the light phase of the day. In contrast, markers of parasympathetic activity were significantly higher during the light compared to the light phase of the day (NN9, p < 0.001; pNN9, p <0.001; SDNN, p < 0.05). The type of stimulus had a significant effect on the cardiovascular response. NN9, pNN9 and SDNN responded to behavioural stimuli less than HR and BP. We observed habituation and a high interindividual response to acoustic stress and a more pronounced and uniform response to air-jet stress. The phase of the day significantly affected the cardiovascular response to applied stressors. In conclusion, the cardiovascular response to stress stimulus exhibited significant light/dark and interindividual variability. Repeated acoustic stress led to habituation, the response was attenuated compared to air-jet stress, and we did not observe cross-reactivity between these different stimuli. Combining PhenoTyper and telemetry, we can reveal specific cardiovascular responses typical for different behavioural strategies.

Keywords: heart rate, blood pressure, telemetry, behavioural stress, PhenoTyper

Funding:APVV-17-0178 and VEGA 1/0492/19

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