Acute restraint stress modifies the heart rate biorhythm in the poststress period

Figures

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  Figure 1. Timeline of the experiment. (A) Acute stress experiment. The transponders were implanted on day 0 (surgery); then, the mice were left undisturbed for one week, and on the next day (one restraint), the mice were restrained for 120 minutes. Thereafter, they were followed using telemetry for the next 5 days (recovery period). (B) Repeated stress experiment. The transponders were implanted on day 0 (surgery); then, the mice were left undisturbed for one week, and on the next day (first restraint), the mice were restrained for 120 minutes. This procedure was repeated the same time of the day for the next 7 days until the 15th day of the experiment (last restraint). Thereafter, they were followed using telemetry for the next 5 days (recovery period).

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  Figure 2. Changes in the heart rate biorhythm parameters in acute stress. Mesor, the median value in the biorhythm, Nmean, night mean, Dmean, day mean, TAUC, the total area under curve. *p < 0.05, difference from prestress period, **p < 0.01, difference from prestress period. ###p < 0.001, difference from WT animals. INT, intact animals, i.e., value in the prestress period (i.e., in unstressed animals), RESTR, the value during the day of restraint, POST1-POST5, the values in poststress days 1–5, HR, heart rate.

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  Figure 3. Changes in the total area under curve (TAUC, top) and difference between day and night means (D-N mean, bottom) in the repeated stress condition. *p < 0.05, difference from prestress period, **p < 0.01, difference from prestress period (i.e., in unstressed animals), ***p < 0.001, difference from prestress period. INT, intact animals, i.e., value in the prestress period, STR 1–7, the value during the first to seventh day of restraint, POST1-POST5, the values in poststress days 1–5, HR, heart rate.

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  Figure 4. Changes in the day mean (Dmean, top) and the night mean (Nmean, bottom) in the repeated stress conditions. *p < 0.05, difference from prestress period, **p < 0.01, difference from prestress period, ***p < 0.001, difference from prestress period. INT, intact animals, i.e., value in the prestress period (i.e., in unstressed animals), STR 1–7, the value during the first to seventh day of restraint, POST1-POST5, the values in poststress days 1–5, HR, heart rate.