Cardiovascular outcomes related to social defeat stress: New insights from resilient and susceptible rats

Figures

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  Fig. 1. Graphical representation of the experimental procedure. Social defeat stress was performed every other day (days 1, 3, 5 and 7) for 7 days, totalizing 4 aggressive encounters. Stress coping phenotypes were identified by the SIT 24 h later. After the phenotyping, animals were used to evaluate the behavioral alterations related to anxiety and depression or were cannulated to the recording of cardiovascular parameters. SIT, social interaction test; EPM, elevated plus maze; FST, forced swim test.

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  Fig. 2. Interaction ratio and time spent in interaction and avoidance zones of the social interaction apparatus in resilient and susceptible phenotypes to social defeat stress. Social interaction test was performed 24 h after the last social defeat episode. Bars represent means +SEM (n = 18–20 animals per group). A, interaction ratio. B, time spent in the interaction zone. C, time spent in the avoidance zone. *, p < 0.05 relative to control group; #, p < 0.05 relative to resilient group; +, p < 0.05 relative to time spent in the no-target phase of the same group.

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  Fig. 3. Anxiety-like behaviors of resilient and susceptible phenotypes to social defeat stress in elevated plus maze. The test was performed 48 h after the last social defeat episode. Bars represent means +SEM (n = 8–10 animals per group). A, number of entries in the closed arms of the apparatus. B, percentage of number of entries and time spent in the open arms of the apparatus. *, p < 0.05 relative to control group; $, p < 0.05 relative to susceptible group.

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  Fig. 4. Depressive-like behaviors of resilient and susceptible phenotypes to social defeat stress in the forced swim test. The test was performed 96 h after the last social defeat episode. Bars represent means +SEM (n = 8–10 animals per group). A, time spent immobile. B, latency to exhibit first immobility episode. C, time spent in active horizontal movements. D, time spent in active vertical movements towards the walls of the apparatus. *, p < 0.05 relative to control group; #, p < 0.05 relative to resilient group.

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  Fig. 5. Coat state deterioration in resilient and susceptible phenotypes to social defeat stress. Fur quality was evaluated right before each aggressive encounter and social interaction test. Bars represent means +SEM (n = 8–12 animals per group). *, p < 0.05 relative to control group; #, p < 0.05 relative to resilient group.

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  Fig. 6. Heart rate and blood pressure during rest in resilient and susceptible phenotypes to social defeat stress. Animals were cannulated 48 h after the last social defeat episode and cardiovascular parameters were recorded 24 h later. Bars represent means +SEM (n = 6–8 animals per group). A, heart rate (HR). B, mean arterial pressure (MAP). C, systolic arterial pressure (SAP). D, diastolic arterial pressure (DAP). *, p < 0.05 relative to control group; #, p < 0.05 relative to resilient group.

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  Fig. 7. Power spectral analyzes of pulse interval in time and frequency domains in resilient and susceptible phenotypes to social defeat stress. Stationary periods of pulse interval were extracted from the registry of resting pulsatile arterial pressure held 72 h after the last social defeat episode. Bars represent means +SEM (n = 6–8 animals per group). A, total variance of pulse interval in the time domain. B, Root Mean Square of the Successive Differences (RMSSD). C, power of oscillatory components in the frequency bands of low frequency (LF, 0.20–0.75 Hz). D, power of oscillatory components in the frequency bands of high frequency (HF, 0.75–3.0 Hz). E, sympathovagal balance calculated using LF/HF ratio. SDPI, standard deviation of pulse interval; LF, low frequency; HF, high frequency. *, p < 0.05 relative to control group; #, p < 0.05 relative to resilient group; $, p < 0.05 relative to susceptible group.

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  Fig. 8. Spontaneous baroreflex gain and effectiveness in resilient and susceptible phenotypes to social defeat stress. Stationary periods of pulse interval and systolic arterial pressure were extracted from the registry of resting pulsatile arterial pressure held 72 h after the last social defeat episode. Bars represent means +SEM (n = 6–8 animals per group). A, baroreflex gain of up, down and all baroreflex sequences. B, baroreflex effectiveness index (BEI). *, p < 0.05 relative to control group; #, p < 0.05 relative to resilient group.

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  Fig. 9. Baroreflex activity during an acute pressure stimulus in resilient and susceptible phenotypes to social defeat stress. Drugs were infused right after the 60 min of resting of recording resting cardiovascular parameters. Points and lines represent means ± SEM (n = 6–8 animals per group). ΔHR, heart rate variation; ΔMAP, mean arterial pressure variation.