Rodent models of depression-cardiovascular comorbidity: Bridging the known to the new

Effects of social-ecological risk factors and resilience on the relationship between metabolic metrics and mental health among young adults

The correlation between metabolic metrics and mental health remains underexplored, with few in-depth studies examining whether this association exists among college students and whether it might be moderated by socio-ecological risk factors (SERFs) and mediated by resilience. A follow-up study design investigated the association between baseline metabolic metrics, SERFs and resilience and mental health. A multivariable linear regression model using the PROCESS method established the relationship of SERFs, resilience and metabolic metrics with mental health. Participants were 794 adolescents (mean age: 18.64 [±0.90] years). In multivariable linear regression, the high-level SERFs (β = 0.124), resilience (β = -0.042), LCI (β = 0.072), and RFM (β = 0.145) were associated with higher depression symptoms, while CVH (β = 0.602), TyG (β = 0.295), TyG-BMI (β = 0.004), and RC (β = -0.041) were not. An association was also observed between SERFs, resilience, RFM and anxiety. Resilience mediated the relationship between metabolic metrics and depression and anxiety, and SERFs moderated this relationship, demonstrating the relationship between resilience, metabolic metrics, SERFs and mental health. By revealing the potential sociological mechanism underlying the relationship between metabolic metrics and adolescents' mental health, this study provides a theoretical basis for further exploration of the biological foundations of mental health.

Role of corticotropin-releasing factor neurotransmission in the lateral hypothalamus on baroreflex impairment evoked by chronic variable stress in rats

Despite the importance of physiological responses to stress in a short-term, chronically these adjustments may be harmful and lead to diseases, including cardiovascular diseases. The lateral hypothalamus (LH) has been reported to be involved in expression of physiological and behavioral responses to stress, but the local neurochemical mechanisms involved are not completely described. The corticotropin-releasing factor (CRF) neurotransmission is a prominent brain neurochemical system implicated in the physiological and behavioral changes induced by aversive threats. Furthermore, chronic exposure to aversive situations affects the CRF neurotransmission in brain regions involved in stress responses. Therefore, in this study, we evaluated the influence of CRF neurotransmission in the LH on changes in cardiovascular function and baroreflex activity induced by chronic variable stress (CVS). We identified that CVS enhanced baseline arterial pressure and impaired baroreflex function, which were followed by increased expression of CRF2, but not CRF1, receptor expression within the LH. Local microinjection of either CRF1 or CRF2 receptor antagonist within the LH inhibited the baroreflex impairment caused by CVS, but without affecting the mild hypertension. Taken together, the findings documented in this study suggest that LH CRF neurotransmission participates in the baroreflex impairment related to chronic stress exposure.

Household air pollution from solid fuel use and depression among adults in rural China: evidence from the China Kadoorie Biobank data

BACKGROUND

Solid fuels are still widely used for cooking in rural China, leading to various health implications. Yet, studies on household air pollution and its impact on depression remain scarce. Using baseline data from the China Kadoorie Biobank (CKB) study, we aimed to investigate the relationship between solid fuel use for cooking and depression among adults in rural China.

METHODS

Data on exposure to household air pollution from cooking with solid fuels were collected and the Chinese version of the World Health Organization Composite International Diagnostic Interview short-form (CIDI-SF) was used to evaluate the status of major depressive episode. Logistic regression analysis was performed to investigate the association between solid fuel use for cooking and depression.

RESULTS

Amongst 283,170 participants, 68% of them used solid fuels for cooking. A total of 2,171 (0.8%) participants reported of having a major depressive episode in the past 12 months. Adjusted analysis showed that participants who had exposure to solid fuels used for cooking for up to 20 years, more than 20 to 35 years, and more than 35 years were 1.09 (95% CI: 0.94-1.27), 1.18 (95% CI: 1.01-1.38), and 1.19 (95% CI: 1.01-1.40) times greater odds of having a major depressive episode, respectively, compared with those who had no previous exposure to solid fuels used for cooking.

CONCLUSION

The findings highlight that longer exposure to solid fuels used for cooking would be associated with increased odds of major depressive episode. In spite of the uncertainty of causal relationship between them, using solid fuels for cooking can lead to undesirable household air pollution. Reducing the use of solid fuels for cooking by promoting the use of clean energy should be encouraged.

The effect of polluting cooking fuels on depression among older adults in six low- and middle-income countries

BACKGROUND

Little is known about the association between polluting cooking fuel and depression among older adults living in low- and middle-income countries (LMICs).

OBJECTIVE

To evaluate the association between polluting cooking fuel and depression in older population of LMICs.

METHODS

We derived data from WHO Study on global AGEing and adult health (SAGE), which was conducted in six LMICs including China, India, Ghana, South Africa, Mexico and Russia. We applied logistic regression with the propensity score method to examine the relationship of polluting cooking fuel and depression among adults ≥50 years old.

RESULTS

Overall, the odds ratio (OR) of depression was 1.57 [95% confidence intervals (CIs), 1.26-1.93] for older adults relying on polluting cooking fuel in six LMICs. In India and China, polluting cooking fuel was associated with depression with ORs of 2.06 (95%CI, 1.44-2.94) and 1.59 (95%CI, 1.01-2.49), respectively. Positive OR of depression was identified for those polluting cooking fuel users aged over 65 years old (OR, 1.65; 95%CI,1.16-2.36) and those aged 50-65 (OR, 1.50; 95%CI,1.14-1.97). Polluting cooking fuel was associated with depression for females (OR, 1.80; 95%CI, 1.32-2.46), however we did not observe significant association for males. Positive effect of polluting cooking fuel was identified in both rural (OR, 1.72; 95%CI, 1.26-2.34) and urban areas (OR, 1.44; 95%CI, 1.07-1.95). For individuals relying on solid fuel, cooking in a room used for living/sleeping and using open stove/fire was associated with depression with ORs of 1.30 (95%CI, 1.14-1.48) and 1.15 (95%CI, 1.01-1.31), respectively. However, no significant effect was identified for hood.

CONCLUSION

Polluting cooking fuel was related to depressive symptoms among older adults in LMICs. In addition, cooking ventilation could be useful intervention to control health hazard of solid fuel.

Anatomical Evidence for the Neural Connection from the Emotional Brain to Autonomic Innervation in the Anterior Chamber Structures of the Eye

OBJECTIVE

Previous studies have shown that the autonomic nervous system (ANS), which can be affected by emotions, is important in the occurrence or progression of glaucoma. The autonomic innervation distributed in the anterior chamber (AC) structures might play an efferent role in the neural regulation of intraocular pressure (IOP). This study aimed to investigate the anatomic neural connection from the emotional brain to autonomic innervation in the AC.

METHODS

A retrograde trans-multisynaptic pseudorabies virus encoded with an enhanced green fluorescent protein (PRV531) and non-trans-synaptic tracer FAST Dil were injected into the right eye of mice, respectively. Fluorescent localization in the emotional brain and preganglionic nuclei was studied. Five and a half days after PRV531 injection into the right AC, fluorescent signals were observed in several emotional brain regions, including the amygdala, agranular insular cortex, lateral septal nuclei, periaqueductal gray, and hypothalamus. Autonomic preganglionic nuclei, including Edinger-Westphal nucleus, superior salivatory nucleus, and intermediolateral nucleus, were labeled using PRV531.

RESULTS

The sensory trigeminal nuclei were not labeled using PRV531. The fluorescence signals in the nuclei mentioned above showed bilateral distribution, primarily on the ipsilateral side. Seven days after injecting FAST Dil into the AC, we observed no FAST Dil-labeled neurons in the central nervous system.

CONCLUSION

Our results indicate a neural connection from the emotional brain to autonomic innervation in the AC, which provides anatomical support for the emotional influence of IOP via the ANS.

Cross-Sectional Study of the Effects of Job Burnout on Immune Function in 105 Female Oncology Nurses at a Tertiary Oncology Hospital

Background

Nurses who work in hospitals experience a high level of burnout and the relationship between immune variables and burnout syndrome has yet to be elucidated. The aim of the present study was to investigate the effects of job burnout on immune function in female oncology nurses in a tertiary oncology hospital in Guangxi, China. The aspects of the human immune system evaluated were humoral and cellular immunity and complement components 3 (C3) and 4 (C4).

Material/Methods

We administered the Maslach Burnout Inventory-General Survey (MBI-GS), which includes scales for emotional exhaustion, depersonalization (DP), and personal accomplishment (PA), to measure variables related to immune function in 105 female nurses in a tertiary oncology hospital in Guangxi, China. Levels of humoral immunity and C3 and C4 were detected with immune turbidimetry. Cellular immunity was assessed with indirect immunofluorescence.

Results

A Spearman rank correlation analysis revealed that levels of C3, C4, and CD4- and CD8-positive T cells were significantly associated with burnout symptoms (P<0.05, P<0.01, and P<0.05, respectively). Furthermore, there was a correlation between demographic data and humoral and cellular immunity (both P<0.05). Multivariable linear regression analysis showed that C4 levels were closely related to DP (P<0.05) and that CD4 and CD8 levels were closely related to PA (P<0.01).

Conclusions

These results suggest that DP and PA have an impact on immune function, and that timely psychological and behavioral interventions can be used to reduce the degree of job burnout among nurses and regulate their immunity, thus enabling them to better serve patients.

Both CRF1 and CRF2 receptors in the bed nucleus of stria terminalis are involved in baroreflex impairment evoked by chronic stress in rats

Chronic exposure to adverse events has been proposed as a prominent factor involved in etiology and progression of cardiovascular dysfunctions in humans and animals. However, the neurobiological mechanisms involved are still poorly understood. In this sense, chronic stress has been reported to evoke neuroplasticity in corticotropin-releasing factor (CRF) neurotransmission in several limbic structures, including the bed nucleus of the stria terminalis. However, a possible involvement of BNST CRF neurotransmission in cardiovascular dysfunctions evoked by chronic stress has never been reported. Thus, this study investigated the involvement of CRF₁ and CRF₂ receptors within the BNST in cardiovascular changes evoked by chronic stress in rats. We identified that exposure to a 10-day chronic variable stress (CVS) protocol decreased expression of both CRF₁ and CRF₂ receptors within the BNST. These effects were followed by increased arterial pressure and impairment of baroreflex function, but without changes on heart rate. Bilateral microinjection of either the selective CRF₁ receptor antagonist CP376395 or the selective CRF₂ receptor antagonist antisauvagine-30 into the BNST did not affect CVS-evoked arterial pressure increase. Nevertheless, BNST treatment with CP376395 decreased both tachycardic and bradycardic responses of the baroreflex in non-stressed rats; but these effects were not identified in chronically stressed animals. BNST pharmacological treatment with antisauvagine-30 decreased the reflex tachycardia in control animals, whereas reflex bradycardic response was increased in CVS animals. Altogether, the results reported in the present study indicate that down regulation of both CRF₁ and CRF₂ receptors within the BNST is involved in baroreflex impairment evoked by chronic stress.

Role of angiotensin receptors in the medial amygdaloid nucleus in autonomic, baroreflex and cardiovascular changes evoked by chronic stress in rats

This study investigated the role of AT₁ , AT₂ and Mas angiotensinergic receptors within the MeA in autonomic, cardiovascular and baroreflex changes evoked by a 10-day (1  hr daily) repeated restraint stress (RRS) protocol. Analysis of cardiovascular function after the end of the RRS protocol indicated increased values of arterial pressure, without heart rate changes. Arterial pressure increase was not affected by acute MeA treatment after the RRS with either the selective AT₁ receptor antagonist losartan, the selective AT₂ receptor antagonist PD123319 or the selective Mas receptor antagonist A-779. Analysis of heart rate variability indicated that RRS increased the sympathetic tone to the heart, which was inhibited by MeA treatment with either losartan, PD123319 or A-779. Baroreflex function assessed using the pharmacological approach via intravenous infusion of vasoactive agents revealed a facilitation of tachycardia evoked by blood pressure decrease in chronically stressed animals, which was inhibited by MeA treatment with losartan. Conversely, baroreflex responses during spontaneous fluctuations of blood pressure were impaired by RRS, and this effect was not affected by injection of the angiotensinergic receptor antagonists into the MeA. Altogether, the data reported in the present study suggest an involvement of both angiotensinergic receptors present in the MeA in autonomic imbalance evoked by RRS, as well as an involvement of MeA AT₁ receptor in the enhanced baroreflex responses during full range of blood pressure changes. Results also indicate that RRS-evoked increase in arterial pressure and impairment of baroreflex responses during spontaneous variations of arterial pressure are independent of MeA angiotensinergic receptors.

Meranzin hydrate elicits antidepressant effects and restores reward circuitry

The burden of depression is enormous, and numerous studies have found that major depressive disorder (MDD) induces cardiovascular disorders (CVD) and functional dyspepsia (FD). Excitingly, meranzin hydrate (MH), an absorbed bioactive compound of Aurantii Fructus Immaturus, reverses psychosocial stress-induced mood disorders, gastrointestinal dysfunction and cardiac disease. Pharmacological methods have repeatedly failed in antidepressant development over the past few decades, but repairing aberrant neural circuits might be a reasonable strategy. This article aimed to explore antidepressant-like effects and potential mechanisms of MH in a rat model of unpredictable chronic mild stress (UCMS). Utilizing blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI), we sought to find reliable neurocircuits or a dominant brain region revealing the multiple effects of MH. The results show that compared with UCMS rats, MH (10 mg/kg/day for 1 week i.g.)-treated rats exhibited decreased depression-like behaviour; increased expression of brain-derived neurotrophic factor (BDNF) in the hippocampal dentate gyrus; and normalized levels of adrenocorticotropic hormone (ACTH), corticosterone (CORT), and acylated ghrelin (AG). Additionally, the UCMS-induced rise in BOLD activation in the reward system was attenuated after MH treatment. A literature search shown that nucleus accumbens (NAc) and hypothalamus of the reward system might reveal multiple effects of MH on MDD-FD-CVD comorbidity. Further research will focus on the role of these two brain regions in treating depression associated with comorbidities.

Physical Activity Promotes Health and Reduces Cardiovascular Mortality in Depressed Populations: A Literature Overview

Major depression is associated with premature mortality, largely explained by heightened cardiovascular burden. This narrative review summarizes secondary literature (i.e., reviews and meta-analyses) on this topic, considering physical exercise as a potential tool to counteract this alarming phenomenon. Compared to healthy controls, individuals with depression consistently present heightened cardiovascular risk, including "classical" risk factors and dysregulation of pertinent homeostatic systems (immune system, hypothalamic-pituitary-adrenal axis and autonomic nervous system). Ultimately, both genetic background and behavioral abnormalities contribute to explain the link between depression and cardiovascular mortality. Physical inactivity is particularly common in depressed populations and may represent an elective therapeutic target to address premature mortality. Exercise-based interventions, in fact, have proven effective reducing cardiovascular risk and mortality through different mechanisms, although evidence still needs to be replicated in depressed populations. Notably, exercise also directly improves depressive symptoms. Despite its potential, however, exercise remains under-prescribed to depressed individuals. Public health may be the ideal setting to develop and disseminate initiatives that promote the prescription and delivery of exercise-based interventions, with a particular focus on their cost-effectiveness.

Habituation of the cardiovascular response to restraint stress is inhibited by exposure to other stressor stimuli and exercise training

This study evaluated the effect of exposure to either a chronic variable stress (CVS) protocol or social isolation, as well as treadmill exercise training, in the habituation of the cardiovascular response upon repeated exposure to restraint stress in rats. The habituation of the corticosterone response to repeated restraint stress was also evaluated. For this, animals were subjected to either acute or 10 daily sessions of 60 min of restraint stress. CVS and social isolation protocols lasted for 10 consecutive days, whereas treadmill training was performed for 1 h per day, 5 days per week for 8 weeks. We observed that the increase in serum corticosterone was reduced during both the stress and the recovery period of the 10th session of restraint. Habituation of the cardiovascular response was identified in terms of a faster return of heart rate to baseline values during the recovery period of the 10th session of restraint. The increase in blood pressure and the decrease in tail skin temperature were similar at the 1st and 10th session of restraint. Exposure to CVS, social isolation or treadmill exercise training inhibited the habituation of the restraint-evoked tachycardia. Additionally, CVS increased the blood pressure response at the 10th session of restraint, whereas social isolation enhanced both the tachycardia during the first session and the drop in skin temperature at the 10th session of restraint. Taken together, these findings provide new evidence that pathologies evoked by stress might be related to impairment in the habituation process to homotypic stressors.

Antidepressant-like effects of pharmacological inhibition of FAAH activity in socially isolated female rats

Pharmacological inhibition of the enzyme fatty acid amide hydrolase (FAAH), which terminates signaling of the endocannabinoid N-arachidonoylethanolamine (or anandamide, AEA), exerts favourable effects in rodent models of stress-related depression. Yet although depression seems to be more common among women than men and in spite of some evidence of sex differences in treatment efficacy, preclinical development of FAAH inhibitors for the pharmacotherapy of stress-related depression has been predominantly conducted in male animals. Here, adult female rats were exposed to six weeks of social isolation and, starting from the second week, treated with the FAAH inhibitor URB694 (0.3 mg/kg/day, i.p.) or vehicle. Compared to pair-housed females, socially isolated female rats treated with vehicle developed behavioral (mild anhedonia, passive stress coping) and physiological (reduced body weight gain, elevated plasma corticosterone levels) alterations. Moreover, prolonged social isolation provoked a reduction in brain-derived neurotrophic factor (BDNF) and AEA levels within the hippocampus. Together, these changes are indicative of an increased risk of developing a depressive-like state. Conversely, pharmacological inhibition of FAAH activity with URB694 restored both AEA and BDNF levels within the hippocampus of socially isolated rats and prevented the development of behavioral and physiological alterations. These results suggest a potential interplay between AEA-mediated signaling and hippocampal BDNF in the pathogenesis of depression-relevant behaviors and physiological alterations and antidepressant action of FAAH inhibition in socially isolated female rats.

The AT1 Receptor Antagonist Losartan Does Not Affect Depressive-Like State and Memory Impairment Evoked by Chronic Stressors in Rats

The present study investigated the effect of the treatment with the angiotensin II type 1 receptor (AT₁) antagonist losartan in the depressive-like state and memory impairment evoked by exposure to either homotypic (i.e., repeated exposure to the same type of stressor) or heterotypic (i.e., exposure to different aversive stimuli) chronic stressors in rats. For this, male Wistar rats were subjected to a 10 days regimen of repeated restraint stress (RRS, homotypic stressor) or chronic variable stress (CVS, heterotypic stressor) while being concurrently treated daily with losartan (30 mg/kg/day, p.o.). Depressive-like state was evaluated by analysis of the alterations considered as markers of depression (decreased sucrose preference and body weight and coat state deterioration), whereas cognitive non-emotional performance was tested using the novel object recognition (NOR) test. Locomotor activity was also evaluated in the open field test. Both RRS and CVS impaired sucrose preference and caused coat state deterioration, whereas only CVS impaired body weight gain. Besides, RRS impaired short-term memory (but not long-term memory) in the NOR test. Neither depressive-like state nor memory impairment evoked by the chronic stressors was affected by the treatment with losartan. Nevertheless, CVS increased the locomotion, which was inhibited by losartan. Taken together, these results provide evidence that the chronic treatment with losartan does not affect the depressive-like state and memory impairment evoked by either homotypic or heterotypic chronic stress regimens in rats.

Alleviating Effect of Antidepressant Treatment on Psychiatric Symptoms and Cardiac Conditions in a Patient with Coronary Slow Flow Comorbid with Depression and Anxiety

Patient: Female, 52

Final Diagnosis: Coronary slow flow

Symptoms: Frequent chest pain • serious TIMI grade 2 flow without any coronary stenosis • comorbid with depression and anxiety

Medication: —

Clinical Procedure: —

Specialty: Psychiatry

Cardiac and behavioral effects of social isolation and experimental manipulation of autonomic balance

Improved understanding of how depression and social isolation interact to increase cardiac morbidity and mortality will improve public health. This experiment evaluated the effect of pharmacological autonomic blockade on cardiac and behavioral reactivity following social isolation in prairie voles. Experiment 1 validated the dose and time course of pharmacological autonomic antagonism of peripheral β-adrenergic (atenolol) and muscarinic cholinergic receptors (atropine methyl nitrate), and Experiment 2 used a novel protocol to investigate behavioral responses in the tail suspension test during pharmacological autonomic blockade as a function of social isolation (vs. paired control). Prairie voles isolated for 4 weeks (vs. paired) displayed significantly elevated heart rate and reduced heart rate variability. Autonomic receptor antagonism by atenolol led to exaggerated reductions in heart rate and standard deviation of normal-to-normal intervals, and lower amplitude of respiratory sinus arrhythmia in the isolated group (vs. paired). Administration of atropine led to an attenuated increase in heart rate in the isolated group (vs. paired), and similar near-zero levels of respiratory sinus arrhythmia amplitude in both groups. During the tail suspension test, isolated animals (vs. paired) displayed significantly greater immobility. In paired animals, atenolol administration did not influence immobility; atropine administration increased the duration of immobility (vs. vehicle). In isolated animals, atenolol administration increased the duration of immobility; atropine did not influence immobility duration (vs. vehicle). The current study contributes to our understanding of differential effects of social isolation and autonomic imbalance on cardiac and behavioral reactivity.

Antidepressant and anxiolytic effects of the proprietary Chinese medicine Shexiang Baoxin pill in mice with chronic unpredictable mild stress

Depression and anxiety often co-occur with cardiac diseases. The Shexiang Baoxin pill (SBP) is a proprietary Chinese medicine initially used to treat cardiac conditions. This study explored whether SBP has antidepressant and anxiolytic effects in addition to hormonal and psychotropic mechanisms. Mice underwent 6 weeks of chronic unpredictable mild stress (CUMS) to induce depression- and anxiety-like behavior. During the 6-week experiment, mice received SBP at intragastric doses of 20.25 mg/kg or 40.5 mg/kg daily. Animals were then tested for depression in sucrose preference, forced-swimming, and tail suspension paradigms, and for anxiety in open field and elevated plus maze tests. Both SBP doses significantly reduced anhedonic behavior in the sucrose preference test; the high SBP dose also increased the number of entries into the central zone of the open field. SBP-treated mice had markedly lower blood levels of corticotrophin-releasing hormone (CRH) and adrenocorticotropic hormone (ACTH) than stressed mice treated with vehicle. Either low- or high-dose SBP reversed stress-induced reductions of norepinephrine (NE) and dopamine (DA) metabolites and the expression levels of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and glial cell-derived neurotrophic factor (GDNF) in related brain regions. These results suggest that SBP could prevent and alleviate prolonged stress-induced anhedonia and anxiety in association with its suppression of the hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, modulation of brain monoamine neurotransmitter metabolism and neurotrophins. SBP may be particularly suitable for the management of depressive and anxiety disorders in patients with cardiac conditions.

Autonomic and Brain Morphological Predictors of Stress Resilience

Stressful life events are an important cause of psychopathology. Humans exposed to aversive or stressful experiences show considerable inter-individual heterogeneity in their responses. However, the majority does not develop stress-related psychiatric disorders. The dynamic processes encompassing positive and functional adaptation in the face of significant adversity have been broadly defined as resilience. Traditionally, the assessment of resilience has been confined to self-report measures, both within the general community and putative high-risk populations. Although this approach has value, it is highly susceptible to subjective bias and may not capture the dynamic nature of resilience, as underlying construct. Recognizing the obvious benefits of more objective measures of resilience, research in the field has just started investigating the predictive value of several potential biological markers. This review provides an overview of theoretical views and empirical evidence suggesting that individual differences in heart rate variability (HRV), a surrogate index of resting cardiac vagal outflow, may underlie different levels of resilience toward the development of stress-related psychiatric disorders. Following this line of thought, recent studies describing associations between regional brain morphometric characteristics and resting state vagally-mediated HRV are summarized. Existing studies suggest that the structural morphology of the anterior cingulated cortex (ACC), particularly its cortical thickness, is implicated in the expression of individual differences in HRV. These findings are discussed in light of emerging structural neuroimaging research, linking morphological characteristics of the ACC to psychological traits ascribed to a high-resilient profile and abnormal structural integrity of the ACC to the psychophysiological expression of stress-related mental health consequences. We conclude that a multidisciplinary approach integrating brain structural imaging with HRV monitoring could offer novel perspectives about brain-body pathways in resilience and adaptation to psychological stress.

Social stress contagion in rats: Behavioural, autonomic and neuroendocrine correlates

The negative emotional consequences associated with life stress exposure in an individual can affect the emotional state of social partners. In this study, we describe an experimental rat model of social stress contagion and its effects on social behaviour and cardiac autonomic and neuroendocrine functions. Adult male Wistar rats were pair-housed and one animal (designated as "demonstrator" (DEM)) was submitted to either social defeat stress (STR) by an aggressive male Wild-type rat in a separate room or just exposed to an unfamiliar empty cage (control condition, CTR), once a day for 4 consecutive days. We evaluated the influence of cohabitation with a STR DEM on behavioural, cardiac autonomic and neuroendocrine outcomes in the cagemate (defined "observer" (OBS)). After repeated social stress, STR DEM rats showed clear signs of social avoidance when tested in a new social context compared to CTR DEM rats. Interestingly, also their cagemate STR OBSs showed higher levels of social avoidance compared to CTR OBSs. Moreover, STR OBS rats exhibited a higher heart rate and a larger shift of cardiac autonomic balance toward sympathetic prevalence (as indexed by heart rate variability analysis) immediately after the first reunification with their STR DEMs, compared to the control condition. This heightened cardiac autonomic responsiveness habituated over time. Finally, STR OBSs showed elevated plasma corticosterone levels at the end of the experimental protocol compared to CTR OBSs. These findings demonstrate that cohabitation with a DEM rat, which has experienced repeated social defeat stress, substantially disrupts social behaviour and induces short-lasting cardiac autonomic activation and hypothalamic-pituitary-adrenal axis hyperactivity in the OBS rat, thus suggesting emotional state-matching between the OBS and the DEM rats. We conclude that this rodent model may be further exploited for investigating the neurobiological bases of negative affective sharing between social partners under chronic social stress conditions.