The negative effects of social bond disruption are partially ameliorated by sertraline administration in prairie voles

Sex differences in heart rate variability measures that predict alcohol drinking in rats

Problem alcohol drinking continues to be a substantial cost and burden. In addition, alcohol consumption in women has increased in recent decades, and women can have greater alcohol problems and comorbidities. Thus, there is a significant need for novel therapeutics to enhance sex-specific, individualized treatment. Heart rate (HR) and HR variability (HRV) are of broad interest because they may be both biomarkers for and drivers of pathological states. HRV reflects the dynamic balance between sympathetic (SNS, 'fight or flight') and parasympathetic (PNS, 'rest and digest') systems. Evidence from human studies suggest PNS predominance in women and SNS in men during autonomic regulation, indicating the possibility of sex differences in risk factors and physiological drivers of problem drinking. To better understand the association between HRV sex differences and alcohol drinking, we examined whether alcohol consumption levels correlated with time domain HRV measures (SDNN and rMSSD) at baseline, at alcohol drinking onset, and across 10 min of drinking, in adult female and male Wistar rats. In particular, we compared both HRV and HR measures under alcohol-only and compulsion-like conditions (alcohol + 10 mg/L quinine), because compulsion can often be a significant barrier to treatment of alcohol misuse. Importantly, previous work supports the possibility that different HRV measures could be interpreted to reflect PNS versus SNS influences. Here, we show that females with higher putative PNS indicators at baseline and at drinking onset had greater alcohol consumption. In contrast, male intake levels related to increased potential SNS measures at drinking onset. Once alcohol was consumed, HR predicted intake level in females, perhaps a pharmacological effect of alcohol. However, HRV changes were greater during compulsion-like intake versus alcohol-only, suggesting HRV changes (reduced SNS in females, reduced PNS and increased HR in males) specifically related to aversion-resistant intake. We find novel and likely clinically relevant autonomic differences associated with biological sex and alcohol drinking, suggesting that different autonomic mechanisms may promote differing aspects of female and male alcohol consumption.

Maladaptive cardiac and behavioral reactivity to repeated vicarious stress exposure in socially bonded male prairie vole siblings

Behaviors, emotions, and cardiovascular functions are influenced by stress. But these detrimental effects are not exclusive to an individual that directly experiences stress. Stress is also experienced vicariously through observation of another individual undergoing stress. The current study used the strong social bonds in socially monogamous prairie voles to determine effects of repeated vicarious stress on cardiac and behavioral outcomes. Male prairie voles were exposed to either a 5-minute open field chamber alone [separate (control)] or while concurrently witnessing their sibling undergo a tail-suspension stressor [concurrent (experimental)], repeated across 4 sessions. Cardiac responses in animals in the open field were evaluated for heart rate and heart rate variability prior to, during, and after each test session, and behaviors were evaluated for motion, exploration, stress reactivity, and anxiety-relevant behaviors during each test session. The concurrent condition (versus separate) displayed increased heart rate and reduced heart rate variability during repeated test sessions, and impaired recovery of these parameters following the test sessions. The pattern of disturbances suggests that both increased sympathetic and reduced parasympathetic influence contributed to the cardiac responses. Animals in the concurrent condition (versus separate) displayed disrupted rearing, grooming, and motion; reduced duration of center section exploration; and increased freezing responses across repeated test sessions. Collectively, cardiac and behavioral stress reactivity are increased as a function of vicarious stress in prairie voles, which are evident across repeated experiences of stress. These results inform our understanding of the experience of vicarious stress in social species, including humans.

Heart rate variability measures indicating sex differences in autonomic regulation during anxiety-like behavior in rats

Introduction

Mental health conditions remain a substantial and costly challenge to society, especially in women since they have nearly twice the prevalence of anxiety disorders. However, critical mechanisms underlying sex differences remain incompletely understood. Measures of cardiac function, including heart rate (HR) and HR variability (HRV), reflect balance between sympathetic (SNS) and parasympathetic (PNS) systems and are potential biomarkers for pathological states.

Methods

To better understand sex differences in anxiety-related autonomic mechanisms, we examined HR/HRV telemetry in food-restricted adult rats during novelty suppression of feeding (NSF), with conflict between food under bright light in the arena center. To assess HRV, we calculated the SDNN (reflective of both SNS and PNS contribution) and rMSSD (reflective of PNS contribution) and compared these metrics to behaviors within the anxiety task.

Results

Females had greater HR and lower SNS indicators at baseline, as in humans. Further, females (but not males) with higher basal HR carried this state into NSF, delaying first approach to center. In contrast, males with lower SNS measures approached and spent more time in the brightly-lit center. Further, females with lower SNS indicators consumed significantly more food. In males, a high-SNS subpopulation consumed no food. Among consumers, males with greater SNS ate more food.

Discussion

Together, these are congruent with human findings suggesting women engage PNS more, and men SNS more. Our previous behavior-only work also observed female differences from males during initial movement and food intake. Thus, high basal SNS in females reduced behavior early in NSF, while subsequent reduced SNS allowed greater food intake. In males, lower SNS increased engagement with arena center, but greater SNS predicted higher consumption. Our findings show novel and likely clinically relevant sex differences in HRV-behavior relationships.

Morphological changes in the basolateral amygdala and behavioral disruptions associated with social isolation

Social isolation and the disruption of established social bonds contribute to several physical and psychological health issues. Animal models are a useful tool for investigating consequences of social stress, including social isolation. The current study examined morphological changes in the basolateral amygdala (BLA) and affect-related behavioral and endocrine changes due to prolonged social isolation, using the translational prairie vole model (Microtus ochrogaster). Adult male prairie voles were either socially paired (control) or isolated from a same-sex sibling for 4 weeks. Following this 4-week period, a subset of animals (n = 6 per condition) underwent a series of behavioral tasks to assess affective, social, and stress-coping behaviors. Plasma was collected following the last behavioral task for stressor-induced endocrine assays. Brains were collected from a separate subset of animals (n = 10 per condition) following the 4-week social housing period for dendritic structure analyses in the BLA. Social isolation was associated with depressive- and anxiety-like behaviors, as well as elevated oxytocin reactivity following a social stressor. Social isolation was also associated with altered amount of dendritic material in the BLA, with an increase in spine density. These results provide further evidence that social isolation may lead to the development of affective disorders. Dysfunction in the oxytocin system and BLA remodeling may mediate these behavioral changes. Further research will promote an understanding of the connections between oxytocin function and structural changes in the BLA in the context of social stress. This research can facilitate novel treatments for alleviating or preventing behavioral and physiological consequences of social stressors in humans.

Depresssion, anxiety and other cognitive consequences of social isolation: Drug and non-drug treatments

OBJECTIVE

During the COVID-19 pandemic, quarantine and staying at home is advised. The social relationship between people has become deficient, and human social isolation (SI) has become the consequence of this situation. It was shown that SI has made changes in hippocampal neuroplasticity, which will lead to poor cognitive function and behavioural abnormalities. There is a connection between SI, learning, and memory impairments. In addition, anxiety-like behaviour and increased aggressive mood in long-term isolation have been revealed during the COVID-19 outbreak.

METHODS

Term searches was done in Google Scholar, Scopus, ScienceDirect, Web of Science and PubMed databases as well as hand searching in key resource journals from 1979 to 2020.

RESULTS

Studies have shown that some drug administrations may positively affect or even prevent social isolation consequences in animal models. These drug treatments have included opioid drugs, anti-depressants, Antioxidants, and herbal medications. In addition to drug interventions, there are non-drug treatments that include an enriched environment, regular exercise, and music.

CONCLUSION

This manuscript aims to review improved cognitive impairments induced by SI during COVID-19.

Behavioral and neuroendocrine consequences of disrupting a long-term monogamous social bond in aging prairie voles

Social support from a spouse, long-term partner, or someone who provides emotional or instrumental support may protect against consequences of aging, including mediating behavioral stress reactivity and altering neurobiological process that underlie short-term stress responses. Therefore, long-term social bonding may have behavioral and neurobiological benefits. The socially monogamous prairie vole provides a valuable experimental model for investigating the benefits of long-term social bonds on short-term stress reactivity in aging animals, given their unique social structure of forming enduring opposite-sex bonds, living in family groups, and bi-parental rearing strategies. Male-female pairs of long-term, cohabitating prairie voles were investigated for short-term behavioral and neuroendocrine stress reactivity following either long-term social pairing (control), or a period of social isolation. In Experiment 1, social isolation was associated with altered behavioral reactivity to an acute swim stressor, and greater neural activation in the hypothalamic paraventricular nucleus, as well as specifically the parvocellular region, following the swim stressor (vs. control). In Experiment 2, social isolation was associated with greater corticosterone reactivity following an acute restraint stressor (vs. control). No sex differences were observed. Exploratory correlation and subgroup analyses revealed systematic relationships among various demographic variables (such as age of the subjects, amount of time the pair cohabitated together, and number of litters the pair reared together) and the behavioral and neuroendocrine outcome measures. These findings may inform our understanding of the benefits of long-term social bonding on modulating short-term behavioral and neuroendocrine responses to stress.LAY SUMMARYReceiving social support from a long-term spouse or partner, or having a strong support network from friends, may have important health benefits as people age. In aging monogamous prairie voles, social isolation from a long-term social partner disrupted behaviors and short-term stress responses, whereas living with a long-term partner protected against these disruptions. This research is important for our understanding of the benefits of social support on stress responses as we age.

Physiological and behavioral responses to observing a sibling experience a direct stressor in prairie voles

Uncontrollable stress precipitates negative mental and physical health outcomes. Furthermore, the vicarious experience of stress (e.g. observing another individual experience a direct stressor) can mimic the effects of directly experiencing the stressor. The current experiment examined the behavioral and physiological effects of the vicarious experience of stress using the socially monogamous prairie vole. Male prairie voles were exposed to either an empty open field chamber, or a chamber in which the animal observed a sibling undergoing a concurrent direct physical stressor (tail suspension test) for five minutes. Exploratory and anxiety-like behaviors were recorded in all observers during the test session. Cardiac indices of heart rate and heart rate variability were recorded in a subset of observers prior to, during, and following the test session. Corticosterone levels were measured in all observers and siblings following the test session. When compared to animals exposed to an empty open field chamber, animals that observed a sibling undergo a direct physical stressor exhibited increased heart rate and circulating corticosterone, and decreased heart rate variability. These physiological stress indicators were supported by behavioral changes, including increased freezing followed immediately by orienting of the head toward the center of the apparatus, and decreased locomotion, grooming, and rearing. These preliminary results suggest that prairie voles experience stress vicariously, and provide a foundation for additional studies focused on the underlying mechanisms of vicarious stress. The use of this model may inform our understanding of the social transmission of stress among social species, including humans.LAY SUMMARYThe experience of stress, including observing stress in a loved one, has negative consequences on mental and physical health. This study used a social rodent (prairie voles) to demonstrate that stress transfers among social individuals, consequently producing an increased physiological and behavioral stress response in prairie voles observing their siblings experience stress. This research informs our understanding of the interactions of social experiences and stress in humans.