Environmental enrichment in mice decreases anxiety, attenuates stress responses and enhances natural killer cell activity

Disturbing sleep in female adolescent mice does not increase vulnerability to depression triggers later in life

Poor sleep quality is a major issue for many adolescents and is associated with fatigue, poor academic performance, and depression. Adolescence is a crucial neurodevelopmental stage where multiple neuropsychiatric illnesses often emerge, suggesting increased central nervous system vulnerability, specifically at this age, which could be exacerbated by poor sleep. Studies on adolescent mice show that sleep deprivation or sleep disturbance (SD) induces structural and functional brain changes, indicating that SD affects the adolescent brain. The long-term consequences of such changes are poorly understood. We hypothesize that SD during adolescence increases vulnerability to future depression triggers in adulthood, such as social isolation or inflammation. To test this, female adolescent mice (post-natal day (P)36) were subjected to SD for seven days, 4 h per day during the light phase (zeitgeber time 2-6). We demonstrate that this SD protocol acutely leads to changes in the expression of Cx3Cr1, and Dnmt3b in the hippocampus and of Htr1a in the prefrontal cortex. To examine the long-term consequences of the SD protocol during adulthood (P77-84), the mice were then either exposed to single housing or received a single injection of lipopolysaccharide (LPS) to mimic known triggers of depression. Behavioral changes were examined using digital ventilated cages to track home-cage activity and the open field and tail suspension tests to assess anxiety- and despair-like behavior, respectively. In contrast to our hypothesis, we did not observe any changes in home-cage activity, anxiety- or despair-like behavior as a result of combining SD in adolescent female mice with a depression trigger in adulthood. We conclude that the adolescent brain is sensitive to SD, but SD during adolescence in mice does not lead to an exacerbated depression-like response to social isolation or inflammation during adulthood.

Early-life environmental enrichment promotes positive animal welfare for juvenile Atlantic salmon (Salmo salar) in aquaculture research

Early life experiences have long-lasting effects on behaviour and physiology, influencing development of adaptive natural behaviours. Enriching farmed environments encourages expression of natural behaviours in captive fish, promoting positive animal welfare, important for conducting valid and reproducible research and informing better management practices. Using juvenile Atlantic Salmon (Salmo salar), we tested whether provision of environmental enrichment in early life improves welfare. Welfare indicators were measured comparing enriched to non-enriched tanks. Morphological (fin damage and body condition), physiological (plasma cortisol) and behavioural traits (activity, group cohesion, and neophobia) were recorded. Molecular expression of brain mRNA transcripts related to stress response, neuroplasticity and serotonergic system was analysed. Environmental enrichment did not affect morphological welfare indicators, activity, or cortisol. Enriched fish were more cohesive than non-enriched fish, less neophobic, with higher serotonergic turnover, suggesting enrichment mitigates against stress, promoting positive emotional states. Genes related to neuronal development and activity (bdnf and ndf1), cellular stress (hsp90 and hsp70), and serotonin synthesis (tph2) increased in enriched fish following stress, enhancing cognitive function. Our findings suggest early life environmental enrichment is advantageous for positive animal welfare by improving emotional states in captive environments, ensuring animals are free of negative experiences and able to access positive ones.

Different social experiences drive the development of divergent stress coping styles in female swordtails (Xiphophorus nigrensis)

Individual variation in stress coping styles is widespread and consequential to health and fitness. Proactive (bold behavior, low stress reactivity, low cognitive flexibility) and reactive (shy behavior, high stress reactivity, high cognitive flexibility) coping styles are found in many species, but the developmental forces shaping them remain elusive. We examined how social influences, specifically mating interactions, shape the development of adult female coping styles with a manipulative rearing experiment using El Abra swordtails, Xiphophorus nigrensis. We raised juvenile females in environments with different male reproductive phenotypes: coercive-only, courting-only, or complex (both coercive and courting males). At adulthood, we measured female stress reactivity (cortisol release following acute stress), boldness (scototaxis and open field responses), and cognitive flexibility (as inhibitory control in a detour task). Females raised in coercive and complex environments developed higher cortisol reactivity than females raised with only courtship. Stress coping trait correlations varied significantly across social environments producing different coping styles across treatments. Traditional proactive and reactive stress coping styles developed in the coercive-only environment with negative correlations between stress response and boldness, stress response and cognitive flexibility, and boldness and cognitive flexibility. Meanwhile, the courtship-only environment produced a negative correlation between stress response and boldness. We thus demonstrate that the relationship between stress response and boldness can be socially modulated. These findings suggest that developmental variation in social experiences can shape suites of traits with complex relationships; and that highly stressful social interactions, such as sexual coercion, can be a strong driver of stress coping styles.

Brush Use in Lot-Fed Cattle Shows Continued Use and Positive Behaviour

Feedlot cattle were assessed for the consistency of enrichment brush use, higher incidence of natural behaviour, and less agonistic or abnormal behaviour compared to cattle without the brush. Cattle were assigned to one of two treatment pens, (1) access to a vertical grooming brush (EB; n = 89) or (2) no access control (CON; n = 80), for a period of 107 days. A Principal Component (PC) analysis was used on pen-side demeanour scores. Statistical analysis on pen-side behaviour and demeanour PCs tested for impact of treatment, day, and time. Frequency of brush use and the duration of each cow-brush interaction did not decrease over the assessment period. Self-grooming and allogrooming did not differ between treatments and were similar in frequency to brush grooming, resulting in total grooming being higher in the EB treatment group (p < 0.05). Cattle in the EB pen were scored as more content (PC 2; p < 0.05) and sociable (PC 3; p < 0.01), while CON cattle were scored as more anxious (PC 3; p < 0.05). Overall, this study suggests that the provision of a brush for enrichment enhanced lot-fed cattle wellbeing and permitted prolonged engagement, making it an effective enrichment device.

Testing perioperative meloxicam analgesia to enhance welfare while preserving model validity in an inflammation-induced seizure model

Despite the international effort to improve laboratory animal welfare through the 3R principles (Reduce, Refine, Replace), many scientists still fail to implement and report their assessment of pain and well-being, likely due to concerns regarding the potential effects of analgesics on experimental outcomes. This study aimed to determine whether refining our viral encephalitis model with perioperative analgesia could enhance well-being and recovery after intracerebral virus infection without impacting disease outcomes. We routinely use the Theiler's Murine Encephalomyelitis Virus (TMEV) model to study virus-induced epilepsy. Given the crucial role of immune cell activation in acute seizure development, we evaluated the effects of the non-steroidal anti-inflammatory drug (NSAID) meloxicam on inflammation, neurodegeneration, and neuronal cell proliferation at 7 days post-infection (dpi). Overall, the impact of virus infection on well-being was less severe than anticipated, and meloxicam treatment did not affect well-being or nest building behavior in TMEV-infected mice. Furthermore, meloxicam treatment did not influence key experimental readouts such as seizure burden, central inflammatory response, neurodegeneration, or neuronal proliferation within the hippocampus. Notably, animals experiencing seizures displayed heightened inflammatory responses and neurodegeneration, which were not influenced by meloxicam treatment. In summary, perioperative analgesia did not compromise key outcome measures such as seizure frequency, inflammation, and neurodegeneration or -regeneration in the TMEV model. However, it also did not add any significant benefits to well-being in the first week after intracranial injections.

Social and nonsocial environmental loss have differential effects on ventral hippocampus-dependent behavior and inhibitory synaptic markers in adult male mice

In humans, psychological loss, whether social or nonsocial, can lead to clinical depression, anxiety disorders, and social memory impairments. Researchers have modeled combined social and nonsocial loss in rodents by transitioning them from social, enriched environments (EE) to individual housing, affecting behaviors related to avoidance, stress coping, and cognitive function. However, it remains unclear if these effects are driven by social or nonsocial loss. We examined the effects of nonsocial loss by housing adult male mice in EE before moving them to standard cages, where they were pair-housed, and compared this to mice experiencing complete social loss. Continuous EE reduced social investigation time while leaving social memory intact, also decreasing avoidance behavior. Nonsocial loss restored social investigation and avoidance behavior to control levels, while social loss impaired social memory and increased avoidance. In rodents, social memory and avoidance require ventral hippocampus (vHIP) neuronal oscillations, which involve parvalbumin-positive (PV+) inhibitory interneurons. We found decreased vHIP PV intensity in the social loss group, with no differences in the nonsocial loss group. Most PV+ cells are surrounded by perineuronal nets (PNNs) concentrating GABAA receptors in their lattice-like holes. Social loss decreased GABAA-δ expression, a subunit associated with extrasynaptic receptors, across PNN+ soma and in PNN holes, while nonsocial loss reduced gephyrin in these regions. These findings suggest social and nonsocial losses differentially affect vHIP function and behavior, with social loss having a more pronounced impact through mechanisms involving PV+ interneurons, PNN structure, and neurotransmitter receptor expression.

Lockbox enrichment facilitates manipulative and cognitive activities for mice

Background

Due to the lack of complexity and variety of stimuli, conventional housing conditions of laboratory mice do not allow these animals to fully express their behavioral repertoire, including manipulative and cognitive activities. Therefore, we designed mechanical puzzles, so-called lockboxes, for mice that can be provided in their home cages. We investigated the impact of the lockbox enrichment on their phenotype and affective state when compared to conventional housing (CH) and super-environmental enrichment (SEE).

Methods

Young adult female C57BL/6JCrl mice were examined before and after 2-month exposure to the different types of enrichment in a phenotyping test battery, including tests for trait and state anxiety-related behavior, calorimetric measurements, body weight measurements, the analysis of stress hormone metabolite concentrations, and sequential problem-solving abilities with a novel lockbox. At the end of the study, adrenal gland weights were determined and pathohistological evaluation was performed. For all continuous variables, the relative variability was calculated.

Results

While the different types of enrichment affected trait anxiety-related behavior, neither state anxiety-related behavior nor physiological variables (i.e., bodyweight, resting metabolic rate, stress hormone metabolite concentrations, adrenal gland weights) were influenced. LE improved sequential problem-solving (i.e., solving novel lockboxes) when compared to SEE. Regardless of the housing condition, the relative variability increased in most variables over time, although the coefficient of variation decreased for some variables, especially in animals with access to LE. There was no evidence of toxicopathological effects associated with the material from which the lockboxes were made.

Conclusions

All lockboxes are available as open-source tool. LE revealed beneficial effects on the affective state of laboratory mice and their performance in solving novel lockboxes. Neither relevant phenotype of the mice nor reproducibility of the data were compromised by LE, similar to SEE. The lockboxes may also be used as novel approach for assessing cognition in mice.

Environmental enrichment and complementary clinical interventions as therapeutic approaches for alcohol use disorder in animal models and humans

Alcohol use disorder (AUD) is a multifactorial disorder arising from a complex interplay of various genetic, environmental, psychological, and social factors. Environmental factors influence alcohol misuse and can lead to AUD. While stress plays a crucial role in the onset and progression of this disorder, environmental enrichment (EE) also influences ethanol-induced behavioral and neurobiological responses. These alterations include reduced ethanol consumption, diminished operant self-administration, attenuated behavioral sensitization, and enhanced conditioned place preference. EE exerts modulatory effects on multiple neurobiological processes, such as the brain-derived neurotrophic factor/TrkB signaling pathway, the oxytocinergic system, and the hypothalamic-pituitary-adrenal axis. EE, which includes stimulating activities to counteract ethanol effects in animal studies, has parallels in human intervention that have shown potential benefits. Physical activity, cognitive behavioral therapy, and meditation, alongside techniques involving cognitive stimulation, social interaction, and recreational activities, may lead to more effective therapeutic outcomes in treatments of AUD.

Effects of temporary access to environmental enrichment on measures of laboratory mouse welfare

Laboratory mice are typically housed in "shoebox" cages with limited opportunities to engage in natural behaviour. Temporary access to environments with increased space and complexity (playpens) may improve mouse welfare. Previous work by our group has shown that mice are motivated to access and use these environments, but it is unknown how other aspects of welfare are impacted. Female C57BL/6J, BALB/cJ, and DBA/2J mice (n = 21; 7 mice per strain) were housed in mixed-strain trios and given temporary access to a large playpen with their cage mates three times per week. Control mice (n = 21; 7 mice per strain) remained in their home cages. Home cage behaviour (development of stereotypic behaviour over time, aggression following cage-changing) and anxiety tests were used to assess how playpen access impacted welfare. Contrary to our predictions, we found increased time spent performing stereotypies in playpen mice; this difference may be related to negative emotional states, increased motivation to escape the home cage, or active coping strategies. Playpen access resulted in strain-dependent improvements in aggression and some measures of anxiety. Aggression was lower for C57BL/6J mice in the playpen treatment following cage changing than it was for C57BL/6J control mice, while playpen mice, and particularly the C57BL/6J strain, spent more time in the center of the open field test and produced fewer fecal boli during anxiety testing, supporting other research showing that strain differences play an important role in behaviour and stress resiliency.

Animal models to study cognitive impairment of chronic kidney disease

Mild cognitive impairment (MCI) is common in people with chronic kidney disease (CKD), and its prevalence increases with progressive loss of kidney function. MCI is characterized by a decline in cognitive performance greater than expected for an individual age and education level but with minimal impairment of instrumental activities of daily living. Deterioration can affect one or several cognitive domains (attention, memory, executive functions, language, and perceptual motor or social cognition). Given the increasing prevalence of kidney disease, more and more people with CKD will also develop MCI causing an enormous disease burden for these individuals, their relatives, and society. However, the underlying pathomechanisms are poorly understood, and current therapies mostly aim at supporting patients in their daily lives. This illustrates the urgent need to elucidate the pathogenesis and potential therapeutic targets and test novel therapies in appropriate preclinical models. Here, we will outline the necessary criteria for experimental modeling of cognitive disorders in CKD. We discuss the use of mice, rats, and zebrafish as model systems and present valuable techniques through which kidney function and cognitive impairment can be assessed in this setting. Our objective is to enable researchers to overcome hurdles and accelerate preclinical research aimed at improving the therapy of people with CKD and MCI.

Environmental Enrichment in Stroke Research: an Update

Environmental enrichment (EE) refers to different forms of stimulation, where the environment is designed to improve the levels of sensory, cognitive, and motor stimuli, inducing stroke recovery in animal models. Stroke is a leading cause of mortality and neurological disability among older adults, hence the importance of developing strategies to improve recovery for such patients. This review provides an update on recent findings, compiling information regarding the parameters affected by EE exposure in both preclinical and clinical studies. During stroke recovery, EE exposure has been shown to improve both the cognitive and locomotor aspects, inducing important neuroplastic alterations, increased angiogenesis and neurogenesis, and modified gene expression, among other effects. There is a need for further research in this field, particularly in those aspects where the evidence is inconclusive. Moreover, it is necessary refine and adapt the EE paradigms for application in human patients.

Long-term music stimulating alleviated the inflammatory responses caused by acute noise stress on the immune organs of broilers by NF-κB signaling pathway

As an environmental enrichment, music can positively influence the immune function, while noise has an adverse effect on the physical and mental health of humans and animals. However, whether music-enriched environments mitigate noise-induced acute stress remains unclear. To investigate the anti-inflammatory effects of music on the immune organs of broiler chickens under conditions of early-life acute noise stress, 140 one-day-old white feather broilers (AA) were randomly divided into four groups: control (C), the music stimulation (M) group, the acute noise stimulation (N) group, the acute noise stimulation followed by music (NM) group. At 14 days of age, the N and NM groups received 120 dB noise stimulation for 10 min for one week. After acute noise stimulation, the NM group and M group were subjected to continuous music stimulation for 14 days (6 h per day, 60 dB). At 28 days of age, the body temperature of the chicks, the histopathological changes, quantification of ROS-positive density and apoptosis positivity in tissues of spleen, thymus, and bursa of Fabricius (BF) were measured. The results showed that acute noise stimulation led to an increase in the number and area of splenic microsomes and the cortex/medulla ratio of the detected immune organs. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) of immune tissues of broilers in N group were decreased compared to the broilers in C group, while the mRNA levels of malondialdehyde (MDA), TNF-α, IL-1, and IL-1β increased. In addition, the gene and protein expression levels of IKK, NF-κB, and IFN-γ of three immune organs from broilers in the N group were increased. Compared to the C and N group, chickens from the NM group showed a decrease in the number and area of splenic follicles, an increase in the activities of SOD and GSH-Px, and a decrease in the expression levels of MDA, TNF-α, IL-1, and IL-1β. Therefore, a music-enriched environment can attenuate oxidative stress induced by acute noise stimulation, inhibiting the activation of the NF-κB signaling pathway and consequently alleviating the inflammatory response in immune organs.

Impact of enriched environment on motor performance and learning in mice

Neuroscience heavily relies on animal welfare in laboratory rodents as it can significantly affect brain development, cognitive function and memory formation. Unfortunately, laboratory animals are often raised in artificial environments devoid of physical and social stimuli, potentially leading to biased outcomes in behavioural assays. To assess this effect, we examined the impact of social and physical cage enrichment on various forms of motor coordination. Our findings indicate that while enriched-housed animals did not exhibit faster learning in eyeblink conditioning, the peak timing of their conditioned responses was slightly, but significantly, improved. Additionally, enriched-housed animals outperformed animals that were housed in standard conditions in the accelerating rotarod and ErasmusLadder test. In contrast, we found no significant effect of enrichment on the balance beam and grip strength test. Overall, our data suggest that an enriched environment can improve motor performance and motor learning under challenging and/or novel circumstances, possibly reflecting an altered state of anxiety.

Brief exposure to enriched environment rapidly shapes the glutamate synapses in the rat brain: A metaplastic fingerprint

Environmental enrichment (EE) has been shown to produce beneficial effects in addiction disorders; however, due to its configurational complexity, the underlying mechanisms are not yet fully elucidated. Recent evidence suggests that EE, acting as a metaplastic agent, may affect glutamatergic mechanisms underlying appetitive memory and, in turn, modulate reward-seeking behaviours: here, we have investigated such a possibility following a brief EE exposure. Adult male Sprague-Dawley rats were exposed to EE for 22 h and the expression of critical elements of the glutamate synapse was measured 2 h after the end of EE in the medial prefrontal cortex (mPFC), nucleus accumbens (NAc) and hippocampus (Hipp) brain areas, which are critical for reward and memory. We focused our investigation on the expression of NMDA and AMPA receptor subunits, their scaffolding proteins SAP102 and SAP97, vesicular and membrane glutamate transporters vGluT1 and GLT-1, and critical structural components such as proteins involved in morphology and function of glutamatergic synapses, PSD95 and Arc/Arg3.1. Our findings demonstrate that a brief EE exposure induces metaplastic changes in glutamatergic mPFC, NAc and Hipp. Such changes are area-specific and involve postsynaptic NMDA/AMPA receptor subunit composition, as well as changes in the expression of their main scaffolding proteins, thus influencing the retention of such receptors at synaptic sites. Our data indicate that brief EE exposure is sufficient to dynamically modulate the glutamatergic synapses in mPFC-NAc-Hipp circuits, which may modulate rewarding and memory processes.

Human social enrichment is linked with reduced mortality in artificially reared ewe lambs

Growth of lambs in an artificial rearing system is key to the economic success of sheep-milking farms. Social enrichment in the form of quiet human contact has been shown to increase growth rates of lambs after weaning, perhaps by reducing stress and enhancing immune function. One hundred fourteen artificially reared dairy ewe lambs were assigned either to a Social condition receiving quiet human company in three 20-min segments per day, or a Control condition without quiet human contact. Feeding and housing conditions were otherwise identical. Starting weights for the Social (M = 6.29 kg; SD = 1.19 kg) and Control (M = 6.38 kg; SD = 0.93 kg) lambs were the same, as were their weights after 3 weeks (Mcontrol  = 8.89 kg, SD = 2.55 kg, Msocial  = 8.63 kg, SD = 2.16 kg). Mortality rates were significantly lower (p = 0.041) in the Social condition (0%) than Control (8%). Thus, social enrichment may be important for the wellbeing of lambs and for economic viability in lamb-rearing.

Increased depression-like behaviors with altered brain dopamine metabolisms in male mice housed in large cages are alleviated by bupropion

Psycho-environmental stress-based animal models of anxiety and depression are useful for investigating pathological mechanisms and drug development. Although several rodent-based studies have reported the beneficial effects of environmental enrichment (EE) on brain plasticity and anxiety- and depression-like behaviors, other studies have reported inverse effects. Here, we found that housing male mice in EE involving large cages and other EE materials increased anxiety- and depression-like behaviors in open field and tail suspension tests (TST). We further confirmed that housing in large cages was sufficient to induce increased depression-like behaviors in the TST and reduce the saccharine preference percentage, a sign of anhedonia, in male mice. In these experiments, the number of animals per cage was equivalent to that in standard cage housing, suggesting that low density in large cages may be a determining factor for behavioral alteration. In mice housed in large cages, sex-specific dysregulation of brain monoamine systems was observed; dopamine turnover to homovanillic acid or norepinephrine in the prefrontal cortex was elevated in males, while serotonin turnover to 5-hydroxyindoleacetic acid in the amygdala was increased in females. Finally, we demonstrated that daily intraperitoneal injections of bupropion, a dopamine and norepinephrine reuptake inhibitor, counteracted large-cage housing-induced changes in depression- and anhedonia-like behaviors in male mice. Our results suggest that housing in large cages with a low density of mice is a novel paradigm to clarify the mechanisms of environmental stress-induced emotional dysregulation and to identify drugs or food factors to alleviate the dysregulation.

Potential resilience treatments for orangutans (Pongo spp.): Lessons from a scoping review of interventions in humans and other animals

Wild orangutans (Pongo spp.) rescued from human-wildlife conflict must be adequately rehabilitated before being returned to the wild. It is essential that released orangutans are able to cope with stressful challenges such as food scarcity, navigating unfamiliar environments, and regaining independence from human support. Although practical skills are taught to orangutans in rehabilitation centres, post-release survival rates are low. Psychological resilience, or the ability to 'bounce back' from stress, may be a key missing piece of the puzzle. However, there is very little knowledge about species-appropriate interventions which could help captive orangutans increase resilience to stress. This scoping review summarises and critically analyses existing human and non-human animal resilience literature and provides suggestions for the development of interventions for orangutans in rehabilitation. Three scientific databases were searched in 2021 and 2023, resulting in 63 human studies and 266 non-human animal studies. The first section brings together human resilience interventions, identifying common themes and assessing the applicability of human interventions to orangutans in rehabilitation. The second section groups animal interventions into categories of direct stress, separation stress, environmental conditions, social stress, and exercise. In each category, interventions are critically analysed to evaluate their potential for orangutans in rehabilitation. The results show that mild and manageable forms of intervention have the greatest potential benefit with the least amount of risk. The study concludes by emphasising the need for further investigation and experimentation, to develop appropriate interventions and measure their effect on the post-release survival rate of orangutans.

Efficacy of Multimodal Sensory Therapy in Adult Acquired Brain Injury: A Systematic Review

Adults who experience an acquired brain injury often experience disorders of consciousness, physical difficulties, and maladaptive behaviours. Multimodal sensory therapy may benefit brain injured patients, however the extent this therapy can facilitate rehabilitation is not well understood. This systematic review aimed to synthesize multimodal sensory therapy research for adults affected by acquired brain injury. PRISMA guidelines were followed and searches for work published up until July 2021 were undertaken in 5 databases, finding 1054 articles. 43 articles were included in the study. Results describe 29 studies related to coma following an acquired brain injury and 14 to no coma studies (mostly stroke). Multimodal sensory therapy was mostly used as a coma arousal technique following traumatic brain injury, finding positive effects. Multimodal sensory therapy was less applied in stroke, no coma rehabilitation, where most studies found improvement in somatosensory sensation and motor control in an affected limb. In several no coma studies, effects were maintained after several months. The most common senses stimulated in coma studies were audio (N = 30), tactile (N = 28), visual (N = 26), olfactory (N = 22), and gustatory (N = 17), while the most common senses stimulated in stroke, no coma studies were proprioception (N = 7), tactile (N = 8), and stereognosis (N = 4). Multimodal sensory therapy can be beneficial for patients, especially those in a minimally conscious state or attempting physical rehabilitation following stroke. Negative findings are infrequent in the current literature base. Multimodal sensory therapy appears to be a low-risk intervention with positive outcomes.

Efficacy of an environmental enrichment intervention for endometriosis: a pilot study

Introduction

We have previously shown that Environmental Enrichment (EE), a multi-modal psychosocial intervention consisting of increased social interaction, novelty, and open spaces, improved disease presentation, anxiety, and immune-related disturbances in the rat model of endometriosis. However, there is a knowledge gap regarding the effects of EE interventions in patients with this painful, inflammatory chronic disease.

Aim

To adapt and test the efficacy of an EE intervention on pelvic pain, mental health, perceived stress, quality of life, and systemic inflammation in endometriosis patients through a randomized clinical trial (RCT).

Materials and methods

A multidisciplinary team with expertise in physiology, neuroscience, psychology, and women's health adapted and implemented a two-arm RCT comparing an EE intervention with a wait-list control group. Six EE modules administered on alternate weeks were provided to patients in the intervention (N = 29); controls received education only. Survey data and biospecimens were collected at baseline, end-of-study, and 3-months post-intervention to assess pain (Brief Pain Inventory, BPI), endometriosis-related quality of life-QoL (Endometriosis Health Profile-30, EHP30), anxiety (Generalized Anxiety Disorder 7, GAD7), depression (Patient Health Questionnaire for Depression 8, PHQ8), pain catastrophizing (Pain Catastrophizing Score, PCS), stress (Perceived Stress Scale-14, PSS14), and saliva cortisol levels (AM, PM).

Results

Compared to the wait-list controls, participants in the EE intervention showed significantly decreased GAD-7 scores at the end of the intervention and 3-month follow-up. Depression, perceived stress, and QoL improved at the 3-month follow-up compared to baseline. While pain levels did not improve, they significantly correlated with anxiety, depression, QoL and pain catastrophizing scores.

Conclusion

This pilot RCT demonstrated significant improvements in anxiety and depressive symptoms, QoL, and perceived stress, supporting enriched environments as an integrative psychosocial intervention to be used as adjuvant to the standard of care for endometriosis pain.

Structural enrichment for laboratory mice: exploring the effects of novelty and complexity

Providing structural enrichment is a widespread refinement method for laboratory rodents and other animals in captivity. So far, animal welfare research has mostly focused on the effect of increased complexity either by accumulating or combining different enrichment items. However, increasing complexity is not the only possibility to refine housing conditions. Another refinement option is to increase novelty by regularly exchanging known enrichment items with new ones. In the present study, we used pair-housed non-breeding female C57BL/6J and DBA/2N mice to investigate the effect of novelty when applying structural enrichment. We used a double cage system, in which one cage served as home cage and the other as extra cage. While the home cage was furnished in the same way for all mice, in the extra cage we either provided only space with no additional enrichment items (space), a fixed set of enrichment items (complexity), or a changing set of enrichment items (novelty). Over 5  weeks, we assessed spontaneous behaviors, body weight, and extra cage usage as indicators of welfare and preference. Our main results showed that mice with access to structurally enriched extra cages (complexity and novelty) spent more time in their extra cages and complexity mice had lower latencies to enter their extra cages than mice with access to the extra cages without any structural enrichment (space). This indicates that the mice preferred the structurally enriched extra cages over the structurally non-enriched space cages. We found only one statistically significant difference between the novelty and complexity condition: during week 3, novelty mice spent more time in their extra cages than complexity mice. Although we did not detect any other significant differences between the novelty and complexity condition in the present study, more research is required to further explore the potential benefits of novelty beyond complexity.

Reduction of restricted repetitive behavior by environmental enrichment: Potential neurobiological mechanisms

Restricted repetitive behaviors (RRB) are one of two diagnostic criteria for autism spectrum disorder and common in other neurodevelopmental and psychiatric disorders. The term restricted repetitive behavior refers to a wide variety of inflexible patterns of behavior including stereotypy, self-injury, restricted interests, insistence on sameness, and ritualistic and compulsive behavior. However, despite their prevalence in clinical populations, their underlying causes remain poorly understood hampering the development of effective treatments. Intriguingly, numerous animal studies have demonstrated that these behaviors are reduced by rearing in enriched environments (EE). Understanding the processes responsible for the attenuation of repetitive behaviors by EE should offer insights into potential therapeutic approaches, as well as shed light on the underlying neurobiology of repetitive behaviors. This review summarizes the current knowledge of the relationship between EE and RRB and discusses potential mechanisms for EE's attenuation of RRB based on the broader EE literature. Existing gaps in the literature and future directions are also discussed.

The systemic effects of the enriched environment on the conditioned fear reaction

In this review, a hypothesis is proposed to explain the beneficial effect of an enriched environment (EE) on the conditioned fear reaction (CFR) from the perspective of a functional system of behavioral control. According to the hypothesis, the EE affects all behavioral act components, including the processing of sensory information, memory, motivational and reinforcing systems, and motor activities, which weakens the CFR. Animals raised in the EE have effects that are comparable to those of context (CTX) and CS pre-exposures at latent inhibition. An abundance of stimuli in the EE and constant contact with them provide the formation of CS-noUS and CTX-noUS connections that later, during CFR learning, slow down and diminish fear. The EE also contributes to faster processing of information and habituation to it. As a result, many stimuli in the context lose their significance, and subjects simply ignore them. And finally, the EE affects the motivational and reinforcing brain mechanisms, induces an impairment of search activity, and worsens memory consolidation, which leads to a reduction of CFR.

MSK1 is required for the beneficial synaptic and cognitive effects of enriched experience across the lifespan

Positive experiences, such as social interaction, cognitive training and physical exercise, have been shown to ameliorate some of the harms to cognition associated with ageing. Animal models of positive interventions, commonly known as environmental enrichment, strongly influence neuronal morphology and synaptic function and enhance cognitive performance. While the profound structural and functional benefits of enrichment have been appreciated for decades, little is known as to how the environment influences neurons to respond and adapt to these positive sensory experiences. We show that adult and aged male wild-type mice that underwent a 10-week environmental enrichment protocol demonstrated improved performance in a variety of behavioural tasks, including those testing spatial working and spatial reference memory, and an enhancement in hippocampal LTP. Aged animals in particular benefitted from enrichment, performing spatial memory tasks at levels similar to healthy adult mice. Many of these benefits, including in gene expression, were absent in mice with a mutation in an enzyme, MSK1, which is activated by BDNF, a growth factor implicated in rodent and human cognition. We conclude that enrichment is beneficial across the lifespan and that MSK1 is required for the full extent of these experience-induced improvements of cognitive abilities, synaptic plasticity and gene expression.

Environmental eustress promotes liver regeneration through the sympathetic regulation of type 1 innate lymphoid cells to increase IL-22 in mice

BACKGROUND AND AIMS

The liver has the unique ability of regeneration, which is extremely important for restoring homeostasis after liver injury. Although clinical observations have revealed an association between psychological stress and the liver, whether stress has a causal influence on the liver regeneration remains markedly less defined.

APPROACH AND RESULTS

Rearing rodents in an enriched environment (EE) can induce eustress or positive psychological stress. Herein, EE-induced eustress was found to significantly enhance the ability of liver regeneration after partial hepatectomy or carbon tetrachloride-induced liver injury based on the more rapid restoration of liver/body weight ratio and the significantly increased number of proliferating hepatocytes in EE mice. Mechanistically, the cytokine array revealed that IL-22 was markedly increased in the regenerating liver in response to EE. Blockade of IL-22 signaling abrogated the enhanced liver regeneration induced by EE. Group 1 innate lymphoid cells (ILCs), including type 1 ILCs (ILC1s), have been identified as the major sources of IL-22 in the regenerating liver. EE housing led to a rapid accumulation of hepatic ILC1s after partial hepatectomy and the EE-induced enhancement of liver regeneration and elevation of IL-22 was nearly eliminated in ILC1-deficient Tbx21-/- mice. Chemical sympathectomy or blockade of β-adrenergic signaling also abolished the effect of EE on ILC1s and attenuated the enhanced liver regeneration of EE-housed mice.

CONCLUSION

The study findings support the brain-liver axis and suggest that environment-induced eustress promotes liver regeneration through the sympathetic nerve/ILC1/IL-22 axis.

The influence of long-term housing in enriched environment on behavior of normal rats and subjected to neonatal pro-inflammatory challenge

It is well known that neonatal pro-inflammatory challenge (NPC) acquire a predisposition to the development of a number of neuropsychiatric diseases: depression, anxiety disorders, autism, attention deficit hyperactivity disorder. Symptoms of these diseases can manifest themselves in adulthood and adolescent after repeated exposure to negative influences. Preventing the development of the negative consequences of NPC is one of the main tasks for researchers. The exposure to an enriched environment (EE) was shown to have anxiolytic, anti-depressive, and pro-cognitive effects. The present work was aimed to investigate the effects of the long-term EE on anxious-depressive and conditioned fear behavior in normal male and female rats and subjected to NPC. The NPC was induced by subcutaneous administration of lipopolysaccharide (LPS, 50 μg/kg) on 3d and 5th PNDs. The control animals received saline (SAL). The rats were placed in the EE from 25 to 120 PND. Animals housed in the standard conditions (STAND) served as controls. In adult female and male rats of the STAND groups, LPS did not affect the anxiety, depressive-like behavior and conditioned fear. The EE increased motor and search activity in males and females. In the open field, the EE reduced anxiety in males of the SAL and LPS groups and in females of SAL groups compared to the STAND housed animals. In the elevated plus maze, the EE decreased anxiety only in males of the SAL group. In the sucrose preference test, the EE did not change sucrose consumption in males and females of SAL and LPS groups, while, in the forced swimming test, the EE reduced depressive-like behavior in females of both SAL and LPS groups. The enrichment decreased the contextual conditioned fear in male and female of SAL groups, but not of the LPS group, and did not affect the cue conditioned fear. The corticosterone reactivity to the forced swimming stress increased in males of the EE groups. The basal level of IL-1beta in blood serum decreased in males of the SAL-EE group. Thus, the EE reduced anxiety in males, depressive-like behavior in females, and contextual conditioned fear in males and females compared to the STAND housed animals. Although the NPC did not affect these behaviors in the STAND groups, LPS prevented the beneficial EE effects on anxiety and conditioned fear. The opposing effects of LPS were dependent on sex and type of testing.

The impact of environmental factors during maternal separation on the behaviors of adolescent C57BL/6 mice

Neonatal maternal separation is a widely used method to construct an early-life stress model in rodents. In this method, pups are separated from their mothers for several hours every day during the first 2 weeks of life, which results in adverse early-life events. It is a known fact that maternal separation can exert a significant impact on the behavior and psychological health, such as anxiety and depression, in adolescent offspring. However, environmental conditions during maternal separation can differ such as the presence of other animals or by placing pups in a different dam. To investigate the differential effects of various conditions of maternal separation on the behavior of adolescent mice, we created the following groups: (1) iMS group: pups were moved to an isolated room with no other adult mice in a nearby cage, (2) eDam group: the pups randomly exchanged their dams, (3) OF group: pups were shifted to another cage with the bedding material containing maternal odor (olfactory stimulation), and (4) MS group: pups were shifted to another vivarium. From postnatal day (PND) 2-20 (i.e., 19 consecutive days), pups were separated from the dam daily for 4 h and exposed to various environments (MS, iMS, eDam, and OF) or were left undisturbed [control (CON) group]. A series of behavioral assessments were conducted to evaluate locomotion, anxiety, recognition, learning, and memory in adolescent offspring. The results showed that neonatal maternal separation led to impaired recognition memory, motor coordination, and motor skill learning across all groups. However, the iMS group exhibited anxiety-like behavior in the elevated plus maze test and enhanced the extinction of fear memory in the auditory fear conditioning test. The OF and eDam groups displayed partially recovered short-term working memory in the Y-maze test but exhibited opposite exploratory behaviors. The OF group spent more time in the center, while the eDam group spent less time. These findings demonstrated that exposure to different environmental conditions during maternal separation causes behavioral alterations in adolescent offspring, providing a potential explanation for the variation in behavioral phenotypes observed in the early-life stress models.

Body, ambient and felt temperature: An attempt to resolve a human and mice dilemma

Mice thermoneutral zone lies at temperatures much higher than expected when considering the geographical extension of the species. Growing evidence shows that mouse-dependent thermogenesis experimentation needs to cope with temperatures below those at which the animals are most comfortable. The associated physiological changes interfere with experimental results, thereby highlighting the apparently trivial subject of room-temperature. Working at above 25 °C is difficult for researchers and animal care technicians. Herein, we explore alternative solutions related to living habits of wild mice that could improve translation of research on mice to humans. Standard murine environments are often colder than those in laboratory facilities and their behavior is mainly characterized by a gregarious, nesting and exploratory way of life. Optimization of their thermal environment can thus also be achieved by avoiding individual housing and providing high-quality nesting material and devices that would allow locomotor activity, hence muscle thermogenesis. These options have additional relevance in terms of animal welfare. When precise monitoring of the temperature is required, temperature-controlled cabinets can be used for the duration of the experiments. During the manipulation of mice, a heated laminar flow hood or tray could create an optimized microenvironment. The specification of temperature-related data in publications should contain information on the translatability of the described mouse models to humans. Furthermore, publications should describe the premises of the laboratory in relation to housing possibilities and murine behavior.

Use of qualitative behavioural assessment to investigate affective states of housed dairy cows under different environmental conditions

In addition to the reduction of suboptimal welfare, there is now a need to provide farmed animals with positive opportunities to provide confidence that they have experienced a life worth living. Diversification of the environment through environmental enrichment strategies is one suggested avenue for providing animals with opportunities for positive experiences. The provision of more stimulating environmental conditions has been widely implemented in other animal production industries, based on evidenced welfare benefits. However, the implementation of enrichment on dairy farms is limited. In addition to this, the relationship between enrichment and dairy cows' affective states is an under-researched area. One specific welfare benefit of enrichment strategies which has been observed in a number of species, is increased affective wellbeing. This study investigated whether the provision of different forms of environmental enrichment resources would impact the affective states of housed dairy cows. This was measured by Qualitative Behavioural Assessment, currently a promising positive welfare indicator. Two groups of cows experienced three treatment periods; (i) access to an indoor novel object, (ii) access to an outdoor concrete yard and (iii) simultaneous access to both resources. Principal component analysis was used to analyse qualitative behavioural assessment scores, which yielded two principal components. The first principal component was most positively associated with the terms “content/relaxed/positively occupied” and had the most negative associations with the terms ‘fearful/bored'. A second principal component was most positively associated with the terms “lively/inquisitive/playful” and was most negatively associated with the terms “apathetic/bored”. Treatment period had a significant effect on both principal components, with cows being assessed as more content, relaxed and positively occupied and less fearful and bored, during periods of access to additional environmental resources. Similarly, cows were scored as livelier, more inquisitive and less bored and apathetic, during treatment periods compared to standard housing conditions. Concurrent with research in other species, these results suggest that the provision of additional environmental resources facilitates positive experiences and therefore enhanced affective states for housed dairy cows.

Rating enrichment items by female group-housed laboratory mice in multiple binary choice tests using an RFID-based tracking system

Laboratory mice spend most of their lives in cages, not experiments, so improving housing conditions is a first-choice approach to improving their welfare. Despite the increasing popularity of enrichment, little is known about the benefits from an animal perspective. For a detailed analysis, we categorized enrichment items according to their prospective use into the categories 'structural', 'housing', and 'foraging'. In homecage-based multiple binary choice tests 12 female C57BL/6J mice chose between enrichment items within the respective categories over a 46-hour period. A new analyzing method combined the binary decisions and ranked the enrichment items within each category by calculating worth values and consensus errors. Although there was no unequivocal ranking that was true in its entire rank order for all individual mice, certain elements (e.g. lattice ball, second plane) were always among the top positions. Overall, a high consensus error in ranking positions reflects strong individual differences in preferences which could not be resolved due to the relatively small sample size. However, individual differences in the preference for enrichment items highlights the importance of a varied enrichment approach, as there does not seem to be one item that satisfies the wants and needs of all individuals to the same degree. An enrichment concept, in which the needs of the animals are central, contributes to a more specific refinement of housing conditions.

Stress Evaluation of Mouse Husbandry Environments for Improving Laboratory Animal Welfare

Animal welfare is recognized as essential for the coexistence of humans and animals. Considering the increased demand and interest in animal welfare, many methods for improving animal welfare are being devised, but which method reduces animal stress has not been scientifically verified. Therefore, reducing animal stress by providing a proper breeding environment and environmental enrichment can be the basis for animal study. In this study, stress levels were assessed based on the mouse-breeding environment. We considered that the higher the body weight and the lower the corticosterone concentration, the lower the stress. According to the results, animals in the individual ventilation cages were determined to have lower serum cortisol concentrations, while the body weight of the animals was increased when in individual ventilation cages compared with individual isolated cages and when providing environmental enrichment compared with group breeding or not providing environmental enrichment. The results provide appropriate guidelines for improving laboratory animal welfare.

Feasibility and acceptability of an adapted environmental enrichment intervention for endometriosis: A pilot study

Introduction

We have previously shown that Environmental Enrichment (EE)-consisting of social support, novelty, and open spaces-decreased disease progression and anxiety in a rat model of endometriosis. We developed a novel EE intervention to be tested in a pilot randomized clinical trial (RCT) in patients with endometriosis, a painful, stressful disease.

Objective

To translate and evaluate the feasibility and acceptability of an adapted EE intervention as an adjuvant to standard-of-care for endometriosis patients.

Methods

Feasibility was assessed through recruitment, enrollment, and adherence rates. Acceptability was evaluated through a post-intervention survey and focus group discussion 3-months after the end of the intervention.

Results

Of the 103 subjects recruited, 64 were randomized to the intervention group and 39 to the control group. At the start of the intervention, the study groups consisted of 29 (intervention) and 27 (control) subjects. Enrollment rates were 45.3% and 69.2%, and adherence rates were 41.4% and 100% for the intervention and control groups, respectively. Delays resulting from natural events (earthquakes, the COVID-19 pandemic) impacted enrollment and adherence rates. The most common reasons for missing an intervention were period pain (39.1%) and work-study (34.8%). There was high acceptability (>80%) of the intervention's logistics. The majority (82.4%) of subjects would continue participating in support groups regularly, and 95.7% would recommend the intervention to other patients.

Conclusions

We showed that EE could be translated into an acceptable integrative multi-modal therapy perceived as valuable among participants who completed the intervention. High attrition/low adherence indicates that additional refinements would be needed to improve feasibility. Acceptability data indicate that EE has the potential to be integrated into the clinical management of patients with endometriosis and other inflammatory, painful disorders. Studies are ongoing to assess the efficacy of EE in improving pain symptoms, mental health, and quality of life (QoL).

Reward enhances resilience to chronic social defeat stress in mice: Neural ECs and mGluR5 mechanism via neuroprotection in VTA and DRN

INTRODUCTION

Stress often leads to emotional disorders such as depression. The reward might render this effect through the enhancement of stress resilience. However, the effect of reward on stress resilience under different intensities of stress needs more evidence, and its potential neural mechanism has been poorly revealed. It has been reported that the endogenous cannabinoid system (ECs) and downstream metabolic glutamate receptor 5 (mGluR5) are closely related to stress and reward, which might be the potential cerebral mechanism between reward and stress resilience, but there is a lack of direct evidence. This study aims to observe the effect of reward on stress resilience under different intensities of stress and further explore potential cerebral mechanisms underlying this effect.

METHODS

Using the chronic social defeat stress model, we applied reward (accompanied by a female mouse) under different intensities of stress in mice during the modeling process. The impact of reward on stress resilience and the potential cerebral mechanism were observed after modeling through behavioral tests and biomolecules.

RESULTS

The results showed that stronger stress led to higher degrees of depression-like behavior. Reward reduced depression-like behavior and enhanced stress resilience (all p-value <0.05) (more social interaction in the social test, less immobility time in the forced swimming test, etc.), with a stronger effect under the large stress. Furthermore, the mRNA expression levels of CB1 and mGluR5, the protein expression level of mGluR5, and the expression level of 2-AG (2-arachidonoylglycerol) in both ventral tegmental area (VTA) and dorsal raphe nucleus (DRN) were significantly upregulated by reward after modeling (all p-value <0.05). However, the protein expression of CB1 in VTA and DRN and the expression of AEA (anandamide) in VTA did not differ significantly between groups. Intraperitoneal injection of a CB1 agonist (URB-597) during social defeat stress significantly reduced depression-like behavior compared with a CB1 inhibitor (AM251) (all p-value <0.05). Interestingly, in DRN, the expression of AEA in the stress group was lower than that of the control group, with or without reward (all p-value <0.05).

DISCUSSION

These findings demonstrate that combined social and sexual reward has a positive effect on stress resilience during chronic social defeat stress, potentially by influencing the ECs and mGluR5 in VTA and DRN.

Rat's response to a novelty and increased complexity of the environment resulting from the introduction of movable vs. stationary objects in the free exploration test

Most animals, including rats, show a preference for more complex environments. This is demonstrated particularly well when complexity increases due to the addition of new elements to the environment. The aim of the study was to investigate the reaction to novelty, understood as a change in environmental properties that involve both changes in complexity and controllability. Controllability may allow for dealing with challenges of an environment of low predictability in a way that the animal's own activity reduces the uncertainty of environmental events. In our study, the animals underwent a spontaneous exploration test in low-stress conditions. After a period of habituation to the experimental arena, additional stationary (increased complexity) and/or movable (increased complexity and controllability) tunnels were introduced, and the reaction of the rats to the novel objects was measured. The results of the study confirmed that an increase in the complexity of the environment through the addition of objects triggers a more intensive exploratory activity in rats. However, an increased spatial complexity combined with the movability of the novel objects seems to result in increased caution towards the novelty after an initial inspection of the changed objects. It suggests that the complexity of the novelty may trigger both neophilia and neophobia depending on the level of the predictability of the novel environment and that the movability of newly introduced objects is not independent of other parameters of the environment.

Pet Owner Perception of Ferret Boredom and Consequences for Housing, Husbandry, and Environmental Enrichment

Boredom is a potential chronic but overlooked animal welfare problem. Caused by monotony, sub-optimal stimulation, and restrictive housing, boredom can therefore affect companion animals, particularly those traditionally caged, such as ferrets. We surveyed owners' (n = 621) perceptions of ferrets' capacity to experience boredom, behaviours they associate with it, and whether their perception of their ferrets' capacity for boredom influenced training techniques, housing, and environmental enrichment (EE). Most (93.0%) owners believed that ferrets could experience boredom, but owners who doubted that ferrets experience boredom (7.0%) provided slightly but significantly fewer EE types to their ferrets. Heat map and classification tree analysis showed that owners identified scratching at enclosure walls (n = 420) and excessive sleeping (n = 312) as distinctive behavioural indicators of ferret boredom. Repetitive pacing (n = 381), yawning (n = 191), and resting with eyes open (n = 171) were also suggested to indicate ferret boredom, but these overlapped with other states. Finally, ferret owners suggested social housing, tactile interaction with humans, and exploration as most important for preventing boredom. These results suggest that pet ferrets are at risk of reduced welfare from owners who doubt they can experience boredom, highlighting an opportunity to improve welfare through information dissemination. We recommend further investigation into ferret boredom capacity, behavioural indicators, and mitigation strategies.

The prevention of home-cage grid climbing affects muscle strength in mice

Experimenters and treatment methods are the major contributors to data variability in behavioral neuroscience. However, home cage characteristics are likely associated with data variability. Mice housed in breeding cages spontaneously exhibit behavioral patterns such as biting into the wire grid and climbing on the grid lid. We aimed to clarify the effect of covering the stainless steel wire grid lid in commonly used home cage with Plexiglas to prevent climbing on muscle strength in mice. Furthermore, we investigated the effects of climbing prevention on activity and anxiety-like behavior, and the impact of climbing prevention during the postnatal development period and adulthood on muscle strength. Muscle strength, anxiety-like behavior, and locomotor activity were assessed by a battery of tests (wire hang, suspension, grip strength, rotarod, elevated-plus maze, and open field tests). Mice prevented from climbing the wire grid during postnatal development displayed lower muscle strength than those able to climb. Moreover, mice prevented from climbing for 3 weeks following maturity had weakened muscles. The muscle strength was decreased with 3 weeks of climbing prevention in even 1-year-old mice. In summary, the stainless steel wire grid in the home cage contributed to the development and maintenance of muscle strength in mice.

Bored at home?—A systematic review on the effect of environmental enrichment on the welfare of laboratory rats and mice

Boredom is an emotional state that occurs when an individual has nothing to do, is not interested in the surrounding, and feels dreary and in a monotony. While this condition is usually defined for humans, it may very well describe the lives of many laboratory animals housed in small, barren cages. To make the cages less monotonous, environmental enrichment is often proposed. Although housing in a stimulating environment is still used predominantly as a luxury good and for treatment in preclinical research, enrichment is increasingly recognized to improve animal welfare. To gain insight into how stimulating environments influence the welfare of laboratory rodents, we conducted a systematic review of studies that analyzed the effect of enriched environment on behavioral parameters of animal well–being. Remarkably, a considerable number of these parameters can be associated with symptoms of boredom. Our findings show that a stimulating living environment is essential for the development of natural behavior and animal welfare of laboratory rats and mice alike, regardless of age and sex. Conversely, confinement and under-stimulation has potentially detrimental effects on the mental and physical health of laboratory rodents. We show that boredom in experimental animals is measurable and does not have to be accepted as inevitable.

The differential effects of brief environmental enrichment following social isolation in rats

Environmental enrichment (EE) in rodents is associated with a wide range of physiological, affective, and cognitive benefits. A seemingly opposite housing condition, social isolation (SI), is used as a rodent model of stress, negatively affecting several neurobiological mechanisms and hampering cognitive performance. Experimental designs that involve switching between these housing conditions produced mixed results. We evaluated different behavioral and cognitive effects of brief EE following long-term, SI-induced stress. We revealed the influence of enrichment after 30 days of isolation on behavioral despair, anxiety-like behavior, and spatial working memory in adult male Wistar rats and found a substantial anxiolytic effect in the experimental (SI to EE) group. Interestingly, rats exposed to EE also showed increased behavioral despair compared with the control (continuous SI) group. There was no difference in spatial working memory performance at the end of a 5-day water Y-maze (WYM) test. However, the SI to EE animals displayed better memory performance in the first 2 days of the WYM, indicating faster learning. In line with this difference, we recorded significantly more c-Fos-immunopositive (c-Fos+) cells in the retrosplenial and perirhinal cortices of the SI to EE animals. The lateral and basolateral nuclei of the amygdala showed no such difference. These results suggest that brief enrichment following isolation stress leads to differential results in affective and cognitive systems.

Once an optimist, always an optimist? Studying cognitive judgment bias in mice

Individuals differ in the way they judge ambiguous information: some individuals interpret ambiguous information in a more optimistic, and others in a more pessimistic way. Over the past two decades, such "optimistic" and "pessimistic" cognitive judgment biases (CJBs) have been utilized in animal welfare science as indicators of animals' emotional states. However, empirical studies on their ecological and evolutionary relevance are still lacking. We, therefore, aimed at transferring the concept of "optimism" and "pessimism" to behavioral ecology and investigated the role of genetic and environmental factors in modulating CJB in mice. In addition, we assessed the temporal stability of individual differences in CJB. We show that the chosen genotypes (C57BL/6J and B6D2F1N) and environments ("scarce" and "complex") did not have a statistically significant influence on the responses in the CJB test. By contrast, they influenced anxiety-like behavior with C57BL/6J mice and mice from the "complex" environment displaying less anxiety-like behavior than B6D2F1N mice and mice from the "scarce" environment. As the selected genotypes and environments did not explain the existing differences in CJB, future studies might investigate the impact of other genotypes and environmental conditions on CJB, and additionally, elucidate the role of other potential causes like endocrine profiles and epigenetic modifications. Furthermore, we show that individual differences in CJB were repeatable over a period of seven weeks, suggesting that CJB represents a temporally stable trait in laboratory mice. Therefore, we encourage the further study of CJB within an animal personality framework.

Environmental enrichment: dissociated effects between physical activity and changing environmental complexity on anxiety and neurogenesis in adult male Balb/C mice

Several factors, including environmental modifications, stimulate neuroplasticity. One type of neuroplasticity consists in the generation of new neurons in the dentate gyrus of the hippocampus. Neurogenesis is modulated by environmental enrichment (ENR, tunnels plus running wheel) and affected by the time of exposure to ENR. Despite the wide use of ENR to stimulate neuroplasticity, the degree to which ENR variations modeled by temporally changing the level of environmental complexity affect hippocampal neurogenesis and anxiety is still unclear. Thus, we investigated the effects of five housing conditions on young adult male Balb/C mice exposed for 42 days. The groups were as follows: standard conditions without ENR, constant ENR complexity, gradual increase of ENR complexity followed by a gradual decrease of ENR complexity, gradual increase of ENR complexity followed by constant ENR complexity, and constant ENR complexity followed by a gradual decrease of ENR complexity. On day 44, mice were exposed to the elevated plus-maze to evaluate anxiety. Further, we analyzed neurogenesis and quantified corticosterone levels. In an additional experiment, we explored the effect of voluntary physical activity on anxiety, neurogenesis, and corticosterone during the variations in ENR complexity. Our results showed that any change in ENR complexity over time reduced anxiety. Also, voluntary physical activity alone or in the context of a complex environment increased doublecortin cell maturation in the granular cell layer of the hippocampus. Finally, our study supports that physical activity acts proneurogenic, whereas any change in environmental complexity decreases anxiety-like behavior. However, the decrease in corticosterone levels elicited by physical activity was lower than the decrease produced by the decrement in environmental complexity.

Environmental Enrichment Facilitates Anxiety in Conflict-Based Tests but Inhibits Predator Threat-Induced Defensive Behaviour in Male Mice

INTRODUCTION

Environmental enrichment (EE) is a useful and sophisticated tool that improves rodents' well-being by stimulating social behaviour and cognitive, motor, and sensory functions. Exposure to EE induces neuroplasticity in different brain areas, including the limbic system, which has been implicated in the control of anxiety and fear. However, the effects of EE on ethologically relevant naturalistic behaviours, such as those displayed by prey in the presence of predators, remain largely unexplored.

MATERIAL AND METHODS

In the present study, we investigated anxiety- and panic attack-like behaviours in a predator (cat)-prey confrontation paradigm and compared them with those in classical assays, such as the elevated plus-maze (EPM), marble-burying, and open field tests (OFTs), using C57BL/6J male mice housed in enriched or standard environments for 6 weeks.

RESULTS

We observed that EE exposure caused enhancement of the levels of anxiety-like behaviours in the EPM and OFTs, increasing risk assessment (an anxiety-related response), and decreasing escape (a panic attack-like response) behaviours during exposure to the predator versus prey confrontation paradigm.

CONCLUSION

Taken together, our findings suggest that enriched external environments can modify the processing of fear- and anxiety-related stimuli in dangerous situations, changing the decision-making defensive strategy.

The Effect of Environmental Enrichment on Laboratory Rare Minnows (Gobiocypris rarus): Growth, Physiology, and Behavior

Simple Summary

Environmental enrichment is an important part of animal welfare. In this study, rare minnow in different rearing conditions underwent comprehensive evaluation regarding growth, anxiety-like behavior, and physiology parameters. Results showed that there were no differences in SGR, anxiety-like behavior, DA, DOPAC, and 5-HIAA levels between control and enriched groups. However, the enriched group had higher cortisol and 5-HT levels. Therefore, researchers should focus on the effect of environmental enrichment regarding the welfare of rare minnow and how it effects the validity of data from laboratory studies.

Abstract

Environmental enrichment is a method to increase environmental heterogeneity, which may reduce stress and improve animal welfare. Previous studies have shown that environmental enrichment can increase the growth rate, decrease aggressive and anxiety-like behaviors, improve learning ability and agility, and reduce cortisol levels in animals. These effects usually differ between species. Unfortunately, habitat enrichment on laboratory fish is poorly studied and seldom adopted in care guidance. Rare minnows (Gobiocypris rarus) have been cultured as a native laboratory fish in China in barren banks without environmental enrichment since 1990; they have been widely used in studies on ecotoxicology, environmental science, and other topics. The purpose of this study was to investigate the effect of environment enrichment on the growth, physiological status, and anxiety-like behavior of laboratory rare minnows. We observed and analyzed SGR, cortisol levels, DA, DOPAC, 5-HT and 5-HIAA, and anxiety-like behavior indexes after one month of treatment in barren (control) and enrichment tanks. We found that there were no significant differences in SGR, anxiety-like behavior, DA, DOPAC, or 5-HIAA levels between the two treatments. However, higher cortisol and 5-HT levels were observed in the enrichment tanks. This study suggests that rare minnows might be influenced by their living environment, and future related studies should consider their environmental enrichment.

Phasic firing of dopaminergic neurons in the ventral tegmental area triggers peripheral immune responses

Dopaminergic neurons in the ventral tegmental area (VTA) play a crucial role in the processing of reward-related information. Recent studies with pharmacological manipulations of VTA neuronal activity demonstrated a VTA-induced immunoenhancement in peripheral organs. Here, to examine the detailed physiological dynamics, we took an optogenetic approach in which VTA dopaminergic neurons were selectively activated with millisecond precision. Optogenetic phasic, rather than tonic, stimulation of VTA dopaminergic neurons increased serum cytokine levels, such as IL-2, IL-4 and TNF-α. These results provide direct evidence to link dopaminergic neuronal phasic firing to peripheral immunity. Next, we tested whether cytokine induction in male mice was boosted by female encounters, a natural condition that induces increased active VTA neurons and gamma power. Female encounters increased serum IL-2 levels, which were abolished by pharmacological inhibition of VTA neuronal activity. Taken together, our results highlight the importance of the brain reward system in the treatment and management of immune-related disorders.

Brief Environmental Enrichment exposure enhances contextual-induced sucrose-seeking with and without memory reactivation in rats

Chronic Environmental Enrichment (EE) has been shown to prevent the relapse to addictive behaviours, such as drug-taking and -seeking. Recently, acute EE was shown to reduce cue-induced sucrose-seeking, but its effects on contextual (Cx)-induced sucrose-seeking is still unknown. Here we report the effects of brief EE exposure on Cx-induced sucrose-seeking with and without prior Cx-memory reactivation. Adult male Sprague-Dawley rats were trained to sucrose self-administration associated to a specific conditioning Cx (CxA), followed by a 7-day extinction in a different Cx (CxB). Afterwards, rats were exposed for 22 h to EE, and 1 h later to either i) Cx-induced sucrose-seeking (1 h, renewal without Cx-memory reactivation), ii) or two different Cx-memory reactivations: short (2-min) and long (15-min) CxA-retrieval session (Cx-Ret). In Cx-Ret experiments, CxA-induced sucrose-seeking test (1 h) was done after a subsequent 3-day extinction phase. The assessment of molecular markers of memory reactivation/reconsolidation, Zif-268 and rpS6P, was performed 2 h after Cx-Ret. Brief EE exposure enhanced Cx-induced sucrose-seeking without and with short but not long Cx-retrieval. Moreover, EE impaired discriminative responding at test prior to long, whereas improved it with or without short Cx-retrieval. Different changes in Zif-268 and rpS6P expression induced by short vs. long Cx-Ret were correlated to behavioural data, suggesting the occurrence of different memory processes affected by EE. Our data show that brief EE exposure may differently affect subsequent appetitive relapse depending on the modality of re-exposure to conditioned context. This finding suggests caution and further studies to understand the proper conditions for the use of EE against appetitive and addiction disorders.

A Possible Anti-anxiety Effect of Appetitive Aggression and a Possible Link to the Work of Donald Winnicott

Various pleasant sensations that give a particularly intense pleasure are able to improve anxiety. In the present study I consider the possibility that their anti-anxiety action depends on the strong pleasure they provide, and I propose a possible mechanism of this action. According to some studies, also appetitive aggression (an aggression that provokes a strong pleasure and that is performed only for the pleasure it provides) can improve anxiety, and in this article I consider the possibility that the pleasure of appetitive aggression is able to reduce anxiety by the same mechanism I have proposed for other intense pleasurable sensations. The aggression performed by a child against the mother or against a substitute for the mother in the first period of life (a period in which this aggression is not dangerous) is a recurring theme throughout the work of of Donald Winnicott. Winnicott stresses that this aggression is necessary for the normal development of the child, and that the child must be free to practise it. According to Winnicott, this aggression is highly pleasurable and is not a response to unpleasant or hostile external situations. For these characteristics it seems to correspond to appetitive aggression in the adult that has been found to be able to reduce anxiety. Consequently, aggression performed by the child in the first period of life may also relieve anxiety, in the same way that appetitive aggression helps against anxiety in the adult. In his writings, Winnicott returns several times to an unthinkable or archaic anxiety that children experience when they feel abandoned by their mother for a period that is too long for them, and all children, according to Winnicott, live on the brink of this anxiety. In this study I propose the hypothesis that aggression in the early period of life may be necessary for children because the intense pleasure it provides may help them against this continuously impending anxiety.

Evaluation of different types of enrichment - their usage and effect on home cage behavior in female mice

Numerous studies ascertained positive effects of enriched environments on the well-being of laboratory animals including behavioral, physiological and neurochemical parameters. Conversely, such conclusions imply impaired animal welfare and health in barren husbandry conditions. Moreover, inappropriate housing of laboratory animals may deteriorate the quality of scientific data. Recommendations for housing laboratory animals stipulate that cages should be enriched to mitigate adverse effects of barren housing. In this context, it is not only unclear what exactly is meant by enrichment, but also how the animals themselves interact with the various items on offer. Focal animal observation of female C57BL/6J mice either housed in conventional (CON) or enriched (ENR) conditions served to analyze the impact of enriching housing on welfare related behavior patterns including stereotypical, maintenance, active social, and inactive behaviors. CON conditions resembled current usual housing of laboratory mice, whereas ENR mice received varying enrichment items including foraging, housing and structural elements, and a running disc. Active and inactive use of these elements was quantitatively assessed. CON mice showed significantly more inactive and stereotypical behavior than ENR mice. ENR mice frequently engaged with all enrichment elements, whereby riddles to obtain food reward and the running disc preferably served for active interactions. Offering a second level resulted in high active and inactive interactions. Structural elements fixed at the cagetop were least attractive for the mice. Overall, the presented data underline the positive welfare benefits of enrichment and that mice clearly differentiate between distinct enrichment types, demonstrating that the perspective of the animals themselves should also be taken into account when specifying laboratory housing conditions. This is particularly important, as the ensuring of animal welfare is an essential prerequisite for reliable, reproducible, and scientifically meaningful results.

A short social interaction between adult and old mice improves the homeostatic systems and increases healthy longevity

The aging process can be influenced by environmental factors, such as the social environment. The continuous cohabitation of the chronologically old mice with adult animals improves them at the behavioral level, immune function, oxidative stress and longevity, but causes a deterioration of these parameters in adults. Therefore, the objective of the study was to study whether the coexistence for only 15 min a day of old mice with adult mice, can produce that improvement and greater longevity in old animals without causing deterioration in adults. For that, old and adult CD1 female mice, after two months of that social interaction, were submitted to a behavioral battery and then peritoneal leukocytes were collected to assess several immune functions, oxidative and inflammatory stress parameters as well as catecholamine concentrations. When the adult mice reached old age, the same parameters were again analyzed. The life span of each animal was also recorded. Plasmatic concentration of oxytocin was also studied. The results showed that old mice presented better behavioral capacity, immunity and oxi-inflammatory state after this social interaction with adult animals, and consequently an extended life span. Adult mice, in general, did not show any changes after social interaction with old animals, but when they achieved old age, improvements of some parameters and of longevity were observed in comparison with animals that never had a that social interaction. In conclusion, a short social interaction between old and adult individuals can be an excellent strategy for improving in both the health state and longevity.

Environmental Enrichment Ameliorates Anxiety-Like Behavior in Rats without Altering Plasma Corticosterone Level

BACKGROUND: Anxiety disorder is one of the most common psychiatric problems. Prolonged stress gives rise to anxiety-like behavior in animals. Environmental interventions influence the outcome of anxiety treatment. Environmental enrichment (EE) can modulate brain’s structure and function. AIM: The objective of the study was to evaluate EE effects on anxiety-like behavior and corticosterone (CORT) level after unpredictable chronic mild stress (UCMS). METHODS: A total of 28 rats were assigned into four groups randomly: Control, UCMS, UCMS+EE, and UCMS+fluoxetine. UCMS, EE, and fluoxetine were given for 21 days. Anxiety behavior was measured on day 22nd using Elevated Plus Maze. Behavioral measurement was based on the total time spent and total entries onto open and closed arms. CORT was measured using ELISA. RESULTS: UCMS increased anxiety-like behavior as seen from reduced number of entries and time spent in open arms as well as increased number of entries and time spent in in closed arms in UCMS group than control. Rats in EE group spent more time and made more entries in the open arms than UCMS group (both p = 0.002). Anxiolytic effect of EE was stronger than fluoxetine. Plasma CORT level among groups did not differ significantly (p = 0.351). CONCLUSION: EE can ameliorate stress-induced anxiety-like behavior without affecting CORT level.