Housing environment influences the need for pain relief during post-operative recovery in mice

Current understanding of the molecular mechanisms of chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is the most common off-target adverse effects caused by various chemotherapeutic agents, such as cisplatin, oxaliplatin, paclitaxel, vincristine and bortezomib. CIPN is characterized by a substantial loss of primary afferent sensory axonal fibers leading to sensory disturbances in patients. An estimated of 19-85% of patients developed CIPN during the course of chemotherapy. The lack of preventive measures and limited treatment options often require a dose reduction or even early termination of life-saving chemotherapy, impacting treatment efficacy and patient survival. In this Review, we summarized the current understanding on the pathogenesis of CIPN. One prominent change induced by chemotherapeutic agents involves the disruption of neuronal cytoskeletal architecture and axonal transport dynamics largely influenced by the interference of microtubule stability in peripheral neurons. Due to an ineffective blood-nerve barrier in our peripheral nervous system, exposure to some chemotherapeutic agents causes mitochondrial swelling in peripheral nerves, which lead to the opening of mitochondrial permeability transition pore and cytochrome c release resulting in degeneration of primary afferent sensory fibers. The exacerbated nociceptive signaling and pain transmission in CIPN patients is often linked the increased neuronal excitability largely due to the elevated expression of various ion channels in the dorsal root ganglion neurons. Another important contributing factor of CIPN is the neuroinflammation caused by an increased infiltration of immune cells and production of inflammatory cytokines. In the central nervous system, chemotherapeutic agents also induce neuronal hyperexcitability in the spinal dorsal horn and anterior cingulate cortex leading to the development of central sensitization that causes CIPN. Emerging evidence suggests that the change in the composition and diversity of gut microbiota (dysbiosis) could have direct impact on the development and progression of CIPN. Collectively, all these aspects contribute to the pathogenesis of CIPN. Recent advances in RNA-sequencing offer solid platform for in silico drug screening which enable the identification of novel therapeutic agents or repurpose existing drugs to alleviate CIPN, holding immense promises for enhancing the quality of life for cancer patients who undergo chemotherapy and improve their overall treatment outcomes.

Evaluation of different methods of environmental enrichment to control anxiety in dogs undergoing hemilaminectomy after acute intervertebral disc extrusion: a randomized double-blinded study

Objective

The goal of this randomized, double-blinded, placebo-controlled study was to evaluate the effect of environmental enrichment (EE) on post-operative pain and anxiety in dogs following hemilaminectomy for acute intervertebral disc extrusion (IVDE).

Methods

Twenty healthy client-owned dogs undergoing a hemilaminectomy for IVDE with the same immediate post-operative analgesia protocol were randomly assigned to either the EE or standard environment (SE) group post-operatively. Recovery was achieved in an intensive care room (SE) or a separate quiet room (EE) equipped with white noise and classical music. EE dogs were also exposed to dog-appeasing pheromones, essential oil scents, and positive human interactions and were provided meals through food toys. A blinded evaluator assessed all dogs using the modified Glasgow Composite Pain Scale (mGCPS) on presentation and at several time points post-operatively. A rescue injection of the opioid methadone was given to the dogs with an mGCPS score of ≥5/20. Dogs received the antidepressant trazodone when anxious behaviors (5 mg/kg) were observed. The mGCPS scores, the latencies to receive the first methadone and trazodone doses and to eat the first meal, the number of methadone and trazodone doses, and the number of meals ingested in the first 24 and 48 h post-surgery were compared using Wilcoxon tests, and Benjamini-Hochberg correction for false discovery rate was applied.

Results

Although median mGCPS scores did not differ between the groups, compared to SE dogs (n = 10), EE dogs (n = 6) received trazodone earlier (p = 0.019), were administered fewer methadone injections at 24 h (p = 0.043), and ate more at 48 h post-surgery (p = 0.007). Therefore, EE and anti-anxiety medications could be beneficial in improving the wellbeing of dogs post-operatively.

Evaluation of Cage Mate-induced Postsurgical Trauma in Mice

Although mice are social animals, individual housing is sometimes requested after surgery. We questioned whether pair-housing mice after surgery resulted in greater trauma to the surgical site as compared with single housing. We further evaluated the effect of individual housing after surgery on the wellbeing of mice that had previously been pair-housed. Female C57Bl/6 mice (age, 6 to 8 wk) were housed as follows: group A, individually housed before and after surgery (n = 10; all 10 mice underwent surgery); group B, pair-housed before surgery but individually housed after surgery (n = 10; all 10 mice received surgery); group C, pair-housed before and after surgery (n = 20; 10 mice underwent surgery but their cage mates did not); and group D, pair-housed before and after surgery (n = 10; all 10 mice underwent surgery). Dependent variables were body weight, body condition, grimace based on real-time scoring, nest building, time to incorporate into nest test (TINT) score, wound trauma score, and missing wound clips. Weight was significantly different between groups A and C both before and after surgery. Mean nest building scores were significantly higher for pair-housed (groups C and D) than for individually housed mice (groups A and B) after surgery while TINT scores were significantly higher for these same groups both before and after surgery. Mean values for body condition, grimace score, wound score, and number of wound clips missing did not differ significantly between any groups either before or after surgery. Taken together, these results suggest that pair housing mice after surgery benefited their wellbeing but did not increase trauma to the surgical incision site or disturb wound clips as compared with individually housed mice. Furthermore, separating previously pair-housed mice (group B) did not affect these measures as compared with individually housed mice (Group A) either before or after surgery.

Efficacy of Supplemental Diet Gels for Preventing Postoperative Weight Loss in Mice ( Mus musculus)

This study investigated whether the use of commercially available diet gels prevented the postoperative weight loss associated with major survival surgery in mice. C57BL/6 mice were divided into 3 groups ( n = 9 per group) that received moistened chow pellets alone or with one of 2 commercially available diet gels. Mice began receiving the test diets 3 d before surgery (baseline) and were weighed daily for 7 d after surgery. On day 0, mice underwent ventral midline laparotomy, during which the intestines were manipulated for 2 min and a segment of jejunum was briefly clamped. Compared with the baseline value for the same group, body weights for the mice that received moistened chow only were significantly lower on all postoperative days (days 1 through 7). In contrast, body weights of mice that received both moistened chow and diet gel differed from baseline only on days 2 and 3 for one product and were never different from baseline for the other product. This study indicates that the combination of diet gel and moistened chow prevented or mitigated postoperative weight loss after a laparotomy procedure in mice.

Effects of a Multimodal Approach Using Buprenorphine with/without Meloxicam on Food Intake, Body Weight, Nest Consolidating Behavior, Burrowing Behavior, and Gastrointestinal Tissues in Postoperative Male Mice

Distress affects animal welfare and scientific data validity. There is a lack of reports on the effects of multimodal analgesic approaches in mice. In this study, under the hypothesis that a multimodal analgesic protocol using buprenorphine with meloxicam has analgesic effects, we evaluated the effects of a multimodal analgesic protocol using buprenorphine with meloxicam on the well-being of mice during analgesic administration by changing the dosage of meloxicam. A total of 42 Slc:ICR male mice were categorized into nonsurgical and surgical groups (7 mice per group) and treated with an anesthetic (isoflurane) and analgesics (buprenorphine ± meloxicam). Analgesics were administered for 48 h after treatment. Buprenorphine (subcutaneous; 0.1 mg/kg/8 h) and meloxicam (subcutaneous; 0, 2.5, or 5 mg/kg/24 h) were administered twice. Body weight, food intake, nest consolidation score, and latency to burrow were evaluated. A significant decrease in food intake was observed 24 h after treatment, while a significant increase was observed 48 h post-treatment in all groups. Body weight showed a decreasing trend but was not significantly reduced. Furthermore, stomach, duodenum, and jejunum tissues showed no morphological abnormalities. Significant differences in burrow diving scores and the latency to burrow were observed between some groups, but these were not regarded as a consequence of the surgery and/or the meloxicam dose. When buprenorphine and meloxicam were combined, administering up to 5 mg/kg/day of meloxicam for 48 h to male mice after abdominal surgery had no significant negative effects on any tested parameters. In conclusion, a multimodal analgesic protocol of buprenorphine with meloxicam is among the options for increasing well-being in mice following abdominal surgery.

Effectiveness of two extended-release buprenorphine formulations during postoperative period in neonatal rats

Information on the effectiveness of a new long-lasting buprenorphine formulation, extended-release buprenorphine, in the neonatal rat is very limited. This study compares whether a high dose of extended-release buprenorphine (XR-Hi) attenuates thermal hypersensitivity for a longer period than a low dose of extended-release buprenorphine (XR-Lo) in a neonatal rat incisional pain model. Two experiments were performed. Experiment one: Male and female postnatal day-5 rat pups (n = 38) were randomly assigned to 1 of 4 treatment groups and received a subcutaneous administration of one of the following: 1) 0.9%NaCl (Saline), 0.1 mL; 2) sustained release buprenorphine (Bup-SR), 1 mg/kg; 3) XR-Lo, 0.65 mg/kg; and 4) XR-Hi, 1.3 mg/kg. Pups were anesthetized with sevoflurane in 100% O₂ and a 5 mm long skin incision was made over the left lateral thigh and underlying muscle dissected. The skin was closed with surgical tissue glue. Thermal hypersensitivity testing (using a laser diode) and clinical observations were conducted 1 hour (h) prior to surgery and subsequently after 1, 4, 8, 24, 48, 72 h of treatment. Experiment two: The plasma buprenorphine concentration level was evaluated at 1, 4, 8, 24, 48, 72 h on five-day-old rat pups. Plasma buprenorphine concentration for all treatment groups remained above the clinically effective concentration of 1 ng/mL for at least 4 h in the Bup-SR group, 8 h in XR-Lo and 24 h in XR-Hi group with no abnormal clinical observations. This study demonstrates that XR-Hi did not attenuate postoperative thermal hypersensitivity for a longer period than XR-Lo in 5-day-old rats; XR-Hi attenuated postoperative thermal hypersensitivity for up to 4 h while Bup-SR and XR-Lo for at least 8 h in this model.

Grimace scale, burrowing, and nest building for the assessment of post-surgical pain in mice and rats-A systematic review

Several studies suggested an informative value of behavioral and grimace scale parameters for the detection of pain. However, the robustness and reliability of the parameters as well as the current extent of implementation are still largely unknown. In this study, we aimed to systematically analyze the current evidence-base of grimace scale, burrowing, and nest building for the assessment of post-surgical pain in mice and rats. The following platforms were searched for relevant articles: PubMed, Embase via Ovid, and Web of Science. Only full peer-reviewed studies that describe the grimace scale, burrowing, and/or nest building as pain parameters in the post-surgical phase in mice and/or rats were included. Information about the study design, animal characteristics, intervention characteristics, and outcome measures was extracted from identified publications. In total, 74 papers were included in this review. The majority of studies have been conducted in young adult C57BL/6J mice and Sprague Dawley and Wistar rats. While there is an apparent lack of information about young animals, some studies that analyzed the grimace scale in aged rats were identified. The majority of studies focused on laparotomy-associated pain. Only limited information is available about other types of surgical interventions. While an impact of surgery and an influence of analgesia were rather consistently reported in studies focusing on grimace scales, the number of studies that assessed respective effects was rather low for nest building and burrowing. Moreover, controversial findings were evident for the impact of analgesics on post-surgical nest building activity. Regarding analgesia, a monotherapeutic approach was identified in the vast majority of studies with non-steroidal anti-inflammatory (NSAID) drugs and opioids being most commonly used. In conclusion, most evidence exists for grimace scales, which were more frequently used to assess post-surgical pain in rodents than the other behavioral parameters. However, our findings also point to relevant knowledge gaps concerning the post-surgical application in different strains, age levels, and following different surgical procedures. Future efforts are also necessary to directly compare the sensitivity and robustness of different readout parameters applied for the assessment of nest building and burrowing activities.

Emerging Role of Translational Digital Biomarkers Within Home Cage Monitoring Technologies in Preclinical Drug Discovery and Development

In drug discovery and development, traditional assessment of human patients and preclinical subjects occurs at limited time points in potentially stressful surroundings (i.e., the clinic or a test arena), which can impact data quality and welfare. However, recent advances in remote digital monitoring technologies enable the assessment of human patients and preclinical subjects across multiple time points in familiar surroundings. The ability to monitor a patient throughout disease progression provides an opportunity for more relevant and efficient diagnosis as well as improved assessment of drug efficacy and safety. In preclinical in vivo animal models, these digital technologies allow for continuous, longitudinal, and non-invasive monitoring in the home environment. This manuscript provides an overview of digital monitoring technologies for use in preclinical studies including their history and evolution, current engagement through use cases, and impact of digital biomarkers (DBs) on drug discovery and the 3Rs. We also discuss barriers to implementation and strategies to overcome them. Finally, we address data consistency and technology standards from the perspective of technology providers, end-users, and subject matter experts. Overall, this review establishes an improved understanding of the value and implementation of digital biomarker (DB) technologies in preclinical research.

Social Buffering as a Tool for Improving Rodent Welfare

The presence of a conspecific can be calming to some species of animal during stress, a phenomenon known as social buffering. For rodents, social buffering can reduce the perception of and reaction to aversive experiences. With a companion, animals may be less frightened in conditioned fear paradigms, experience faster wound healing, show reduced corticosterone responses to novelty, and become more resilient to everyday stressors like cage-cleaning. Social buffering works in diverse ways across species and life stages. For example, social buffering may rely on specific bonds and interactions between individuals, whereas in other cases, the mere presence of conspecific cues may reduce isolation stress. Social buffering has diverse practical applications for enhancing rodent wellbeing (some of which can be immediately applied, while others need further development via welfare-oriented research). Appropriate social housing will generally increase rodents' abilities to cope with challenges, with affiliative cage mates being the most effective buffers. Thus, when rodents are scheduled to experience distressing research procedures, ensuring that their home lives supply high degrees of affiliative, low stress social contact can be an effective refinement. Furthermore, social buffering research illustrates the stress of acute isolation: stressors experienced outside the cage may thus be less impactful if a companion is present. If a companion cannot be provided for subjects exposed to out-of-cage stressors, odors from unstressed animals can help ameliorate stress, as can proxies such as pieces of synthetic fur. Finally, in cases involving conditioned fear (the learned expectation of harm), newly providing social contact during exposure to negative conditioned stimuli (CS) can modify the CS such that for research rodents repeatedly exposed to aversive stimuli, adding conspecific contact can reduce their conditioned fear. Ultimately, these benefits of social buffering should inspire the use of creative techniques to reduce the impact of stressful procedures on laboratory rodents, so enhancing their welfare.

Effects of Multimodal Analgesic Protocol, with Buprenorphine and Meloxicam, on Mice Well-Being: A Dose Finding Study

The anesthetic or analgesic agent of choice, route and frequency of anesthetic or analgesic administration, and stressors induce distress during the perioperative period. We evaluated a multimodal analgesic protocol using buprenorphine and meloxicam on the well-being of mice. Twenty-four Slc:ICR male mice were divided into control, anesthesia + analgesia, and surgery + anesthesia + analgesia groups. Tap water (orally: PO) and water for injection (subcutaneous: SC) were administered to the control group. Buprenorphine was administered twice (SC, 0.1 mg/kg/8 h) and meloxicam was administered thrice (PO, 5 mg/kg/24 h) to the anesthesia + analgesia and surgery + anesthesia + analgesia groups. The mice were subjected to laparotomy and assessed for several parameters. Even in absence of surgical pain, the anesthesia + analgesia group presented the same negative effects as the surgery + anesthesia + analgesia group. This multimodal analgesic protocol for mice was expected to have an analgesic effect on pain associated with laparotomy but was not sufficient to prevent food intake and weight decrease. This does not negate the need to administer analgesics, but suggests the need to focus on and care not only about the approach to relieve pain associated with surgery, but also other types of distresses to minimize negative side effects that may interfere with postoperative recovery in mice.

Using approach latency and anticipatory behaviour to assess whether voluntary playpen access is rewarding to laboratory mice

Laboratory mice are typically housed in “shoebox" cages that limit the expression of natural behaviours. Temporary access to more complex environments (playpens) may improve their welfare. We aimed to assess if access to playpens is rewarding for conventionally-housed mice and to document mouse behaviour during playpen access. Female C57BL/6J, BALB/cJ, and DBA/2J mice were provided temporary access to a large enriched playpen three times per week; control mice remained in their home cages. We measured latency to enter playpens and anticipatory behaviour to determine if access was rewarding, and recorded mouse behaviour during playpen sessions. Over time, playpen mice entered the playpen more quickly; latency declined from 168 ± 22 to 13 ± 2 s over the 14-d trial. As expected, playpen mice showed an increase in anticipatory behaviour before playpen access (mean ± SE = 19.7 ± 2.6 behavioural transitions), while control mice showed no change in anticipatory behaviour relative to baseline values (2.4 ± 1.6 transitions). Mice in the playpen performed more ambulatory behaviours than control mice who remained in home cages (21.5 ± 0.7 vs 6.9 ± 1.1 observations of 25 total observations). We conclude that conventionally-housed mice find voluntary playpen access rewarding, and suggest this as a useful option for providing laboratory mice with access to more complex environments.

Automated home-cage monitoring as a potential measure of sickness behaviors and pain-like behaviors in LPS-treated mice

The use of endotoxin, such as lipopolysaccharide (LPS) as a model of sickness behavior, has attracted recent attention. To objectively investigate sickness behavior along with its pain-like behaviors in LPS-treated mice, the behavioral measurement requires accurate methods, which reflects clinical relevance. While reflexive pain response tests have been used for decades for pain assessment, its accuracy and clinical relevance remain problematic. Hence, we used automated home-cage monitoring LABORAS to evaluate spontaneous locomotive behaviors in LPS-induced mice. LPS-treated mice displayed sickness behaviors including pain-like behaviors in automated home-cage monitoring characterized by decreased mobile behaviors (climbing, locomotion, rearing) and increased immobility compared to that of the control group in both short- and long-term locomotive assessments. Here, in short-term measurement, both in the open-field test and automated home-cage monitoring, mice demonstrated impaired locomotive behaviors. We also assessed 24 h long-term locomotor activity in the home-cage system, which profiled the diurnal behaviors of LPS-stimulated mice. The results demonstrated significant behavioral impairment in LPS-stimulated mice compared to the control mice in both light and dark phases. However, the difference is more evident in the dark phase compared to the light phase owing to the nocturnal activity of mice. In addition, the administration of indomethacin as a pharmacological intervention improved sickness behaviors in the open-field test as well as automated home-cage monitoring, confirming that automated home-cage monitoring could be potentially useful in pharmacological screening. Together, our results demonstrate that automated home-cage monitoring could be a feasible alternative to conventional methods, such as the open-field test and combining several behavioral assessments may provide a better understanding of sickness behavior and pain-like behaviors in LPS-treated mice.

Automated home-cage for the evaluation of innate non-reflexive pain behaviors in a mouse model of inflammatory pain

The failure to develop analgesic drugs is attributed not only to the complex and diverse pathophysiology of pain in humans but also to the poor experimental design and poor preclinical assessment of pain. Although considerable efforts have been devoted to overcoming the relevant problems, many features of the behavioral pain assessment remain to be characterized. For example, a decreased locomotor activity as a common presentation of pain-like behavior has yet to be described. Studies on mice experimentally induced with carrageenan have provided opportunities to explore pain-related behaviors in automated home-cage monitoring. Through this approach, the locomotor activities of mice with carrageenan-induced inflammatory pain can be precisely and objectively captured. Here, we found that the mobile behaviors of mice reduced, and their immobility increased, indicating that carrageenan induction in mice caused a significant decrease in locomotor activity. These non-reflexive pain behaviors were strongly correlated with the reflexive pain behaviors measured via von Frey and plantar tests. Furthermore, the pharmacological intervention using indomethacin improved the locomotor activity of mice with carrageenan-induced pain. Thus, the analysis of the locomotor activity in automated home-cage monitoring is useful for studying the behavioral analgesia and the pharmacological screening of analgesic drugs. The combined evaluation of reflexive and non-reflexive pain behaviors enhances the translational utility of preclinical pain research in rodents.

Flood Resilience of Housing Infrastructure Modeling and Quantification Using a Bayesian Belief Network

Resilience is the capability of a system to resist any hazard and revive to a desirable performance. The consequences of such hazards require the development of resilient infrastructure to ensure community safety and sustainability. However, resilience-based housing infrastructure design is a challenging task due to a lack of appropriate post-disaster datasets and the non-availability of resilience models for housing infrastructure. Hence, it is necessary to build a resilience model for housing infrastructure based on a realistic dataset. In this work, a Bayesian belief network (BBN) model was developed for housing infrastructure resilience. The proposed model was tested in a real community in Northeast India and the reliability, recovery, and resilience of housing infrastructure against flood hazards for that community were quantified. The required data for resilience quantification were collected by conducting a field survey and from public reports and documents. Lastly, a sensitivity analysis was performed to observe the critical parameters of the proposed BBN model, which can be used to inform designers, policymakers, and stakeholders in making resilience-based decisions.

Long-Term Effect of Environmental Enrichment on Reproductive Performance of Swiss Webster Mice and Their Female Offspring

Simple Summary

The aim of this study was to evaluate the effect of the implementation of an environmental enrichment (EE) plan on reproductive performance in mice, applied during one year period in Swiss Webster breeders and their female offspring used as recipients for embryo transfer. Birth rate, litter size, pups’ weight at weaning, interlitter interval and time to first litter were compared against a control group that did not receive EE. In mice breeders, EE significantly increased pups’ weight compared to control group (p < 0.01), without changing any other reproductive parameters. In the offspring females used as recipients, EE did not modify reproductive parameters. Our results demonstrate that this enrichment plan, which is usually applied in mouse facilities for animal well-being, enhances pup’s weight at weaning, with no negative effects on the reproductive performance of Swiss Webster mice.

Abstract

The aim of this study was to evaluate the effect of an environmental enrichment (EE) plan on the reproductive performance of Swiss Webster mice and their female offspring used as recipients for embryo transfer. A total of 54 breeder mice and 60 F1 females, used as foster mothers, were allocated in two experimental groups to receive or not receive EE for physical well-being. Reproductive outcomes of the Swiss trios such as birth rate and pup number, litter size, pups’ weight at weaning, interlitter interval and time to first litter were analyzed. Environmental enrichment significantly increased pups weight from breeding trios compared to the control group (14.4 ± 0.1 vs. 13.8g ± 0.1, EE vs. control, respectively; p < 0.01). Other parameters did not differ between both groups. Reproductive parameters of female offspring used as recipients for embryo transfer did not differ among groups subjected or not to EE. These data demonstrate that the EE protocol applied in Swiss Webster breeder mice positively enhanced pups weight, and did not interfere with other reproductive outcomes. In conclusion, this study supports the implementation of EE plans usually applied for animal welfare in mouse facilities with slight improvement in reproductive performance.

Hens with benefits: Can environmental enrichment make chickens more resilient to stress?

Resilience, the degree to which individuals are physiologically and behaviourally impacted by stressors, can be enhanced by positive experiences (e.g. positive moods in human, environmental enrichment in rodents). Such effects are important for human health, but could also have important animal welfare implications in terms of farm, laboratory and zoo animals' abilities to cope with stressors. Here we investigated whether enrichments can increase resilience in chickens, the world's most abundant agricultural animal. The stress reactivity of laying hens housed for 5-6 weeks in enriched environments was compared to that of controls housed in smaller, emptier, less preferred pens, via: 1) startle reflex amplitudes to an abrupt, intense sensory stimulus (a light flash); and 2) autonomic responses to restraint and the sudden appearance of a novel object, assessed from decreases in comb temperature. Startle amplitudes were consistently reduced in the enriched hens, exerted with around one sixth the force seen in control hens. Maximum comb temperature decreases, and latencies for comb temperatures to return to prestress levels, also both fell by around a third. Enrichment thus reduced hens' intrinsic behavioural and physiological responses to standardized stressors (doing so even outside the home pen), just as occurs in laboratory rodents. Enrichment also reduced baseline comb temperature, suggesting that this could be a non-invasive indicator of welfare. Altered judgment biases did not seem to be the mechanism. Further work should now investigate the processes underlying the apparently enhanced stress resilience of animals housed in preferred conditions, and also investigate baseline comb temperature as a chronic stress indicator in poultry.

Group and Single Housing of Male Mice: Collected Experiences from Research Facilities in Sweden

Simple Summary

The mouse is the most commonly used mammal in scientific research, and housed in research facilities around the world. Mice are a social species, but when housing male mice together in a confined environment in the laboratory, aggression is often observed and can be problematic. Fighting or trying to avoid fighting can be stressful. Furthermore, fighting can lead to injuries which can sometimes be fatal. Mouse aggression is therefore a significant welfare problem and has implications on the 3Rs (Replacing, Reducing, and Refining animal use in scientific procedures and education). In this study, we used a survey and workshops to collect the experiences of animal technicians, veterinarians, and researchers at Swedish research animal facilities relating to mouse aggression and what methods of preventing aggression they practice. Both group housing and single-housing as a consequence of aggression was perceived as problematic and stressful for the animals. In line with current recommendations from the literature, participants perceived that aggression occurred less if mice were grouped with litter mates at an early age, that nesting material was transferred at cage cleaning, and disturbance was kept to a minimum. Experience from practice will play a valuable part in developing guidelines for group-housed male mice.

Abstract

Animals used for scientific purposes are protected by EU legislation. Social animals should be kept in stable groups that enable species-typical social behavior and provide individuals with social comfort. However, when group-housing male mice, aggression within the homecage is a common husbandry and welfare problem. Excessive fighting and injuries due to aggression can cause pain and stress, resulting in individuals being euthanized or housed individually. In addition, stress can alter physiological parameters, risking scientific validity and generating larger sample sizes. Mouse aggression, and the consequences thereof, thus opposes the 3R goals of Refining the methods to minimize potential pain and suffering and Reducing the number of animals used. Animal technicians, veterinarians, and scientists using animals have valuable information on how these problems are experienced and handled in practice. We assembled these experiences from laboratory animal facilities in Sweden, mapping problems observed and identifying strategies used to prevent mouse aggression. In line with current literature, less aggression was perceived if mice were grouped before sexual maturity, re-grouping avoided and nesting material transferred at cage cleaning. Preventing aggression will minimize pain and suffering and enable housing of stable groups, leading to more reliable scientific outcomes and is thus of high 3Rs relevance.

Ethical considerations in fish research

Fishes are used in a wide range of scientific studies, from conservation research with potential benefits to the species used to biomedical research with potential human benefits. Fish research can take place in both laboratories and field environments and methods used represent a continuum from non-invasive observations, handling, through to experimental manipulation. While some countries have legislation or guidance regarding the use of fish in research, many do not and there exists a diversity of scientific opinions on the sentience of fish and how we determine welfare. Nevertheless, there is a growing pressure on the scientific community to take more responsibility for the animals they work with through maximising the benefits of their research to humans or animals while minimising welfare or survival costs to their study animals. In this review, we focus primarily on the refinement of common methods used in fish research based on emerging knowledge with the aim of improving the welfare of fish used in scientific studies. We consider the use of anaesthetics and analgesics and how we mark individuals for identification purposes. We highlight the main ethical concerns facing researchers in both laboratory and field environments and identify areas that need urgent future research. We hope that this review will help inform those who wish to refine their ethical practices and stimulate thought among fish researchers for further avenues of refinement. Improved ethics and welfare of fishes will inevitably lead to increased scientific rigour and is in the best interests of both fishes and scientists.

The Effects of Enriched Environmental Intervention on the Parturition Outcome and Filial Health of Pregnant Mice With Chronic Pain

Chronic pain (CP) adversely impacts people's health. However, the influence of CP on pregnant women and their fetuses remains unclear. Few reasonable interventions have been offered to these women. This study aimed to examine the effects of enriched environmental intervention (EEI) on the delivery outcome and offspring health of pregnant mice with CP. Forty pregnant mice were equally and randomly divided into four groups (control, sham, CP, and CP + EEI). Monoarthritis was induced by subcutaneous injection of the complete Freund's adjuvant (100 μg/100 μl) into the left hind paw of mice on Day 0 of gestation. Sham mice received 100 µl of sterile phosphate-buffered saline subcutaneously. General health status and delivery outcomes of pregnant mice and general physical status, growth, and development of offspring were observed and compared between groups. CP mice exhibited less weight gain, higher rate of premature delivery, smaller litter size, lower live birth rate, lower filial birth weight, shorter filial tail length, and lower filial rates of achieving righting reflex and crawling compared to mice in the control/sham/CP + EEI groups. There were no significant differences between mice in the CP + EEI group and those in the control and sham groups. CP during pregnancy led to serious adverse impacts on both the mother and fetus mice in this study, and EEI was an effective treatment for these effects.

Development of the Digital Arthritis Index, a Novel Metric to Measure Disease Parameters in a Rat Model of Rheumatoid Arthritis

Despite a broad spectrum of anti-arthritic drugs currently on the market, there is a constant demand to develop improved therapeutic agents. Efficient compound screening and rapid evaluation of treatment efficacy in animal models of rheumatoid arthritis (RA) can accelerate the development of clinical candidates. Compound screening by evaluation of disease phenotypes in animal models facilitates preclinical research by enhancing understanding of human pathophysiology; however, there is still a continuous need to improve methods for evaluating disease. Current clinical assessment methods are challenged by the subjective nature of scoring-based methods, time-consuming longitudinal experiments, and the requirement for better functional readouts with relevance to human disease. To address these needs, we developed a low-touch, digital platform for phenotyping preclinical rodent models of disease. As a proof-of-concept, we utilized the rat collagen-induced arthritis (CIA) model of RA and developed the Digital Arthritis Index (DAI), an objective and automated behavioral metric that does not require human-animal interaction during the measurement and calculation of disease parameters. The DAI detected the development of arthritis similar to standard in vivo methods, including ankle joint measurements and arthritis scores, as well as demonstrated a positive correlation to ankle joint histopathology. The DAI also determined responses to multiple standard-of-care (SOC) treatments and nine repurposed compounds predicted by the SMarTR^TM Engine to have varying degrees of impact on RA. The disease profiles generated by the DAI complemented those generated by standard methods. The DAI is a highly reproducible and automated approach that can be used in-conjunction with standard methods for detecting RA disease progression and conducting phenotypic drug screens.

Introducing Therioepistemology: the study of how knowledge is gained from animal research

This focus issue of Lab Animal coincides with a tipping point in biomedical research. For the first time, the scale of the reproducibility and translatability crisis is widely understood beyond the small cadre of researchers who have been studying it and the pharmaceutical and biotech companies who have been living it. Here we argue that an emerging literature, including the papers in this focus issue, has begun to congeal around a set of recurring themes, which themselves represent a paradigm shift. This paradigm shift can be characterized at the micro level as a shift from asking "what have we controlled for in this model?" to asking "what have we chosen to ignore in this model, and at what cost?" At the macro level, it is a shift from viewing animals as tools (the furry test tube), to viewing them as patients in an equivalent human medical study. We feel that we are witnessing the birth of a new discipline, which we term Therioepistemology, or the study of how knowledge is gained from animal research. In this paper, we outline six questions that serve as a heuristic for critically evaluating animal-based biomedical research from a therioepistemological perspective. These six questions sketch out the broad reaches of this new discipline, though they may change or be added to as this field evolves. Ultimately, by formalizing therioepistemology as a discipline, we can begin to discuss best practices that will improve the reproducibility and translatability of animal-based research, with concomitant benefits in terms of human health and animal well-being.

Laboratory environmental factors and pain behavior: the relevance of unknown unknowns to reproducibility and translation

The poor record of basic-to-clinical translation in recent decades has led to speculation that preclinical research is "irreproducible", and this irreproducibility in turn has largely been attributed to deficiencies in reporting and statistical practices. There are, however, a number of other reasonable explanations of both poor translation and difficulties in one laboratory replicating the results of another. This article examines these explanations as they pertain to preclinical pain research. I submit that many instances of apparent irreproducibility are actually attributable to interactions between the phenomena and interventions under study and "latent" environmental factors affecting the rodent subjects. These environmental variables-often causing stress, and related to both animal husbandry and the specific testing context-differ greatly between labs, and continue to be identified, suggesting that our knowledge of their existence is far from complete. In pain research in particular, laboratory stressors can produce great variability of unpredictable direction, as stress is known to produce increases (stress-induced hyperalgesia) or decreases (stress-induced analgesia) in pain depending on its parameters. Much greater attention needs to be paid to the study of the laboratory environment if replication and translation are to be improved.

The effect of early life experience, environment, and genetic factors on spontaneous home-cage aggression-related wounding in male C57BL/6 mice

Aggression is a major welfare issue in mice, particularly when mice unfamiliar to each other are first placed in cages, as happens on receipt from a vendor, and following cage cleaning. Injuries from aggression are the second leading cause of unplanned euthanasia in mice, following ulcerative dermatitis. Commonly employed strategies for reducing aggression-related injury are largely anecdotal, and may even be counterproductive. Here we report a series of experiments testing potential explanations and interventions for post-shipping aggression-related injuries in C57BL/6 mice. First, we examined the effects of weaning: testing whether manipulating weaning age reduced aggression-related injuries, and if repeated mixing of weaned mice before shipping increased these injuries. Contrary to our predictions, repeated mixing did not increase post-shipping injurious aggression, and early weaning reduced aggression-related injuries. Second, we examined potential post-shipping interventions: testing whether lavender essential oil applied to the cage reduced aggression-related injuries, and whether a variety of enrichments decreased injurious aggression. Again, contrary to predictions, lavender increased wounding, and none of the enrichments reduced it. However, consistent with the effects of weaning age in the first experiment, cages with higher mean body weight showed elevated levels of aggression-related wounding. Finally, we tested whether C57BL/6 substrains and identification methods affected levels of intra-cage wounding from aggression. We found no effect of strain, but cages where mice were ear-notched for identification showed higher levels of wounding than cages where mice were tail-tattooed. Overall, these results emphasize the multifactorial nature of home-cage injurious aggression, and the importance of testing received wisdom when it comes to managing complex behavioral and welfare problems. In terms of practical recommendations to reduce aggressive wounding in the home cage, tail tattooing is recommended over ear notching and late weaning should be avoided.

Adult Hippocampal Neurogenesis along the Dorsoventral Axis Contributes Differentially to Environmental Enrichment Combined with Voluntary Exercise in Alleviating Chronic Inflammatory Pain in Mice

Cognitive behavioral therapy, such as environmental enrichment combined with voluntary exercise (EE-VEx), is under active investigation as an adjunct to pharmaceutical treatment for chronic pain. However, the effectiveness and underlying mechanisms of EE-VEx remain unclear. In mice with intraplantar injection of complete Freund's adjuvant, our results revealed that EE-VEx alleviated perceptual, affective, and cognitive dimensions of chronic inflammatory pain. These effects of EE-VEx on chronic pain were contingent on the occurrence of adult neurogenesis in the dentate gyrus in a functionally dissociated manner along the dorsoventral axis: neurogenesis in the ventral dentate gyrus participated in alleviating perceptual and affective components of chronic pain by EE-VEx, whereas neurogenesis in the dorsal dentate gyrus was involved in EE-VEx's cognitive-enhancing effects. Chronic inflammatory pain was accompanied by decreased levels of brain-derived neurotrophic factor (BDNF) in the dentate gyrus, which were reversed by EE-VEx. Overexpression of BDNF in the dentate gyrus mimicked the effects of EE-VEx. Our results demonstrate distinct contribution of adult hippocampal neurogenesis along the dorsoventral axis to EE-VEx's beneficial effects on different dimensions of chronic pain.SIGNIFICANCE STATEMENT Environmental enrichment combined with voluntary exercise (EE-VEx) is under active investigation as an adjunct to pharmaceutical treatment for chronic pain, but its effectiveness and underlying mechanisms remain unclear. In a mouse model of inflammatory pain, the present study demonstrates that the beneficial effects of EE-VEx on chronic pain depend on adult neurogenesis with a dorsoventral dissociation along the hippocampal axis. Adult neurogenesis in the ventral dentate gyrus participates in alleviating perceptual and affective components of chronic pain by EE-VEx, whereas that in the dorsal pole is involved in EE-VEx's cognitive-enhancing effects in chronic pain.

Voluntary and evoked behavioral correlates in inflammatory pain conditions under different social housing conditions

Most preclinical pain models rely on short-duration stimulus-evoked hind paw measurements even though chronic pain is usually a day and night experience. Pain is a debilitating condition that influences the sociability and the ability for voluntary tasks, but the relevant behavioral readouts for these aspects are mostly underrepresented in the literature. Moreover, we lack standardization in most behavioral paradigms. Important aspects are herewith the combination and duration of particular behavioral tasks and the effects of social environment. We aimed at thoroughly investigating stimulus-evoked and voluntary behavioral parameters in the Complete Freund's Adjuvant model of unilateral hind paw inflammation in male mice. Moreover, we analyzed the impact of different social housing conditions. We used a portfolio of classical response measurements, detailed gait analysis, using 2 different measuring systems (Dynamic weight bearing and CatWalk), as well as observer-independent voluntary wheel running and homecage monitoring in a longitudinal time frame. The impact of grouped or isolated housing was investigated in all behavioral paradigms. We observed that unilateral hind paw inflammation provoked changes in several behaviors. Among these were wheel running activity and different homecage activity parameters. Stimulus-evoked hypersensitivity lasted much longer than gait abnormalities and decreased voluntary wheel running activity. Similar effects were monitored in both social housing conditions. This is the first longitudinal study providing detailed insights into various voluntary behavioral parameters related to pain in a unilateral inflammatory model. Stimulus-evoked behavioral changes lasted longer than changes in voluntary behavioral parameters, and the social environment hardly affects these changes.

Environmental and Pharmacological Manipulations Blunt the Stress Response of Zebrafish in a Similar Manner

Here we provide evidence that both pharmacological and environmental manipulations similarly blunt the cortisol release in response to an acute stressor in adult zebrafish. Different groups of fish were maintained isolated or group-housed in barren or enriched tanks, and then exposed or not to diazepam or fluoxetine. Acute stress increased cortisol levels in group-housed zebrafish maintained in barren environment. Single-housed zebrafish displayed a blunted cortisol response to stress. Environmental enrichment also blunted the stress response and this was observed in both isolated and group-housed fish. The same blunting effect was observed in zebrafish exposed to diazepam or fluoxetine. We highlighted environmental enrichment as an alternative and/or complimentary therapeutic for reducing stress and as a promoter of animal welfare.

EXPRESS: Voluntary and evoked behavioral correlates in neuropathic pain states under different housing conditions

Background

There is an urgent need to develop and incorporate novel behavioral tests in classically used preclinical pain models. Most rodent studies are based upon stimulus-evoked hindpaw measurements even though chronic pain is usually a day and night experience. Chronic pain is indeed a debilitating condition that influences the sociability and the ability for voluntary tasks, but the relevant behavioral readouts for these aspects are mostly under-represented in the literature. Moreover, we lack standardization in most behavioral paradigms to guarantee reproducibility and ensure adequate discussion between different studies. This concerns not only the combination, application, and duration of particular behavioral tasks but also the effects of different housing conditions implicating social isolation.

Results

Our aim was to thoroughly characterize the classically used spared nerve injury model for 12 weeks following surgery. We used a portfolio of classical stimulus-evoked response measurements, detailed gait analysis with two different measuring systems (Dynamic weight bearing (DWB) system and CatWalk), as well as observer-independent voluntary wheel running and home cage monitoring (Laboras system). Additionally, we analyzed the effects of social isolation in all behavioral tasks. We found that evoked hypersensitivity temporally matched changes in static gait parameters, whereas some dynamic gait parameters were changed in a time-dependent manner. Interestingly, voluntary wheel running behavior was not affected in spared nerve injury mice but by social isolation. Besides a reduced climbing activity, spared nerve injury mice did not showed tremendous alterations in the home cage activity.

Conclusion

This is the first longitudinal study providing detailed insights into various voluntary behavioral parameters related to pain and highlights the importance of social environment on spontaneous non-evoked behaviors in a mouse model of chronic neuropathy. Our results provide fundamental considerations for future experimental planning and discussion of pain-related behavioral changes.

Effect of environment on the long-term consequences of chronic pain

Much evidence from pain patients and animal models shows that chronic pain does not exist in a vacuum but has varied comorbidities and far-reaching consequences. Patients with long-term pain often develop anxiety and depression and can manifest changes in cognitive functioning, particularly with working memory. Longitudinal studies in rodent models also show the development of anxiety-like behavior and cognitive changes weeks to months after an injury causing long-term pain. Brain imaging studies in pain patients and rodent models find that chronic pain is associated with anatomical and functional alterations in the brain. Nevertheless, studies in humans reveal that lifestyle choices, such as the practice of meditation or yoga, can reduce pain perception and have the opposite effect on the brain as does chronic pain. In rodent models, studies show that physical activity and a socially enriched environment reduce pain behavior and normalize brain function. Together, these studies suggest that the burden of chronic pain can be reduced by nonpharmacological interventions.

Effects of experimental housing conditions on recovery of laboratory mice

The beneficial effects of environment and social support during disease recovery in humans are widely accepted. Because laboratory mice are social animals and are highly motivated to interact with each other and with their environment, it is very likely that environmental and social factors are also beneficial to their recovery from experimental interventions or spontaneous diseases. The beneficial effects of enriched environments have been particularly well analyzed in the field of brain disorders, but several studies suggest that positive social contact and a complex and familiar environment may also support recovery from injury, from invasive procedures such as surgery or from spontaneously occurring diseases. The author reviews relevant publications on the effects of environment and social housing on recovery from disease or surgery in laboratory mice and other rodents. She concludes that in addition to promoting animal welfare, provision of optimal experimental housing conditions might also contribute to the clinical relevance of preclinical animal models by more closely simulating the environmental and social characteristics of disease recovery in humans.

Pain in aquatic animals

Recent developments in the study of pain in animals have demonstrated the potential for pain perception in a variety of wholly aquatic species such as molluscs, crustaceans and fish. This allows us to gain insight into how the ecological pressures and differential life history of living in a watery medium can yield novel data that inform the comparative physiology and evolution of pain. Nociception is the simple detection of potentially painful stimuli usually accompanied by a reflex withdrawal response, and nociceptors have been found in aquatic invertebrates such as the sea slug Aplysia. It would seem adaptive to have a warning system that allows animals to avoid life-threatening injury, yet debate does still continue over the capacity for non-mammalian species to experience the discomfort or suffering that is a key component of pain rather than a nociceptive reflex. Contemporary studies over the last 10 years have demonstrated that bony fish possess nociceptors that are similar to those in mammals; that they demonstrate pain-related changes in physiology and behaviour that are reduced by painkillers; that they exhibit higher brain activity when painfully stimulated; and that pain is more important than showing fear or anti-predator behaviour in bony fish. The neurophysiological basis of nociception or pain in fish is demonstrably similar to that in mammals. Pain perception in invertebrates is more controversial as they lack the vertebrate brain, yet recent research evidence confirms that there are behavioural changes in response to potentially painful events. This review will assess the field of pain perception in aquatic species, focusing on fish and selected invertebrate groups to interpret how research findings can inform our understanding of the physiology and evolution of pain. Further, if we accept these animals may be capable of experiencing the negative experience of pain, then the wider implications of human use of these animals should be considered.

The effects of environmental enrichment and age-related differences on inhibitory avoidance in zebrafish (Danio rerio Hamilton)

The inhibitory avoidance paradigm allows the study of mechanisms underlying learning and memory formation in zebrafish (Danio rerio Hamilton). For zebrafish, the physiology and behavior associated with this paradigm are as yet poorly understood. We therefore assessed the effects of environmental enrichment and fish age on inhibitory avoidance learning. Fish raised in an environmentally enriched tank showed decreased anxiety-like behavior and increased exploration. Enrichment greatly reduced inhibitory avoidance in 6-month (6M)- and 12-month (12 M)-old fish. Following inhibitory avoidance, telencephalic mRNA levels of proliferating cell nuclear antigen (pcna), neurogenic differentiation (neurod), cocaine- and amphetamine-regulated transcript 4 (cart4), and cannabinoid receptor 1 (cnr1) were lower in enriched-housed fish, while the ratios of mineralocorticoid receptor (nr3c2)/glucocorticoid receptor α [nr3c1(α)] and glucocorticoid receptor β [nr3c1(β)]/glucocorticoid receptor α [nr3c1(α)] were higher. This was observed for 6M-old fish only, not for 24-month (24 M) old fish. Instead, 24 M-old fish showed delayed inhibitory avoidance, no effects of enrichment, and reduced expression of neuroplasticity genes. Overall, our data show strong differences in inhibitory avoidance behavior between zebrafish of different ages and a clear reduction in avoidance behavior following housing under environmental enrichment.

Assessment of postsurgical distress and pain in laboratory mice by nest complexity scoring

Preliminary studies have suggested a correlation between postsurgical pain and nest building behaviour in laboratory mice. However, there is no standardized measure for estimating pain by means of nest building performance. Here, we investigated nest building under various conditions, and scored nest complexity to assess postsurgical pain. Mice of both sexes, different strains [C57BL/6J, DBA/2J, and B6D2-Tg(Pr-mSMalphaActin)V5rCLR-25], and kept under different housing conditions, showed no differences in their latency to use the offered nest material. Healthy female C57BL/6J mice were engaged 4.3% of the day with nest building and showed three peaks of this behaviour: in the beginning and middle of the light phase, and in the second half of the dark phase. For assessment of postsurgical pain, female C57BL/6J mice underwent a sham embryo transfer +/− different doses of the analgesic carprofen or control treatment. Nest complexity scoring at 9 h after the experimental treatments (i.e. at the end of the light phase) resulted in less than 10% of animals with noticeably manipulated nest material (nestlet) after surgery and more than 75% of healthy mice having built identifiable-to-complex nests or had noticeably manipulated nestlets, while animals after anaesthesia-only showed intermediate nest complexity. Carprofen analgesia resulted in no (5 mg/kg) or only slight (50 mg/kg) improvement of nest complexity after surgery. Thus, nest complexity scoring can be incorporated into daily laboratory routine and can be used in mice as a sensitive tool for detecting reduced wellbeing and general condition, but probably not for determining the efficacy of pain treatment.

"Bedside-to-Bench" Behavioral Outcomes in Animal Models of Pain: Beyond the Evaluation of Reflexes

Despite the myriad promising new targets and candidate analgesics recently identified in preclinical pain studies, little translation to novel pain medications has been generated. The pain phenotype in humans involves complex behavioral alterations, including changes in daily living activities and psychological disturbances. These behavioral changes are not reflected by the outcome measures traditionally used in rodents for preclinical pain testing, which are based on reflexes evoked by sensory stimuli of different types (mechanical, thermal or chemical). These measures do not evaluate the impact of the pain experience on the global behavior or disability of the animals, and therefore only consider a limited aspect of the pain phenotype. The development of relevant new outcomes indicative of pain to increase the validity of animal models of pain has been increasingly pursued over the past few years. The aim has been to translate “bedside-to-bench” outcomes from the human pain phenotype to rodents, in order to complement traditional pain outcomes by providing a closer and more realistic measure of clinical pain in rodents. This review summarizes and discusses the most important nonstandard outcomes for pain assessment in preclinical studies. The advantages and drawbacks of these techniques are considered, and their potential impact on the validation of potential analgesics is evaluated.

Alleviation of chronic neuropathic pain by environmental enrichment in mice well after the establishment of chronic pain

Background

In animal models, the impact of social and environmental manipulations on chronic pain have been investigated in short term studies where enrichment was implemented prior to or concurrently with the injury. The focus of this study was to evaluate the impact of environmental enrichment or impoverishment in mice three months after induction of chronic neuropathic pain.

Methods

Thirty-four CD-1 seven to eight week-old male mice were used. Mice underwent surgery on the left leg under isoflurane anesthesia to induce the spared nerve injury model of neuropathic pain or sham condition. Mice were then randomly assigned to one of four groups: nerve injury with enriched environment (n = 9), nerve injury with impoverished environment (n = 8), sham surgery with enriched environment (n = 9), or sham surgery with impoverished environment (n = 8). The effects of environmental manipulations on mechanical (von Frey filaments) heat (hot plate) and cold (acetone test) cutaneous hypersensitivities, motor impairment (Rotarod), spontaneous exploratory behavior (open field test), anxiety-like behavior (elevated plus maze) and depression-like phenotype (tail suspension test) were assessed in neuropathic and control mice 1 and 2 months post-environmental change. Finally, the effect of the environment on spinal expression of the pro-nociceptive neuropeptides substance P and CGRP form the lumbar spinal cord collected at the end of the study was evaluated by tandem liquid chromatography mass spectrometry.

Results

Environmental enrichment attenuated nerve injury-induced hypersensitivity to mechanical and cold stimuli. In contrast, an impoverished environment exacerbated mechanical hypersensitivity. No antidepressant effects of enrichment were observed in animals with chronic neuropathic pain. Finally, environmental enrichment resulted lower SP and CGRP concentrations in neuropathic animals compared to impoverishment. These effects were all observed in animals that had been neuropathic for several months prior to intervention.

Conclusions

These results suggest that environmental factors could play an important role in the rehabilitation of chronic pain patients well after the establishment of chronic pain. Enrichment is a potentially inexpensive, safe and easily implemented non-pharmacological intervention for the treatment of chronic pain.

Experimental and husbandry procedures as potential modifiers of the results of phenotyping tests

To maximize the sensitivity of detecting affects of genetic variants in mice, variables have been minimized through the use of inbred mouse lines, by eliminating infectious organisms and controlling environmental variables. However, the impact of standard animal husbandry and experimental procedures on the validity of experimental data is under appreciated. In this study we monitored the impact of these procedures by using parameters that reflect stress and physiological responses to it. Short-term measures included telemetered heart rate and systolic arterial pressure, core body temperature and blood glucose, while longer-term parameters were assessed such as body weight. Male and female C57BL6/NTac mice were subjected to a range of stressors with different perceived severities ranging from repeated blood glucose and core temperature measurement procedures, intra-peritoneal injection and overnight fasting to cage transport and cage changing.

Our studies reveal that common husbandry and experimental procedures significantly influence mouse physiology and behaviour. Systolic arterial pressure, heart rate, locomotor activity, core temperature and blood glucose were elevated in response to a range of experimental procedures. Differences between sexes were evident, female mice displayed more sustained cardiovascular responses and locomotor activity than male mice. These results have important implications for the design and implementation of multiple component experiments where the lasting effects of stress from previous tests may modify the outcomes of subsequent ones.

Individual housing of female mice: influence on postsurgical behaviour and recovery

Individual housing of laboratory mice may increase vulnerability to surgical stress, and interfere with postsurgical recovery. To analyse the effect of housing conditions on recovery, pair- and single-housed female C57BL/6J mice underwent a minor laparotomy +/− analgesia, anaesthesia only or no treatment. Animals were monitored using non-invasive methods during the immediate postsurgical period to assess pain and general impairment. While no appearance or posture abnormalities were observed postexperiment, home cage behaviours were affected distinctly. Discriminant analysis identified self-grooming, locomotion, climbing and resting as mainly responsible for experimental group separation. Behavioural rhythmicity was disrupted, and behaviours related to wellbeing, such as nest building, climbing and burrowing, decreased. Behavioural pain signs (e.g. press) increased. Most behavioural alterations showed a gradation between treatments, e.g. burrowing latency ranged from an intermediate level following anaesthesia only and surgery with analgesia, to pronounced prolongation after surgery without analgesia. Significantly lower burrowing performance after surgery without analgesia in individually-housed animals indicates better recovery in pairs. Social interaction in pairs – an important component of normal behaviour (64%) and a potential indicator for direct social support – was nearly absent (0.3–0.5%). While anaesthesia and surgery resulted in clear changes in behaviour, differences between housing conditions were minor. Hence, despite a tendency towards better recovery in pairs, we found no distinct negative effect of individual housing. In conclusion, both housing conditions are acceptable during the period immediately following minor surgery, though social housing is always preferable in female mice.

The psychology of wound healing

PURPOSE OF REVIEW

Research into the effects of psychological factors on wound healing represents an ideal research model for psychoneuroimmunology, as both the impact on clinically relevant health outcomes and the underlying biological mechanisms can be examined. Mounting interest in this topic from biological scientists, psychologists, and medical specialists has resulted in new findings that are discussed in this review.

RECENT FINDINGS

Known psychological influences on wound healing include stress as well as coping styles, positive affect, environmental enrichment, and social support. Research has highlighted the roles of oxytocin, vasopressin, epinephrine, cortisol, and leukocyte redistribution in wound healing. Clinical significance has been demonstrated by a growing number of studies in patient populations. Furthermore, pragmatic interventions with clinical samples have demonstrated clear benefits of psychological interventions on wound healing.

SUMMARY

Recent studies add to growing evidence that psychology impacts wound repair, and highlight in particular the positive role of social support on modulating the negative effects of stress. The first few studies to demonstrate that psychological interventions can improve healing in clinical populations are exciting developments. New knowledge of psychobiological mechanisms provides opportunities to develop further interventions to improve health outcomes.