Understanding behaviour: the relevance of ethological approaches in laboratory animal science

Effects of social housing conditions on ethanol-induced behavioral sensitization in Swiss mice

RATIONALE

In previous animal model studies, it was shown that drug sensitization is dependent upon physical environmental conditions. However, the effects of social housing conditions on drug sensitization is much less known.

OBJECTIVE

The aim of the present study was to investigate the effects of social conditions, through the size of housing groups, on ethanol stimulant effects and ethanol-induced behavioral sensitization in mice.

MATERIALS AND METHODS

Male and female Swiss mice were housed in groups of different sizes (isolated mice, two mice per cage, four mice per cage and eight mice per cage) during a six-week period. A standard paradigm of ethanol-induced locomotor sensitization was then started with one daily injection of 2.5 g/kg ethanol for 8 consecutive days.

RESULTS

The results show that social housing conditions affect the acute stimulant effects of ethanol. The highest stimulant effects were observed in socially isolated mice and then gradually decreased as the size of the group increased. Although the rate of ethanol sensitization did not differ between groups, the ultimate sensitized levels of ethanol-induced stimulant effects were significantly reduced in mice housed in groups of eight.

CONCLUSIONS

These results are consistent with the idea that higher levels of acute and sensitized ethanol stimulant effects are observed in mice housed in stressful housing conditions, such as social isolation.

Exposure to soiled bedding reduces abnormal repetitive behaviors in mice

Hygiene management protocols in laboratory mouse husbandries worldwide most commonly employ soiled bedding-exposed sentinel mice to monitor the occurrence of infections in mouse colonies. Using this approach, sentinel mice repeatedly receive a mixture of used bedding, supplied by a variety of cages of a defined hygienic unit for a period of several months. Hereby, microorganisms shed in the used bedding can infect the sentinel animals and can be detected in subsequent health monitoring procedures. However, murine excrements carry more than only microorganisms. Mouse feces and urine also contain a multitude of olfactory molecules, which the animals use to code information about social status and context. However, if and how the persistent and repeated experience with these odor cues affects the behavior of sentinel mice, has not yet been explored. To address this question, we conducted a longitudinal study for neurochemical output parameters related to an organism’s responsiveness to challenging conditions, and for the exploratory assessment of a panel of home cage behaviors in soiled bedding and control female C57BL/6J mice. We found that the number of mice showing abnormal repetitive behaviors, including barbering and bar mouthing, was lower in the soiled bedding group. While neutrophil/lymphocyte ratios and fecal corticosterone metabolites did not differ between groups, the within-group variance of the neutrophil/lymphocyte ratio was reduced in the soiled bedding group. These results show that the occurrence of abnormal repetitive behaviors is lower in sentinel than in control mice and suggest a beneficial effect of soiled bedding on the welfare of laboratory mice and on outcome variability.

Frontal neurons driving competitive behaviour and ecology of social groups

Competitive interactions have a vital role in the ecology of most animal species^1-3 and powerfully influence the behaviour of groups^4,5. To succeed, individuals must exert effort based on not only the resources available but also the social rank and behaviour of other group members^2,6,7. The single-cellular mechanisms that precisely drive competitive interactions or the behaviour of social groups, however, remain poorly understood. Here we developed a naturalistic group paradigm in which large cohorts of mice competitively foraged for food as we wirelessly tracked neuronal activities across thousands of unique interactions. By following the collective behaviour of the groups, we found neurons in the anterior cingulate that adaptively represented the social rank of the animals in relation to others. Although social rank was closely behaviourally linked to success, these cells disambiguated the relative rank of the mice from their competitive behaviour, and incorporated information about the resources available, the environment, and past success of the mice to influence their decisions. Using multiclass models, we show how these neurons tracked other individuals within the group and accurately predicted upcoming success. Using neuromodulation techniques, we also show how the neurons conditionally influenced competitive effort-increasing the effort of the animals only when they were more dominant to their groupmates and decreasing it when they were subordinate-effects that were not observed in other frontal lobe areas. Together, these findings reveal cingulate neurons that serve to adaptively drive competitive interactions and a putative process that could intermediate the social and economic behaviour of groups.

Salt as a non-caloric behavioral modifier: A review of evidence from pre-clinical studies

Though excess salt intake is well-accepted as a dietary risk factor for cardiovascular diseases, relatively little has been explored about how it impacts behavior, despite the ubiquity of salt in modern diets. Given the challenges of manipulating salt intake in humans, non-human animals provide a more tractable means for evaluating behavioral sequelae of high salt. By describing what is known about the impact of elevated salt on behavior, this review highlights how underexplored salt's behavioral effects are. Increased salt consumption in adulthood does not affect spontaneous anxiety-related behaviors or locomotor activity, nor acquisition of maze or fear tasks, but does impede expression of spatial/navigational and fear memory. Nest building is reduced by heightened salt in adults, and stress responsivity is augmented. When excess salt exposure occurs during development, and/or to parents, offspring locomotion is increased, and both spatial memory expression and social investigation are attenuated. The largely consistent findings reviewed here indicate expanded study of salt's effects will likely uncover broader behavioral implications, particularly in the scarcely studied female sex.

Measuring Behavior in the Home Cage: Study Design, Applications, Challenges, and Perspectives

The reproducibility crisis (or replication crisis) in biomedical research is a particularly existential and under-addressed issue in the field of behavioral neuroscience, where, in spite of efforts to standardize testing and assay protocols, several known and unknown sources of confounding environmental factors add to variance. Human interference is a major contributor to variability both within and across laboratories, as well as novelty-induced anxiety. Attempts to reduce human interference and to measure more "natural" behaviors in subjects has led to the development of automated home-cage monitoring systems. These systems enable prolonged and longitudinal recordings, and provide large continuous measures of spontaneous behavior that can be analyzed across multiple time scales. In this review, a diverse team of neuroscientists and product developers share their experiences using such an automated monitoring system that combines Noldus PhenoTyper® home-cages and the video-based tracking software, EthoVision® XT, to extract digital biomarkers of motor, emotional, social and cognitive behavior. After presenting our working definition of a "home-cage", we compare home-cage testing with more conventional out-of-cage tests (e.g., the open field) and outline the various advantages of the former, including opportunities for within-subject analyses and assessments of circadian and ultradian activity. Next, we address technical issues pertaining to the acquisition of behavioral data, such as the fine-tuning of the tracking software and the potential for integration with biotelemetry and optogenetics. Finally, we provide guidance on which behavioral measures to emphasize, how to filter, segment, and analyze behavior, and how to use analysis scripts. We summarize how the PhenoTyper has applications to study neuropharmacology as well as animal models of neurodegenerative and neuropsychiatric illness. Looking forward, we examine current challenges and the impact of new developments. Examples include the automated recognition of specific behaviors, unambiguous tracking of individuals in a social context, the development of more animal-centered measures of behavior and ways of dealing with large datasets. Together, we advocate that by embracing standardized home-cage monitoring platforms like the PhenoTyper, we are poised to directly assess issues pertaining to reproducibility, and more importantly, measure features of rodent behavior under more ethologically relevant scenarios.

A Case Study on the Behavioural Effect of Positive Reinforcement Training in a Novel Task Participation Test in Göttingen Mini Pigs

In laboratory animal research, many procedures will be stressful for the animals, as they are forced to participate. Training animals to cooperate using clicker training (CT) or luring (LU) may reduce stress levels, and thereby increase animal welfare. In zoo animals, aquarium animals, and pets, CT is used to train animals to cooperate during medical procedures, whereas in experimental research, LU seem to be the preferred training method. This descriptive case study aims to present the behaviour of CT and LU pigs in a potentially fear-evoking behavioural test-the novel task participation test-in which the pigs walked a short runway on a novel walking surface. All eight pigs voluntarily participated, and only one LU pig showed body stretching combined with lack of tail wagging indicating reduced welfare. All CT pigs and one LU pig displayed tail wagging during the test, indicating a positive mental state. Hence, training pigs to cooperate during experimental procedures resulted in a smooth completion of the task with no signs of fear or anxiety in seven out of eight animals. We suggest that training laboratory pigs prior to experimental procedures or tests should be done to ensure low stress levels.

The acoustic startle reflex as a tool for assessment of odor environment effects on affective states in laboratory mice

Apart from self and conspecific odors, odors from other species also influence the affective states in laboratory mice (Mus musculus musculus) in their home cages and during experimental procedures, possibly inducing confusion and inconsistency in experimental data. Thus, it is important to detect the types of animal odors associated with housing, husbandry, and laboratory practice that can arouse different types of affective changes in mice. Here, we aimed to test the effectiveness of the acoustic startle reflex (ASR) in detecting changes in the affective states of laboratory mice due to animal-derived-odor as it has a non-zero baseline, and can be enhanced or attenuated by positive or negative affective shifts, respectively. We used ASR to examine the affective changes in mice that were induced by bedding odors and an alarm pheromone. The odor of bedding obtained from the mice' home cages significantly attenuated the ASR, suggesting positive affective shifts in the test mice, whereas that from bedding obtained from rat cages significantly enhanced the ASR, suggesting negative affective shifts. No significant changes in ASR were observed in mice presented with the odor of bedding obtained from cages of unfamiliar conspecifics. In contrast, there was significant ASR enhancement in mice exposed to volatile components of alarm pheromones trapped in water, suggesting negative affective shifts. Thus, our findings show that ASR may be a valuable tool in assessing the effects of odors on the affective states in laboratory mice.

The social life of Norway rats (Rattus norvegicus)

The Norway rat has important impacts on our life. They are amongst the most used research subjects, resulting in ground-breaking advances. At the same time, wild rats live in close association with us, leading to various adverse interactions. In face of this relevance, it is surprising how little is known about their natural behaviour. While recent laboratory studies revealed their complex social skills, little is known about their social behaviour in the wild. An integration of these different scientific approaches is crucial to understand their social life, which will enable us to design more valid research paradigms, develop more effective management strategies, and to provide better welfare standards. Hence, I first summarise the literature on their natural social behaviour. Second, I provide an overview of recent developments concerning their social cognition. Third, I illustrate why an integration of these areas would be beneficial to optimise our interactions with them.

Technology or ecology? New tools to assess cognitive judgement bias in mice

Cognitive judgement bias tests have become important new tools for the assessment of animal emotions. They allow for the inference of an animal's emotional state based on ambiguous cue interpretations. As mice are the predominantly used animal model for cognitive and behavioural neuroscience, research in this field would considerably benefit from the development of suitable judgement bias tests for this species. Against this background, we aimed to implement two different active choice cognitive judgement bias paradigms for mice in a methodological study. For this purpose, two experiments were conducted: in experiment I, an automated, vision-based touchscreen technique was applied, allowing for the direct translation of tasks from rodents to humans and vice versa. Experiment II comprised a task relying on more ecologically relevant cues in form of tunnels of different lengths. While the touchscreen task was characterized by automation-related advantages such as the possibility to present many trials per session and a high convenience for the experimenter, the tunnel task was learned faster by the mice. In both tests, however, the response to the trained and ambiguous conditions resulted in a graded curve, the basic requirement for proving task validity. Thus, both the translational touchscreen task as well as the ecologically more relevant tunnel task could successfully be implemented and provide new tools for the future assessment of cognitive judgement biases in mice.

To Group or Not to Group? Good Practice for Housing Male Laboratory Mice

Simple Summary

Wild mice live in territories inhabited by one adult male, several females, and their offspring. This cannot be replicated in the laboratory, so male mice are usually housed in single-sex groups or individually. However, there can be serious animal welfare problems associated with both these approaches, such as lack of social contact when housed individually or aggression between males when kept in groups. Group housing is widely recommended to give male laboratory mice the opportunity to behave as ‘social animals’, but social stress can be detrimental to the welfare of these animals, even without injurious fighting. All of this can also affect the quality of the science, giving rise to ethical concerns. This review discusses whether it is in the best welfare interests of male mice to be housed in groups, or alone. We conclude that it is not possible to give general recommendations for good practice for housing male laboratory mice, as responses to single- and group-housing can be highly context-dependent. The welfare implications of housing protocols should be researched and considered in each case.

Abstract

It is widely recommended to group-house male laboratory mice because they are ‘social animals’, but male mice do not naturally share territories and aggression can be a serious welfare problem. Even without aggression, not all animals within a group will be in a state of positive welfare. Rather, many male mice may be negatively affected by the stress of repeated social defeat and subordination, raising concerns about welfare and also research validity. However, individual housing may not be an appropriate solution, given the welfare implications associated with no social contact. An essential question is whether it is in the best welfare interests of male mice to be group- or singly housed. This review explores the likely impacts—positive and negative—of both housing conditions, presents results of a survey of current practice and awareness of mouse behavior, and includes recommendations for good practice and future research. We conclude that whether group- or single-housing is better (or less worse) in any situation is highly context-dependent according to several factors including strain, age, social position, life experiences, and housing and husbandry protocols. It is important to recognise this and evaluate what is preferable from animal welfare and ethical perspectives in each case.

Neuroprotective Effect of Grewia carpinifolia Extract against Vanadium Induced Behavioural Impairment

Vanadium (V), a heavy metal, has been reported to induce central nervous system toxicity leading to various behavioural impairments. It is characterized by the production of reactive oxygen. The present study was designed to test the possibility of Grewia carpinifolia ethanolic extract in preventing behavioural alterations following acute vanadium toxicity in mice. Twenty five Swiss albino mice (25—27 g) were completely randomized into 5 groups (A—E) of 5 animals each. Group A received distilled water and served as a control; group B, received vitamin E (500 mg.kg−1 b. w. every 72 hours), a known antioxidant orally, along with a daily dose of sodium metavanadate intraperitoneally (i. p.) for 7 days; group C and group D received Grewia carpinifolia leaf extract at 100 and 200 mg.kg−1 b.w orally respectively, along with the sodium metavanadate i. p. for 7 days; while group E received sodium metavanadate i. p. only for 7 days. The behavioural and motor functions were analysed by the open field, negative geotaxis, and hanging wire tests; the daily body and brain weights were recorded. Grewia carpinifolia ethanolic extracts significantly reduced the number of grooming, stretched attend posture, and freezing time that were significantly increased in the vanadium only group and also enhanced the vestibular functions. In addition, the latent time spent on the hanging wire in groups simultaneously administered with the extract and V compared favourably (P > 0.05) with the control groups but a decrease in latent time was observed in the V only group. The results suggest that acute V toxicity results in various behavioural deficits and support a possible role of Grewia carpinifolia as a protective agent against acute vanadium-toxicity with a better result at 200 mg.kg−1 b. w.

Olfaction variation in mouse husbandry and its implications for refinement and standardization: UK survey of animal scents

Olfaction plays a crucial role in mouse communication, providing information about genetic identity, physiological status of conspecifics and alerting mice to potential predators. Scents of animal origin can trigger physiological and behavioural responses that could affect experimental responses and impact positively or negatively on mouse welfare. Additionally, differing olfactory profiles could help explain variation in results between laboratories. A survey was sent to animal research units in the UK to investigate potential transfer of scents of animal origin during routine husbandry procedures, and responses were obtained from animal care workers and researchers using mice in 51 institutions. The results reveal great diversity between animal units regarding the relevant husbandry routines covered. Most [71%] reported housing non-breeding male and female mice in the same room, with 76% reporting that hands were not washed and gloves not changed between handling male and female mice. The most commonly reported species housed in the same facility as mice was the rat (91%), and 41% of respondents were aware that scents from rats could affect mice. Changing of gloves between handling mice and other species was reported by 79% of respondents. Depending on the aspect considered, between 18 and 33% of respondents believed human and non-human animal odours would strongly affect mouse physiology, behaviour or standardization, while approximately 32–54% believed these effects would be weak. This indicates uncertainty regarding the significance of these factors. Understanding and controlling these practices could reduce unwanted variability in experimental results and maximize welfare.

Mouse Social Interaction Test (MoST): a quantitative computer automated analysis of behavior

Rodents are the most commonly used preclinical model of human disease assessing the mechanism(s) involved as well as the role of genetics, epigenetics, and pharmacotherapy on this disease as well as identifying vulnerability factors and risk assessment for disease critical in the development of improved treatment strategies. Unfortunately, the majority of rodent preclinical studies utilize single housed approaches where animals are either entirely housed and tested in solitary environments or group housed but tested in solitary environments. This approach, however, ignores the important contribution of social interaction and social behavior. Social interaction in rodents is found to be a major criterion for the ethological validity of rodent species-specific behavioral characteristics (Zurn et al. 2007; Analysis 2011). It is also well established that there is significant and growing number of reports, which illustrates the important role of social environment and social interaction in all diseases, with particularly significance in all neuropsychiatric diseases. Thus, it is imperative that research studies be able to add large-scale evaluations of social interaction and behavior in mice and benefit from automated tracking of behaviors and measurements by removing user bias and by quantifying aspects of behaviors that cannot be assessed by a human observer. Single mouse setups have been used routinely, but cannot be easily extended to multiple-animal studies where social behavior is key, e.g., autism, depression, anxiety, substance and non-substance addictive disorders, aggression, sexual behavior, or parenting. While recent efforts are focusing on multiple-animal tracking alone, a significant limitation remains the lack of insightful measures of social interactions. We present a novel, non-invasive single camera-based automated tracking method described as Mouse Social Test (MoST) and set of measures designed for estimating the interactions of multiple mice at the same time in the same environment interacting freely. Our results show measurement of social interactions and designed to be adaptable and applicable to most existing home cage systems used in research, and provide a greater level of detailed analysis of social behavior than previously possible. The present study describes social behaviors assessed in a home cage environment setup containing six mice that interact freely over long periods of time, and we illustrate how these measures can be interpreted and combined to classify rodent social behaviors. In addition, we illustrate how these measures can be interpreted and combined to classify and analyze comprehensively rodent behaviors involved in several neuropsychiatric diseases as well as provide opportunity for the basic research of rodent behavior previously not possible.

Maternal Oxytocin Is Linked to Close Mother-Infant Proximity in Grey Seals (Halichoerus grypus)

Maternal behaviour is a crucial component of reproduction in all mammals; however the quality of care that mothers give to infants can vary greatly. It is vital to document variation in maternal behaviour caused by the physiological processes controlling its expression. This underlying physiology should be conserved throughout reproductive events and should be replicated across all individuals of a species; therefore, any correlates to maternal care quality may be present across many individuals or contexts. Oxytocin modulates the initiation and expression of maternal behaviour in mammals; therefore we tested whether maternal plasma oxytocin concentrations correlated to key maternal behaviours in wild grey seals (Halichoerus grypus). Plasma oxytocin concentrations in non-breeding individuals (4.3 ±0.5 pg/ml) were significantly lower than those in mothers with dependent pups in both early (8.2 ±0.8 pg/ml) and late (6.9 ±0.7 pg/ml) lactation. Maternal plasma oxytocin concentrations were not correlated to the amount of nursing prior to sampling, or a mother’s nursing intensity throughout the dependant period. Mothers with high plasma oxytocin concentrations stayed closer to their pups, reducing the likelihood of mother-pup separation during lactation which is credited with causing starvation, the largest cause of pup mortality in grey seals. This is the first study to link endogenous oxytocin concentrations in wild mammalian mothers with any type of maternal behaviour. Oxytocin’s structure and function is widely conserved across mammalian mothers, including humans. Defining the impact the oxytocin system has on maternal behaviour highlights relationships that may occur across many individuals or species, and such behaviours heavily influence infant development and an individual’s lifetime reproductive success.

Housing conditions and sacrifice protocol affect neural activity and vocal behavior in a songbird species, the zebra finch (Taeniopygia guttata)

Individual cages represent a widely used housing condition in laboratories. This isolation represents an impoverished physical and social environment in gregarious animals. It prevents animals from socializing, even when auditory and visual contact is maintained. Zebra finches are colonial songbirds that are widely used as laboratory animals for the study of vocal communication from brain to behavior. In this study, we investigated the effect of single housing on the vocal behavior and the brain activity of male zebra finches (Taeniopygia guttata): male birds housed in individual cages were compared to freely interacting male birds housed as a social group in a communal cage. We focused on the activity of septo-hypothalamic regions of the "social behavior network" (SBN), a set of limbic regions involved in several social behaviors in vertebrates. The activity of four structures of the SBN (BSTm, medial bed nucleus of the stria terminalis; POM, medial preoptic area; lateral septum; ventromedial hypothalamus) and one associated region (paraventricular nucleus of the hypothalamus) was assessed using immunoreactive nuclei density of the immediate early gene Zenk (egr-1). We further assessed the identity of active cell populations by labeling vasotocin (VT). Brain activity was related to behavioral activities of birds like physical and vocal interactions. We showed that individual housing modifies vocal exchanges between birds compared to communal housing. This is of particular importance in the zebra finch, a model species for the study of vocal communication. In addition, a protocol that daily removes one or two birds from the group affects differently male zebra finches depending of their housing conditions: while communally-housed males changed their vocal output, brains of individually housed males show increased Zenk labeling in non-VT cells of the BSTm and enhanced correlation of Zenk-revealed activity between the studied structures. These results show that housing conditions must gain some attention in behavioral neuroscience protocols.

Olfactory variation in mouse husbandry and its implications for refinement and standardization: UK survey of non-animal scents

With their highly sensitive olfactory system, the behaviour and physiology of mice are not only influenced by the scents of conspecifics and other species, but also by many other chemicals in the environment. The constraints of laboratory housing limit a mouse's capacity to avoid aversive odours that could be present in the environment. Potentially odorous items routinely used for husbandry procedures, such as sanitizing products and gloves, could be perceived by mice as aversive or attractive, and affect their behaviour, physiology and experimental results. A survey was sent to research institutions in the UK to enquire about husbandry practices that could impact on the olfactory environment of the mouse. Responses were obtained from 80 individuals working in 51 institutions. Husbandry practices varied considerably. Seventy percent of respondents reported always wearing gloves for handling mice, with nitrile being the most common glove material (94%) followed by latex (23%) and vinyl (14%). Over six different products were listed for cleaning surfaces, floors, anaesthesia and euthanasia chambers and behavioural apparatus. In all cases Trigene™ (now called Anistel™) was the most common cleaning product used (43, 41, 40 and 49%, respectively). Depending on the attribute considered, between 7 and 19% of respondents thought that cleaning products definitely, or were likely to, have strong effects on standardization, mouse health, physiology or behaviour. Understanding whether and how these odours affect mouse welfare will help to refine mouse husbandry and experimental procedures through practical recommendations, to improve the quality of life of laboratory animals and the experimental data obtained.

The Use of Refuges by Communally Housed Cats

Simple Summary

Captive domestic cats frequently suffer from the lack of physical space and opportunities to perform species-typical behaviors, such as climbing or hiding. Environmental enrichment is a technique that helps transform the space available to animals into a more appropriate habitat. In this study, we tested horizontal and vertical refuge boxes as environmental enrichment for cats living communally in a cat rescue shelter. The provision of boxes in the environment increases the use of available space by the cats. We suggest this improves the cats’ welfare while in communally-housed rescue shelters.

Abstract

The increase of domestic animals kept in shelters highlights the need to ensure animal welfare. Environmental enrichment can improve animal welfare in many ways, such as encouraging captive animals to use all the space available to them. The effects of physical environmental enrichment on the spatial distribution and behavioral repertoire of 35 neutered domestic cats housed communally were analyzed. The provision of boxes in the environment increases the use of available space by the cats. We suggest this improves the cats’ welfare while in communally-housed rescue shelters. The frequencies of active and especially inactive behaviors also increased in the enriched condition. In a test with vertical environmental enrichment, the animals showed an increased length of stay in refuges located at a height of 0.5 m compared to those on the ground (0.0 m). However, the entry frequency was higher in refuges at 0.0 m. Both horizontal and vertical environmental enrichment increased the use of available space, demonstrating that box refuges as enrichment are effective in providing a refuge when at a height, or a place to explore at ground level. We suggest it enhances the welfare of cats in communally housed shelters. This information adds to the body of evidence relating to cat enrichment and can be useful in designing cat housing in veterinary clinics, research laboratories, shelters and domestic homes.

Correlations of behavioral deficits with brain pathology assessed through longitudinal MRI and histopathology in the R6/1 mouse model of Huntington's disease

Huntington's disease (HD) is caused by the expansion of a CAG repeat in the huntingtin (HTT) gene. The R6 mouse models of HD express a mutant version of exon 1 HTT and typically develop motor and cognitive impairments, a widespread huntingtin (HTT) aggregate pathology and brain atrophy. Unlike the more commonly used R6/2 mouse line, R6/1 mice have fewer CAG repeats and, subsequently, a less rapid pathological decline. Compared to the R6/2 line, fewer descriptions of the progressive pathologies exhibited by R6/1 mice exist. The association between the molecular and cellular neuropathology with brain atrophy, and with the development of behavioral phenotypes remains poorly understood in many models of HD. In attempt to link these factors in the R6/1 mouse line, we have performed detailed assessments of behavior and of regional brain abnormalities determined through longitudinal, in vivo magnetic resonance imaging (MRI), as well as an end-stage, ex vivo MRI study and histological assessment. We found progressive decline in both motor and non-motor related behavioral tasks in R6/1 mice, first evident at 11 weeks of age. Regional brain volumes were generally unaffected at 9 weeks, but by 17 weeks there was significant grey matter atrophy. This age-related brain volume loss was validated using a more precise, semi-automated Tensor Based morphometry assessment. As well as these clear progressive phenotypes, mutant HTT (mHTT) protein, the hallmark of HD molecular pathology, was widely distributed throughout the R6/1 brain and was accompanied by neuronal loss. Despite these seemingly concomitant, robust pathological phenotypes, there appeared to be little correlation between the three main outcome measures: behavioral performance, MRI-detected brain atrophy and histopathology. In conclusion, R6/1 mice exhibit many features of HD, but the underlying mechanisms driving these clear behavioral disturbances and the brain volume loss, still remain unclear.

How to improve housing conditions of laboratory animals: the possibilities of environmental refinement

Housing systems for captive animals have often been designed on the basis of economic and ergonomic considerations, such as equipment, costs, space, workload, ability to observe the animals and to maintain a certain degree of hygiene, with little or no consideration for animal welfare. Environmental refinement can be defined as any modification in the environment of captive animals that seeks to enhance the physical and psychological well-being of the animals by providing stimuli which meet the animals' species-specific needs. This article provides an overview of environmental factors that influence the well-being of captive animals with specific reference to the needs of the most common laboratory species. It is important to evaluate environmental refinement in terms of the benefit to the animal, by assessing the use of and preference for certain enrichment, the effect on behaviour, and the performance of species-typical behaviour on physiological parameters. It is also necessary to evaluate the impact of refinement on scientific outcome, including whether and how statistical power is affected. Communication and team work between animal welfare scientists, animal research scientists, institutional animal welfare officers, veterinarians and animal ethics committees, animal facility management and personnel, are essential for success.

Shelter choice by Syrian hamsters (Mesocricetus auratus) in the laboratory

The preference of Syrian hamsters (Mesocricetus auratus) for different in-cage shelters was tested. First, 15 males and 15 females were made to choose between a cage with a shelter and one without. Different shelters were tested consecutively: short (10-cm) or medium (15-cm) pipes made of black acrylonitrile butadiene styrene (ABS), 7.6 cm in diameter and open at both ends; and short or medium boxes made of black acrylic panels and open at only one end. The strongest use of the shelter cage for nesting (about 75% of days) was in the case of the medium, open pipe, for both males and females. The strongest use of the shelter itself for nesting was also in the case of the medium open pipe (52% of days). A second experiment gave a choice between pairs of shelters (of seven different types) to 10 males and 10 females. Both sexes nested significantly more in a medium pipe closed at one end than under a wheel, and tended to nest more in that medium, semi-closed pipe than in a medium, open pipe. Also, females tended to nest more in the medium, semi-closed pipe than under an aluminium cover. Other pairings did not yield significant differences. Direct use of the shelters for nesting was rather low, except for the medium, semi-closed pipe (about 50% of days). Semi-closed ABS pipes are inexpensive, easy to clean, and do not interfere with running wheels, and they could be recommended as environmental enrichment for hamsters.

A guide to defining and implementing protocols for the welfare assessment of laboratory animals: eleventh report of the BVAAWF/FRAME/RSPCA/UFAW Joint Working Group on Refinement

The refinement of husbandry and procedures to reduce animal suffering and improve welfare is an essential component of humane science. Successful refinement depends upon the ability to assess animal welfare effectively, and detect any signs of pain or distress as rapidly as possible, so that any suffering can be alleviated. This document provides practical guidance on setting up and operating effective protocols for the welfare assessment of animals used in research and testing. It sets out general principles for more objective observation of animals, recognizing and assessing indicators of pain or distress and tailoring these to individual projects. Systems for recording indicators, including score sheets, are reviewed and guidance is set out on determining practical monitoring regimes that are more likely to detect any signs of suffering. This guidance is intended for all staff required to assess or monitor animal welfare, including animal technologists and care staff, veterinarians and scientists. It will also be of use to members of ethics or animal care and use committees. A longer version of this document, with further background information and extra topics including training and information sharing, is available on the Laboratory Animals website.

Conditioned response suppression in the IntelliCage: assessment of mouse strain differences and effects of hippocampal and striatal lesions on acquisition and retention of memory

The IntelliCage allows fully automated continuous testing of various behaviours in the home cage environment without handling the mice. Here we tested whether conditioned avoidance is retained after a time period delay spent outside the IntelliCage. During the training, nosepokes in one of the four learning corners were punished with an air-puff. After 24h of training, the mice were placed in regular cages for 24h. During the last 18h of this interval, the mice were water deprived and then returned to the IntelliCage for a probe trial where drinking was allowed in all corners. The C57BL/6 mice developed a significant suppression of nosepoking in the punished corner during training, and the avoidance was carried over to the following probe trial. Repetition of the experiment by delivering punishment in a different corner assigned to individual mice revealed a similar performance pattern. Comparison between the different strains revealed a reduced nosepoke suppression in DBA/2 and B6D2F1 mice as compared to C57BL/6 mice in the probe trial, despite similar error rates during the training with short (1-s) air-puffs. However, the performance of the three strains in the probe trial were equalised when the air-puffs were prolonged until the end of the corner visit. Significant extinction of the nosepoke suppression occurred after 6 days. A prolonged interval (7 days) between the training and the probe trial resulted in a loss of suppression in DBA/2 mice, but not in C57BL/6 and B6D2F1 mice. Additional experiments revealed that performance in the probe trial was dependent on a complex set of intramaze cues. Testing of mice with bilateral excitotoxic lesions of the hippocampus or dorso-lateral striatum revealed that learning this task was dependent on an intact hippocampus, but not on an intact striatum. In summary, the conditioned nosepoke suppression test presented here is sensitive to both genetic differences and hippocampal lesions. This test could be applied to the screening of mutant mice with impaired hippocampal functions more efficiently than those of the standard memory tests.