Determining the value of preferred goods based on consumer demand in a home-cage based test for mice

From the preference of one good over another, the strength of the preference cannot automatically be inferred. While money is the common denominator to assess the value of goods in humans, it appears difficult at first glance to put a price tag on the decisions of laboratory animals. Here we used consumer demand tests to measure how much work female mice expend to obtain access to different liquids. The mice could each choose between two liquids, one of which was free. The amount of work required to access the other liquid, by contrast, increased daily. In this way, the value of the liquid can be determined from a mouse's microeconomic perspective. The unique feature is that our test was carried out in a home-cage based setup. The mice lived in a group but could individually access the test-cage, which was connected to the home-cage via a gate. Thereby the mice were able to perform their task undisturbed by group members and on a self-chosen schedule with minimal influence by the experimenter. Our results show that the maximum number of nosepokes depends on the liquids presented. Mice worked incredibly hard for access to water while a bitter-tasting solution was offered for free whereas they made less nosepokes for sweetened liquids while water was offered for free. The results demonstrate that it is possible to perform automated and home-cage based consumer demand tests in order to ask the mice not only what they like best but also how strong their preference is

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

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

Mouse strain dependent differences in the analgesic effect of buprenorphine

Die Verwendung einer optimalen Analgesie sollte oberste Priorität in der Versuchstierkunde haben und ist nicht nur aus ethischen, sondern auch aus rechtlichen Gründen verpflichtend. Laut nationalen und internationalen Versuchstierstatistiken ist die Maus mit ca. 70 % die am häufigsten verwendete Spezies. Opioide werden gewöhnlich zur perioperativen Behandlung von moderaten bis schweren Schmerzen eingesetzt. Aufgrund der langanhaltenden Wirkung und geringen unerwünschten Nebenwirkungen wird für die Spezies Maus bevorzugt das Opioid Buprenorphin verwendet. Unterschiedliche Empfehlungen bzgl. Dosierung, Applikationsart und -intervall führen jedoch zu Unstimmigkeiten in dessen Anwendung. Obwohl mausstammspezifische Unterschiede in der Wirkung von Opioiden bekannt sind, sind diese bisher für die analgetische Wirkung von Buprenorphin noch nicht eindeutig geklärt und finden daher keine Berücksichtigung in den Empfehlungen. Das Ziel der hier vorliegenden Arbeit war es daher, den analgetischen Effekt von Buprenorphin in drei häufig verwendeten Maus-Inzuchtstämmen (C57BL/6J, Balb/cJ, 129S1/SvImJ) zu untersuchen und zu prüfen, ob eventuelle Unterschiede in der Wirkung auf eine veränderte Metabolisierung zurückzuführen sind. Hierfür wurden die basale Schmerzempfindlichkeit sowie der analgetische Effekt von Buprenorphin (0,42 mg/kg, 4,0 mg/kg) unter Verwendung der Incremental Hot Plate in vivo getestet. Serum- und Gehirnkonzentrationen von Buprenorphin und seiner Metaboliten wurden bestimmt, um ggf. pharmakokinetisch-bedingte Veränderungen aufzudecken. Darüber hinaus wurden in vitro die für die Metabolisierung von Buprenorphin relevanten CYP3A Isozyme hinsichtlich der mRNA Expression, des Proteingehalts und der Aktivität, untersucht. Die verwendeten Mausstämme unterschieden sich deutlich in ihrer basalen Schmerzempfindlichkeit, wobei Balb/cJ Mäuse am sensitivsten und 129S1/SvImJ Mäuse am wenigsten sensitiv waren. Die Applikation von Buprenorphin führte zu einem dosis- und stammesabhängigen analgetischen Effekt. Die Dosiserhöhung von Buprenorphin steigerte die Antinozizeption beim C57BL/6J und Balb/cJ Stamm, wohingegen der analgetische Effekt beim 129S1/SvImJ Stamm stagnierte. Serum- und Gehirnkonzentrationen von Buprenorphin und seiner Metaboliten waren dosisabhängig und unterschieden sich bei einer Dosis von 4,0 mg/kg Buprenorphin zwischen den Stämmen. Das Verhältnis von Buprenorphin und seinen Metaboliten im Blut sowie die Verteilung zwischen Gehirn und Blut zeigten keine Dosis- und nur geringe Stammesunterschiede, die aber nicht mit der analgetischen Wirkung korrelierten. Darüber hinaus wurden keine Stammesunterschiede in der Aktivität und im Proteingehalt der CYP3A Isozyme detektiert. Auf mRNA Ebene wurden Stammesunterschiede bei einigen CYP3A Isozymen detektiert. Jedoch konnte kein Zusammenhang zwischen mRNA und Aktivitätsdaten nachgewiesen werden. Die Ergebnisse der vorliegenden Studie zeigen, dass die Applikation von Buprenorphin mausstammspezifisch gestaltet werden sollte. Nur so kann Schmerzen optimal vorgebeugt und unerwünschte Nebenwirkungen vermieden werden. Die beobachteten Unterschiede auf pharmakokinetischer Ebene können den unterschiedlichen analgetischen Effekt von Buprenorphin in den drei Mausstämmen nicht ausreichend erklären. Möglicherweise spielen pharmakodynamische Mechanismen eine übergeordnete Rolle, welche in weiterführenden Studien untersucht werden sollen. Die Ergebnisse sollen die wissenschaftliche Gemeinschaft für die Verwendung einer optimierten Analgesie sensibilisieren und somit aktiv zum Tierschutz in der Versuchstierkunde beitragen.The optimal dosage of analgesics should be state-of-the-art in laboratory animal sciences and is not only a question of animal welfare but also a legal provision. According to current national and international statistics on laboratory animals, the mouse is the most commonly used species with approximately 70 %. Opioid analgesics are commonly used for perioperative care of moderate to severe pain in mice. Among the numerous opioid drugs available, buprenorphine is the preferred analgesic due to its long-lasting effect and little adverse side effects. Vast differences in recommendations for dosage, application route and application intervals lead to uncertainties for appropriate administration and counteract optimal pain management. Although strain differences in the analgesic efficacy for opioids in mice are known, they have not been sufficiently investigated for buprenorphine, and consequently have not been taken into account in current recommendations. Therefore, the present study aimed to elucidate the influence of strain differences on the analgesic effect of buprenorphine. Hence, basal pain sensitivity and the analgesic effect of buprenorphine (0.42 mg/kg, 4.0 mg/kg) were tested in vivo using three popular mouse strains (male C57BL/6J, Balb/cJ, 129S1/SvImJ) on the Incremental Hot Plate. As pharmacokinetic mechanisms might play a crucial role influencing the analgesic outcome, phase-I and -II metabolism were assessed. Thus, the metabolically relevant CYP3A isozymes were investigated in vitro in regard to mRNA expression, protein content and activity. Moreover, serum and brain concentrations of buprenorphine and its metabolites were analyzed in order to investigate alterations in the metabolism. Basal pain sensitivity differed considerably between the mouse strains with Balb/cJ mice being the most and 129S1/SvImJ mice the least sensitive strain. The application of buprenorphine led to dose and strain dependent analgesic differences. While the analgesic effect of buprenorphine increased in C57BL/6J and Balb/cJ mice with the higher administered dose, the analgesic effect remained stable in 129S1/SvImJ mice. Serum and blood concentrations of buprenorphine and its metabolites were dose and partly strain dependent (4.0 mg/kg dose group). The metabolic ratio in blood and distribution between brain and blood showed no dose and only slight strain dependent variations, which did not correspond with the analgesic effect of buprenorphine. Additionally, no strain dependent differences for CYP3A activity and protein content could be detected in vitro, whereas at mRNA expression level slight strain differences were present. However, the mRNA expression differences of some CYP3A isozymes were not in accordance with activity data. Thus, administration of buprenorphine for optimal pain management should be adapted to the respective mouse strain to avoid pain or adverse side effects. However, strain differences in the analgesic effect of buprenorphine could not be explained by differences in pharmacokinetics. Hence, differences in pharmacodynamic parameters are more likely and should be investigated in further studies. In summary, the results of this study should sensitize the scientific community to optimize pain management in order to contribute to laboratory animal welfare in life sciences.BMBF, 031A262D, Berlin-Brandenburger Forschungsplattform BB3R mit integriertem Graduiertenkolleg ‘Innovationen in der 3R-Forschung - Gentechnik, Tissue Engineering und Bio-informatik‘ - Teilprojekt 4 - Entwicklung einer individualisierten Schmerztherapie bei Mäusestämme

Assessing Affective State in Laboratory Rodents to Promote Animal Welfare—What Is the Progress in Applied Refinement Research?

An animal’s capacity to suffer is a prerequisite for any animal welfare concern, and the minimization of suffering is a key aim of refinement research. In contrast to the traditional focus on avoiding or reducing negative welfare states, modern animal welfare concepts highlight the importance of promoting positive welfare states in laboratory animals. Reliable assessments of affective states, as well as the knowledge of how to elicit positive affective states, are central to this concept. Important achievements have been made to assess pain and other negative affective states in animals in the last decades, but it is only recently that the neurobiology of positive emotions in humans and animals has been gaining more interest. Thereby, the need for promotion of positive affective states for laboratory animals is gaining more acceptance, and methods allowing the assessment of affective states in animals have been increasingly introduced. In this overview article, we present common and emerging methods to assess affective states in laboratory rodents. We focus on the implementation of these methods into applied refinement research to identify achieved progress as well as the future potential of these tools to improve animal welfare in animal-based research

Assessing Affective State in Laboratory Rodents to Promote Animal Welfare—What Is the Progress in Applied Refinement Research?

An animal’s capacity to suffer is a prerequisite for any animal welfare concern, and the minimization of suffering is a key aim of refinement research. In contrast to the traditional focus on avoiding or reducing negative welfare states, modern animal welfare concepts highlight the importance of promoting positive welfare states in laboratory animals. Reliable assessments of affective states, as well as the knowledge of how to elicit positive affective states, are central to this concept. Important achievements have been made to assess pain and other negative affective states in animals in the last decades, but it is only recently that the neurobiology of positive emotions in humans and animals has been gaining more interest. Thereby, the need for promotion of positive affective states for laboratory animals is gaining more acceptance, and methods allowing the assessment of affective states in animals have been increasingly introduced. In this overview article, we present common and emerging methods to assess affective states in laboratory rodents. We focus on the implementation of these methods into applied refinement research to identify achieved progress as well as the future potential of these tools to improve animal welfare in animal-based research

Repeatability analysis improves the reliability of behavioral data.

Reliability of data has become a major concern in the course of the reproducibility crisis. Especially when studying animal behavior, confounding factors such as novelty of the test apparatus can lead to a wide variability of data which may mask treatment effects and consequently lead to misinterpretation. Habituation to the test situation is a common practice to circumvent novelty induced increases in variance and to improve the reliability of the respective measurements. However, there is a lack of published empirical knowledge regarding reasonable habituation procedures and a method validation seems to be overdue. This study aimed at setting up a simple strategy to increase reliability of behavioral data measured in a familiar test apparatus. Therefore, exemplary data from mice tested in an Open Field (OF) arena were used to elucidate the potential of habituation and how reliability of measures can be confirmed by means of a repeatability analysis using the software R. On seven consecutive days, male C57BL/6J, BALB/cJ and 129S1/SvImJ mice were tested in an OF arena once daily and individual mouse behavior was recorded. A repeatability analysis was conducted with regard to repeated trials of habituation. Our data analysis revealed that monitoring animal behavior during habituation is important to determine when individual differences of the measurements are stable. Repeatability values from distance travelled and average activity increased over the habituation period, revealing that around 60% of the variance of the data can be explained by individual differences between mice. The first day of habituation was significantly different from the following 6 days. A three-day habituation period appeared to be sufficient in this study. Overall, these results emphasize the importance of habituation and in depth analysis of habituation data to define the correct starting point of the experiment for improving the reliability and reproducibility of experimental data