Variations in the behaviors to novel objects among five inbred strains of mice

Role of Environment and Experimenter in Reproducibility of Behavioral Studies With Laboratory Mice

Behavioral phenotyping of mice has received a great deal of attention during the past three decades. However, there is still a pressing need to understand the variability caused by environmental and biological factors, human interference, and poorly standardized experimental protocols. The inconsistency of results is often attributed to the inter-individual difference between the experimenters and environmental conditions. The present work aims to dissect the combined influence of the experimenter and the environment on the detection of behavioral traits in two inbred strains most commonly used in behavioral genetics due to their contrasting phenotypes, the C57BL/6J and DBA/2J mice. To this purpose, the elevated O-maze, the open field with object, the accelerating rotarod and the Barnes maze tests were performed by two experimenters in two diverse laboratory environments. Our findings confirm the well-characterized behavioral differences between these strains in exploratory behavior, motor performance, learning and memory. Moreover, the results demonstrate how the experimenter and the environment influence the behavioral tests with a variable-dependent effect, often with mutually exclusive contributions. In this context, our study highlights how both the experimenter and the environment can have an impact on the strain effect size without altering the direction of the conclusions. Importantly, the general agreement on the results is reached by converging evidence from multiple measures addressing the same trait. In conclusion, the present work elucidates the contribution of both the experimenter and the laboratory environment in the intricate field of reproducibility in mouse behavioral phenotyping.

Promoting and Optimizing the Use of 3D-Printed Objects in Spontaneous Recognition Memory Tasks in Rodents: A Method for Improving Rigor and Reproducibility

Spontaneous recognition memory tasks are widely used to assess cognitive function in rodents and have become commonplace in the characterization of rodent models of neurodegenerative, neuropsychiatric and neurodevelopmental disorders. Leveraging an animal’s innate preference for novelty, these tasks use object exploration to capture the what, where and when components of recognition memory. Choosing and optimizing objects is a key feature when designing recognition memory tasks. Although the range of objects used in these tasks varies extensively across studies, object features can bias exploration, influence task difficulty and alter brain circuit recruitment. Here, we discuss the advantages of using 3D-printed objects in rodent spontaneous recognition memory tasks. We provide strategies for optimizing their design and usage, and offer a repository of tested, open-source designs for use with commonly used rodent species. The easy accessibility, low-cost, renewability and flexibility of 3D-printed open-source designs make this approach an important step toward improving rigor and reproducibility in rodent spontaneous recognition memory tasks.

Phenotyping spontaneous locomotor activity in inbred and outbred mouse strains by using Digital Ventilated Cages

Mouse strains differ markedly in all behaviors, independently of their genetic background. We undertook this study to disentangle the diurnal activity and feature key aspects of three non-genetically altered mouse strains widely used in research, C57BL/6NCrl (inbred), BALB/cAnNCrl (inbred) and CRL:CD1(ICR) (outbred). With this aim, we conducted a longitudinal analysis of the spontaneous locomotor activity of the mice during a 24-h period for 2 months, in two different periods of the year to reduce the seasonality effect. Mice (males and females) were group-housed in Digital Ventilated Cages (Tecniplast), mimicking standard housing conditions in research settings and avoiding the potential bias provided in terms of locomotor activity by single housing. The recorded locomotor activity was analyzed by relying on different and commonly used circadian metrics (i.e., day and night activity, diurnal activity, responses to lights-on and lights-off phases, acrophase and activity onset and regularity disruption index) to capture key behavioral responses for each strain. Our results clearly demonstrate significant differences in the circadian activity of the three selected strains, when comparing inbred versus outbred as well as inbred strains (C57BL/6NCrl versus BALB/cAnNCrl). Conversely, males and females of the same strain displayed similar motor phenotypes; significant differences were recorded only for C57BL/6NCrl and CRL:CD1(ICR) females, which displayed higher average locomotor activity from prepuberty to adulthood. All strain-specific differences were further confirmed by an unsupervised machine learning approach. Altogether, our data corroborate the concept that each strain behaves under characteristic patterns, which needs to be taken into consideration in the study design to ensure experimental reproducibility and comply with essential animal welfare principles.

Ontogeny of spontaneous recognition memory in rodents

Spontaneous recognition memory tasks explore thewhat,whereandwhencomponents of recognition memory. These tasks are widely used in rodents to assess cognitive function across the lifespan. While several neurodevelopmental and mental disorders present symptom onset in early life, very little is known about how memories are expressed in early life, and as a consequence how they may be affected in pathological conditions. In this review, we conduct an analysis of the studies examining the expression of spontaneous recognition memory in young rodents. We compiled studies using four different tasks: novel object recognition, object location, temporal order recognition and object place. First, we identify major sources of variability between early life spontaneous recognition studies and classify them for later comparison. Second, we use these classifications to explore the current knowledge on the ontogeny of each of these four spontaneous recognition memory tasks. We conclude by discussing the possible implications of the relative time of onset for each of these tasks and their respective neural correlates. In compiling this research, we hope to advance on establishing a developmental timeline for the emergence of distinct components of recognition memory, while also identifying key areas of focus for future research. Establishing the ontogenetic profile of rodent spontaneous recognition memory tasks will create a necessary blueprint for cognitive assessment in animal models of neurodevelopmental and mental disorders, a first step towards improved and earlier diagnosis as well as novel intervention strategies.

Contrasting characteristic behaviours among common laboratory mouse strains

Mice are widely used to model wide-ranging human neurological disorders, from development to degenerative pathophysiology. Behavioural and molecular characteristics of these mouse models are influenced by the genetic background of each strain. Among the most commonly used strains, the inbred C57BL/6J, BALB/c, CBA and 129SvEv lines and the CD1 outbred line are particularly predominant. Despite their prevalence, comparative performance of these strains on many standard behavioural tests commonly used to assess neurological conditions remains diffusely and indirectly accessible in the literature. Given that independent studies may be conducted with mice of differing genetic backgrounds, any variation in characteristic behavioural responses of specific strains should be delineated in order to properly interpret results among studies. Thus, in the present study, we aimed to characterize these commonly used mice strains through several standard behavioural tests. Here, we found that animals from different genetic background strains exhibited varying behavioural patterns when assessed for sociability/novelty, memory function, and negative behaviours like despair and stress calls. These results suggest that genetic variation among strains may be responsible-in part-for strain-specific behavioural phenotypes and potential predisposition to some neurological disorders.

Inactivation of the Mouse L-Proline Transporter PROT Alters Glutamatergic Synapse Biochemistry and Perturbs Behaviors Required to Respond to Environmental Changes

The endogenous neutral amino acid L-proline exhibits a variety of physiological and behavioral actions in the nervous system, highlighting the importance of accurately regulating its extracellular abundance. The L-proline transporter PROT (Slc6A7) is believed to control the spatial and temporal distribution of L-proline at glutamatergic synapses by rapid uptake of this amino acid into presynaptic terminals. Despite the importance of members of the Slc6 transporter family regulating neurotransmitter signaling and homeostasis in brain, evidence that PROT dysfunction supports risk for mental illness is lacking. Here we report the disruption of the PROT gene by homologous recombination. Mice defective in PROT displayed altered expression of glutamate transmission-related synaptic proteins in cortex and thalamus. PROT deficiency perturbed mouse behavior, such as reduced locomotor activity, decreased approach motivation and impaired memory extinction. Thus, our study demonstrates that PROT regulates behaviors that are needed to respond to environmental changes in vivo and suggests that PROT dysfunctions might contribute to mental disorders showing altered response choice following task contingency changes.

Younger vampire bats (Desmodus rotundus) are more likely than adults to explore novel objects

The effects of age on neophobia and exploration are best described in birds and primates, and broader comparisons require reports from other taxa. Here we present data showing age-dependent exploration in a long-lived social species, the common vampire bat (Desmodus rotundus). A previous study found that vampire bats regurgitated food to partners trapped in a cage. Interestingly, while only a few adult bats visited the trapped bat, in every trial all or most of the eight young males in the colony would visit the trapped bat without feeding it. To test whether this behavioral difference resulted from age class differences in exploration, we compared responses of the bats to a trapped conspecific versus an inanimate novel object. Some adults and young showed interest in trapped conspecifics, but only the young males explored the novel objects. Additional novel object tests in a second captive colony showed that higher rates of novel object exploration were shown by young of both sexes. Our results corroborate past findings from other mammals and birds that age predicts exploration. If age-dependent exploration is indeed adaptive, then the role of age as a predictor of exploration tendency should depend on species-specific life history traits. Finally, because younger vampire bats also appear to have higher exposure to pathogens such as rabies virus, there may be implications for pathogen transmission if younger and more exploratory vampire bats are more likely to feed on novel hosts.

Strain differences in the development of cisplatin-induced pica behavior in mice

INTRODUCTION

Pica behavior, kaolin ingestion, in rats and mice can be used as an assessment of nausea and vomiting; however, we observed that the incidence of pica behavior in ICR strain mice varied markedly. We investigated the susceptibility of four strains of mice (ICR, BALB/c, C57BL/6, and DBA/2) to the development of pica behavior.

METHODS

Mice received cisplatin (7.5 mg/kg, i.p.) with or without a serotonin 5-HT₃ receptor antagonist (granisetron: 0.1 mg/kg, i.p.) or tachykinin NK₁ receptor antagonist (fosaprepitant: 30 mg/kg, i.p.), and then their daily kaolin intake was measured for 2 days. We examined the expression of preprotachykinin (PPT)-A mRNA in the medulla of cisplatin-treated mice 8 and 32 h after drug administration.

RESULTS

All mice except for ICR strain significantly increased kaolin intake after cisplatin administration. Among the tested strains, DBA/2 mice compared to BALB/c and C57BL/6 mice notably showed pica behavior on both days (P < 0.0001). The expression of PPT-A mRNA was significantly increased 8 h after cisplatin administration in all strains, but the increase remained on the second day only in DBA/2 mice (P < 0.05). Granisetron significantly inhibited pica behavior in DBA/2 mice on the first day (P < 0.0001), but not the second day; however, fosaprepitant completely inhibited the pica behavior on both days (P < 0.001).

DISCUSSION

These results indicate that cisplatin-induced pica behavior in mice is likely to be influenced by the genotype, and that DBA/2 mice are useful to analyze the emetogenic or anti-emetic potential of drugs in preclinical studies.

Disturbances of novel object exploration and recognition in a chronic ketamine mouse model of schizophrenia

Schizophrenia is a chronic and devastating disease with an overall lifetime risk of 1%. While positive symptoms of schizophrenia such as hallucinations and delusions are reduced by antipsychotic medication based on the inhibition of type 2 dopaminergic receptors (D2R), negative symptoms (e.g. reduced motivation) and cognitive symptoms (e.g. impaired working memory) of schizophrenia are not effectively treated by current medication. This dichotomy might arise in part because of our limited understanding of the pathophysiology of negative and cognitive symptoms in schizophrenia. In addition to genetic approaches, chronic systemic application of NMDA inhibitors such as ketamine have been used to generate rodent models, which displayed several relevant endophenotypes related to negative and cognitive symptoms and might thus facilitate mechanistic studies into the underlying pathophysiology. In this context, previous behavioral testing identified impairments in novel object recognition memory as a key feature in chronic NMDA-inhibitor schizophrenia rodent models. Using a chronic ketamine mouse model, we have however identified are more complex behavioral phenotype including deficits in novel space and novel object exploration in combination deficits in short-term novel object recognition memory. These impairments in novelty discrimination are in line with prefrontal and hippocampal reductions in parvalbumin-expression as well as reduced expression of the early immediate gene c-fos after novel-object exploration in hippocampal areas in our model. Our results indicate that adult C57Bl6N mice chronically treated with ketamine display combined impairments in novelty exploration and recognition, which might represent both motivational (negative) and cognitive symptoms of schizophrenia.

Aggressive temperament predicts ethanol self-administration in late adolescent male and female rhesus macaques

RATIONALE

Anxiety and aggression are associated with ethanol self-administration, but these behaviors can serve as either risk factors for or consequences of heavy drinking in rodents and humans. Baseline levels of aggressive-like and anxious-like behavior in non-human primates have not yet been characterized in relation to future or prior ethanol intake.

OBJECTIVE

The objective of the study was to test the association between temperament at baseline with future ethanol self-administration in late adolescent male (n = 21) and female (n = 11) rhesus monkeys.

METHODS

Shortly after entering the laboratory and before exposure to ethanol, the Human Intruder Test (HIT) and the Novel Object Test (NOT) were used to determine baseline anxious-like and aggressive-like behavior in age-matched male and female rhesus monkeys (Macaca mulatta). The monkeys were induced to drink ethanol 4 % (w/v) using a schedule-induced polydipsia procedure, followed by "open-access" ethanol self-administration in which the monkeys were allowed a choice of water or 4 % ethanol (w/v) for 22 h/day for 52 weeks.

RESULTS

Aggressive monkeys self-administered more ethanol and attained higher blood ethanol concentrations (BECs). No significant differences in ethanol intakes or BECs were found between anxious and non-anxious monkeys or between behaviorally inhibited and non-inhibited monkeys. Baseline aggressive behavior positively correlated with ethanol intake and intoxication.

CONCLUSIONS

Baseline reactive aggression was associated with higher future ethanol intake and intoxication. While significant sex differences in HIT reactivity were observed, the relationship between aggression and ethanol drinking was observed across sex and is not sex-specific.

A Morphological and Morphometric Study of Bite Marks Caused by Mice (Mus Musculus) on Different Baits for Forensic Purposes

In animal bites, the dental attributes can be fundamental in identifying the marks made by various species on different matrices. Although rodent bite marks have been studied in the context of postmortem interference, little research has used different baits to analyze these marks linking not only specific behavior patterns but also the possibility of structural damage. Twenty mice (Mus musculus) were exposed to different baits to study their bite marks in a controlled model. The known pattern of parallel and multiple grooves has been seen in all baits, but polyvinyl chloride and fiber-optic cable were significantly different between each other and the other baits. Some baits showed patterns of anchorage of the upper incisors and space between the lower incisors when gnawing. This technical note represents a novel model of analysis where veterinarians and/or dentists may be asked to give an opinion on alleged animal bite marks.

Sleep deprivation effects on object discrimination task in zebrafish (Danio rerio)

The zebrafish is an ideal vertebrate model for neurobehavioral studies with translational relevance to humans. Many aspects of sleep have been studied, but we still do not understand how and why sleep deprivation alters behavioral and physiological processes. A number of hypotheses suggest its role in memory consolidation. In this respect, the aim of this study was to analyze the effects of sleep deprivation on memory in zebrafish (Danio rerio), using an object discrimination paradigm. Four treatments were tested: control, partial sleep deprivation, total sleep deprivation by light pulses, and total sleep deprivation by extended light. The control group explored the new object more than the known object, indicating clear discrimination. The partially sleep-deprived group explored the new object more than the other object in the discrimination phase, suggesting a certain degree of discriminative performance. By contrast, both total sleep deprivation groups equally explored all objects, regardless of their novelty. It seems that only one night of sleep deprivation is enough to affect discriminative response in zebrafish, indicating its negative impact on cognitive processes. We suggest that this study could be a useful screening tool for cognitive dysfunction and a better understanding of the effect of sleep-wake cycles on cognition.

Medial septal GABAergic projection neurons promote object exploration behavior and type 2 theta rhythm

Exploratory drive is one of the most fundamental emotions, of all organisms, that are evoked by novelty stimulation. Exploratory behavior plays a fundamental role in motivation, learning, and well-being of organisms. Diverse exploratory behaviors have been described, although their heterogeneity is not certain because of the lack of solid experimental evidence for their distinction. Here we present results demonstrating that different neural mechanisms underlie different exploratory behaviors. Localized Cav3.1 knockdown in the medial septum (MS) selectively enhanced object exploration, whereas the null mutant (KO) mice showed enhanced-object exploration as well as open-field exploration. In MS knockdown mice, only type 2 hippocampal theta rhythm was enhanced, whereas both type 1 and type 2 theta rhythm were enhanced in KO mice. This selective effect was accompanied by markedly increased excitability of septo-hippocampal GABAergic projection neurons in the MS lacking T-type Ca(2+) channels. Furthermore, optogenetic activation of the septo-hippocampal GABAergic pathway in WT mice also selectively enhanced object exploration behavior and type 2 theta rhythm, whereas inhibition of the same pathway decreased the behavior and the rhythm. These findings define object exploration distinguished from open-field exploration and reveal a critical role of T-type Ca(2+) channels in the medial septal GABAergic projection neurons in this behavior.

The effect of isoflurane anaesthesia and buprenorphine on the mouse grimace scale and behaviour in CBA and DBA/2 mice

Prevention or alleviation of pain in laboratory mice is a fundamental requirement of in vivo research. The mouse grimace scale (MGS) has the potential to be an effective and rapid means of assessing pain and analgesic efficacy in laboratory mice. Preliminary studies have demonstrated its potential utility for assessing pain in mouse models that involve potentially painful procedures. The next step in validation is to determine if the other procedures that are integral to these models, i.e. anaesthesia or analgesia, result in any changes in MGS score which would need to be taken into account when using this tool to assess post-procedural pain. Here, spontaneous behaviour and MGS data for CBA and DBA/2 mice were recorded at baseline and following either isoflurane anaesthesia (suitable to perform abdominal surgery) or 0.05 mg/kg s.c. buprenorphine. In line with previous studies, isoflurane anaesthesia alone had limited effects on the spontaneous behaviour in either strain of mice. Administration of buprenorphine resulted in increased periods of activity e.g. walking and chewing bedding in CBA mice. These effects were not demonstrated in DBA/2 mice. In comparison, buprenorphine alone had no impact on MGS score in either strain of mice, however DBA/2 mice showed a significant increase in MGS score following isoflurane anaesthesia. The presence of this increased MGS score must be taken into account when attempting to use the MGS to assess pain in DBA/2 mice. Further work should be carried out to establish the presence of this isoflurane effect in other strains and the potential influence of gender on the MGS. This further validation is necessary prior to implementation of this technique in clinical scenarios.

Different attentional abilities among inbred mice strains using virtual object recognition task (VORT): SNAP25⁺/⁻ mice as a model of attentional deficit

Autism spectrum disorder (ASD), attention-deficit hyperactivity disorder (ADHD), schizophrenia, Alzheimer's and Parkinson's disease are characterized by attentional deficits. In the present study we first applied the virtual object recognition test (VORT), where 3D objects were replaced with highly discriminated geometrical shapes and presented on two 3.5-inch widescreen displays, in different inbred mice strains (C57BL/6N, DBA/2J, BALB/cJ), in comparison with the standard object recognition test (NOR). In both NOR and VORT, there was a progressive decay of performance in terms of reduced discrimination index from 5 min to 72 h of inter-trial delay in all strains. However, BALB/cJ inbred mice showed a better long lasting performance than C57BL/6N and DBA/2J, when tested in NOR. In VORT, BALB/cJ showed the best performance. Total exploration time was always higher in BALB/cJ than C57BL/6N and DBA/2J mice. C57BL/6N were less explorative strain than DBA/2J and BALB/cJ mice. When VORT was applied to SNAP-25(+/-) mice, an impairment in both NOR and VORT was shown. However, when moving shapes were applied, these heterozygous mice improved their performance, suggesting that the introduction of motion is a strong cue that makes the task more valuable to study attention deficits. Taken together, these data indicate that VORT provides a useful and rapid tool to identify the attentional deficit in different inbred strains and genetically modified mice, enhancing the value of psychiatric mouse models.

Spontaneous object recognition: a promising approach to the comparative study of memory

Spontaneous recognition of a novel object is a popular measure of exploratory behavior, perception and recognition memory in rodent models. Because of its relative simplicity and speed of testing, the variety of stimuli that can be used, and its ecological validity across species, it is also an attractive task for comparative research. To date, variants of this test have been used with vertebrate and invertebrate species, but the methods have seldom been sufficiently standardized to allow cross-species comparison. Here, we review the methods necessary for the study of novel object recognition in mammalian and non-mammalian models, as well as the results of these experiments. Critical to the use of this test is an understanding of the organism's initial response to a novel object, the modulation of exploration by context, and species differences in object perception and exploratory behaviors. We argue that with appropriate consideration of species differences in perception, object affordances, and natural exploratory behaviors, the spontaneous object recognition test can be a valid and versatile tool for translational research with non-mammalian models.

3D video analysis of the novel object recognition test in rats

The novel object recognition (NOR) test has been widely used to test memory function. We developed a 3D computerized video analysis system that estimates nose contact with an object in Long Evans rats to analyze object exploration during NOR tests. The results indicate that the 3D system reproducibly and accurately scores the NOR test. Furthermore, the 3D system captures a 3D trajectory of the nose during object exploration, enabling detailed analyses of spatiotemporal patterns of object exploration. The 3D trajectory analysis revealed a specific pattern of object exploration in the sample phase of the NOR test: normal rats first explored the lower parts of objects and then gradually explored the upper parts. A systematic injection of MK-801 suppressed changes in these exploration patterns. The results, along with those of previous studies, suggest that the changes in the exploration patterns reflect neophobia to a novel object and/or changes from spatial learning to object learning. These results demonstrate that the 3D tracking system is useful not only for detailed scoring of animal behaviors but also for investigation of characteristic spatiotemporal patterns of object exploration. The system has the potential to facilitate future investigation of neural mechanisms underlying object exploration that result from dynamic and complex brain activity.

Selective knockout of the casein kinase 2 in d1 medium spiny neurons controls dopaminergic function

BACKGROUND

Dopamine, crucial for the regulation of motor function and reward, acts through receptors mainly expressed in striatum as well as cortex. Dysregulation of dopaminergic signaling is associated with various neuropsychiatric disorders. Consequently, dopamine-regulating drugs are effectively used in treating these disorders, such as L-DOPA for Parkinson's disease, methylphenidate for attention-deficit/hyperactivity disorder, or antipsychotics for schizophrenia. As a result, there has been much interest in dissecting signaling networks in the two morphologically indistinguishable D1- and D2-receptor-expressing medium spiny neurons. Our previous results highlighted a role for casein kinase 2 (CK2) in the modulation of dopamine D1 receptor (D1R) signaling in cells.

METHODS

To study the importance of CK2 in vivo, we have selectively knocked out CK2, in either D1- or D2-medium spiny neurons (MSNs) and characterized the mice behaviorally and biochemically (n = 4-18).

RESULTS

The D1-MSN knockout mice exhibited distinct behavioral phenotypes including novelty-induced hyperlocomotion and exploratory behavior, defective motor control, and motor learning. All of these behavioral traits are indicative of dysregulated dopamine signaling and the underlying mechanism appears to be an alteration of D1R signaling. In support of this hypothesis, D1R levels were upregulated in the knockout mice, as well as phosphorylation of DARPP-32 (dopamine- and cyclic adenosine monophosphate [cAMP]-regulated phospho-protein of 32 kDa), most of the behavioral phenotypes were abolished by the D1R antagonist, SCH23390, and the D2-MSN knockout mice displayed no obvious behavioral phenotype.

CONCLUSIONS

A single kinase, CK2, in D1-MSNs significantly alters dopamine signaling, a finding that could have therapeutic implications for disorders characterized by dopamine imbalance such as Parkinson's disease, attention-deficit/hyperactivity disorder, and schizophrenia.

Not all mice are equal: welfare implications of behavioural habituation profiles in four 129 mouse substrains

Safeguarding the welfare of animals is an important aim when defining housing and management standards in animal based, experimental research. While such standards are usually defined per animal species, it is known that considerable differences between laboratory mouse strains exist, for example with regard to their emotional traits. Following earlier experiments, in which we found that 129P3 mice show a lack of habituation of anxiety related behaviour after repeated exposure to an initially novel environment (non-adaptive profile), we here investigated four other 129 inbred mouse substrains (129S2/SvPas, 129S2/SvHsd (exp 1); 129P2 and 129X1 (exp 2)) on habituation of anxiety related behaviour. Male mice of each strain were repeatedly placed in the modified hole board test, measuring anxiety-related behaviour, exploratory and locomotor behaviour. The results reveal that all four substrains show a lack of habituation behaviour throughout the period of testing. Although not in all of the substrains a possible confounding effect of general activity can be excluded, our findings suggest that the genetic background of the 129 substrains may increase their vulnerability to cope with environmental challenges, such as exposure to novelty. This vulnerability might negatively affect the welfare of these mice under standard laboratory conditions when compared with other strains. Based on our findings we suggest to consider (sub)strain-specific guidelines and protocols, taking the (subs)train-specific adaptive capabilities into account.

Characterization of an alcohol addiction-prone phenotype in mice

Human studies indicate that high impulsivity, novelty seeking and anxiety predispose individuals to alcohol abuse. Unclear, however, is whether the same phenotypes can be observed in laboratory animals prone to uncontrolled alcohol drinking. To characterize a novelty-seeking trait, anxiety, impulsivity, compulsivity and the motivation for natural rewards in mice, numerous tests were performed in the automated IntelliCage learning system. The same mice then had extended access to alcohol for 70 days, followed by the evaluation of addiction-like behaviors, including (1) the motivation for alcohol in a progressive-ratio schedule of reinforcement; (2) persistent and compulsive alcohol seeking and taking during signaled 'no alcohol' periods and (3) when subjected to punishment; and (4) the intensity of relapse after alcohol withdrawal. Our data suggest that high levels of anxiety-related traits (i.e. low novelty seeking, low resistance to punishment and a high level of compulsive behaviors) and high impulsivity predict addiction-like alcohol drinking in mice. Future studies are, however, warranted to create a valid model of alcohol addiction in mice in the IntelliCage system.

Novel object exploration in mice: not all objects are created equal

Object exploration is an increasingly popular experimental paradigm in behavioral sciences. We have begun a series of studies with mice specifically looking at the parameters that influence behaviors in this test. The aim of the present study was to examine the effect of object type on performance in the object exploration test. More specifically, adult male C57BL/6J mice were trained and tested using objects that could be climbed (CLIMB) or with those that could only be touched (TOUCH). The results show that activity is affected by the presentation of objects, with object type interacting with some of these changes. C57 mice explored objects that can be climbed over significantly longer than objects that can only be touched and a more rapid habituation was observed using objects that could only be touched. Robust recognition memory was observed in both groups of mice, however mice in the CLIMB group exhibited a significantly greater discrimination index compared to mice in the TOUCH group. Taken together, these findings demonstrate that the selection of objects is of critical importance and it is recommended that special attention be given to the functional (affordant) properties of the objects to-be-used in future studies.

Pharmacological modulation of anxiety-like phenotypes in adult zebrafish behavioral models

Zebrafish (Danio rerio) are becoming increasingly popular in neurobehavioral research. Here, we summarize recent data on behavioral responses of adult zebrafish to a wide spectrum of putative anxiolytic and anxiogenic agents. Using the novel tank test as a sensitive and efficient behavioral assay, zebrafish anxiety-like behavior can be bi-directionally modulated by drugs affecting the gamma-aminobutyric acid, monoaminergic, cholinergic, glutamatergic and opioidergic systems. Complementing human and rodent data, zebrafish drug-evoked phenotypes obtained in this test support this species as a useful model for neurobehavioral and psychopharmacological research.

Differences in spatio-temporal behavior of zebrafish in the open tank paradigm after a short-period confinement into dark and bright environments

The open tank paradigm, also known as novel tank diving test, is a protocol used to evaluate the zebrafish behavior. Several characteristics have been described for this species, including scototaxis, which is the natural preference for dark environments in detriment of bright ones. However, there is no evidence regarding the influence of “natural stimuli” in zebrafish subjected to novelty-based paradigms. In this report, we evaluated the spatio-temporal exploratory activity of the short-fin zebrafish phenotype in the open tank after a short-period confinement into dark/bright environments. A total of 44 animals were individually confined during a 10-min single session into one of three environments: black-painted, white-painted, and transparent cylinders (dark, bright, and transparent groups). Fish were further subjected to the novel tank test and their exploratory profile was recorded during a 15-min trial. The results demonstrated that zebrafish increased their vertical exploratory activity during the first 6-min, where the bright group spent more time and travelled a higher distance in the top area. Interestingly, all behavioral parameters measured for the dark group were similar to the transparent one. These data were confirmed by automated analysis of track and occupancy plots and also demonstrated that zebrafish display a classical homebase formation in the bottom area of the tank. A detailed spatio-temporal study of zebrafish exploratory behavior and the construction of representative ethograms showed that the experimental groups presented significant differences in the first 3-min vs. last 3-min of test. Although the main factors involved in these behavioral responses still remain ambiguous and require further investigation, the current report describes an alternative methodological approach for assessing the zebrafish behavior after a forced exposure to different environments. Additionally, the analysis of ethologically-relevant patterns across time could be a potential phenotyping tool to evaluate the zebrafish exploratory profile in the open tank task.

Sociability and motor functions in Shank1 mutant mice

Autism is a neurodevelopmental disorder characterized by aberrant reciprocal social interactions, impaired communication, and repetitive behaviors. While the etiology remains unclear, strong evidence exists for a genetic component, and several synaptic genes have been implicated. SHANK genes encode a family of synaptic scaffolding proteins located postsynaptically on excitatory synapses. Mutations in SHANK genes have been detected in several autistic individuals. To understand the consequences of SHANK mutations relevant to the diagnostic and associated symptoms of autism, comprehensive behavioral phenotyping on a line of Shank1 mutant mice was conducted on multiple measures of social interactions, social olfaction, repetitive behaviors, anxiety-related behaviors, motor functions, and a series of control measures for physical abilities. Results from our comprehensive behavioral phenotyping battery indicated that adult Shank1 null mutant mice were similar to their wildtype and heterozygous littermates on standardized measures of general health, neurological reflexes and sensory skills. Motor functions were reduced in the null mutants on open field activity, rotarod, and wire hang, replicating and extending previous findings (Hung et al., 2008). A partial anxiety-like phenotype was detected in the null mutants in some components of the light ↔ dark task, as previously reported (Hung et al., 2008) but not in the elevated plus-maze. Juvenile reciprocal social interactions did not differ across genotypes. Interpretation of adult social approach was confounded by a lack of normal sociability in wildtype and heterozygous littermates. All genotypes were able to discriminate social odors on an olfactory habituation/dishabituation task. All genotypes displayed relatively high levels of repetitive self-grooming. Our findings support the interpretation that Shank1 null mice do not demonstrate autism-relevant social interaction deficits, but confirm and extend a role for Shank1 in motor functions.

Behavioural battery testing: evaluation and behavioural outcomes in 8 inbred mouse strains

The use of large scale behavioural batteries for the discovery of novel genes underlying behavioural variation has considerable potential. Building a broad behavioural profile serves to better understand the complex interplay of overlapping genetic factors contributing to various paradigms, underpinning a systems biology approach. We devised a battery of tests to dissect and characterise the genetic bases of behavioural phenotypes, but firstly undertook to evaluate several aspects considered potentially confounding for mapping quantitative traits. These included investigating: individual versus sibling housing; testing at different times during the day; battery versus non-battery testing; and initial placement within the light-dark box. Furthermore, we assessed how behavioural profiles differed in our battery across 8 inbred strains. Overall, we found the behavioural battery was most sensitive to paired-housing effects, where weight and some measures in the open field, elevated plus maze and light-dark box differed significantly between sibling housed and singly housed mice. Few large effects were found for testing at different times of day and battery versus non-battery testing. Placement in the light-dark box influenced activity and duration measures, which profoundly affected the analysis outcome. Behavioural profiles across eight inbred strains (C57BL/6J, 129S1/SvImJ, A/J, BALB/cByJ, C3H/HeJ, DBA/2J, FVB/NJ, and SJL/J) demonstrated some robust strain ranking differences for measures in the open field and light-dark tests in our battery. However, some tests such as the elevated plus maze produced incongruous strain ranking effects across measures. The findings reported herein bear out the promise of behavioural batteries for mapping naturally occurring variation in mouse reference populations.

Identifying emotional adaptation: behavioural habituation to novelty and immediate early gene expression in two inbred mouse strains

Normal anxiety is an adaptive emotional response. However, when anxiety appears to lack adaptive value, it might be defined as pathological. Adaptation in animals can be assessed for example by changes in behavioural responses over time, i.e. habituation. We hypothesize that non-adaptive anxiety might be reflected by impaired habituation. To test our hypothesis, we repeatedly exposed male mice from two inbred strains to a novel environment, the modified hole board. BALB/cJ mice were found to be initially highly anxious, but subsequently habituated to the test environment. In contrast, 129P3/J mice initially showed less anxiety-related behaviour compared with the BALB/cJ mice but no habituation in anxiety-related behaviour was observed. Notably, anxiety-related behaviour even increased during the experimental period. Complementary, 129P3/J mice did not show habituation in other parameters such as locomotor and exploratory activity, whereas significant changes appeared in these behaviours in BALB/c mice. Finally, the expression of the immediate early gene c-fos differed between the two strains in distinct brain areas, known to regulate the integration of emotional and cognitive processes. These results suggest that 129P3/J mice might be a promising (neuro)-behavioural animal model for non-adaptive, i.e. pathological anxiety.

Role of dopamine D1 receptors in novelty seeking in adult female Long-Evans rats

Adult Long-Evans ovariectomized female rats received injections of the DA D1 antagonist SCH 23390 (0, 0.03 and 0.3mg/kg, i.p.) and were observed in an open field apparatus (OFA) with a novel object. Results indicate that a significant effect of SCH 23390 was found on several measures of novelty seeking and activity, with the high dose producing a significant decrease in (1) approaches to and (2) rears while approaching the novel object, (3) latency to interact with the novel object, (4) in time interacting with the novel object, (5) anxious behavior (as measured by rears) and (6) locomotor activity (LMA), as compared to both the saline and low dose. Interestingly, the effects of SCH 23390 on approaches and rears were not significant when LMA was factored into the analysis (repeated measures ANCOVA), however, marked results were still found on time interacting with the novel object. These data demonstrate that SCH 23390 produced dose-dependent effects on novelty seeking that were independent of LMA, implicating D1 receptors in the incentive-motivational aspect of novelty seeking in adult gonadectomized female rats.

Specific roles of GABA(B(1)) receptor isoforms in cognition

The GABA(B) receptor is a heterodimer of GABA(B(1)) and GABA(B(2)) subunits. There are two isoforms of the GABA(B(1)) subunit: GABA(B(1a)) and GABA(B(1b)). Recent studies with mutant mice suggest a differential role for the two GABA(B(1)) isoforms in behavioural processes. As pharmacological and genetic studies have implicated GABA(B) receptors in cognition we investigated the behaviour of GABA(B(1a))(-/-) and GABA(B(1b))(-/-) mice in different types of cognitive paradigms. GABA(B(1a))(-/-) and GABA(B(1b))(-/-) mice were both impaired relative to wildtype controls in a continuous spontaneous alternation behaviour test of working spatial memory. In contrast to the reported phenotype of GABA(B(1))(-/-) mice, however, neither GABA(B(1a))(-/-) nor GABA(B(1b))(-/-) mice were deficient in a passive avoidance task. On the other hand, GABA(B(1a))(-/-) mice were impaired in familiar and novel object recognition. We conclude that GABA(B(1)) isoforms contribute differentially to GABA(B) receptor-mediated cognitive processes.

Behavioral neuroscience, exploration, and K.C. Montgomery's legacy

Exploration is a key animal and human behavior. Kay C. Montgomery (1921-1956) has made an important contribution to behavioral neuroscience of exploration, as well as motivation and learning. His works have many important applications to current experimental models of stress, fear and memory, continuing to influence research in this field. This paper, dedicated to the 85th anniversary of Montgomery's birth, and 50 years since his tragic death, summarizes Montgomery's contribution to behavioral neuroscience, and discusses its current importance for further progress in this field. It is aimed at neuroscientists with strong interests in both theory of animal exploration and motivation, and the history of behavioral neuroscience.

Computer automated movement detection for the analysis of behavior

Currently, measuring ethanol behaviors in flies depends on expensive image analysis software or time intensive experimental observation. We have designed an automated system for the collection and analysis of locomotor behavior data, using the IEEE 1394 acquisition program dvgrab, the image toolkit ImageMagick and the programming language Perl. In the proposed method, flies are placed in a clear container and a computer-controlled camera takes pictures at regular intervals. Digital subtraction removes the background and non-moving flies, leaving white pixels where movement has occurred. These pixels are tallied, giving a value that corresponds to the number of animals that have moved between images. Perl scripts automate these processes, allowing compatibility with high-throughput genetic screens. Four experiments demonstrate the utility of this method, the first showing heat-induced locomotor changes, the second showing tolerance to ethanol in a climbing assay, the third showing tolerance to ethanol by scoring the recovery of individual flies, and the fourth showing a mouse's preference for a novel object. Our lab will use this method to conduct a genetic screen for ethanol-induced hyperactivity and sedation, however, it could also be used to analyze locomotor behavior of any organism.

Feeling strained? Influence of genetic background on depression-related behavior in mice: a review

Depression is a growing pandemic in developed societies. The use of inbred mouse strains in pre-clinical psychiatric research has proven to be a valuable resource. Firstly, they provide the background for genetic manipulations that aid in the discovery of molecular pathways that may be involved in major depression. Further, inbred mouse strains are also being used in the determination of genetic and environmental influences that may pre-dispose or trigger depression-related behavior. This review aims to highlight the utility of inbred mouse strains in depression research, while providing an overview of the current state of research into behavioral differences between strains in paradigms commonly used in the field. Neurochemical differences that may underlie strain differences are examined, and some caveats and cautions associated with the use of inbred strains are highlighted.