Adolescent Exploratory Strategies and Behavioral Types in the Multivariate Concentric Square FieldTM Test

Acute caffeine differently affects risk-taking and the expression of BDNF and of adenosine and opioid receptors in rats with high or low anxiety-like behavior

Anxiety disorders are common psychiatric conditions with a partially elucidated neurobiology. Caffeine, an unspecific adenosine receptor antagonist, is a common psychostimulant with anxiogenic effects in sensitive individuals. High doses of caffeine produce anxiety-like behavior in rats but it is not known if this is specific for rats with high baseline anxiety-like behavior. Thus, the aim of this study was to investigate general behavior, risk-taking, and anxiety-like behavior, as well as mRNA expression (adenosine A2A and A1, dopamine D2, and, μ, κ, δ opioid, receptors, BDNF, c-fos, IGF-1) in amygdala, caudate putamen, frontal cortex, hippocampus, hypothalamus, after an acute dose of caffeine. Untreated rats were screened using the elevated plus maze (EPM), giving each rat a score on anxiety-like behavior based on their time spent in the open arms, and categorized into a high or low anxiety-like behavior group accordingly. Three weeks after categorization, the rats were treated with 50 mg/kg caffeine and their behavior profile was studied in the multivariate concentric square field (MCSF) test, and one week later in the EPM. qPCR was performed on selected genes and corticosterone plasma levels were measured using ELISA. The results demonstrated that the high anxiety-like behavior rats treated with caffeine spent less time in risk areas of the MCSF and resituated towards the sheltered areas, a behavior accompanied by lower mRNA expression of adenosine A2A receptors in caudate putamen and increased BDNF expression in hippocampus. These results support the hypothesis that caffeine affects individuals differently depending on their baseline anxiety-like behavior, possibly involving adenosine receptors. This highlights the importance of adenosine receptors as a possible drug target for anxiety disorders, although further research is needed to fully elucidate the neurobiological mechanisms of caffeine on anxiety disorders.

Behavioral profiling of SLC38A10 knockout mice using the multivariate concentric square fieldTM test

Introduction

SLC38A10 is a gene that encodes the SLC38A10 protein, also known as SNAT10. The SLC38 family is evolutionary old, and SLC38A10 is one of the oldest members of the family. It is ubiquitously expressed, and its substrates are glutamine, glutamate, alanine, aspartate, and serine. However, little is known about its biological importance.

Methods

In the current study, an SLC38A10 knockout mouse was run in the multivariate concentric square field ^TM (MCSF) test. The MCSF test gives the mouse a choice of areas to explore; sheltered areas, elevated and illuminated areas, or open spaces, and a behavioral profile is obtained. The multivariate data obtained were analyzed (i) for each parameter, (ii) parameters grouped into functional categories, and (iii) with a principal component analysis.

Results

In the trend analysis, knockout mice had a decreased exploratory behavior compared to controls but did not show a distinct grouping in the principal component analysis.

Discussion

There was not a pronounced difference in the behavioral profile in SLC38A10 knockout mice compared to their wild-type controls, although subtle alterations in zones associated with exploratory behavior and risk assessment in female and male knockout mice, respectively, could be observed. These results imply that a loss of function of the SLC38A10 protein in mice does not drastically alter behavior in the MSCF test.

Modeling Parkinson's disease-related symptoms in alpha-synuclein overexpressing mice

BACKGROUND

Intracellular deposition of alpha-synuclein (α-syn) as Lewy bodies and Lewy neurites is a central event in the pathogenesis of Parkinson's disease (PD) and other α-synucleinopathies. Transgenic mouse models overexpressing human α-syn, are useful research tools in preclinical studies of pathogenetic mechanisms. Such mice develop α-syn inclusions as well as neurodegeneration with a topographical distribution that varies depending on the choice of promoter and which form of α-syn that is overexpressed. Moreover, they display motor symptoms and cognitive disturbances that to some extent resemble the human conditions.

PURPOSE

One of the main motives for assessing behavior in these mouse models is to evaluate the potential of new treatment strategies, including their impact on motor and cognitive symptoms. However, due to a high within-group variability with respect to such features, the behavioral studies need to be applied with caution. In this review, we discuss how to make appropriate choices in the experimental design and which tests that are most suitable for the evaluation of PD-related symptoms in such studies.

METHODS

We have evaluated published results on two selected transgenic mouse models overexpressing wild type (L61) and mutated (A30P) α-syn in the context of their validity and utility for different types of behavioral studies.

CONCLUSIONS

By applying appropriate behavioral tests, α-syn transgenic mouse models provide an appropriate experimental platform for studies of symptoms related to PD and other α-synucleinopathies.

The zebrafish Multivariate Concentric Square Field: A Standardized Test for Behavioral Profiling of Zebrafish (Danio rerio)

The zebrafish (Danio rerio) is an important model organism in the study of the neurobiological basis of human mental disorders. Yet the utility of this species is limited by the quality of the phenotypical characterization tools available. Here, we present a complex testing environment for the quantification of explorative behavior in adult zebrafish, the zebrafish Multivariate Concentric Square Field™ (zMCSF), adapted from the rodent equivalent that has been used in > 40 studies. The apparatus consists of a central open area which is surrounded by a dark corner with a roof (DCR), corridors, and an inclined ramp. These areas differ in illumination, water depth, and are sheltered or exposed to different degrees. We quantified behavior of male and female wild-caught and AB strain zebrafish in the zMCSF (day 1) and cross-validated these results using the novel tank diving test (NTDT) (day 2). To assess the effect of repeated testing, AB zebrafish we tested a second time in both tests 1 week later (on days 7 and 8). We detected strong differences between the strains, with wild zebrafish swimming faster and spending more time in the corridors and on the ramp, while they avoided the open area in the center. AB zebrafish were less hesitant to enter the center but avoided the ramp, and often left one or more zones unexplored. No major sex differences in exploratory behavior were detected in either strain, except for a slightly higher velocity of AB males which has been reported before. Importantly, the zMCSF was largely resilient to repeated testing. The diving test revealed only one difference confined to one sex; wild females paid more visits to the top third than AB females. In isolation, this finding could lead to the conclusion that wild zebrafish are more risk-taking, which is incorrect given this strain's avoidance of open areas. To conclude, our results suggest that the zMCSF presents a sophisticated behavioral tool that can distinguish between different magnitudes and types of risk, allowing the user to create an intricate behavioral profile of individual adult zebrafish.

Behavioral Profiles of Adolescent Alcohol-Preferring/Non-preferring (P/NP) and High/Low Alcohol-Drinking (HAD/LAD) Rats Are Dependent on Line but Not Sex

Initial contact with alcohol generally occurs during adolescence, and high consumption during this period is associated with increased risk for later alcohol (AUDs) and/or substance use disorders (SUDs). Rodents selectively bred for high or low alcohol consumption are used to identify behavioral characteristics associated with a propensity for high or low voluntary alcohol intake. The multivariate concentric square field™ (MCSF) is a behavioral test developed to study rodents in a semi-naturalistic setting. Testing in the MCSF creates a comprehensive behavioral profile in a single trial. The current aim was to examine the behavioral profiles of adolescent, bidirectionally selectively bred male and female high alcohol-consuming (P and HAD1/2) and low alcohol-consuming (NP and LAD1/2) rat lines, and outbred Wistar rats. Alcohol-naïve rats were tested once in the MCSF at an age between postnatal days 30 and 35. No common behavioral profile was found for either high or low alcohol-consuming rat lines, and the effect of sex was small. The P/NP and HAD2/LAD2 lines showed within pair-dependent differences, while the HAD1/LAD1 lines were highly similar. The P rats displayed high activity and risk-associated behaviors, whereas HAD2 rats displayed low activity, high shelter-seeking behavior, and open area avoidance. The results from P rats parallel clinical findings that denser family history and risk-taking behavior are strong predictors of future AUDs, often with early onset. Contrarily, the HAD2 behavioral profile was similar to individuals experiencing negative emotionality, which also is associated with a vulnerability to develop, often with a later onset, AUDs and/or SUDs.

Effects of escalating versus fixed ethanol exposure on ∆FosB expression in the mesocorticolimbic pathway in adolescent and adult rats

Background: We have reported induction of ∆FosB in adolescent rats that drank less ethanol than adults yet exhibited a progressive increase in ethanol intake.Objective: To test the hypothesis that an escalating pattern of ethanol exposure is more effective to induce ∆FosB expression [at prelimbic cortex (PrL), nucleus accumbens core and shell, striatum, basolateral amygdala (BLA) and central amygdala (CeC)] than a pattern equated for number of exposures yet employing a fixed ethanol dose.Methods: Adolescent and adult (Exp. 1, n = 48) male and female (n = 24 of each sex) or only adult male (Exp. 2, n = 36) Wistar rats were intermittently intubated with vehicle, escalating (from 0.5 to 2.5 g/kg) or fixed (2.0 g/kg) doses of ethanol, across 18 sessions. ∆FosB induction was assessed using immunohistochemistry. Ethanol intake, anxiety and risk-taking were assessed (in adults only) via two-bottles tests and the multivariate concentric square field.Results: Both patterns heightened ∆FosB levels similarly in adolescents and adults and in males and females. Fixed dosing induced ∆FosB in all areas (p < .05) except the CeC, whereas the escalating pattern induced ∆FosB in the PrL and BLA only (p < .05). Ethanol intake was initially lower in ethanol pre-exposed subjects than in control subjects (p < .05). Rats exposed to the fixed pattern exhibited enhanced risk-taking behavior (p < .05).Conclusions: The results agree with studies showing ethanol-mediated induction of ∆FosB in reward areas and indicate that, following ethanol intubations, this induction is similar in adolescents and adults. The induction of ∆FosB seems not necessarily associated with susceptibility for ethanol intake.

Exploratory drive, fear, and anxiety are dissociable and independent components in foraging mice

Anxiety-like behavior of rodents is frequently accompanied by reduced exploration. Here, we identify dissociable components of anxiety, fear, and exploratory drive of sated and foraging mice. With the help of behavioral assays, including the open field task, elevated plus maze, dark-light transition task, and beetle mania task, we demonstrate a general increase in exploration by food restriction. Food-restricted mice bred for high anxiety behavior (HAB) showed ameliorated anxiety- but not fear-related behavior. By means of principal component analysis, we identified three independent components, which resemble the behavioral dimensions proposed by Gray's Reinforcement Sensitivity Theory (approach behavior, avoidance behavior, and decision making). Taken together, we demonstrate anxiolytic consequences of food restriction in a mouse model of anxiety disorders that can be dissociated from a general increase in foraging behavior.

Can the Hole-Board Test Predict a Rat's Exploratory Behavior in a Free-Exploration Test?

This study focuses on the rat activity in a hole-board setting that we considered a type of exploratory behavior. The general hypothesis is based on the claim that a motivational mechanism is central to both the response to novelty in a highly familiarized environment and the activity in the hole-board apparatus. Our sample consisted of 80 experimentally naive Lister Hooded rats. All rats were tested in the hole-board apparatus. Twenty individuals with the highest hole-board scores and twenty subjects with the lowest hole-board scores subsequently underwent an established free-exploration test. In our study, the scores obtained in the hole-board test had little predictive value for the rats' activity in the free-exploration test. Based on our previous experience in studying exploratory behavior in the free-exploration test and the data presented in this paper, we suggest that the hole-board test is not an appropriate tool for measuring exploratory behavior in laboratory rodents.

The effects of age, sex, and handling on behavioral parameters in the multivariate concentric square field™ test

The multivariate concentric square field™ (MCSF) is a complex and ethologically relevant apparatus that is designed to measure several behavioral parameters within the same test session including risk-taking, risk-assessment, shelter-seeking (anxiety relieving), exploration, and general activity. While several studies have behaviorally and pharmacologically validated the use of the MCSF in adults, far fewer have used adolescents. Given the well-established link between adolescence and risk-taking, it is important to validate use of the MCSF in adolescence. The present study compared the effects of age, sex, and handling on behavioral categories in the MCSF. In addition, principal component analyses were used to compare the underlying behavioral components in adolescent and adult Sprague-Dawley rats. Results revealed that handling increased risk-taking and reduced shelter-seeking. Females were more exploratory than males, but no compelling age differences in risk-taking or risk-assessment were found. Principal component analyses revealed six major principal components for both adolescents and adults with the first and second components consisting mainly of center/center circle, risk-assessment, and shelter-seeking variables in adolescence, and general activity and center/center circle variables in adults. These results confirm age differences in the underlying behavioral components in the MCSF.

Environmental enrichment during adolescence heightens ethanol intake in female, but not male, adolescent rats that are selectively bred for high and low ethanol intake during adolescence

Background: Discriminating between adolescents who will eventually have ethanol use problems from those who do not is important. Environmental enrichment is a promising approach to reduce drug-related problems, but its impact on ethanol's effects and intake is being scrutinized. Objective: We tested the effects of environmental enrichment on ethanol intake, preference, and anxiety-like response as well as shelter seeking and risk-taking behaviors. Methods: Experiment 1 examined ethanol intake, preference, and anxiety-like responses in 46 male and 54 female Wistar rats that were derived from a short-term breeding program that selected for high and low ethanol drinking during adolescence (ADHI₂ and ADLO₂ lines, respectively). Shelter-seeking and risk-taking behaviors were assessed (Experiment 2) in ADHI₂ and ADLO₂ rats (73 males, 76 females) reared under environmental enrichment or standard housing conditions and given doses of ethanol (2.5 g/kg, intraperitoneal) for 3 weeks. Environmental enrichment was applied on postnatal days 21-42. Ethanol intake was measured on postnatal days 42-68. Anxiety-like behavior and exploratory responses were assessed using the light-dark box and multivariate concentric square field test. Results: In Experiment 1, environmental enrichment increased ethanol intake in female, but not male, ADHI₂ and ADLO₂ rats (p < 0.05). In the baseline measurement of Experiment 2, ADHI₂ rats exhibited reduced risk-taking and increased anxiety-like behavior (p < .05). After exposure to environmental enrichment the ADHI and ADLO rats, both males and females, exhibited increased risk-taking and exploratory behavior (p < 0.05). Conclusions: Environmental enrichment appears to increase ethanol intake in female rats by promoting the exploration of new environments or stimuli. The findings indicate that environmental enrichment increased ethanol intake in female, but not male, rats. Clinical programs that treat alcohol use disorder by emphasizing environmental stimulation should be designed with caution.

Behavioral Phenotyping for Down Syndrome in Mice

Down syndrome (DS) is the most frequent genetic cause of intellectual disability, characterized by alterations in different behavioral symptom domains: neurodevelopment, motor behavior, and cognition. As mouse models have the potential to generate data regarding the neurological basis for the specific behavioral profile of DS, and may indicate pharmacological treatments with the potential to affect their behavioral phenotype, it is important to be able to assess disease-relevant behavioral traits in animal models in order to provide biological plausibility to the potential findings. The field is at a juncture that requires assessments that may effectively translate the findings acquired in mouse models to humans with DS. In this article, behavioral tests are described that are relevant to the domains affected in DS. A neurodevelopmental behavioral screen, the balance beam test, and the Multivariate Concentric Square Field test to assess multiple behavioral phenotypes and locomotion are described, discussing the ways to merge these findings to more fully understand cognitive strengths and weaknesses in this population. New directions for approaches to cognitive assessment in mice and humans are discussed. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Preweaning neurodevelopmental battery Basic Protocol 2: Balance beam Basic Protocol 3: Multivariate concentric square field test (MCSF).

Prediction of ethanol self-administration in pre-weanling, adolescent, and young adult rats

Alcohol (ethanol) use is almost normative by late adolescence, in most western countries. It is important to identify factors that distinguish those who progress from alcohol initiation to sustained use of the drug, from those that keep a controlled pattern of drinking. The factors precipitating this transition may change across development. This study analyzed associations between behavioral endophenotypes and ethanol intake at three developmental periods. Exp. 1 measured ethanol drinking at postnatal day 18, via an intraoral infusion procedure, in male or female pre-weanling rats screened for anxiety response in the light-dark box test and for distance traveled in a novel open field. Exp. 2 measured, in juvenile/adolescent or young adult rats, the association between shelter seeking, exploratory/risk-taking behaviors, anxiety or hedonic responses, and ethanol intake. Ethanol intake in pre-weanlings was explained by distance traveled in a novel environment, whereas anxiety responses, measured in the multivariate concentric square field apparatus (MSCF), selectively predicted ethanol intake at adolescence, but not at adulthood. Those juvenile/adolescents with lower mean duration of visit to areas of the MSCF that evoke anxiogenic responses exhibited heightened ethanol intake. These findings suggest that the association between anxiety and ethanol intake may be specifically relevant during adolescence.

Evaluation of the therapeutic potential of Epigallocatechin-3-gallate (EGCG) via oral gavage in young adult Down syndrome mice

Epigallocatechin-3-gallate (EGCG) is a candidate therapeutic for Down syndrome (DS) phenotypes based on in vitro inhibition of DYRK1A, a triplicated gene product of Trisomy 21 (Ts21). Consumption of green tea extracts containing EGCG improved some cognitive and behavioral outcomes in DS mouse models and in humans with Ts21. In contrast, treatment with pure EGCG in DS mouse models did not improve neurobehavioral phenotypes. This study tested the hypothesis that 200 mg/kg/day of pure EGCG, given via oral gavage, would improve neurobehavioral and skeletal phenotypes in the Ts65Dn DS mouse model. Serum EGCG levels post-gavage were significantly higher in trisomic mice than in euploid mice. Daily EGCG gavage treatments over three weeks resulted in growth deficits in both euploid and trisomic mice. Compared to vehicle treatment, EGCG did not significantly improve behavioral performance of Ts65Dn mice in the multivariate concentric square field, balance beam, or Morris water maze tasks, but reduced swimming speed. Furthermore, EGCG resulted in reduced cortical bone structure and strength in Ts65Dn mice. These outcomes failed to support the therapeutic potential of EGCG, and the deleterious effects on growth and skeletal phenotypes underscore the need for caution in high-dose EGCG supplements as an intervention in DS.

Behavioral Profiling in Early Adolescence and Early Adulthood of Male Wistar Rats After Short and Prolonged Maternal Separation

Early-life stress and its possible correlations to genes, environment, and later health outcomes can only be studied retrospectively in humans. Animal models enable the exploration of such connections with prospective, well-controlled study designs. However, with the recent awareness of replicability issues in preclinical research, the reproducibility of results from animal models has been highlighted. The present study aims to reproduce the behavioral effects of maternal separation (MS) previously observed in the multivariate concentric square field^TM (MCSF) test. A second objective was to replicate the adolescent behavioral profiles previously described in the MCSF test. Male rats, subjected to short or prolonged MS or standard rearing, were subjected to behavioral testing in early adolescence and early adulthood. As seen in previous studies, the behavioral effects of MS in the MCSF were small at both tested time points. When tested in early adolescence, the animals exhibited a similar behavioral profile as previously seen, and the finding of adolescent behavioral types was also reproduced. The distribution of animals into the behavioral types was different than in the initial study, but in a manner consistent with developmental theories, as the current cohort was younger than the previous. Notably, the Shelter seeker behavioral type persisted through development, while the Explorer type did not. The lack of basal behavioral effect after MS is in line with the literature on this MS paradigm; the working hypothesis is that the prolonged MS gives rise to a phenotype predisposed to negative health outcomes but which is not apparent without additional provocation.