Behavioral phenotypes of inbred mouse strains: implications and recommendations for molecular studies

Targeting GLP-1 receptors to reduce nicotine use disorder: Preclinical and clinical evidence

Nicotine use disorder (NUD) remains a leading cause of preventable death in the U.S. Unfortunately, current FDA-approved pharmacotherapies for smoking cessation have limited efficacy and are associated with high rates of relapse. One major barrier to long-term smoking abstinence is body weight gain during withdrawal. Nicotine withdrawal-induced body weight gain can also lead to development of chronic disease states like obesity and type II diabetes mellitus. Therefore, it is critical to identify novel pharmacotherapies for NUD that decrease relapse and nicotine withdrawal symptoms including body weight gain. Recent studies demonstrate that glucagon-like peptide-1 receptor (GLP-1R) agonists attenuate voluntary nicotine taking and seeking and prevent withdrawal-induced hyperphagia and body weight gain. Emerging evidence also suggests that GLP-1R agonists improve cognitive deficits, as well as depressive- and anxiety-like behaviors, which contribute to smoking relapse during withdrawal. While further studies are necessary to fully characterize the effects of GLP-1R agonists on NUD and understand the mechanisms by which GLP-1R agonists decrease nicotine withdrawal-mediated behaviors, the current literature supports GLP-1R-based approaches to treating NUD.

Measuring the replicability of our own research

In the study of transgenic mouse models of neurodevelopmental and neurodegenerative disorders, we use batteries of tests to measure deficits in behaviour and from the results of these tests, we make inferences about the mental states of the mice that we interpret as deficits in "learning", "memory", "anxiety", "depression", etc. This paper discusses the problems of determining whether a particular transgenic mouse is a valid mouse model of disease X, the problem of background strains, and the question of whether our behavioural tests are measuring what we say they are. The problem of the reliability of results is then discussed: are they replicable between labs and can we replicate our results in our own lab? This involves the study of intra- and inter- experimenter reliability. The variables that influence replicability and the importance of conducting a complete behavioural phenotype: sensory, motor, cognitive and social emotional behaviour are discussed. Then the thorny question of failure to replicate is examined: Is it a curse or a blessing? Finally, the role of failure in research and what it tells us about our research paradigms is examined.

Exercise Training Alleviates Symptoms and Cognitive Decline in a Reserpine-induced Fibromyalgia Model by Activating Hippocampal PGC-1α/FNDC5/BDNF Pathway

The purpose of this study was to assess, from a behavioral, biochemical, and molecular standpoint, how exercise training affected fibromyalgia (FM) symptoms in a reserpine-induced FM model and to look into the potential involvement of the hippocampal PGC-1α/FNDC5/BDNF pathway in this process. Reserpine (1 mg kg-1) was subcutaneously injected once daily for three consecutive days and then the rats were exercised for 21 days. Mechanical allodynia was evaluated 1, 11, and 21 days after the last injection. At the end of the exercise training protocol forced swim, open field and Morris water maze tests were performed to assess depression, locomotion and cognition, respectively. Additionally, biochemical and molecular markers related to the pathogenesis of the FM and cognitive functions were measured. Reserpine exposure was associated with a decrease in locomotion, an increase in depression, an increase in mechanical allodynia, and a decrease in spatial learning and memory (p < 0.05). These behavioral abnormalities were found to be correlated with elevated blood cytokine levels, reduced serotonin levels in the prefrontal cortex, and altered PGC-1α/FNDC5/BDNF pathway in the hippocampus (p < 0.05). Interestingly, exercise training attenuated all the neuropathological changes mentioned above (p < 0.05). These results imply that exercise training restored behavioral, biochemical, and molecular changes against reserpine-induced FM-like symptoms in rats, hence mitigating the behavioral abnormalities linked to pain, depression, and cognitive functioning.

Establishment of a zebrafish inbred strain, M-AB, capable of regular breeding and genetic manipulation

Inbred strains of organisms are genetically highly uniform and thus useful for life science research. We have previously reported the ongoing generation of the zebrafish IM strain from the India (IND) strain through full sib-pair mating for 16 generations. However, the IM fish laid a small number of offspring and had a short lifespan, implying the need for discreet care in breeding. Here, we report the subsequent establishment of IM strain as well as the generation of a new inbred zebrafish strain, Mishima-AB (M-AB). M-AB was derived from the *AB strain by full sib-pair mating for over 20 generations, which fulfills the general criterion for the establishment of an inbred strain. In contrast to the IM case, maintenance of the M-AB strain by sib-pair mating required almost no special handling. Genome sequencing of IM individuals from the 47th generation and M-AB individuals from the 27th generation revealed that SNP-based genomic heterogeneity across whole-genome nucleotides was 0.008% and 0.011%, respectively. These percentages were much lower than those of the parental IND (0.197%) and *AB (0.086%) strains. These results indicate that the genomes of these inbred strains were highly homogenous. We also demonstrated the successful microinjection of antisense morpholinos, CRISPR/Cas9, and foreign genes into M-AB embryos at the 1-cell stage. Overall, we report the establishment of a zebrafish inbred strain, M-AB, which is capable of regular breeding and genetic manipulation. This strain will be useful for the analysis of genetically susceptible phenotypes such as behaviors, microbiome features and drug susceptibility.

Long-term calorie restriction prevented memory impairment in middle-aged male mice and increased a marker of DNA oxidative stress in hippocampal dentate gyrus

Calorie restriction (CR) is a non-invasive and economic approachknown to increase healthspan and life expectancy, through a decrease in oxidative stress, an increase in neurotrophins, among other benefits. However, it is not clear whether its benefit could be noted earlier, as at the beginning of middle-age. Hence, weaimed to determine whether six months of long-term CR, from early adulthood to the beginning of middle age (10 months of age) could positively affect cognitive, neurochemical, and behavioral parameters. Male C57BL6/J mice were randomly distributed into Young Control (YC, ad libitum food), Old Control (OC, ad libitum food), and Old Restricted (OR, 30 % of caloric restriction) groups. To analyze the cognitive and behavioral aspects, the novel object recognition task (NOR), open field, and elevated plus maze tests were performed. In addition, immunohistochemistry targetingΔFosB (neuronal activity), brain-derived neurotrophic factor (BDNF) and the DNA oxidative damage (8OHdG) in hippocampal subfields CA1, CA2, CA3, and dentate gyrus (DG), and in basolateral amygdala and striatum were performed. Our results showed that long-term CR prevented short-term memory impairment related to aging and increased 8OHdG in hippocampal DG. BDNF was not involved in the effects of either age or CR on memory at middle-age, as it increased in CA3 of the OC group but was not altered in OR. Regarding anxiety-type behavior, no parameter showed differences between the groups. In conclusion, while the effects of long-term CR on anxiety-type behavior were inconclusive, it mitigated the memory deficit related to aging, which was accompanied by an increase in hippocampal 8OHdG in DG. Future studies should investigate whether the benefits of CR would remain if the restriction were interrupted after this long-term protocol.

Appetitively motivated tasks in the IntelliCage reveal a higher motivational cost of spatial learning in male than female mice

The IntelliCage (IC) permits the assessment of the behavior and learning abilities of mice in a social home cage context. To overcome water deprivation as an aversive driver of learning, we developed protocols in which spatial learning is motivated appetitively by the preference of mice for sweetened over plain water. While plain water is available at all times, only correct task responses give access to sweetened water rewards. Under these conditions, C57BL/6J mice successfully mastered a corner preference task with the reversal and also learned a more difficult time-place task with reversal. However, the rate of responding to sweetened water decreased strongly with increasing task difficulty, indicating that learning challenges and reduced success in obtaining rewards decreased the motivation of the animals to seek sweetened water. While C57BL/6J mice of both sexes showed similar initial taste preferences and learned similarly well in simple learning tasks, the rate of responding to sweetened water and performance dropped more rapidly in male than in female mice in response to increasing learning challenges. Taken together, our data indicate that male mice can have a disadvantage relative to females in mastering difficult, appetitively motivated learning tasks, likely due to sex differences in value-based decision-making.

Three methods of behavioural testing to measure anxiety - A review

Behavioural test is very useful to assess the anxiety activity, screen new anxiolytic drugs, explore the pathogenesis of anxiety disorders. Methods of behavioural testing that reflects different aspects of anxiety emotionality simultaneously have always been a critical issue for academics. In this paper, we reviewed previous methods to use behavioural test to evaluate the anxiety activity. A single test was used to measure only one aspect of anxiety emotionality. A battery of behavioural tests could get a comprehensive information of anxiety profile. In one single trial, open field test, elevated plus maze and light/dark box are integrated to assess different types of emotional behaviours. This new paradigm is useful for evaluating multiple dimensions of behaviours simultaneously, minimizing general concerns about previous test experience and inter-test intervals between tests. It is proposed as a promising alternative to using test battery.

Mice Recognise Mice in Neighbouring Rearing Cages and Change Their Social Behaviour

Mice are social animals that change their behaviour primarily in response to visual, olfactory, and auditory information from conspecifics. Rearing conditions such as cage size and colour are important factors influencing mouse behaviour. In recent years, transparent plastic cages have become standard breeding cages. The advantage of using a transparent cage is that the experimenter can observe the mouse from outside the cage without touching the cage. However, mice may recognise the environment outside the cage and change their behaviour. We speculated that mice housed in transparent cages might recognise mice in neighbouring cages. We used only male mice in this experiment. C57BL/6 mice were kept in transparent rearing cages with open lids, and the cage positions were maintained for 3 weeks. Subsequently, we examined how mice behaved toward cagemate mice, mice from neighbouring cages, and mice from distant cages. We compared the level of interest in mice using a social preference test. Similar to previous reports, subject mice showed a high degree of interest in unfamiliar mice from distant cages. By contrast, subject mice reacted to mice from neighbouring cages as familiar mice, similar to cagemate mice. This suggests that mice housed in transparent cages with open lids perceive the external environment and identify mice in neighbouring cages. Researchers should pay attention to the environment outside the mouse cage, especially for the social preference test.

Effects of home-cage elevation on behavioral tests in mice

BACKGROUND

Research reproducibility is a common problem in preclinical behavioral science. Mice are an important animal model for studying human behavioral disorders. Experimenters, processing methods, and rearing environments are the main causes of data variability in behavioral neuroscience. It is likely that mice adapt their behavior according to the environment outside the breeding cage. We speculated that mice housed on elevated shelves and mice housed on low shelves might have differently altered anxiety-like behavior toward heights.

PURPOSE

The purpose of this study was to investigate potential behavioral changes in mice raised at different heights for 3 weeks. Changes in behavior were examined using various experimental tests.

RESULTS

Mice housed on elevated shelves showed reduced anxiety-like behavior in a light/dark traffic test compared with mice housed on low shelves. There were no significant differences between the two groups in terms of activity, exploratory behavior, muscle strength, or depression-like behavior.

CONCLUSIONS

Our results indicate that different cage heights and corresponding light exposure may alter the anxiety-like behavior of mice in response to brightness. Researchers need to carefully control the cage height and light intensity experienced by the mice to produce reproducible test results.

Sex differences in avoidance behavior and cued threat memory dynamics in mice: Interactions between estrous cycle and genetic background

Anxiety disorders are the most prevalent mental illnesses worldwide, exhibit high heritability, and affect twice as many women as men. To evaluate potential interactions between genetic background and cycling ovarian hormones on sex differences in susceptibility to negative valence behaviors relevant to anxiety disorders, we assayed avoidance behavior and cued threat memory dynamics in gonadally-intact adult male and female mice across four common inbred mouse strains: C57Bl/6J, 129S1/SVlmJ, DBA/2J, and BALB/cJ. Independent of sex, C57Bl/6J mice exhibited low avoidance but high threat memory, 129S1/SvlmJ mice high avoidance and high threat memory, DBA/2J mice low avoidance and low threat memory, and BALB/cJ mice high avoidance but low threat memory. Within-strain comparisons revealed reduced avoidance behavior in the high hormone phase of the estrous cycle (proestrus) compared to all other estrous phases in all strains except DBA/2J, which did not exhibit cycle-dependent behavioral fluctuations. Robust and opposing sex differences in threat conditioning and extinction training were found in the C57Bl/6J and 129S1/SvlmJ lines, whereas no sex differences were observed in the DBA/2J or BALB/cJ lines. C57Bl/6J males exhibited enhanced acute threat memory, whereas 129S1/SvlmJ females exhibited enhanced sustained threat memory, compared to their sex-matched littermates. These effects were not mediated by estrous cycle stage or sex differences in active versus passive defensive behavioral responses. Our data demonstrate that core features of behavioral endophenotypes relevant to anxiety disorders, such as avoidance and threat memory, are genetically driven yet dissociable and can be influenced further by cycling ovarian hormones.

Behavioral and genetic architecture of fear conditioning and related phenotypes

Contextual fear conditioning is a form of Pavlovian learning during which an organism learns to fear previously neutral stimuli following their close temporal presentation with an aversive stimulus. In mouse models, freezing behavior is typically used to quantify learned fear. This dependent variable is the sum of multiple processes, including associative/configural learning, fear and anxiety, and general activity. To explore phenotypic constructs underlying contextual fear conditioning and correlated behaviors, as well as factors that may contribute to individual differences in learning and mental health, we tested BXD recombinant inbred strains previously found to show extreme contextual fear conditioning phenotypes and BXD parental strains, C57BL/6J and DBA/2J, in a series of tests including locomotor, anxiety, contextual/cued fear conditioning and non-associative hippocampus-dependent learning behaviors. Hippocampal expression of two previously identified candidate genes for contextual fear conditioning was also quantified. Behavioral and gene expression data were analyzed using exploratory factor analysis (EFA), which suggested five unique constructs representing activity/anxiety/exploration, associative fear learning, anxiety, post-shock freezing, and open field activity phenotypes. Associative fear learning and expression of one candidate gene, Hacd4, clusteredas a construct withinthefactor analysis. Post-shock freezingduring fear conditioning and expression of candidate gene Ptprd emerged as another unique construct, highlighting theindependenceof freezing after footshock from other fear conditioning variables in the current dataset.EFA results additionally suggest shared phenotypic variance in adaptive murine behaviors related to anxiety, general activity, and exploration. These findings inform understanding of fear learning and underlying biological mechanisms that may interact to produce individual differences in fear- and learning-related behaviors in mice.

Acute repeated cage exchange stress modifies urinary stress and plasma metabolic profiles in male mice

Exposure to a novel environment is psychologically and physically stressful for humans and animals. The response has been reported to involve enhanced sympathetic nervous system activity, but changes in nutrient levels under stress are not fully understood. As a form of exposure to a novel environment, repeated cage exchange (CE, four times at 2-h intervals for 8 h from 08:00 h) during the light phase with no restraint on movement was applied to A/J mice, a strain particularly prone to stress. Body temperature was measured with a temperature-sensing microchip implanted in the interscapular region. The stress conditions and anxiety level were evaluated by measuring urinary catecholamines and corticosterone and by performing an anxiety-like behavior test, respectively. Major nutrients such as glucose, fatty acids, and amino acids in the plasma were also examined. CE mice showed a significant increase in body temperature with each CE. They also showed a significantly greater reduction of body weight change, more water intake, and higher levels of urinary catecholamines and corticosterone and anxiety-like behavior score than control mice. The model revealed a significantly lower plasma glucose level and higher levels of several essential amino acids, such as branched-chain amino acids and phenylalanine, than those of control mice. Meanwhile, free fatty acids and several amino acids such as arginine, aspartic acid, proline, threonine, and tryptophan in both sets of mice were significantly decreased from the corresponding levels at 08:00 h, while similar plasma levels were exhibited between mice with and without CE. In conclusion, repeated CE stress was associated with changes in glucose and amino acids in plasma. Although further study is needed to clarify how these changes are specifically linked to anxiety-like behavior, this study suggests the potential for nutritional intervention to counter stress in humans exposed to novel environments.

Acclimation and Blood Sampling: Effects on Stress Markers in C57Bl/6J Mice

Blood sampling in rodents is common practice in scientific studies. Some of the refined methods widely used are the puncture of the saphenous vein or tail vein, or even tail docking. The handling needs of these different blood sampling methods are different and can directly affect stress, increasing the variability of the study. Moreover, there is less aversion and stress if the animal is accustomed to the environment, handling and technique. Therefore, our study aimed to assess the influence of these three blood sampling techniques (saphenous puncture, tail vein puncture and tail vein docking) and the use of previous acclimation on different indicators of animal stress, assessing blood glucose concentrations and faecal corticosterone metabolites (FCMs). Twenty-four young adult male and female C57Bl6/J mice were divided in three groups by sampling method: tail docking (TD), saphenous vein puncture (SV) and caudal vein puncture (CV) groups. All mice were studied with and without acclimation, which was performed during 9 consecutive days. The results showed that both males and females present very similar responses to the different handling and sampling methods without significant differences. Nevertheless, acclimation in all sampling methods decreased glucose and FCM levels significantly. The method that obtained the lowest glucose and FCM levels with significance was saphenous vein puncture. Therefore, we can say that it causes less stress when performing prior acclimation, even when this involves greater handling of the animal. Our results contribute to refinement within the 3R concept and could serve researchers to programme and select a good handling technique and a welfare-friendly blood sampling method for their experiments.

Classification of multiple emotional states from facial expressions in head-fixed mice using a deep learning-based image analysis

Facial expressions are widely recognized as universal indicators of underlying internal states in most species of animals, thereby presenting as a non-invasive measure for assessing physical and mental conditions. Despite the advancement of artificial intelligence-assisted tools for automated analysis of voluminous facial expression data in human subjects, the corresponding tools for mice still remain limited so far. Considering that mice are the most prevalent model animals for studying human health and diseases, a comprehensive characterization of emotion-dependent patterns of facial expressions in mice could extend our knowledge on the basis of emotions and the related disorders. Here, we present a framework for the development of a deep learning-powered tool for classifying facial expressions in head-fixed mouse. We demonstrate that our machine vision was capable of accurately classifying three different emotional states from lateral facial images in head-fixed mouse. Moreover, we objectively determined how our classifier characterized the differences among the facial images through the use of an interpretation technique called Gradient-weighted Class Activation Mapping. Importantly, our machine vision presumably discerned the data by leveraging multiple facial features. Our approach is likely to facilitate the non-invasive decoding of a variety of emotions from facial images in head-fixed mice.

Nature and nurture: comparing mouse behavior in classic versus revised anxiety-like and social behavioral assays in genetically or environmentally defined groups

Widely used rodent anxiety assays like the elevated plus maze (EPM) and the open field test (OFT) are often conflated with rodents' natural preference for dark over light environments or protected over open spaces. The EPM and OFT have been used for many decades, yet have also been criticized by generations of behavioral scientists. Several years ago, two revised anxiety assays were designed to improve upon the "classic" tests by excluding the possibility to avoid or escape aversive areas of each maze. The 3-D radial arm maze (3DR) and the 3-D open field test (3Doft) each consist of an open space connected to ambiguous paths toward uncertain escape. This introduces continual motivational conflict, thereby increasing external validity as an anxiety model. But despite this improvement, the revised assays have not caught on. One issue may be that studies to date have not directly compared classic and revised assays in the same animals. To remedy this, we contrasted behavior in a battery of assays (EPM, OFT, 3DR, 3Doft, and a sociability test) in mice defined either genetically by isogenic strain, or environmentally by postnatal experience. Findings indicate that the optimal assay to assess anxiety-like behavior may depend upon grouping variable (e.g. genetic versus environment). We argue that the 3DR may be the most ecologically valid of the anxiety assays tested, while the OFT and 3Doft provided the least useful information. Finally, exposure to multiple assays significantly affected sociability measures, raising concerns for designing and interpreting batteries of behavioral tests in mice.

Strain-dependent effects on neurobehavioral and seizure phenotypes in Scn2aK1422E mice

Pathogenic variants in SCN2A are associated with a range of neurodevelopmental disorders (NDD). Despite being largely monogenic, SCN2A-related NDD show considerable phenotypic variation and complex genotype-phenotype correlations. Genetic modifiers can contribute to variability in disease phenotypes associated with rare driver mutations. Accordingly, different genetic backgrounds across inbred rodent strains have been shown to influence disease-related phenotypes, including those associated with SCN2A-related NDD. Recently, we developed a mouse model of the variant SCN2A-p.K1422E that was maintained as an isogenic line on the C57BL/6J (B6) strain. Our initial characterization of NDD phenotypes in heterozygous Scn2aK1422E mice revealed alterations in anxiety-related behavior and seizure susceptibility. To determine if background strain affects phenotype severity in the Scn2aK1422E mouse model, phenotypes of mice on B6 and [DBA/2J×B6]F1 hybrid (F1D2) strains were compared. Convergent evidence from neurobehavioral assays demonstrated lower anxiety-like behavior in Scn2aK1422E mice compared to wild-type and further suggested that this effect is more pronounced on the B6 background compared to the F1D2 background. Although there were no strain-dependent differences in occurrence of rare spontaneous seizures, response to the chemoconvulsant kainic acid revealed differences in seizure generalization and lethality risk, with variation based on strain and sex. Continued examination of strain-dependent effects in the Scn2aK1422E mouse model could reveal genetic backgrounds with unique susceptibility profiles that would be relevant for future studies on specific traits and enable the identification of highly penetrant phenotypes and modifier genes that could provide clues about the primary pathogenic mechanism of the K1422E variant.

The animacy advantage in memory occurs under self-paced study conditions, but participants' metacognitive beliefs can deter it

Introduction

Animacy distinguishes living (animate) things from non-living (inanimate) things. People tend to devote attention and processing to living over nonliving things, resulting in a privileged status for animate concepts in human cognition. For example, people tend to remember more animate than inanimate items, a phenomenon known as the "animacy effect" or "animacy advantage." To date, however, the exact cause(s) of this effect is unknown.

Methods

We examined the animacy advantage in free-recall performance under computer-paced versus self-paced study conditions and using three different sets of animate and inanimate stimuli (Experiments 1 and 2). We also measured participants' metacognitive beliefs (expectations) about the task before it began (Experiment 2).

Results

We consistently obtained an animacy advantage in free-recall, regardless of whether participants studied the materials under computer-paced or self-paced conditions. Those in self-paced conditions spent less time studying items than did those in computer-paced conditions, but overall levels of recall and the occurrence of the animacy advantage were equivalent by study method. Importantly, participants devoted equivalent study time to animate and inanimate items in self-paced conditions, so the animacy advantage in those conditions cannot be attributed to study time differences. In Experiment 2, participants who believed that inanimate items were more memorable instead showed equivalent recall and study time for animate and inanimate items, suggesting that they engaged in equivalent processing of animate and inanimate items. All three sets of materials reliably produced an animacy advantage, but the effect was consistently larger for one set than the other two, indicating some contribution of item-level properties to the effect.

Discussion

Overall, the results suggest that participants do not purposely allocate greater processing to animate over inanimate items, even when study is self-paced. Rather, animate items seem to naturally trigger greater richness of encoding than do inanimate items and are then better remembered, although under some conditions participants might engage in deeper processing of inanimate items which can reduce or eliminate the animacy advantage. We suggest that researchers might conceptualize mechanisms for the effect as either centering on intrinsic, item-level properties of the items or centering on extrinsic, processing-based differences between animate and inanimate items.

Age, β-endorphin, and sex dependent effects of maternal separation on locomotor activity, anxiety-like behavior, and alcohol reward

Introduction

Childhood adversity is pervasive and linked to numerous disadvantages in adulthood, including physical health problems, mental illness, and substance use disorders. Initial sensitivity to the rewarding effects of alcohol predicts the risk of developing an alcohol use disorder, and may be linked to developmental stress. The opioid peptide β-endorphin (β-E) regulates the stress response and is also implicated in the risk for excessive alcohol consumption.

Methods

We explored the influence of β-E in an animal model of early life adversity using controlled maternal separation by evaluating changes in locomotor activity, anxiety-like behavior, and the initial rewarding effects of alcohol in a single exposure conditioned place preference paradigm in control C57BL/6J and β-E deficient β-E +/+ 0.129S2-Pomc tm1Low/J; β-E −/− mice. Maternal separation (MS) occurred for 3 h each day from post-natal days (PND) 5–18 in approximately half the subjects.

Results

Maternal interactions increased following the separation protocol equally in both genotypes. MS and control subjects were tested as adolescents (PND 26–32) or adults (PND 58–72); the effects of MS were generally more pronounced in older subjects. Adults were more active than adolescents in the open field, and MS decreased activity in adolescent mice but increased it in adults. The increase in adult activity as a result of early life stress depended on both β-E and sex. β-E also influenced the effect of maternal separation on anxiety-like behavior in the Elevated Plus Maze. MS promoted rewarding effects of alcohol in male β-E deficient mice of either age, but had no effect in other groups.

Discussion

Taken together, these results suggest that the effects of MS develop over time and are β-E and sex dependent and may aid understanding of how individual differences influence the impact of adverse childhood experiences.

Lactiplantibacillus plantarum N-1 improves autism-like behavior and gut microbiota in mouse

Introduction

The gut-brain axis has been widely recognized in autism spectrum disorder (ASD), and probiotics are considered to potentially benefit the rescuing of autism-like behaviors. As a probiotic strain, Lactiplantibacillus plantarumN-1(LPN-1) was utilized to investigate its effects on gut microbiota and autism-like behaviors in ASD mice constructed by maternal immune activation (MIA).

Methods

Adult offspring of MIA mice were given LPN-1 at the dosage of 2  ×  109  CFU/g for 4  weeks before subject to the behavior and gut microbiota evaluation.

Results

The behavioral tests showed that LPN-1 intervention was able to rescue autism-like behaviors in mice, including anxiety and depression. In which the LPN-1 treatment group increased the time spent interacting with strangers in the three-chamber test, their activity time and distance in the central area increased in the open field test, and their immobility time decreased when hanging their tails. Moreover, the supplementation of LPN-1 reversed the intestinal flora structure of ASD mice by enhancing the relative abundance of the pivotal microorganisms of Allobaculum and Oscillospira, while reducing those harmful ones like Sutterella at the genus level.

Discussion

These results suggested that LPN-1 supplementation may improve autism-like behaviors, possibly via regulating the gut microbiota.

Oxytocin receptor is not required for social attachment in prairie voles

Prairie voles are among a small group of mammals that display long-term social attachment between mating partners. Many pharmacological studies show that signaling via the oxytocin receptor (Oxtr) is critical for the display of social monogamy in these animals. We used CRISPR mutagenesis to generate three different Oxtr-null mutant prairie vole lines. Oxtr mutants displayed social attachment such that males and females showed a behavioral preference for their mating partners over a stranger of the opposite sex, even when assayed using different experimental setups. Mothers lacking Oxtr delivered viable pups, and parents displayed care for their young and raised them to the weanling stage. Together, our studies unexpectedly reveal that social attachment, parturition, and parental behavior can occur in the absence of Oxtr signaling in prairie voles.

Fighting secondary triple-negative breast cancer in cerebellum: A powerful aid from a medicinal mushrooms blend

Breast cancer (BC) is the second most common cause of brain metastasis onset in patients, with the cerebellum accounting for the 33% of cases. In the current study, using a 4T1 triple-negative mouse BC model, we revealed that an orally administered medicinal mushrooms (MM) blend, rich in β-glucans, played a direct and specific anti-cancer action on cerebellar metastases, also bettering locomotor performances. The neuroprotective effect of the MM blend plays through (i) a direct and specific inhibition of cerebellar metastatization pattern typical of TNBC (with an induced reduction of about 50% of metastases density) and (ii) the regulation of apoptosis and proliferation-related genes, as suggested by expression changes of specific molecular markers, i.e. PCNA, p53, Bcl2, BAX, CASP9, CASP3, Hsp70 and AIF. Therefore, inhibiting the metastatization process, triggering a significant apoptosis increase, and lessening cell proliferation, this MM supplement, employed as adjuvant treatment in association with conventional therapy, could represent a promising approach, in the field of Integrative Oncology, for patients' management in both prevention and treatment of brain metastases from BC.

Twenty years of discoveries emerging from mouse models of autism

More than 100 single gene mutations and copy number variants convey risk for autism spectrum disorder. To understand the extent to which each mutation contributes to the trajectory of individual symptoms of autism, molecular genetics laboratories have introduced analogous mutations into the genomes of laboratory mice and other species. Over the past twenty years, behavioral neuroscientists discovered the consequences of mutations in many risk genes for autism in animal models, using assays with face validity to the diagnostic and associated behavioral symptoms of people with autism. Identified behavioral phenotypes complement electrophysiological, neuroanatomical, and biochemical outcome measures in mutant mouse models of autism. This review describes the history of phenotyping assays in genetic mouse models, to evaluate social and repetitive behaviors relevant to the primary diagnostic criteria for autism. Robust phenotypes are currently employed in translational investigations to discover effective therapeutic interventions, representing the future direction of an intensely challenging research field.

Ghrelin receptor agonist MK0677 and overnight fasting do not rescue deficient fear extinction in 129S1/SvImJ mice

The hunger hormone ghrelin has been implicated in the modulation of anxiety- and fear-related behaviors in rodents and humans, while its dysregulation may be associated with psychiatric illness. Along these lines, the ghrelin system has been suggested as a potential target to facilitate fear extinction, which is the main mechanism underlying cognitive behavioral therapy. So far, this hypothesis has not been tested in individuals that have difficulties to extinguish fear. Thus, we investigated pharmacological (ghrelin receptor agonist MK0677) and non-pharmacological (overnight fasting) strategies to target the ghrelin system in the 129S1/SvImJ (S1) mouse strain, which models the endophenotype of impaired fear extinction that has been associated with treatment resistance in anxiety and PTSD patients. MK0677 induced food intake and overnight fasting increased plasma ghrelin levels in S1 mice, suggesting that the ghrelin system is responsive in the S1 strain. However, neither systemic administration of MK0677 nor overnight fasting had an effect on fear extinction in S1 mice. Similarly, our groups previously reported that both interventions did not attenuate fear in extinction-competent C57BL/6J mice. In summary, our findings are in contrast to several studies reporting beneficial effects of GHSR agonism and overnight fasting on fear- and anxiety-related behaviors in rodents. Rather, our data agree with accumulating evidence of divergent behavioral effects of ghrelin system activation and underscore the hypothesis that potential benefits of targeting the ghrelin system in fear extinction may be dependent on factors (e.g., previous stress exposure) that are not yet fully understood.

Sex-Specific Differences in the Transcriptome of the Human Dorsolateral Prefrontal Cortex in Schizophrenia

Schizophrenia presents clinical and biological differences between males and females. This study investigated transcriptional profiles in the dorsolateral prefrontal cortex (DLPFC) using postmortem data from the largest RNA-sequencing (RNA-seq) database on schizophrenic cases and controls. Data for 154 male and 113 female controls and 160 male and 93 female schizophrenic cases were obtained from the CommonMind Consortium. In the RNA-seq database, the principal component analysis showed that sex effects were small in schizophrenia. After we analyzed the impact of sex-specific differences on gene expression, the female group showed more significantly changed genes compared with the male group. Based on the gene ontology analysis, the female sex-specific genes that changed were overrepresented in the mitochondrion, ATP (phosphocreatine and adenosine triphosphate)-, and metal ion-binding relevant biological processes. An ingenuity pathway analysis revealed that the differentially expressed genes related to schizophrenia in the female group were involved in midbrain dopaminergic and γ-aminobutyric acid (GABA)-ergic neurons and microglia. We used methylated DNA-binding domain-sequencing analyses and microarray to investigate the DNA methylation that potentially impacts the sex differences in gene transcription using a maternal immune activation (MIA) murine model. Among the sex-specific positional genes related to schizophrenia in the PFC of female offspring from MIA, the changes in the methylation and transcriptional expression of loci ACSBG1 were validated in the females with schizophrenia in independent postmortem samples by real-time PCR and pyrosequencing. Our results reveal potential genetic risks in the DLPFC for the sex-dependent prevalence and symptomology of schizophrenia.

Partial changes in apoptotic pathways in hippocampus and hypothalamus of Cc2d1a heterozygous

Alterations in the apoptosis pathway have been linked to changes in serotonin levels seen in autistic patients. Cc2d1a is a repressor of the HTR1A gene involved in the serotonin pathway. The hippocampus and hypothalamus of Cc2d1a ± mice were analyzed for the expression of apoptosis markers (caspase 3, 8 and 9). Gender differences were observed in the expression levels of the three caspases consistent with some altered activity in the open-field assay. The number of apoptotic cells was significantly increased. We concluded that apoptotic pathways are only partially affected in the pathogenesis of the Cc2d1a heterozygous mouse model. A) Apoptosis is suppressed because the cell does not receive a death signal, or the receptor cannot activate the caspase 8 pathway despite the death signal. B) Since Caspase 8 and Caspase 3 expression is downregulated in our mouse model, the mechanism of apoptosis is not activated.

Differential patterns of opioid and dopamine D1 receptor antagonism on nutritive and non-nutritive sweetener intakes in C57BL/6:129 hybrid mice relative to inbred C57BL/6 and 129 mice

Opioid and dopamine (DA) D1 receptor antagonists differentially reduce nutritive and non-nutritive sweetener intakes in inbred mouse strains. Sucrose intake was more effectively reduced by naltrexone in C57BL/6 (B6) mice relative to 129P3 (129) mice, but more effectively reduced by SCH23390 in 129 mice relative to B6 mice. Opioid and DA D1 antagonists differentially reduced saccharin intakes in B6 mice relative to other strains. Given these differential patterns in sweetener intake in B6 and 129 mice, the present study examined whether systemic naltrexone (0.01-5 mg/kg) and SCH23390 (50-1600 nmol/kg) reduced intakes of 10 % sucrose or 0.2 % saccharin solutions over a 120 min time course in first-generation hybrid mice (B6:129) of B6 and 129 parents and reduced low-nutritive sweetener intakes in 129 mice. Naltrexone (5 mg/kg) significantly reduced 10 % sucrose intake in B6:129 hybrid mice more like that of 129 than B6 mice. In contrast, SCH23390 (400-1600 nmol/kg) reduced 10 % sucrose intake in B6:129 hybrid mice more effectively than that observed in B6 or 129 parental strains. Because 129 mice consumed relatively low amounts of 0.2 % saccharin, they were tested with a more attractive low-nutritive solution containing 0.2 % saccharin and 2 % sucrose. Naltrexone failed to reduce saccharin intake in B6:129 hybrid mice but suppressed saccharin+sucrose intake in 129 mice more like that observed in B6 mice. SCH23390 similarly inhibited saccharin or saccharin+sucrose intakes in hybrid B6:129, 129, and B6 mice with B6 mice more resistant to the lowest SCH23390 dose. Thus, whereas sucrose intake in B6:129 hybrid mice exhibited similar sensitivity to opioid and to a lesser degree DA D1 antagonism to their 129, but not B6 parents, opioid and DA D1 mediation of low- and non-nutritive sweet intake produced unique profiles among B6:129 hybrid and B6 and 129 strains which does not support a simple heritability explanation.

Cognitive impairment, depressive-like behaviors and hippocampal microglia activation following exposure to air pollution nanoparticles

Air pollution particulate matter (PM) is a world risk factor that the effects of long-term exposure to these factors in terms of damage to cardiovascular and pulmonary function are well known, but little is known comparatively about the effects of PM on emotional and cognitive processes. Exposure to PM can adversely affect the central nervous system (CNS) by inflammatory pathways and activation of reactive oxygen species (ROS) associated with urban air pollution PM. Therefore, we investigated whether prolonged exposure to diesel exhaust particles (DEPs) affects hippocampal inflammatory cytokines and emotional and cognition responses. Male mice were exposed to DEPs for 6 and 12 weeks. DEP-exposed mice indicated more disorders in depressive-like responses and spatial memory and learning than in control groups. Pro-inflammatory cytokine expression in tge hippocampus was increased among mice exposed to DEPs. The number of activated microglia increased in the dentate gyrus (DG) and CA1 regions of the hippocampus in DEP-exposed mice. These results show that chronic exposure to DEPs can alter neurobehavioral and impair cognition. Generally, these findings reaffirm the importance of protecting from exposure to ambient PM2.5 and also advance our understanding of the toxic actions of air pollution nanoparticles.

Male scent but not courtship vocalizations induce estrus in wild female house mice

Exposure to males or male urinary scent can induce and accelerate the rate of female estrous cycling in house mice ("Whitten effect"), and this response has been replicated many times since its discovery over 60 years ago. Here, we tested whether exposing female mice to recordings of male courtship ultrasonic vocalizations (USVs) induces estrous cycling, and whether exposure to both male scent and USVs has a stronger effect than to either of these stimuli alone. We conducted our study with 60 wild-derived female house mice (Mus musculus musculus). After singly housing females for 14 days, we monitored estrous stages via vaginal cytology for two weeks while isolated from males or male stimuli. We continued monitoring estrus for two more weeks during experimental exposure to one of four different types of stimuli: (1) clean bedding and background noise playback (negative control); (2) recordings of male USVs (16 min per day) and clean bedding (male USV treatment); (3) soiled male bedding and background noise playback (male odor treatment; positive control); or (4) male USVs and soiled male bedding (male odor and USV treatment). Females were then paired with males to test whether any of the four treatments influenced female reproduction (especially latency to birth). We confirmed that exposure to male odor increased female cycling, as expected, but exposure to recordings of male USVs had no effect on estrus. Females exposed to both USVs and odor went through more cycles compared to controls, but did not differ significantly from exposure to male odor (and background noise). After pairing females with a male, females showing male odor-induced cycling produced their first litter sooner than controls, whereas USVs did not have such an effect. This is the first study to our knowledge to show that male odor induces estrus in wild house mice and to show functional effects on reproduction. Our results do not support the hypothesis that male vocalizations induce female estrus, although we suggest other approaches that could be used to further test this hypothesis.

Modeling integrated stress, sleep, fear and neuroimmune responses: Relevance for understanding trauma and stress-related disorders

Sleep and stress have complex interactions that are implicated in both physical diseases and psychiatric disorders. These interactions can be modulated by learning and memory, and involve additional interactions with the neuroimmune system. In this paper, we propose that stressful challenges induce integrated responses across multiple systems that can vary depending on situational variables in which the initial stress was experienced, and with the ability of the individual to cope with stress- and fear-inducing challenges. Differences in coping may involve differences in resilience and vulnerability and/or whether the stressful context allows adaptive learning and responses. We provide data demonstrating both common (corticosterone, SIH and fear behaviors) and distinguishing (sleep and neuroimmune) responses that are associated with an individual's ability to respond and relative resilience and vulnerability. We discuss neurocircuitry regulating integrated stress, sleep, neuroimmune and fear responses, and show that responses can be modulated at the neural level. Finally, we discuss factors that need to be considered in models of integrated stress responses and their relevance for understanding stress-related disorders in humans.

Conditioned medium from BV2 microglial cells having polyleucine specifically alters startle response in mice

Repeat-associated non-AUG translation (RAN translation) is observed in transcripts that are causative for polyglutamine (polyQ) diseases and generates proteins with mono amino acid tracts such as polyalanine (polyA), polyleucine (polyL) and polyserine (polyS) in neurons, astrocytes and microglia. We have previously shown that microglia with aggregated polyQ led to defective differentiation and degeneration of neuron-like cells. However, it has not been determined whether only microglia containing a specific RAN product, but not other RAN products, is harmful in vitro and in vivo. Here we show that polyL-incorporating microglia specifically led to altered startle response in mice. Aggregated polyA, polyS and polyL induced aberrant differentiation of microglia-like BV2 cells. Differentiated PC12 cells treated with conditioned medium (CM) of polyS- and polyL- but not polyA-incorporating microglia-like BV2 cells showed retraction of neurites and loss of branch of neurites. Injection of the polyL-CM, but not polyA-CM and polyS-CM, into the lateral ventricle lowered startle response in mice. Consistently, polyL induced the highest expression of CD68 in BV2 cells. The lowered startle response was replicated in mice given the polyL-CM in the caudal pontine reticular nucleus (PnC), the key region of startle response. Thus, endogenous RAN proteins having polyL derived from polyQ diseases-causative genes in microglia might specifically impair startle response.

Biochemical and behavioural profile of NTBC treated Tyrosinemie type 1 mice

BACKGROUND

Tyrosinemia type 1 (HT1) is a rare metabolic disorder caused by a defect in the tyrosine catabolic pathway. Since HT1 patients are treated with NTBC, outcome improved and life expectancy greatly increased. However extensive neurocognitive and behavioural problems have been described, which might be related to treatment with NTBC, the biochemical changes induced by NTBC, or metabolites accumulating due to the enzymatic defect characterizing the disease.

OBJECTIVE

To study the possible pathophysiological mechanisms of brain dysfunction in HT1, we assessed blood and brain LNAA, and brain monoamine neurotransmitter metabolite levels in relation to behavioural and cognitive performance of HT1 mice.

DESIGN

C57BL/6 littermates were divided in three different experimental groups: HT1, heterozygous and wild-type mice (n = 10; 5 male). All groups were treated with NTBC and underwent cognitive and behavioural testing. One week after behavioural testing, blood and brain material were collected to measure amino acid profiles and brain monoaminergic neurotransmitter levels.

RESULTS

Irrespective of the genetic background, NTBC treatment resulted in a clear increase in brain tyrosine levels, whereas all other brain LNAA levels tended to be lower than their reference values. Despite these changes in blood and brain biochemistry, no significant differences in brain monoamine neurotransmitter (metabolites) were found and all mice showed normal behaviour and learning and memory.

CONCLUSION

Despite the biochemical changes, NTBC and genotype of the mice were not associated with poorer behavioural and cognitive function of the mice. Further research involving dietary treatment of FAH-/- are warranted to investigate whether this reveals the cognitive impairments that have been seen in treated HT1 patients.

Confirmation of Decreased Rates of Cerebral Protein Synthesis In Vivo in a Mouse Model of Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder that results in intellectual disability and, in ∼50% of patients, autism spectrum disorder. The protein products that are altered in TSC (TSC1 and TSC2) form a complex to inhibit the mammalian target of rapamycin [mTOR; mTOR complex 1 (mTORC1)] pathway. This pathway has been shown to affect the process of mRNA translation through its action on ribosomal protein S6 and 4-elongation binding protein 1. It is thought that mutations in the TSC proteins lead to upregulation of the mTORC1 pathway and consequently an increase in protein synthesis. Unexpectedly, our previous study of a mouse model of TSC (Tsc2Djk +/) demonstrated decreased in vivo rates of protein synthesis throughout the brain. In the present study, we confirm those results in another Tsc2+/- mouse model, one with a different mutation locus and on a mixed background (Tsc2Mjg +/-). We also examine mTORC1 signaling and possible effects of prior isoflurane anesthesia. Because measurements of protein synthesis rates in vivo require surgical preparation of the animal and anesthesia, we examine mTORC1 signaling pathways both under baseline conditions and following recovery from anesthesia. Our results demonstrate regionally selective effects of prior anesthesia. Overall, our results in both in vivo models suggest differences to the central hypothesis regarding TSC and show the importance of studying protein synthesis in vivo Significance StatementProtein synthesis is an important process for brain function. In the disorder, tuberous sclerosis complex (TSC), the inhibition of the mammalian target of rapamycin (mTOR) pathway is reduced and this is thought to lead to excessive protein synthesis. Most studies of protein synthesis in models of TSC have been conducted in vitro We report here confirmation of our previous in vivo study showing decreased brain protein synthesis rates in a second mouse model of TSC, results counter to the central hypothesis regarding TSC. We also explore the possible influence of prior isoflurane exposure on signaling pathways involved in regulation of protein synthesis. This study highlights a novel aspect of TSC and the importance of studying cellular processes in vivo.

Not All Mice Are Created Equal: Interval Timing Accuracy and Scalar Timing in 129, Swiss-Webster, and C57BL/6 Mice

Many species, including humans, show both accurate timing − appropriate time estimation in the seconds to minutes range − and scalar timing − time estimation error varies linearly with estimated duration. Behavioral paradigms aimed at investigating interval timing are expected to evaluate these dissociable characteristics of timing. However, when evaluating interval timing in models of neuropsychiatric disease, researchers are confronted with a lack of adequate studies about the parent (background) strains, since accuracy and scalar timing have only been demonstrated for the C57BL/6 strain of mice (Buhusi, Aziz, Winslow, Carter, Swearingen, & Buhusi (2009) Behav. Neurosci., 123, 1102–1113). We used a peak-interval (PI) procedure with three intervals − a protocol in which other species, including humans, demonstrate accurate, scalar timing − to evaluate timing accuracy and scalar timing in three strains of mice frequently used in genetic and behavioral studies: 129, Swiss-Webster (SW), and C57BL/6. C57BL/6 mice showed accurate, scalar timing, while 129 and SW mice showed departures from accuracy and/or scalar timing. Results suggest that the genetic background/strain of the mouse is a critical variable for studies investigating interval timing in genetically engineered mice. Our study validates the PI procedure with multiple intervals as a proper technique, and the C57BL/6 strain as the most suitable genetic background to date for behavioral investigations of interval timing in genetically engineered mice modeling human disorders. In contrast, studies using mice in 129, SW, or mixed-background strains should be interpreted with caution, and thorough investigations of accuracy and scalar timing should be conducted before a less studied strain of mouse is considered for use in timing studies.

Exposure to urban air pollution particulate matter: neurobehavioral alteration and hippocampal inflammation

Air pollution is associated with many neurodevelopmental and neurological disorders in human populations. Rodent models show similar neurotoxic effects of urban air pollution ultrafine particulate matter (UFPs < 100 nm (PM0.1)), collected by different methods or from various sources. Exposure to ultrafine particulate matter (UFPs < 100 nm (PM0.1)) can be adversely impacting the central nervous system (CNS) by the activation of proinflammatory pathways and reactive oxygen species associated with air pollution particulate matter. We investigated hippocampal inflammatory cytokines, neurobehavioral alteration, and neuronal morphology following exposure to diesel exhaust particles (DEPs) in mice. Male mice were DEPs exposed for 14 weeks. Mice exposed to DEPs showed more disorders in spatial memory and learning and depressive-like responses than control mice. Expression of hippocampal pro-inflammatory cytokine was increased among DEPs exposure mice. The density of neurons in hippocampus CA1, CA3, and dentate gyrus (DG) regions decreased in DEPs mice. Overall, these findings show that prolonged exposure to DEPs in the world's major cities can alter neurobehavioral and impair cognition.

Inbred Mice Again at Stake: How the Cognitive Profile of the Wild-Type Mouse Background Discloses Pathogenic Effects of APP Mutations

Increasing efforts have been made in the last decades to increase the face validity of Alzheimer's disease (AD) mouse models. Main advancements have consisted in generating AD mutations closer to those identified in humans, enhancing genetic diversity of wild-type backgrounds, and choosing protocols much apt to reveal AD-like cognitive dysfunctions. Nevertheless, two aspects remain less considered: the cognitive specialization of inbred strains used as recipient backgrounds of mutations and the heuristic importance of studying destabilization of memory circuits in pre-symptomatic mice facing cognitive challenges. This article underscores the relevance of these behavioral/experimental aspects by reviewing data which show that (i) inbred mice differ in their innate predisposition to rely on episodic vs. procedural memory, which implicates differential sensitivity to mutations aimed at disrupting temporal lobe-dependent memory, and that (ii) investigating training-driven neural alterations in asymptomatic mutants unveils early synaptic damage, which considerably anticipates detection of AD first signs.

Behavioral characteristics of dopamine D5 receptor knockout mice

Major psychiatric disorders such as attention-deficit/hyperactivity disorder and schizophrenia are often accompanied by elevated impulsivity. However, anti-impulsive drug treatments are still limited. To explore a novel molecular target, we examined the role of dopamine D₅ receptors in impulse control using mice that completely lack D₅ receptors (D5KO mice). We also measured spontaneous activity and learning/memory ability because these deficits could confound the assessment of impulsivity. We found small but significant effects of D₅ receptor knockout on home cage activity only at specific times of the day. In addition, an analysis using the q-learning model revealed that D5KO mice displayed lower behavioral adjustment after impulsive actions. However, our results also showed that baseline impulsive actions and the effects of an anti-impulsive drug in D5KO mice were comparable to those in wild-type littermates. Moreover, unlike previous studies that used other D₅ receptor-deficient mouse lines, we did not observe reductions in locomotor activity, working memory deficits, or severe learning deficits in our line of D5KO mice. These findings demonstrate that D₅ receptors are dispensable for impulse control. Our results also indicate that time series analysis and detailed analysis of the learning process are necessary to clarify the behavioral functions of D₅ receptors.

Deep phenotyping reveals movement phenotypes in mouse neurodevelopmental models

BACKGROUND

Repetitive action, resistance to environmental change and fine motor disruptions are hallmarks of autism spectrum disorder (ASD) and other neurodevelopmental disorders, and vary considerably from individual to individual. In animal models, conventional behavioral phenotyping captures such fine-scale variations incompletely. Here we observed male and female C57BL/6J mice to methodically catalog adaptive movement over multiple days and examined two rodent models of developmental disorders against this dynamic baseline. We then investigated the behavioral consequences of a cerebellum-specific deletion in Tsc1 protein and a whole-brain knockout in Cntnap2 protein in mice. Both of these mutations are found in clinical conditions and have been associated with ASD.

METHODS

We used advances in computer vision and deep learning, namely a generalized form of high-dimensional statistical analysis, to develop a framework for characterizing mouse movement on multiple timescales using a single popular behavioral assay, the open-field test. The pipeline takes virtual markers from pose estimation to find behavior clusters and generate wavelet signatures of behavior classes. We measured spatial and temporal habituation to a new environment across minutes and days, different types of self-grooming, locomotion and gait.

RESULTS

Both Cntnap2 knockouts and L7-Tsc1 mutants showed forelimb lag during gait. L7-Tsc1 mutants and Cntnap2 knockouts showed complex defects in multi-day adaptation, lacking the tendency of wild-type mice to spend progressively more time in corners of the arena. In L7-Tsc1 mutant mice, failure to adapt took the form of maintained ambling, turning and locomotion, and an overall decrease in grooming. However, adaptation in these traits was similar between wild-type mice and Cntnap2 knockouts. L7-Tsc1 mutant and Cntnap2 knockout mouse models showed different patterns of behavioral state occupancy.

LIMITATIONS

Genetic risk factors for autism are numerous, and we tested only two. Our pipeline was only done under conditions of free behavior. Testing under task or social conditions would reveal more information about behavioral dynamics and variability.

CONCLUSIONS

Our automated pipeline for deep phenotyping successfully captures model-specific deviations in adaptation and movement as well as differences in the detailed structure of behavioral dynamics. The reported deficits indicate that deep phenotyping constitutes a robust set of ASD symptoms that may be considered for implementation in clinical settings as quantitative diagnosis criteria.

Secondary auditory cortex mediates a sensorimotor mechanism for action timing

The ability to accurately determine when to perform an action is a fundamental brain function and vital to adaptive behavior. The behavioral mechanism and neural circuit for action timing, however, remain largely unknown. Using a new, self-paced action timing task in mice, we found that deprivation of auditory, but not somatosensory or visual input, disrupts learned action timing. The hearing effect was dependent on the auditory feedback derived from the animal's own actions, rather than passive environmental cues. Neuronal activity in the secondary auditory cortex was found to be both correlated with and necessary for the proper execution of learned action timing. Closed-loop, action-dependent optogenetic stimulation of the specific task-related neuronal population within the secondary auditory cortex rescued the key features of learned action timing under auditory deprivation. These results unveil a previously underappreciated sensorimotor mechanism in which the secondary auditory cortex transduces self-generated audiomotor feedback to control action timing.

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.

Anxiolytic-like Effects of the Positive GABAB Receptor Modulator GS39783 Correlate with Mice’s Individual Basal Anxiety and Stress Reactivity

Positive gamma-aminobutyric acid type B (GABA_B) receptor modulators such as GS39783 have showed anxiolytic-like effects in several studies while such effects were absent in other studies. These conflicting findings led us hypothesize that the anxiolytic-like effects of such compounds depend on the individual basal anxiety and/or the anxiogenic properties of the used tests. The present study addresses this hypothesis by testing GS39783 effects on mice’s anxiety-like behavior in a light–dark box. We found that GS39783 had no effects on a whole-group level. However, after grouping the mice for their basal anxiety, GS39783 reduced anxiety-like behavior in the subgroup with highest basal anxiety. Moreover, GS39783 effects correlated with individual basal anxiety. Next, the anxiogenic properties of the light–dark box test were increased by prior stress exposure. Again, GS39783 was not effective on a whole-group level. However, GS39783 had an anxiolytic-like effect in the most stress-responsive subgroup. Moreover, GS39783 effects correlated with individual stress responsiveness. Finally, we show that GS39783 brain levels were within a behaviorally relevant range. Overall, our study demonstrates that GS39783 effects depend on individual basal anxiety and stress responsiveness. This suggests that anxiety tests should generally be designed to capture individual basal anxiety and/or stress responsiveness as well as individual compound effects.

AhR/IL-22 pathway as new target for the treatment of post-infectious irritable bowel syndrome symptoms

Alterations in brain/gut/microbiota axis are linked to Irritable Bowel Syndrome (IBS) physiopathology. Upon gastrointestinal infection, chronic abdominal pain and anxio-depressive comorbidities may persist despite pathogen clearance leading to Post-Infectious IBS (PI-IBS). This study assesses the influence of tryptophan metabolism, and particularly the microbiota-induced AhR expression, on intestinal homeostasis disturbance following gastroenteritis resolution, and evaluates the efficacy of IL-22 cytokine vectorization on PI-IBS symptoms. The Citrobacter rodentium infection model in C57BL6/J mice was used to mimic Enterobacteria gastroenteritis. Intestinal homeostasis was evaluated as low-grade inflammation, permeability, mucosa-associated microbiota composition, and colonic sensitivity. Cognitive performances and emotional state of animals were assessed using several tests. Tryptophan metabolism was analyzed by targeted metabolomics. AhR activity was evaluated using a luciferase reporter assay method. One Lactococcus lactis strain carrying an eukaryotic expression plasmid for murine IL-22 (L. lactisIL-22) was used to induce IL-22 production in mouse colonic mucosa. C. rodentium-infected mice exhibited persistent colonic hypersensitivity and cognitive impairments and anxiety-like behaviors after pathogen clearance. These post-infectious disorders were associated with low-grade inflammation, increased intestinal permeability, decrease of Lactobacillaceae abundance associated with the colonic layer, and increase of short-chain fatty acids (SCFAs). During post-infection period, the indole pathway and AhR activity were decreased due to a reduction of tryptophol production. Treatment with L. lactisIL-22 restored gut permeability and normalized colonic sensitivity, restored cognitive performances and decreased anxiety-like behaviors. Data from the video-tracking system suggested an upgrade of welfare for mice receiving the L.lactisIL-22 strain. Our findings revealed that AhR/IL-22 signaling pathway is altered in a preclinical PI-IBS model. IL-22 delivering alleviate PI-IBS symptoms as colonic hypersensitivity, cognitive impairments, and anxiety-like behaviors by acting on intestinal mucosa integrity. Thus, therapeutic strategies targeting this pathway could be developed to treat IBS patients suffering from chronic abdominal pain and associated well-being disorders.

A Systematic, Open-Science Framework for Quantification of Cell-Types in Mouse Brain Sections Using Fluorescence Microscopy

The ever-expanding availability and evolution of microscopy tools has enabled ground-breaking discoveries in neurobiology, particularly with respect to the analysis of cell-type density and distribution. Widespread implementation of many of the elegant image processing tools available continues to be impeded by the lack of complete workflows that span from experimental design, labeling techniques, and analysis workflows, to statistical methods and data presentation. Additionally, it is important to consider open science principles (e.g., open-source software and tools, user-friendliness, simplicity, and accessibility). In the present methodological article, we provide a compendium of resources and a FIJI-ImageJ-based workflow aimed at improving the quantification of cell density in mouse brain samples using semi-automated open-science-based methods. Our proposed framework spans from principles and best practices of experimental design, histological and immunofluorescence staining, and microscopy imaging to recommendations for statistical analysis and data presentation. To validate our approach, we quantified neuronal density in the mouse barrel cortex using antibodies against pan-neuronal and interneuron markers. This framework is intended to be simple and yet flexible, such that it can be adapted to suit distinct project needs. The guidelines, tips, and proposed methodology outlined here, will support researchers of wide-ranging experience levels and areas of focus in neuroscience research.

The composition of human vaginal microbiota transferred at birth affects offspring health in a mouse model

Newborns are colonized by maternal microbiota that is essential for offspring health and development. The composition of these pioneer communities exhibits individual differences, but the importance of this early-life heterogeneity to health outcomes is not understood. Here we validate a human microbiota-associated model in which fetal mice are cesarean delivered and gavaged with defined human vaginal microbial communities. This model replicates the inoculation that occurs during vaginal birth and reveals lasting effects on offspring metabolism, immunity, and the brain in a community-specific manner. This microbial effect is amplified by prior gestation in a maternal obesogenic or vaginal dysbiotic environment where placental and fetal ileum development are altered, and an augmented immune response increases rates of offspring mortality. Collectively, we describe a translationally relevant model to examine the defined role of specific human microbial communities on offspring health outcomes, and demonstrate that the prenatal environment dramatically shapes the postnatal response to inoculation.

Development of Mixed Anxiety/Depression-Like State as a Consequence of Chronic Anxiety: Review of Experimental Data

The review presents experimental data considered from the point of view of dynamic changes in the brain neurochemistry, physiology, and behavior of animals during the development of mixed anxiety/depression-like disorder caused by chronic social stress from norm to severe psychopathology. Evidences are presented to support the hypothesis that chronic anxiety rather than social defeat stress is an etiological factor in depression. The consequences of chronic anxiety for human health and social life are discussed.

Dopamine Neurons That Cotransmit Glutamate, From Synapses to Circuits to Behavior

Discovered just over 20 years ago, dopamine neurons have the ability to cotransmit both dopamine and glutamate. Yet, the functional roles of dopamine neuron glutamate cotransmission and their implications for therapeutic use are just emerging. This review article encompasses the current body of evidence investigating the functions of dopamine neurons of the ventral midbrain that cotransmit glutamate. Since its discovery in dopamine neuron cultures, further work in vivo confirmed dopamine neuron glutamate cotransmission across species. From there, growing interest has led to research related to neural functioning including roles in synaptic signaling, development, and behavior. Functional connectome mapping reveals robust connections in multiple forebrain regions to various cell types, most notably to cholinergic interneurons in both the medial shell of the nucleus accumbens and the lateral dorsal striatum. Glutamate markers in dopamine neurons reach peak levels during embryonic development and increase in response to various toxins, suggesting dopamine neuron glutamate cotransmission may serve neuroprotective roles. Findings from behavioral analyses reveal prominent roles for dopamine neuron glutamate cotransmission in responses to psychostimulants, in positive valence and cognitive systems and for subtle roles in negative valence systems. Insight into dopamine neuron glutamate cotransmission informs the pathophysiology of neuropsychiatric disorders such as addiction, schizophrenia and Parkinson Disease, with therapeutic implications.

Evaluation of Potential Sustainable Bedding Substrates Focusing on Preference, Behavior, and Stress Physiology in Rats-A Pilot Study

Ensuring optimal housing conditions for laboratory animals is a crucial prerequisite for high-quality and ethically justifiable in vivo science. In addition to guaranteeing animal welfare and promoting scientific validity, environmental sustainability is also increasingly gaining attention in laboratory animal facilities. Consequently, comprehensive management of such aspects is one of the core tasks of any research vivarium. Hygienic monitoring and adhering to standardized experimental protocols have been highlighted in the past; nevertheless, various environmental aspects of housing animals still need to be evaluated in greater depth. In this pilot study, we aimed at assessing the suitability of spelt and corncob as economical and ecologically friendly bedding substrates as compared with commonly used aspen wood chips. Therefore, following a descriptive study design, we examined the preferences of male and female Wistar rats for corncob and spelt under specific conditions. In addition, we evaluated potential effects on behavior, metabolism, and stress physiology. The type of bedding did not seem to influence behavior in the observed parameters but did have time- and sex-dependent effects on blood glucose. Furthermore, housing animals on spelt led to a significant reduction in food consumption, probably compensated for by the intake of spelt, and although it did not influence glucose levels, it may have certainly impacted the nutrient supply. Our descriptive pilot study, therefore, highlights the importance of a thorough condition-associated evaluation of even seemingly marginal environmental factors, when balancing potential cost-benefit advances in sustainability and questions of standardization and reproducibility of experimental protocols.

Behavior Testing in Rodents: Highlighting Potential Confounds Affecting Variability and Reproducibility

Rodent models of brain disorders including neurodevelopmental, neuropsychiatric, and neurodegenerative diseases are essential for increasing our understanding of underlying pathology and for preclinical testing of potential treatments. Some of the most important outcome measures in such studies are behavioral. Unfortunately, reports from different labs are often conflicting, and preclinical studies in rodent models are not often corroborated in human trials. There are many well-established tests for assessing various behavioral readouts, but subtle aspects can influence measurements. Features such as housing conditions, conditions of testing, and the sex and strain of the animals can all have effects on tests of behavior. In the conduct of behavior testing, it is important to keep these features in mind to ensure the reliability and reproducibility of results. In this review, we highlight factors that we and others have encountered that can influence behavioral measures. Our goal is to increase awareness of factors that can affect behavior in rodents and to emphasize the need for detailed reporting of methods.

Comprehensive characterization of motor and coordination functions in three adolescent wild-type mouse strains

Neuropsychiatric disorders are often associated with motor and coordination abnormalities that have important implications on the etiology, pathophysiology, and management of these disorders. Although the onset of many neuropsychiatric disorders including autism spectrum disorder, schizophrenia, and attention-deficit hyperactivity disorder emerges mainly during infancy and adolescence, most of the behavioral studies in mice modeling neuropsychiatric phenotypes are performed in adult animals, possibly missing valuable phenotypic information related to the effect of synaptic maturation during development. Here, we examined which behavioral tests assessing both motor and coordination functions can be performed in mice at two different adolescent stages. As strain and sex affect mouse behavior, our experiments covered both male and female mice of three inbred wild-type strains, C57BL/6N, DBA/2, and FVB/N. Adolescent mice of both postnatal days (P)22-30 and P32-40 developmental stages were capable of mastering common motor and coordination tests. However, results differed significantly between strains and sexes. Moreover, the 10-day interval between the two tested cohorts uncovered a strong difference in the behavioral results, confirming the significant impact of maturation on behavioral patterns. Interestingly, the results of distinct behavioral experiments were directly correlated with the weight of mice, which may explain the lack of reproducibility of some behavioral results in genetically-modified mice. Our study paves the way for better reproducibility of behavioral tests by addressing the effect of the developmental stage, strain, sex, and weight of mice on achieving the face validity of neuropsychiatric disorder-associated motor dysfunctions.