Effect of pre- versus post-weaning environmental disturbances on social behaviour in mice

The 3-hit animal models of schizophrenia: Improving strategy to decipher and treat the disease?

Schizophrenia is a complex disease related to combination and interactions between genetic and environmental factors, with an epigenetic influence. After the development of the first mono-factorial animal models of schizophrenia (1-hit), that reproduced patterns of either positive, negative and/or cognitive symptoms, more complex models combining two factors (2-hit) have been developed to better fit with the multifactorial etiology of the disease. In the two past decades, a new way to design animal models of schizophrenia have emerged by adding a third hit (3-hit). This review aims to discuss the relevance of the risk factors chosen for the tuning of the 3-hit animal models, as well as the validities measurements and their contribution to schizophrenia understanding. We intended to establish a comprehensive overview to help in the choice of factors for the design of multiple-hit animal models of schizophrenia.

Early life experience and sex influence acoustic repertoire use in wild-born, but hand-reared, captive cheetahs (Acinonyx jubatus)

Early deprivation of adult influence is known to have long-lasting effects on social abilities, notably communication skills, as adults play a key role in guiding and regulating the behavior of youngsters, including acoustic repertoire use in species in which vocal production is not learned. Cheetahs grow up alongside their mother for 18 months, thus maternal influences on the development of social skills are likely to be crucial. Here, we investigated the impact of early maternal deprivation on vocal production and use in 12 wild-born cheetahs, rescued and subsequently hand-reared either at an early (less than 2 months) or a later stage of development. We could distinguish 16 sound types, produced mostly singly but sometimes in repeated or multitype sound sequences. The repertoire of these cheetahs did not differ fundamentally from that described in other studies on adult cheetahs, but statistical analyses revealed a concurrent effect of both early experience and sex on repertoire use. More specifically, early-reared males were characterized by a high proportion of Purr, Meow, and Stutter; early-reared females Mew, Growl, Hoot, Sneeze, and Hiss; late-reared males Meow, Mew, Growl, and Howl; and late-reared females mostly Meow. Our study demonstrates therefore the long-term effects of maternal deprivation on communication skills in a limited-vocal learner and its differential effect according to sex, in line with known social differences and potential differential maternal investment. More generally, it emphasizes the critical importance to consider the past history of the subjects (e.g., captive/wild-born, mother/hand-reared, early/late-mother-deprived, etc.) when studying social behavior, notably acoustic communication.

Enduring effects of early-life adversity on reward processes: A systematic review and meta-analysis of animal studies

Two-thirds of individuals experience adversity during childhood such as neglect, abuse or highly-stressful events. Early-life adversity (ELA) increases the life-long risk of developing mood and substance use disorders. Reward-related deficits has emerged as a key endophenotype of such psychiatric disorders. Animal models are invaluable for studying how ELA leads to reward deficits. However, the existing literature is heterogenous with difficult to reconcile findings. To create an overview, we conducted a systematic review containing multiple meta-analyses regarding the effects of ELA on reward processes overall and on specific aspects of reward processing in animal models. A comprehensive search identified 120 studies. Most studies omitted key details resulting in unclear risk of bias. Overall meta-analysis showed that ELA significantly reduced reward behaviors (SMD: -0.42 [-0.60; -0.24]). The magnitude of ELA effects significantly increased with longer exposure. When reward domains were analyzed separately, ELA only significantly dampened reward responsiveness (SMD: -0.525[-0.786; -0.264]) and social reward processing (SMD: -0.374 [-0.663; -0.084]), suggesting that ELA might lead to deficits in specific reward domains.

Effects of early life adversities upon memory processes and cognition in rodent models

Exposure to stressors in early postnatal life induces long-lasting modifications in brainfunction.Thisplasticity,an essential characteristic of the brain that enables adaptation to the environment, may also induce impairments in some psychophysiological functions, including learning and memory. Early life stress (ELS) has long-term effects on thehypothalamic-pituitary-adrenal axisresponse to stressors, and has been reported to lead toneuroinflammation,altered levelsof neurotrophic factors, modifications inneurogenesis andsynaptic plasticity,with changes in neurotransmitter systems and network functioning. In this review, we focus on early postnatal stress in animal models and their effects on learning and memory.Many studies have reported ELS-induced impairments in different types of memories, including spatial memory, fear memory, recognition (both for objects and social) memory, working memory and reversal learning. Studies are not always in agreement, however, no effects, or sometimes facilitation, being reported, depending on the nature and intensity of the early intervention, as well as the age when the outcome was evaluated and the sex of the animals. When considering processes occurring after consolidation, related with memory maintenance or modification, there are a very reduced number of reports. Future studies addressing the mechanisms underlying memory changes for ELS should shed some light on the understanding of the different effects induced by stressors of different types and intensities on cognitive functions.

Deprivation of direct adult contact during development affects social representation in a songbird

Social cognition involves a wide array of skills that are built largely through interactions with conspecifics and therefore depend upon early social experience. Motivation for social stimuli is a key feature of social behavior and an operant conditioning task showed that isolated wild-caught adult starlings (Sturnus vulgaris) are highly motivated to access pictures of other starlings. Here, we show that hand-raised adult starlings maintained in groups of peers throughout development but without any contact with adult models were not or only poorly motivated to access pictures of conspecifics. Moreover, they did not prefer pictures of starlings to pictures of landscapes, unlike birds wild-caught as adults. These results raise questions about the role of social experience during development, particularly with adult models, in the development of social motivation and of social representation in general.

Combination of MAP6 deficit, maternal separation and MK801 in female mice: A 3-hit animal model of neurodevelopmental disorder with cognitive deficits

Schizophrenia is a major psychiatric disease still lacking efficient treatment, particularly for cognitive deficits. To go further in research of new treatments that would encompass all the symptoms associated with this pathology, preclinical animal models need to be improved. To date, the aetiology of schizophrenia is unknown, but there is increasing evidence to highlight its multifactorial nature. We built a new neurodevelopmental mouse model gathering a triple factor combination (3-M): a genetic factor (partial deletion of MAP6 gene), an early stress (maternal separation) and a late pharmacological factor (MK801 administration, 0.05 mg/kg, i.p., daily for 5 days). The effects of each factor and of their combination were investigated on several behaviours including cognitive functions. While each individual factor induced slight deficits in one or another behavioural test, 3-M conditioning induces a wider phenotype with hyperlocomotion and cognitive deficits (working memory and social recognition). This study confirms the hypothesis that genetic, environmental and pharmacological factors, even if not deleterious by themselves, could act synergistically to induce a deleterious behavioural phenotype. It moreover encourages the use of such combined models to improve translational research on neurodevelopmental disorders.

Functional Dysregulations in CA1 Hippocampal Networks of a 3-Hit Mouse Model of Schizophrenia

For a better translation from treatment designs of schizophrenia to clinical efficiency, there is a crucial need to refine preclinical animal models. In order to consider the multifactorial nature of the disorder, a new mouse model associating three factors (genetic susceptibility-partial deletion of the MAP6 gene, early-life stress-maternal separation, and pharmacological treatment-chronic Δ-9-tetrahydrocannabinol during adolescence) has recently been described. While this model depicts a schizophrenia-like phenotype, the neurobiological correlates remain unknown. Synaptic transmission and functional plasticity of the CA1 hippocampal region of male and female 3-hit mice were therefore investigated using electrophysiological recordings on the hippocampus slice. While basal excitatory transmission remained unaffected, NMDA receptor (NMDAr)-mediated long-term potentiation (LTP) triggered by theta-burst (TBS) but not by high-frequency (HFS) stimulation was impaired in 3-hit mice. Isolated NMDAr activation was not affected or even increased in female 3-hit mice, revealing a sexual dimorphism. Considering that the regulation of LTP is more prone to inhibitory tone if triggered by TBS than by HFS, the weaker potentiation in 3-hit mice suggests a deficiency of intrinsic GABA regulatory mechanisms. Indeed, NMDAr activation was increased by GABAA receptor blockade in wild-type but not in 3-hit mice. This electrophysiological study highlights dysregulations of functional properties and plasticity in hippocampal networks of 3-hit mice, one of the mechanisms suspected to contribute to the pathophysiology of schizophrenia. It also shows differences between males and females, supporting the sexual dimorphism observed in the disorder. Combined with the previously reported study, the present data reinforce the face validity of the 3-hit model that will help to consider new therapeutic strategies for psychosis.

A new 3-hit mouse model of schizophrenia built on genetic, early and late factors

Whether the etiology of schizophrenia remains unknown, its multifactorial aspect is conversely now well admitted. However, most preclinical models of the disease still rely on a mono-factorial construction and do not allow discover unequivocal treatments, particularly for negative and cognitive symptoms. The main interaction factors that have been implicated in schizophrenia are a genetic predisposition and unfavorable environmental factors. Here we propose a new animal model combining a genetic predisposition (1st hit: partial deletion of MAP-6 (microtubule-associated protein)) with an early postnatal stress (2nd hit: 24 h maternal separation at post-natal day 9), and a late cannabinoid exposure during adolescence (3rd hit: tetrahydrocannabinol THC from post-natal day 32 to 52; 8 mg/kg/day). The 2-hit mice displayed spatial memory deficits, decreased cortical thickness and fractional anisotropy of callosal fibers. The 3-hit mice were more severely affected as attested by supplementary deficits such a decrease in spontaneous activity, sociability-related behavior, working memory performances, an increase in anxiety-like behavior, a decrease in hippocampus volume together with impaired integrity of corpus callosum fibers (less axons, less myelin). Taken together, these results show that the new 3-hit model displays several landmarks mimicking negative and cognitive symptoms of schizophrenia, conferring a high relevance for research of new treatments. Moreover, this 3-hit model possesses a strong construct validity, which fits with gene x environment interactions hypothesis of schizophrenia. The 2-hit model, which associates maternal separation with THC exposure in wild-type mice gives a less severe phenotype, and could be useful for research on other forms of psychiatric diseases.

Early life stress due to repeated maternal separation alters the working memory acquisition brain functional network

Unfortunately, adverse environments in early life are frequently found in most human populations. Early life stress leads to diverse cognitive impairments, some of them related to learning and memory and executive functions such as working memory (WM). We employ an animal model of early stress using repeated maternal separation (MS) for 4 h a day on 21 consecutive days, pre-weaning. In adulthood, we tested their spatial WM using the Morris water maze. MS subjects showed a marked delay in the acquisition of the task. In addition, we explored brain energy oxidative metabolism and found an increase in cytochrome c oxidase (CCO) activity in the cingulate cortex, anterior thalamus, and supramammillary areas, indicating an intense effort to successfully solve the WM task. However, decreased CCO activity was found in the medial-medial mammillary nucleus in MS animals, which would partially explain the delayed acquisition of the WM task. Further studies are needed to explore the long-term alterations produced by early stress. LAY SUMMARY A stressful environment caused by the separation of baby rats from the mother for several hours a day in the first stages of postnatal life can be devastating to brain cells, making them look for alternative sources of energy, among other changes. These alterations in brain functional networks would lead to cognitive impairments such as the delayed acquisition of new learning and strategies.

The relevance of a rodent cohort in the Consortium on Individual Development

One of the features of the Consortium on Individual Development is the existence of a rodent cohort, in parallel with the human cohorts. Here we give an overview of the current status. We first elaborate on the choice of rat and mouse models mimicking early life adverse or beneficial conditions during development. We performed a systematic literature search on early life adversity and adult social behavior to address the status quo. Next, we describe the behavioral tasks we used and designed to examine behavioral control and social competence in rodents. The results so far indicate that manipulation of the environment in the first postnatal week only subtly affects social behavior. Stronger effects were seen in the model that targeted early adolescence; once adult, these rats are characterized by increased attention, a higher degree of impulsiveness and reduced social interest in peers. Many experiments in our rodent models with tightly controlled conditions were inspired by findings in human cohorts, and now allow in-depth mechanistic investigations. Vice versa, some of the findings in rodents are currently followed up by dedicated investigations in the human cohorts. This exemplifies the added value of animal investigations in a consortium encompassing primarily human developmental cohorts.

Sociability development in mice with cell-specific deletion of the NMDA receptor NR1 subunit gene

Social affiliative behavior is an important component of everyday life in many species and is likely to be disrupted in disabling ways in various neurodevelopmental and neuropsychiatric disorders. Therefore, determining the mechanisms involved in these processes is crucial. A link between N-methyl-d-aspartate (NMDA) receptor function and social behaviors has been clearly established. The cell types in which NMDA receptors are critical for social affiliative behavior, however, remain unclear. Here, we use mice carrying a conditional allele of the NMDA R1 subunit to address this question. Mice bearing a floxed NMDAR1 (NR1) allele were crossed with transgenic calcium/calmodulin-dependent kinase IIα (CaMKIIα)-Cre mice or parvalbumin (PV)-Cre mice targeting postnatal excitatory forebrain or PV-expressing interneurons, respectively, and assessed using the three-chambered Social Approach Test. We found that deletion of NR1 in PV-positive interneurons had no effect on social sniffing, but deletion of NR1 in glutamatergic pyramidal cells resulted in a significant increase in social approach behavior, regardless of age or sex. Therefore, forebrain excitatory neurons expressing NR1 play an important role in regulating social affiliative behavior.

Anxiety-like behaviour assessments of adolescent rats after repeated maternal separation during early life

Maternal separation (MS) plays a central role in developing physiology and psychology during the individual ontogeny process. MS is used to research the neurobiological mechanisms of mental disorders and early life stress. In this study, we investigated the effects of repeated MS and early handling (EH) on locomotor activity in an open-field test, a light–dark box test and an elevated plus-maze test of adolescent rats. The results showed that MS reduced locomotor activities in the open-field test, and increased anxiety-like behaviours in the light–dark box test and the elevated plus-maze test in adolescent rats. These tests indicated that early life stress caused by MS might induce anxiety-like behaviours during adolescence. However, compared with the control group, both the MS and EH groups showed conflicting anxiety levels. The results also suggested that females were more prone to showing anxiety-like behaviour compared with males when suffering from high-intensity stimulation. However, because of the low anxiety level associated with EH, the sex difference in behaviour was not significant. The present study provides novel insights into the effects of MS and EH on behaviour, which shows unique anxiety levels different in adolescent male and female rats.

The other side of the coin: Hypersociability

Affiliative social motivation and behavior, that is, sociability that includes attachment, prosocial behavior (sharing, caring and helping) and empathy (the ability to understand and share the feelings of others), has high variability in the human population, with a portion of people outside of the normal range. While psychiatric disorders and autism spectrum disorders are typically associated with a deficit in social behavior, the opposite trait of hypersociability and indiscriminate friendliness are exhibited by individual with specific neurodevelopmental disorders and following early adverse care. Here we discuss both genetic and environmental factors that cause or increase the risk for developing pathological hypersociability from human to rodent models.

Honey bee (Apis mellifera) sociability and nestmate affiliation are dependent on the social environment experienced post-eclosion

Underpinning the formation of a social group is the motivation of individuals to aggregate and interact with conspecifics, termed sociability. Here, we developed an assay, inspired by vertebrate approaches to evaluate social behaviours, to simultaneously examine the development of honey bee (Apis mellifera) sociability and nestmate affiliation. Focal bees were placed in a testing chamber which was separated from groups of nestmates and conspecific non-nestmates by single-layer mesh screens. Assessing how much time bees spent contacting the two mesh screens allowed us to quantify simultaneously how much bees sought proximity and interaction with other bees and their preference for nestmates over non-nestmates. Both sociability and nestmate affiliation could be detected soon after emergence as an adult. Isolation early in adult life impaired honey bee sociability but there was no evidence for a critical period for the development of the trait, as isolated bees exposed to their hive for 24 h when as old as 6 days still recovered high levels of sociability. Our data show that, even for advanced social insects, sociability is a developmental phenomenon and experience dependent.

Differential impact of Met receptor gene interaction with early-life stress on neuronal morphology and behavior in mice

Early adversity in childhood increases the risk of anxiety, mood, and post-traumatic stress disorders in adulthood, and specific gene-by-environment interactions may increase risk further. A common functional variant in the promoter region of the gene encoding the human MET receptor tyrosine kinase (rs1858830 ‘C’ allele) reduces expression of MET and is associated with altered cortical circuit function and structural connectivity. Mice with reduced Met expression exhibit changes in anxiety-like and conditioned fear behavior, precocious synaptic maturation in the hippocampus, and reduced neuronal arbor complexity and synaptogenesis. These phenotypes also can be produced independently by early adversity in wild-type mice. The present study addresses the outcome of combining early-life stress and genetic influences that alter timing of maturation on enduring functional and structural phenotypes. Using a model of reduced Met expression (Met^+/−) and early-life stress from postnatal day 2–9, social, anxiety-like, and contextual fear behaviors in later life were measured. Mice that experienced early-life stress exhibited impairments in social interaction, whereas alterations in anxiety-like behavior and fear learning were driven by Met haploinsufficiency, independent of rearing condition. Early-life stress or reduced Met expression decreased arbor complexity of ventral hippocampal CA1 pyramidal neurons projecting to basolateral amygdala. Paradoxically, arbor complexity in Met^+/− mice was increased following early-life stress, and thus not different from arbors in wild-type mice raised in control conditions. The changes in dendritic morphology are consistent with the hypothesis that the physiological state of maturation of CA1 neurons in Met^+/− mice influences their responsiveness to early-life stress. The dissociation of behavioral and structural changes suggests that there may be phenotype-specific sensitivities to early-life stress.

Data calibration and reduction allows to visualize behavioural profiles of psychosocial influences in mice towards clinical domains

Psychosocial stress-particularly in combination with genetic vulnerability-is a critical environmental risk factor for psychiatric diseases in humans. Isolation rearing (IR) and social defeat (SD) paradigms model psychosocial risk factors in rodents, while enriched environment (EE) protects them from behavioural deficits. Studying the influence of various environmental conditions, e.g., on genetic mouse models can help to dissect the complex gene-environment relationships underlying human psychiatric diseases. Such studies may require analysing multiple mouse cohorts; however, the comparability of behavioural experiments is challenging and often compromised by practical limitations such as group sizes and influences of handling. Therefore, protocol standardization as well as appropriate statistical normalization is necessary to compare different experiments. In this study, we analysed two independent cohorts to compare the behavioural profiles of wild-type male mice subjected to IR and SD. In both cases, EE conditions served as a reference. Multivariate statistics was applied to merge the data from individual measures into broader categories (such as curiosity, anxiety and fear memory) by estimating their calibrated joint effect within a category. Plotting and overlaying these calibrated effect sizes in a single graph allowed intuitive comparison of IR and SD behavioural profiles. This approach allows analysing multiple behavioural tests at once, which is more relevant to psychiatric syndromes than focusing on single behavioural measures. Our method revealed that motivation and fear memory are impaired by both conditions, whereas ambulation and pain sensitivity are affected only by IR and curiosity is mainly diminished upon SD. Thus, IR could be a paradigm of choice in studies focusing on positive symptoms, while SD might be more relevant for negative and cognitive symptoms.

The different effects of maternal separation on spatial learning and reversal learning in rats

Early postnatal maternal separation (MS) can play an important role in the development of psychopathologies during ontogeny. In the present study, we investigated the effects of repeated MS (4h per day from postnatal day (PND) 1 to 21) on locomotor activity and anxiety behavior in open field, spatial learning and reversal learning in Morris water maze of male and female juvenile (PND 21), adolescent (PND 35) and early adult (PND 56) Wistar rats. The results indicated that MS increased locomotor activity of rats across all ages and reduced anxiety behavior of adolescent rats in open field test. MS also increased swim distance in spatial learning and decreased escape latency in reversal learning in adolescent and early adult rats. Additionally, for socially reared rats, there was increased spontaneous locomotion with age, decreased reversal learning ability with age. The present study provides novel insights into the consequences of MS and demonstrates unique age-dependent changes at the behavioral levels.

Effects of maternal separation on behavior and brain damage in adult rats exposed to neonatal hypoxia-ischemia

Animal studies suggest that maternal separation, a widely used paradigm to study the effects of early life adversity, exerts a profound and life-long impact on both brain and behavior. The aim of the current study was to investigate whether adverse early life experiences interact with neonatal hypoxia-ischemia, affecting the outcome of this neurological insult at both functional and structural levels during adulthood. Rat pups were separated from their mothers during postnatal days 1-6, for either a short (15 min) or prolonged (180 min) period, while another group was left undisturbed. On postnatal day 7, a subgroup from each of the three postnatal manipulations was exposed to a hypoxic-ischemic episode. Behavioral examination took place approximately at three months of age and included tests of learning and memory (Morris water maze, novel object and novel place recognition), as well as motor coordination (rota-rod). We found that both prolonged maternal separation and neonatal hypoxia-ischemia impaired the animals' spatial learning and reference memory. Deficits in spatial but not visual recognition memory were detected only in hypoxic-ischemic rats. Interestingly, prolonged maternal separation prior to neonatal hypoxia-ischemia augmented the reference memory impairments. Histological analysis of infarct size, hippocampal area and thickness of corpus callosum did not reveal any exacerbation of damage in hypoxic-ischemic rats that were maternally separated for a prolonged period. These are the first data suggesting that an adverse postnatal environmental manipulation of just 6 days causes long-term effects on spatial learning and memory and may render the organism more vulnerable to a subsequent insult.

Maternal separation modifies behavioural and neuroendocrine responses to stress in CCR7 deficient mice

Alterations in immune function of various humoral and cellular factors, including chemokines, secondary to early stress may play a role in the enhanced vulnerability to psychiatric conditions in those with a history of childhood adversity. C57BL/6 (WT) mice and mice deficient for the chemokine receptor type 7 (CCR7(-/-)) were used to determine the effects of maternal separation on a range of behaviours and the biological stress response. Unpredictable maternal separation (MS) was conducted for 3h daily from postnatal day 1 to 14, with subsequent behavioural testing at 10 weeks of age. Corticosterone was quantified in 11-week-old mice. Maternally separated (MS) CCR7(-/-), but not WT mice, displayed reduced interest in social novelty compared to CCR7(-/-) naïve mice. Separated CCR7(-/-) mice also exhibited significantly lower serum corticosterone concentrations compared to non-separated mice. CCR7(-/-) mice spent less time in the centre during an open field test and more time in the closed arm of the elevated zero maze compared to their wild-type (WT) controls suggesting they were more anxious, however, no difference was observed between MS and control mice in either strain or test. Together these findings suggest that CCR7 is involved in mediating social behaviour and stress response following maternal separation, whereas other behaviours such as anxiety appear to be modified by CCR7 independent of maternal separation. The observed altered cell-mediated immune function possibly underlying the behavioural and neuroendocrine differences in CCR7(-/-) mice following maternal separation requires further investigation.

Cognitive, emotional and neurochemical effects of repeated maternal separation in adolescent rats

As an adverse early life experience, maternal separation (MS) induces profound neurochemical, cognitive and emotional dysfunction. Previous studies have reported that MS affected prepulse inhibition (PPI), anxiety-related behaviors, dopaminergic and serotonergic activity in adult rats, and in the present study, we investigated the effects of repeated (4h/day) maternal separation during postnatal days 1-21 on PPI and anxiety-related behaviors in an elevated plus maze, as well as dopamine D2 receptor (DRD2) and 5-HT1A receptor expression in the medial prefrontal cortex (mPFC), nucleus accumbens (NAc) and hippocampus in adolescent rats. Our findings show that repeated MS results in reduced PPI, increased anxiety-related behaviors, decreased DRD2 protein expression in the NAc and hippocampus, and decreased 5-HT1A protein expression in the mPFC and hippocampus in adolescent rats. These data further demonstrate that MS can be used as an animal model of neuropsychiatric disease.

Characterizing social behavior in genetically targeted mouse models of brain disorders

Fragile X syndrome, the leading inherited cause of mental retardation and autism spectrum disorders worldwide, is caused by a tandem repeat expansion in the FMR1 (fragile X mental retardation 1) gene. It presents with a distinct behavioral phenotype which overlaps significantly with that of autism. Emerging evidence suggests that tandem repeat polymorphisms (TRPs) might also play a key role in modulating disease susceptibility for a range of common polygenic disorders, including the broader autism spectrum of disorders (ASD) and other forms of psychiatric illness such as schizophrenia, depression, and bipolar disorder [1]. In order to understand how TRPs and associated gene mutations mediate pathogenesis, various mouse models have been generated. A crucial step in such functional genomics is high-quality behavioral and cognitive phenotyping. This chapter presents a basic behavioral battery for standardized tests for assaying social phenotypes in mouse models of brain disorders, with a focus on aggression.

Impact of early adverse experience on complexity of adult-generated neurons

New neurons continue to be generated in the dentate gyrus (DG) region of the hippocampus throughout adulthood, and abnormal regulation of this process has emerged as an endophenotype common to several psychiatric disorders. Previous research shows that genetic risk factors associated with schizophrenia alter the maturation of adult-generated neurons. Here, we investigate whether early adversity, a potential environmental risk factor, similarly influences adult neurogenesis. During the first 2 weeks of postnatal life, mice were subject to repeated and unpredictable periods of separation from their mothers. When the mice reached adulthood, pharmacological and retroviral labelling techniques were used to assess the generation and maturation of new neurons. We found that adult mice that were repeatedly separated from their mothers early in life had similar rates of proliferation in the DG, but had fewer numbers of cells that survived and differentiated into neurons. Furthermore, neurons generated in adulthood had less complex dendritic arborization and fewer dendritic spines. These findings indicate that early adverse experience has a long-lasting impact on both the number and the complexity of adult-generated neurons in the hippocampus, suggesting that the abnormal regulation of adult neurogenesis associated with psychiatric disorders could arise from environmental influence alone, or from complex interactions of environmental factors with genetic predisposition.

Automated three-chambered social approach task for mice

Autism is diagnosed by three major symptom categories: unusual reciprocal social interactions, impaired communication, and repetitive behaviors with restricted interests. Direct social approach in mice has strong face validity to simple social approach behaviors in humans, which are frequently impaired in autism. This unit presents a basic protocol for a standardized, high-throughput social approach test for assaying mouse sociability. Our automated three-chambered social approach task quantifies direct social approach behaviors when a subject mouse is presented with the choice of spending time with either a novel mouse or a novel object. Sociability is defined as the subject mouse spending more time in the chamber containing the novel target mouse than in the chamber containing the inanimate novel object. The Basic Protocol describes procedures for testing one subject at a time in a single apparatus. A Support Protocol addresses data collection.