Enhanced harm detection following maternal separation: Transgenerational transmission and reversibility by inhaled amiloride.

Early-life adversities are associated with altered defensive responses. Here, we demonstrate that the repeated cross-fostering (RCF) paradigm of early maternal separation is associated with enhancements of distinct homeostatic reactions: hyperventilation in response to hypercapnia and nociceptive sensitivity, among the first generation of RCF-exposed animals, as well as among two successive generations of their normally reared offspring, through matrilineal transmission. Parallel enhancements of acid-sensing ion channel 1 (ASIC1), ASIC2, and ASIC3 messenger RNA transcripts were detected transgenerationally in central neurons, in the medulla oblongata, and in periaqueductal gray matter of RCF-lineage animals. A single, nebulized dose of the ASIC-antagonist amiloride renormalized respiratory and nociceptive responsiveness across the entire RCF lineage. These findings reveal how, following an early-life adversity, a biological memory reducible to a molecular sensor unfolds, shaping adaptation mechanisms over three generations. Our findings are entwined with multiple correlates of human anxiety and pain conditions and suggest nebulized amiloride as a therapeutic avenue.

Early Social Enrichment Modulates Tumor Progression and p53 Expression in Adult Mice.

Epidemiological evidence indicates that stress and aversive psychological conditions can affect cancer progression, while well-being protects against it. Although a large set of studies have addressed the impact of stress on cancer, not much is known about the mechanisms that protect from cancer in healthy psychological conditions. C57BL/6J mouse pups were exposed to an environmental enrichment condition consisting of being raised until weaning by the biological lactating mother plus a non-lactating virgin female (LnL = Lactating and non-Lactating mothers). The Control group consisted of mice raised by a single lactating mother (L = Lactating). Four months after weaning, mice from LnL and L conditions were exposed to intramuscular injection of 3-methylcolantrene (3MCA), a potent tumorigenic drug, and onset and progression of 3MCA-induced fibrosarcomas were monitored over time. Pups from the LnL compared to the L group received more parental care and were more resilient to stressful events during the first week of life. In association, the onset of tumors in LnL adults was significantly delayed. At the molecular level, we observed increased levels of wild-type p53 protein in tumor samples of LnL compared to L adults and higher levels of its target p21 in healthy muscles of LnL mice compared to the L group, supporting the hypothesis of potential involvement of p53 in tumor development. Our study sustains the model that early life care protects against tumor susceptibility.

Early life adversity affecting the attachment bond alters ventral tegmental area transcriptomic patterning and behavior almost exclusively in female mice.

Early life experiences that affect the attachment bond formation can alter developmental trajectories and result in pathological outcomes in a sex-related manner. However, the molecular basis of sex differences is quite unknown. The dopaminergic system originating from the ventral tegmental area has been proposed to be a key mediator of this process. Here we exploited a murine model of early adversity (Repeated Cross Fostering, RCF) to test how interfering with the attachment bond formation affects the VTA-related functions in a sex-specific manner. Through a comprehensive behavioral screening, within the NiH RDoC framework, and by next-generation RNA-Seq experiments, we analyzed the long-lasting effect of RCF on behavioral and transcriptional profiles related to the VTA, across two different inbred strains of mouse in both sexes. We found that RCF impacted to an extremely greater extent VTA-related behaviors in females than in males and this result mirrored the transcriptional alterations in the VTA that were almost exclusively observed in females. The sexual dimorphism was conserved across two different inbred strains in spite of their divergent long lasting consequences of RCF exposure. Our data suggest that to be female primes a sub-set of genes to respond to early environmental perturbations. This is, to the best of our knowledge, the first evidence of an almost exclusive effect of early life experiences on females, thus mirroring the extremely stronger impact of precocious aversive events reported in clinical studies in women.

Animal models of developmental dyslexia: Where we are and what we are missing.

Developmental dyslexia (DD) is a complex neurodevelopmental disorder and the most common learning disability among both school-aged children and across languages. Recently, sensory and cognitive mechanisms have been reported to be potential endophenotypes (EPs) for DD, and nine DD-candidate genes have been identified. Animal models have been used to investigate the etiopathological pathways that underlie the development of complex traits, as they enable the effects of genetic and/or environmental manipulations to be evaluated. Animal research designs have also been linked to cutting-edge clinical research questions by capitalizing on the use of EPs. For the present scoping review, we reviewed previous studies of murine models investigating the effects of DD-candidate genes. Moreover, we highlighted the use of animal models as an innovative way to unravel new insights behind the pathophysiology of reading (dis)ability and to assess cutting-edge preclinical models.

Mouse model of panic disorder: Vulnerability to early environmental instability is strain-dependent.

Early life experiences and genetic background shape phenotypic variation. Several mouse models based on early treatments have evaluated short- and long-term phenotypic alterations and explored their molecular mechanisms. The instability of maternal cues was used to model human separation anxiety in outbred mice, one of the etiopathogenetic factors that predict panic disorder (PD). Application of the repeated cross-fostering (RCF) protocol to inbred strains (C57 and DBA) allowed us to measure differential responses to the same experimental manipulation. Ultrasounds emitted during isolation indicated that after RCF, pups from both strains lose their ability to be comforted by nest cues, but the frequency modulation of separation calls increased in RCF-C57 and decreased in RCF-DBA mice. No strain-specific difference in olfactory ability explained these responses in RCF-exposed mice. Rather, disruption of the infant-mother bond may differentially affect separation calls in the two strains. Moreover, the RCF-associated increased respiratory response to hypercapnia-an endophenotype of human PD documented among mice outbred strains-was replicated in the C57 strain only. We suggest that RCF-induced instability of the early environment affects emotionality and respiratory physiology differentially, depending on pups' genetic background. These strain-specific responses provide a lead to understand differential vulnerability to emotional disorders.

Resilience to anhedonia-passive coping induced by early life experience is linked to a long-lasting reduction of Ih current in VTA dopaminergic neurons.

Exposure to aversive events during sensitive developmental periods can affect the preferential coping strategy adopted by individuals later in life, leading to either stress-related psychiatric disorders, including depression, or to well-adaptation to future adversity and sources of stress, a behavior phenotype termed "resilience". We have previously shown that interfering with the development of mother-pups bond with the Repeated Cross Fostering (RCF) stress protocol can induce resilience to depression-like phenotype in adult C57BL/6J female mice. Here, we used patch-clamp recording in midbrain slice combined with both in vivo and ex vivo pharmacology to test our hypothesis of a link between electrophysiological modifications of dopaminergic neurons in the intermediate Ventral Tegmental Area (VTA) of RCF animals and behavioral resilience. We found reduced hyperpolarization-activated (Ih) cation current amplitude and evoked firing in VTA dopaminergic neurons from both young and adult RCF female mice. In vivo, VTA-specific pharmacological manipulation of the Ih current reverted the pro-resilient phenotype in adult early-stressed mice or mimicked behavioral resilience in adult control animals. This is the first evidence showing how pro-resilience behavior induced by early events is linked to a long-lasting reduction of Ih current and excitability in VTA dopaminergic neurons.

Evaluation of µ-Opioid System Functionality in Mouse Pups: Ultrasonic Vocalizations as an Index of Infant Attachment.

The evaluation of ultrasonic vocalizations (USVs) during isolation in 6-8-day-old mouse pups can give an indication of the perception of pups' discomfort and need for caretaker presence to overcome the unpleasant condition. Time spent vocalizing changed according to opioid activation, stress exposure, and genetic profile of pups. Deficits in attachment suggest altered opioid functioning and predisposal for long-term defective social behaviors and reward processes.

Behavioral, neuromorphological, and neurobiochemical effects induced by omega-3 fatty acids following basal forebrain cholinergic depletion in aged mice.

BACKGROUND: In recent years, mechanistic, epidemiologic, and interventional studies have indicated beneficial effects of omega-3 polyunsaturated fatty acids (n-3 PUFA) against brain aging and age-related cognitive decline, with the most consistent effects against Alzheimer's disease (AD) confined especially in the early or prodromal stages of the pathology. In the present study, we investigated the action of n-3 PUFA supplementation on behavioral performances and hippocampal neurogenesis, volume, and astrogliosis in aged mice subjected to a selective depletion of basal forebrain cholinergic neurons. Such a lesion represents a valuable model to mimic one of the most reliable hallmarks of early AD neuropathology. METHODS: Aged mice first underwent mu-p75-saporin immunotoxin intraventricular lesions to obtain a massive cholinergic depletion and then were orally supplemented with n-3 PUFA or olive oil (as isocaloric control) for 8 weeks. Four weeks after the beginning of the dietary supplementation, anxiety levels as well as mnesic, social, and depressive-like behaviors were evaluated. Subsequently, hippocampal morphological and biochemical analyses and n-3 PUFA brain quantification were carried out. RESULTS: The n-3 PUFA treatment regulated the anxiety alterations and reverted the novelty recognition memory impairment induced by the cholinergic depletion in aged mice. Moreover, n-3 PUFA preserved hippocampal volume, enhanced neurogenesis in the dentate gyrus, and reduced astrogliosis in the hippocampus. Brain levels of n-3 PUFA were positively related to mnesic abilities. CONCLUSIONS: The demonstration that n-3 PUFA are able to counteract behavioral deficits and hippocampal neurodegeneration in cholinergically depleted aged mice promotes their use as a low-cost, safe nutraceutical tool to improve life quality at old age, even in the presence of first stages of AD.

Xlr4 as a new candidate gene underlying vulnerability to cocaine effects.

Although several studies have been performed in rodents, non-human primates and humans, the biological basis of vulnerability to develop cocaine addiction remains largely unknown. Exposure to critical early events (as Repeated Cross Fostering (RCF)) has been reported to increase sensitivity to cocaine effects in adult C57BL/6J female mice. Using a microarray approach, here we report data showing a strong engagement of X-linked lymphocyte-regulated 4a and 4b (Xlr4) genes in cocaine effects. The expression of Xlr4, a gene involved in chromatin remodeling and dendritic spine morphology, was reduced into the Nucleus Accumbens (NAc) of adult RCF C57BL/6J female. We used virally mediated accumbal Xlr4 down-modulation (AAVXlr4-KD) to investigate the role of this gene in vulnerability to cocaine effects. AAVXlr4-KD animals show a potentiated behavioral and neurochemical response to cocaine, reinstatement following cocaine withdrawal and cocaine-induced spine density alterations in the Medium-Sized Spiny Neurons of NAc. We propose Xlr4 as a new candidate gene mediating the cocaine effects.

Sex-dependent effects of early unstable post-natal environment on response to positive and negative stimuli in adult mice.

Alterations in early environmental conditions that interfere with the creation of a stable mother-pup bond have been suggested to be a risk factor for the development of stress-related psychopathologies later in life. The long-lasting effects of early experiences are mediated by changes in various cerebral circuits, such as the corticolimbic system, which processes aversive and rewarding stimuli. However, it is evident that the early environment is not sufficient per se to induce psychiatric disorders; interindividual (eg, sex-based) differences in the response to environmental challenges exist. To examine the sex-related effects that are induced by an early experience on later events in adulthood, we determine the enduring effects of repeated cross-fostering (RCF) in female and male C57BL/6J mice. To this end, we assessed the behavioral phenotype of RCF and control (male and female) mice in the saccharine preference test and cocaine-induced conditioned place preference to evaluate the response to natural and pharmacological stimuli and in the elevated plus maze test and forced swimming test to measure their anxiety- and depression-like behavior. We also evaluated FST-induced c-Fos immunoreactivity in various brain regions that are engaged in the response to acute stress exposure (FST). Notably, RCF has opposing effects on the adult response to these tests between sexes, directing male mice toward an "anhedonia-like" phenotype and increasing the sensitivity for rewarding stimuli in female mice.

Amiloride modulation of carbon dioxide hypersensitivity and thermal nociceptive hypersensitivity induced by interference with early maternal environment.

BACKGROUND: Early life adversities are risk factors for anxiety disorders and for pain syndromes, which are, in turn, highly comorbid with anxiety disorders. Repeated cross-fostering mouse pups to adoptive lactating females induces epigenetic modification and heightened mRNA-expression of the acid-sensing-ion-channel-1 gene, altered nociception, and hypersensitivity to 6% carbon dioxide air mixtures, a trait marker of specific human anxiety disorders such as, most clearly and prominently, panic disorder. AIMS: We hypothesized that the acid-sensing ion channel inhibitor amiloride can modulate repeated cross-fostering animals' exaggerated responses to carbon dioxide and nociceptive thermal stimulation. METHODS: Respiratory carbon dioxide sensitivity was assessed by plethysmography during 6% carbon dioxide air mixture challenges, and nociception was assessed by latency of paw withdrawal to thermal stimulation, in repeated cross-fostering and control animals. To circumvent the blood-brain barrier, prior to testing, amiloride was nebulized in a plethysmograph. Data were analyzed by general linear models. RESULTS: Analyses of tidal volume responses to 6% carbon dioxide of animals pre-treated with nebulized amiloride/saline in a randomized crossover design showed significant modulatory effect of amiloride, and amiloride×repeated cross-fostering interaction. In contrast, repeated cross-fostering animals' responses to 6% carbon dioxide after intraperitoneal amiloride, saline, or no treatment, were no different. Analyses of responses to thermal stimuli showed a significant modulatory effect of nebulized amiloride, and repeated cross-fostering×amiloride interaction. CONCLUSIONS: Single-dose nebulized amiloride decreased repeated cross-fostering animals' carbon dioxide sensitivity and nociception indices to levels that were no different from those of control animals. Inasmuch as these results pertain to human anxiety and/or pain hypersensitivity, our findings provide a rationale for studying inhaled amiloride in some anxiety disorders and/or pain syndromes.

Conserved DNA Methylation Signatures in Early Maternal Separation and in Twins Discordant for CO2 Sensitivity.

Respiratory and emotional responses to blood-acidifying inhalation of CO2 are markers of some human anxiety disorders, and can be enhanced by repeatedly cross-fostering (RCF) mouse pups from their biological mother to unrelated lactating females. Yet, these dynamics remain poorly understood. We show RCF-associated intergenerational transmission of CO2 sensitivity in normally-reared mice descending from RCF-exposed females, and describe the accompanying alterations in brain DNA methylation patterns. These epigenetic signatures were compared to DNA methylation profiles of monozygotic twins discordant for emotional reactivity to a CO2 challenge. Altered methylation was consistently associated with repeated elements and transcriptional regulatory regions among RCF-exposed animals, their normally-reared offspring, and humans with CO2 hypersensitivity. In both species, regions bearing differential methylation were associated with neurodevelopment, circulation, and response to pH acidification processes, and notably included the ASIC2 gene. Our data show that CO2 hypersensitivity is associated with specific methylation clusters and genes that subserve chemoreception and anxiety. The methylation status of genes implicated in acid-sensing functions can inform etiological and therapeutic research in this field.

Early-onset behavioral and neurochemical deficits in the genetic mouse model of phenylketonuria.

Phenylketonuria (PKU) is one of the most common human inborn errors of metabolism, caused by phenylalanine hydroxylase deficiency, leading to high phenylalanine and low tyrosine levels in blood and brain causing profound cognitive disability, if untreated. Since 1960, population is screened for hyperphenylalaninemia shortly after birth and submitted to early treatment in order to prevent the major manifestations of the disease. However, the dietetic regimen (phenylalanine free diet) is difficult to maintain, and despite the recommendation to a strict and lifelong compliance, up to 60% of adolescents partially or totally abandons the treatment. The development and the study of new treatments continue to be sought, taking advantage of preclinical models, the most used of which is the PAHenu2 (BTBR ENU2), the genetic murine model of PKU. To date, adult behavioral and neurochemical alterations have been mainly investigated in ENU2 mice, whereas there are no clear indications about the onset of these deficiencies. Here we investigated and report, for the first time, a comprehensive behavioral and neurochemical assay of the developing ENU2 mice. Overall, our findings demonstrate that ENU2 mice are significantly smaller than WT until pnd 24, present a significant delay in the acquisition of tested developmental reflexes, impaired communicative, motor and social skills, and have early reduced biogenic amine levels in several brain areas. Our results extend the understanding of behavioral and cerebral abnormalities in PKU mice, providing instruments to an early preclinical evaluation of the effects of new treatments.

Sensitivity to cocaine in adult mice is due to interplay between genetic makeup, early environment and later experience.

Although early aversive postnatal events are known to increase the risk to develop psychiatric disorders later in life, rarely they determine alone the nature and outcome of the psychopathology, indicating that interaction with genetic factors is crucial for expression of psychopathologies in adulthood. Moreover, it has been suggested that early life experiences could have negative consequences or confer adaptive value in different individuals. Here we suggest that resilience or vulnerability to adult cocaine sensitivity depends on a "triple interaction" between genetic makeup x early environment x later experience. We have recently showed that Repeated Cross Fostering (RCF; RCF pups were fostered by four adoptive mothers from postnatal day 1 to postnatal day 4. Pups were left with the last adoptive mother until weaning) experienced by pups affected the response to a negative experience in adulthood in opposite direction in two genotypes leading DBA2/J, but not C57BL/6J mice, toward an "anhedonia-like" phenotype. Here we investigate whether exposure to a rewarding stimulus, instead of a negative one, in adulthood induces an opposite behavioral outcome. To test this hypothesis, we investigated the long-lasting effects of RCF on cocaine sensitivity in C57 and DBA female mice by evaluating conditioned place preference induced by different cocaine doses and catecholamine prefrontal-accumbal response to cocaine using a "dual probe" in vivo microdialysis procedure. Moreover, cocaine-induced c-Fos activity was assessed in different brain regions involved in processing of rewarding stimuli. Finally, cocaine-induced spine changes were evaluated in the prefrontal-accumbal system. RCF experience strongly affected the behavioral, neurochemical and morphological responses to cocaine in adulthood in opposite direction in the two genotypes increasing and reducing, respectively, the sensitivity to cocaine in C57 and DBA mice.

Age-specific autistic-like behaviors in heterozygous Fmr1-KO female mice.

Fragile X syndrome (FXS) is a major developmental disorder and the most frequent monogenic cause of autism. Surprisingly, most existing studies on the Fmr1-KO mouse model for FXS have focused on males, although FX women, who are mostly heterozygous for the Fmr1 mutation, are known to exhibit several behavioral deficits, including autistic-like features. Furthermore, most animal research has been carried out on adults only; so that little is known about the age progression of the behavioral phenotype of Fmr1 mutants, which is a crucial issue to optimize the impact of therapeutic interventions. Here, we performed an extensive analysis of autistic-like social behaviors in heterozygous (HET) Fmr1-KO females and their WT littermates at different ages. No behavioral difference between HET and WT mice was observed at infancy, but some abnormalities in social interaction and communication were first detected at juvenile age. At adulthood some of these alterations disappeared, but avoidance of social novelty appeared, together with other FXS-relevant behavioral deficits, such as hyperactivity and reduced contextual fear response. Our data provide for the first time evidence for the presence of autistic-relevant behavioral abnormalities in Fmr1-HET female mice, demonstrating the utility of this mouse line to model autistic-like behaviors in both sexes. These results also highlight the importance of taking into account age differences when using the Fmr1-KO mouse model, suggesting that the early post-natal phases are the most promising target for preventive interventions and the adult age is the most appropriate to investigate the behavioral impact of potential therapies. Autism Res 2017. © 2017 International Society for Autism Research, Wiley Periodicals, Inc. Autism Res 2017, 10: 1067-1078. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

Treatment Approaches in Rodent Models for Autism Spectrum Disorder.

Recent years have seen an impressive amount of research devoted to the developing of therapies to treat autism spectrum disorder (ASD). This work has been largely based on rodent models, employing a multitude of genetic and environmental manipulations. Unfortunately, the task of identifying suitable treatments for ASD is extremely challenging, due to a variety of problems specific to the research in this field. Here, we first discuss these problems, including (I) the presence of a large variety of rodent models (often without universal consensus on their validity), (II) the difficulties in choosing the most appropriate behavioural markers to assess the efficacy of possible treatments, (III) the limited knowledge we still have of the neurobiological bases of ASD pathology and of its aetiology, and (IV) the complexity of ASD itself, including a highly heterogeneous group of disorders sometimes with markedly different symptoms (therefore unlikely to be treated with the same approaches). Second, we give a critical overview of the most relevant advances in designing treatments for ASD, focusing on the most commonly used animal model, the laboratory mouse. We include pharmacological and non-pharmacological approaches, underlining their specific advantages, but also their current limitations especially in relation to the problems discussed before. Finally, we highlight the theoretical (e.g. the combination of multiple rather than single treatments) and methodological (e.g. use of single-gene mouse models) approaches that seem more promising to us, suggesting various strategies that can be adopted to simplify the complex field of research on treatments for ASD.

Social threat exposure in juvenile mice promotes cocaine-seeking by altering blood clotting and brain vasculature.

Childhood maltreatment is associated with increased severity of substance use disorder and frequent relapse to drug use following abstinence. However, the molecular and neurobiological substrates that are engaged during early traumatic events and mediate the greater risk of relapse are poorly understood and knowledge of risk factors is to date extremely limited. In this study, we modeled childhood maltreatment by exposing juvenile mice to a threatening social experience (social stressed, S-S). We showed that S-S experience influenced the propensity to reinstate cocaine-seeking after periods of withdrawal in adulthood. By exploring global gene expression in blood leukocytes we found that this behavioral phenotype was associated with greater blood coagulation. In parallel, impairments in brain microvasculature were observed in S-S mice. Furthermore, treatment with an anticoagulant agent during withdrawal abolished the susceptibility to reinstate cocaine-seeking in S-S mice. These findings provide novel insights into a possible molecular mechanism by which childhood maltreatment heightens the risk for relapse in cocaine-dependent individuals.

Early Social Enrichment Improves Social Motivation and Skills in a Monogenic Mouse Model of Autism, the Oprm1 (-/-) Mouse.

Environmental enrichment has been proven to have positive effects on both behavioral and physiological phenotypes in rodent models of mental and neurodevelopmental disorders. In this study, we used mice lacking the µ-opioid receptor gene (Oprm1 (-/-)), which has been shown to have deficits in social competence and communication, to assess the hypothesis that early enrichment can ameliorate sociability during development and adulthood. Due to the immaturity of sensory-motor capabilities of young pups, we chose as environmental stimulation a second lactating female, who provided extra maternal care and stimulation from birth. The results show that double mothering normalized the abnormal response to maternal separation in Oprm1 (-/-) pups and increased social motivation in juveniles and adult knockout mice. Additionally, we observed that Oprm1 (-/-) mice act as less attractive social partners than wild types, which suggests that social motivation can be modulated by the stimulus employed. This experiment supports previous findings suggesting that early social environmental stimulation has profound and long-term beneficial effects, encouraging the use of nonpharmacological interventions for the treatment of social defects in neurodevelopmental diseases.

Histone Modifications in a Mouse Model of Early Adversities and Panic Disorder: Role for Asic1 and Neurodevelopmental Genes.

Hyperventilation following transient, CO2-induced acidosis is ubiquitous in mammals and heritable. In humans, respiratory and emotional hypersensitivity to CO2 marks separation anxiety and panic disorders, and is enhanced by early-life adversities. Mice exposed to the repeated cross-fostering paradigm (RCF) of interference with maternal environment show heightened separation anxiety and hyperventilation to 6% CO2-enriched air. Gene-environment interactions affect CO2 hypersensitivity in both humans and mice. We therefore hypothesised that epigenetic modifications and increased expression of genes involved in pH-detection could explain these relationships. Medullae oblongata of RCF- and normally-reared female outbred mice were assessed by ChIP-seq for H3Ac, H3K4me3, H3K27me3 histone modifications, and by SAGE for differential gene expression. Integration of multiple experiments by network analysis revealed an active component of 148 genes pointing to the mTOR signalling pathway and nociception. Among these genes, Asic1 showed heightened mRNA expression, coherent with RCF-mice's respiratory hypersensitivity to CO2 and altered nociception. Functional enrichment and mRNA transcript analyses yielded a consistent picture of enhancement for several genes affecting chemoception, neurodevelopment, and emotionality. Particularly, results with Asic1 support recent human findings with panic and CO2 responses, and provide new perspectives on how early adversities and genes interplay to affect key components of panic and related disorders.

Unstable Maternal Environment Affects Stress Response in Adult Mice in a Genotype-Dependent Manner.

Early postnatal events exert powerful effects on development, inducing persistent functional alterations in different brain network, such as the catecholamine prefrontal-accumbal system, and increasing the risk of developing psychiatric disorders later in life. However, a vast body of literature shows that the interaction between genetic factors and early environmental conditions is crucial for expression of psychopathologies in adulthood. We evaluated the long-lasting effects of a repeated cross-fostering (RCF) procedure in 2 inbred strains of mice (C57BL/6J, DBA/2), known to show a different susceptibility to the development and expression of stress-induced psychopathologies. Coping behavior (forced swimming test) and preference for a natural reinforcing stimulus (saccharine preference test) were assessed in adult female mice of both genotypes. Moreover, c-Fos stress-induced activity was assessed in different brain regions involved in stress response. In addition, we evaluated the enduring effects of RCF on catecholamine prefrontal-accumbal response to acute stress (restraint) using, for the first time, a new "dual probes" in vivo microdialysis procedure in mouse. RCF experience affects behavioral and neurochemical responses to acute stress in adulthood in opposite direction in the 2 genotypes, leading DBA mice toward an "anhedonic-like" phenotype and C57 mice toward an increased sensitivity for a natural reinforcing stimulus.