Plasticity of the GABA(A) receptor subunit cassette in response to stressors in reactive versus resilient mice

Agarwood essential oil inhalation exerts antianxiety and antidepressant effects via the regulation of Glu/GABA system homeostasis

Depression and anxiety are common diseases that endanger the physical and mental health of individuals. Agarwood incense inhalation has been used as a traditional Chinese medicine for relaxation and to improve sleep for centuries. In a previous study by the authors it was demonstrated that agarwood essential oil (AEO) injection exerted anxiolytic and antidepressant effects. Therefore the present study further investigated the anxiolytic and antidepressant effects of AEO inhalation on anxiolytic mice induced by M-chlorophenylpiperazine and depressive mice induced by chronic unpredictable mild stress. The results demonstrated that AEO exerted a significant anxiolytic effect, whereby autonomous movements were inhibited during the light dark exploration test and open field test. Furthermore, the tail suspension test and the forced swimming test demonstrated that AEO also exerted an antidepressant effect, whereby the immobility times were decreased. Moreover, AEO was determined to increase the levels of 5-hydroxytryptamine, γ-aminobutyric acid (GABA) A receptor (GABA_A) and glutamate (Glu) in anxiolytic mice and inhibit the levels of GABA_A and Glu in depressive mice. Further investigations into how AEO affected the Glu/GABA system demonstrated that AEO markedly increased the protein expression levels of GABA transaminase (GABAT), glutamate metabotropic receptor 5 (GRM5), glutamate ionotropic receptor AMPA type subunit 1 (GluR1) and vesicular glutamate transporter 1 (VGluT1). Furthermore, AEO reduced the expression levels of GABAT, glutamate ionotropic receptor NMDA type subunit 2B and GRM5, and enhanced the expression levels of GluR1 and VGluT1. These results demonstrated that AEO potentially possesses antianxiety and antidepressant properties. The present study determined that the mechanism was related to the regulation of Glu/GABA neurotransmitter system homeostasis.

Central and cardiac stress resiliences consistently linked to integrated immuno-neuroendocrine responses across stress models in male mice

Stress resilience, and behavioural and cardiovascular impacts of chronic stress, are theorised to involve integrated neuro-endocrine/inflammatory/transmitter/trophin signalling. We tested for this integration, and whether behaviour/emotionality, together with myocardial ischaemic tolerance, are consistently linked to these pathways across diverse conditions in male C57Bl/6 mice. This included: Restraint Stress (RS), 1 hr restraint/day for 14 days; Chronic Unpredictable Mild Stress (CUMS), 7 stressors randomised over 21 days; Social Stress (SS), 35 days social isolation with brief social encounters in final 13 days; and Control conditions (CTRL; un-stressed mice). Behaviour was assessed via open field (OFT) and sucrose preference (SPT) tests, and neurobiology from frontal cortex (FC) and hippocampal transcripts. Endocrine factors, and function and ischaemic tolerance in isolated hearts, were also measured. Model characteristics ranged from no behavioural or myocardial changes with homotypic RS, to increased emotionality and cardiac ischaemic injury (with apparently distinct endocrine/neurobiological profiles) in CUMS and SS models. Highly integrated expression of HPA axis, neuro-inflammatory, BDNF, monoamine, GABA, cannabinoid and opioid signalling genes was confirmed across conditions, and consistent/potentially causal correlations identified for: i) Locomotor activity (noradrenaline, ghrelin; FC Crhr1, Tnfrsf1b, Il33, Nfkb1, Maoa, Gabra1; hippocampal Il33); ii) Thigmotaxis (adrenaline, leptin); iii) Anxiety-like behaviour (adrenaline, leptin; FC Tnfrsf1a; hippocampal Il33); iv) Depressive-like behaviour (ghrelin; FC/hippocampal s100a8); and v) Cardiac stress-resistance (noradrenaline, leptin; FC Il33, Tnfrsf1b, Htr1a, Gabra1, Gabrg2; hippocampal Il33, Tnfrsf1a, Maoa, Drd2). Data support highly integrated pathway responses to stress, and consistent adipokine, sympatho-adrenergic, inflammatory and monoamine involvement in mood and myocardial disturbances across diverse conditions.

Activation of LXRβ Signaling in the Amygdala Confers Anxiolytic Effects Through Rebalancing Excitatory and Inhibitory Neurotransmission upon Acute Stress

The balance of major excitatory (glutamate, Glu) and inhibitory (γ-aminobutyric acid, GABA), named as E/I neurotransmission, is critical for proper information processing. Anxiety-like responses upon stress are accompanied by abnormal alterations in the formation and function of synapses, resulting in the imbalance of E/I neurotransmission in the amygdala. Liver X receptors (LXRs), including LXRα and LXRβ isoforms, are nuclear receptors responsible for regulating central nervous system (CNS) functions besides maintaining metabolic homeostasis. However, little is known about the contribution of LXRs in E/I balance in regulating anxiety-related behaviors induced by stress. In this study, we found stress-induced anxiety led to the expression reduction of LXRβ not LXRα in mice amygdala. GW3965, a dual agonist for both LXRα and LXRβ, alleviated anxiety-like behaviors of stressed mice through activation of LXRβ, confirmed by the knockdown of LXRβ mediated by lentiviral shRNAs in the basolateral amygdala (BLA). This was paralleled by correcting the disequilibrium of E/I neurotransmission in the stressed BLA. Importantly, GW3965 exerted anxiolytic effects by correcting the promoted amplitude and frequency of miniature excitatory postsynaptic current (mEPSC), and augmenting the decreased that of miniature inhibitory postsynaptic current (mIPSC) in the stressed BLA. This suggests that stress-induced anxiety-like behaviors can largely be ascribed to the deficit of LXRβ signaling in E/I neurotransmission in BLA. These findings highlight the deficiency of LXRβ signaling in the amygdala linked to anxiety disorder, and LXRβ activation may represent a potential novel target for anxiety treatment with an alteration in synaptic transmission in the amygdala.

Pro-neurogenic effect of fluoxetine in the olfactory bulb is concomitant to improvements in social memory and depressive-like behavior of socially isolated mice

Although loneliness is a human experience, it can be estimated in laboratory animals deprived from physical contact with conspecifics. Rodents under social isolation (SI) tend to develop emotional distress and cognitive impairment. However, it is still to be determined whether those conditions present a common neural mechanism. Here, we conducted a series of behavioral, morphological, and neurochemical analyses in adult mice that underwent to 1 week of SI. We observed that SI mice display a depressive-like state that can be prevented by enriched environment, and the antidepressants fluoxetine (FLX) and desipramine (DES). Interestingly, chronic administration of FLX, but not DES, was able to counteract the deleterious effect of SI on social memory. We also analyzed cell proliferation, neurogenesis, and astrogenesis after the treatment with antidepressants. Our results showed that the olfactory bulb (OB) was the neurogenic niche with the highest increase in neurogenesis after the treatment with FLX. Considering that after FLX treatment social memory was rescued and depressive-like behavior decreased, we propose neurogenesis in the OB as a possible mechanism to unify the FLX ability to counteract the deleterious effect of SI.

Pleiotropic actions of allopregnanolone underlie therapeutic benefits in stress-related disease

For several years, research from around the world has suggested that the neuroactive steroid (3α,5α)-3-hydroxypregnan-20-one (allopregnanolone) may have therapeutic potential for treatment of various stress-related diseases including post-traumatic stress disorder (PTSD), depression, alcohol use disorders (AUDs), as well as neurological and psychiatric conditions that are worsened in the presence of stress, such as multiple sclerosis, schizophrenia, and seizure disorders. In this review, we make the argument that the pleiotropic actions of allopregnanolone account for its ability to promote recovery in such a wide variety of illnesses. Likewise, the allopregnanolone precursors, pregnenolone and progesterone, share many actions of allopregnanolone. Of course, pregnenolone and progesterone lack direct effects on GABA_A receptors, but these compounds are converted to allopregnanolone in vivo. This review presents a theoretical framework for understanding how endogenous neurosteroids that regulate 1) γ-aminobutyric acid (GABA)_A receptors, 2) corticotropin releasing factor (CRF) and 3) pro-inflammatory signaling in the innate immune system and brain could play a key role in both the prevention and treatment of stress-related disease. We further discuss cautions and limitations of allopregnanolone or precursor therapy as well as the need for more clinical studies.

Brain neurotransmitters in an animal model with postpartum depressive-like behavior

Post-Partum Depression (PPD) occurs in 15% of pregnancies and its patho-physiology is not known. We studied female BALB/c ("depressive") and C57BL/6 (control) mice as a model for PPD and assessed their behavior and correlates with brain neurotransmitters (NTs) - norepinephrine, dopamine, serotonin and intermediates, during the pre-pregnancy (PREP), pregnancy (PREG) and post-partum (PP) periods. Depressive-like behavior was evaluated by the Open Field (OFT), Tail Suspension (TST) and Forced Swim (FST) tests. Neurotransmitters (NTs) were determined in the striatum (care-giving), hippocampus (cognitive function) and hypothalamus (maternal care & eating behavior). In the BALB/c mice, while their performance in all behavioral tests was significantly reduced during pregnancy and P-P indicative of the development of depressive-like responses, no changes were observed in the C57BL/6 mice. Changes in NTs in BALB/C were as follows: PREP, all NTs in the three brain areas were decreased, although an increase in dopamine release was observed in the hippocampus. PREG: No changes were observed in the NTs except for a decrease in 5-HT in the striatum. P-P: striatum, low 5-HT, NE and dopamine; Hippocampus: low 5-HT, NE and high Dopamine; hypothalamus: all NTs increased, especially NE. Following pregnancy and delivery, the BALB/c mice developed depressive-like behavior associated with a significant decrease in 5-HT, dopamine and NE in the striatum and 5-HT and NE in the hippocampus. Dopamine increased in the latter together with a significant increase in all NTs in the hypothalamus. These findings suggest that the development of PPD may be associated with NT changes. Normalization of these alterations may have a role in the treatment of PPD.

Chronic stress in Lizards: Studies on the Behavior and Benzodiazepine Receptors in Liolaemus koslowskyi and Cnemidophorus tergolaevigatus

Behavioral and physiological adaptive responses of animals facing chronic exposure to a single stressor may allow them to overcome its negative effects for future exposures to similar stressful situations. At chemical level, the GABA_A /benzodiazepine complex is considered one of the main receptor systems involved in the modulation of stress-induced responses. Here, we describe the behavioral responses of two different lizard species, Liolaemus koslowskyi and Cnemidophorus tergolaevigatus exposed to three potential chronic stressful treatments: (a) high temperature, (b) forced swimming, and (c) simulated predator. Additionally, we aimed to determine in those lizards whether the central-type benzodiazepine receptor (CBR; an allosteric modulator site of the GABA_A receptor) is related to adaptive responses to those stressful stimulations. Our results revealed that the simulated predator was the stress condition that showed the largest difference in behavioral responses between the two species, resembling previously described strategies in nature. The basal affinity of CBRs (obtained from undisturbed animals) showed differences between both species, and the simulated predator was the only stressor that altered the affinity of CBRs. L. koslowskyi CBRs showed a decreased receptor affinity, whereas C. tergolaevigatus showed an increased receptor affinity in comparison to their respective control groups. We show for the first time the effects of different types of stressors upon behavioral responses and CBR biochemical parameters in two lizard species. Our findings suggest a potential GABA/benzodiazepine role in the ability of lizards to cope with a repeated exposure to a stressful (e.g., predator) condition.

Paraquat and psychological stressor interactions as pertains to Parkinsonian co-morbidity

A number of epidemiological and experimental studies have implicated the non-selective herbicide, paraquat, in the development of sporadic Parkinson's disease (PD). While preclinical research has focused mainly on elucidating the nigrostriatal effects of paraquat, relatively little data are available concerning non-motor brain systems and inflammatory immune processes (which have been implicated in PD). Hence, in the present study, we sought to take a multi-system approach to characterize the influence of paraquat upon extra-nigrostriatal brain regions, as well ascertain whether the impact of the pesticide might be enhanced in the context of chronic intermittent stressor exposure. Our findings support the contention that paraquat itself acted as a systemic stressor, with the pesticide increasing plasma corticosterone, as well as altering neurochemical activity in the locus coeruleus, paraventricular nucleus of the hypothalamus, nucleus accumbens, dorsal striatum, and central amygdala. However, with the important exception striatal dopamine turnover, the stressor treatment did not further augment these effects. Additionally, paraquat altered inter-cytokine correlations and, to a lesser extent, circulating cytokine levels, and concomitant stress exposure modulated some of these effects. Finally, paraquat provoked significant (albeit modest) reductions of sucrose preference and weight gain, hinting at possible anhendonic-like or sickness responses. These data suggest that, in addition to being a well known oxidative stress generator, paraquat can act as a systemic stressor affecting hormonal and neurochemical activity, but largely not interacting with a concomitant stressor regimen.

Behavior and brain gene expression changes in mice exposed to preimplantation and prenatal stress

Preimplantation culture of mouse embryos has been suggested to result in reduced anxiety-like behavior in adulthood. Here, we investigated the effects of in vitro fertilization (IVF), embryo culture, and different diets on anxiety-like behavior using the elevated plus maze (EPM). We hypothesized that exposure to suboptimal conditions during the preimplantation stage would interact with the suboptimal diet to alter behavior. The expression of genes related to anxiety was then assessed by quantitative real-time polymerase chain reaction in various brain regions. When fed a normal diet during gestation and a moderately high-fat Western diet (WD) postnatally, naturally conceived (NC) and IVF mice showed similar anxiety-like behavior on the EPM. However, when fed a low-protein diet prenatally and a high-fat diet postnatally (LP/HF), NC mice showed a modest increase in anxiety-like behavior, whereas IVF mice showed the opposite: a strongly reduced anxiety-like behavior on the EPM. The robust reduction in anxiety-like behavior in IVF males fed the LP/HF diets was, intriguingly, associated with reduced expression of MAO-A, CRFR2, and GABA markers in the hypothalamus and cortex. These findings are discussed in relation to the developmental origin of health and disease hypothesis and the 2-hit model, which suggests that 2 events, occurring at different times in development, can act synergistically with long-term consequences observed during adulthood.

GAD65 haplodeficiency conveys resilience in animal models of stress-induced psychopathology

GABAergic mechanisms are critically involved in the control of fear and anxiety, but their role in the development of stress-induced psychopathologies, including post-traumatic stress disorder (PTSD) and mood disorders is not sufficiently understood. We studied these functions in two established mouse models of risk factors for stress-induced psychopathologies employing variable juvenile stress and/or social isolation. A battery of emotional tests in adulthood revealed the induction of contextually generalized fear, anxiety, hyperarousal and depression-like symptoms in these paradigms. These reflect the multitude and complexity of stress effects in human PTSD patients. With factor analysis we were able to identify parameters that reflect these different behavioral domains in stressed animals and thus provide a basis for an integrated scoring of affectedness more closely resembling the clinical situation than isolated parameters. To test the applicability of these models to genetic approaches we further tested the role of GABA using heterozygous mice with targeted mutation of the GABA synthesizing enzyme GAD65 [GAD65(+/−) mice], which show a delayed postnatal increase in tissue GABA content in limbic and cortical brain areas. Unexpectedly, GAD65(+/−) mice did not show changes in exploratory activity regardless of the stressor type and were after the variable juvenile stress procedure protected from the development of contextual generalization in an auditory fear conditioning experiment. Our data demonstrate the complex nature of behavioral alterations in rodent models of stress-related psychopathologies and suggest that GAD65 haplodeficiency, likely through its effect on the postnatal maturation of GABAergic transmission, conveys resilience to some of these stress-induced effects.

Phenotypic instability between the near isogenic substrains BALB/cJ and BALB/cByJ

Closely related substrains of inbred mice often show phenotypic differences that are presumed to be caused by recent mutations. The substrains BALB/cJ and BALB/cByJ, which were separated in 1935, have been reported to show numerous highly significant behavioral and morphological differences. In an effort to identify some of the causal mutations, we phenotyped BALB/cJ and BALB/cByJ mice as well as their F1, F2, and N2 progeny for behavioral and morphological phenotypes. We also generated whole-genome sequence data for both inbred strains (~3.5× coverage) with the intention of identifying polymorphic markers to be used for linkage analysis. We observed significant differences in body weight, the weight of the heart, liver, spleen and brain, and corpus callosum length between the two substrains. We also observed that BALB/cJ animals showed greater anxiety-like behavior in the open field test, less depression-like behavior in the tail suspension test, and reduced aggression compared to BALB/cByJ mice. Some but not all of these physiological and behavioral results were inconsistent with prior publications. These inconsistencies led us to suspect that the differences were due to, or modified by, non-genetic factors. Thus, we did not perform linkage analysis. We provide a comprehensive summary of the prior literature about phenotypic differences between these substrains as well as our current findings. We conclude that many differences between these strains are unstable and therefore ill-suited to linkage analysis; the source of this instability is unclear. We discuss the broader implications of these observations for the design of future studies.

CRH receptor antagonism reverses the effect of social subordination upon central GABAA receptor binding in estradiol-treated ovariectomized female rhesus monkeys

Persistent exposure to environmental stressors causes dysregulation of the limbic-hypothalamic-pituitary-adrenal (LHPA) axis and alters GABAA receptor (GABAAR) levels throughout the brain. Social subordination in socially housed female rhesus results in distinctive stress-related physiological and behavioral phenotypes that are dependent on the ovarian hormone estradiol (E2). In the present study, we utilized ovariectomized adult female rhesus monkeys undergoing hormone replacement with E2 to test the hypothesis that the chronic psychosocial stress of subordination alters GABAAR binding potential (GABAAR BPND) in limbic regions implicated in emotional processing including the prefrontal cortex, temporal lobe (amygdala and hippocampus), and hypothalamus. Furthermore, we tested the hypothesis that peripheral administration of a corticotropin-releasing hormone (CRH) receptor antagonist (astressin B) would reverse the alterations in GABAAR binding within these regions in subordinate females. After subjects received astressin B or saline for three consecutive days, GABAAR BPND was determined by positron emission tomography (PET) using (18)F-flumazenil as a radioligand. T1-weighted structural magnetic resonance imaging scans were also acquired for PET scan co-registration, in order to perform a region of interest analysis using the pons as a reference region. Compared to socially dominant females, subordinate females exhibited increased GABAAR BPND in the prefrontal cortex but not in the temporal lobe or the hypothalamus. Administration of astressin B eliminated the status difference in GABAAR BPND in the prefrontal cortex, suggesting that the chronic stressor of social subordination modulates GABAergic tone via effects on CRH and the LHPA axis, at least in prefrontal regions.

Molecular pathway reconstruction and analysis of disturbed gene expression in depressed individuals who died by suicide

Molecular mechanisms behind the etiology and pathophysiology of major depressive disorder and suicide remain largely unknown. Recent molecular studies of expression of serotonin, GABA and CRH receptors in various brain regions have demonstrated that molecular factors may contribute to the development of depressive disorder and suicide behaviour. Here, we used microarray analysis to examine the expression of genes in brain tissue (frontopolar cortex) of individuals who had been diagnosed with major depressive disorder and died by suicide, and those who had died suddenly without a history of depression. We analyzed the list of differentially expressed genes using pathway analysis, which is an assumption-free approach to analyze microarray data. Our analysis revealed that the differentially expressed genes formed functional networks that were implicated in cell to cell signaling related to synapse maturation, neuronal growth and neuronal complexity. We further validated these data by randomly choosing (100 times) similarly sized gene lists and subjecting these lists to the same analyses. Random gene lists did not provide highly connected gene networks like those generated by the differentially expressed list derived from our samples. We also found through correlational analysis that the gene expression of control participants was more highly coordinated than in the MDD/suicide group. These data suggest that among depressed individuals who died by suicide, wide ranging perturbations of gene expression exist that are critical for normal synaptic connectively, morphology and cell to cell communication.

Short- and long-term effects of juvenile stressor exposure on the expression of GABAA receptor subunits in rats

During the juvenile period rodents are particularly sensitive to stressors. Aversive events encountered during this period may have enduring effects that are not evident among animals initially stressed as adults. Interestingly, experiencing stressor during juvenile period was found to elicit a biphasic behavioral pattern over the course of development. During the juvenile period, the expression of several GABAA receptor subunits is subject to elevated plasticity, rendering the GABAergic system sensitive to stressors. In the present investigation, animals were exposed to a juvenile variable stressor regimen (JUV-S) at 27-29 postnatal days (PND): 27 PND-acute swim stress (10 min), 28 PND-elevated platform stress (3 sessions×30 min each), and 29 PND-restraint (2 h). One hour following the last exposure to stressor or in adulthood (60 PND), anxiety-related behaviors were assessed in a 5-min elevated plus maze test. The western blotting technique was used to evaluate whether the juvenile stress induced behavioral pattern will be accompanied by respective changes in GABAA α1, α2, and α3 protein expression in male rats. Our findings further established that juvenile stressor elicits hyper-reactivity when rats were tested as juveniles, whereas rats exhibited reduced activity and increased anxiety when tested as adults. Additionally, the effects of juvenile stressor on α1, α2, and α3 were more pronounced among juvenile stressed rats that were challenged as adults compared with rats that were only challenged as juveniles. Interestingly, the stress-induced modulation of the subunits was particularly evident in the amygdala, a brain region closely associated with anxiety. Thus, age- and region-specific alterations of the α subunits may contribute to the age-specific behavioral alterations observed following juvenile stress exposure.

Stressor exposure of male and female juvenile mice influences later responses to stressors: modulation of GABAA receptor subunit mRNA expression

Stressors encountered during the juvenile period may have persistent effects on later behavioral and neurochemical functioning and may influence later responses to stressors. In the current investigation, we evaluated the influence of stressor exposure applied during the juvenile period (26-28 days of age) on anxiety-related behavior, plasma corticosterone and on GABA(A) α2, α3, α5 and γ2 mRNA expression within the prefrontal cortex (PFC) and amygdala measured during adulthood. These changes were monitored in the absence of a further challenge, as well as in response to either a social or a non-social psychogenic stressor administered during adulthood. Exposure to an acute adult stressor elicited anxiety in females and was still more pronounced among females that had also experienced the juvenile stressor. Among males, arousal and impulsivity predominated so that anxiety responses were less notable. Furthermore, experiencing the stressor as a juvenile influenced adult GABA(A) subunit expression, as did the adult stressor experience. These changes were differentially expressed in males and females. Moreover, these subunit variations were further moderated among mice that stressed as juveniles and were again exposed to an adult stressor. Interestingly, under conditions in which the juvenile stressor increased the expression of a particular subunit, exposure to a further stressor in adulthood resulted in the γ-aminobutyric acid (GABA) subunit variations being attenuated in both sexes. The current results suggest that juvenile and adult stressor experiences elicit variations of GABA(A) receptor subunit expression that are region-specific as well as sexually-dimorphic. Stressful events during the juvenile period may have pronounced proactive effects on anxiety-related behaviors, but linking these to specific GABA(A) subunits is made difficult by the diversity of GABA changes that are evident as well as the dimorphic nature of these variations. Nevertheless, these GABA(A) sex-specific subunit variations may be tied to the differences in anxiety in males and females.

Differential effects of etifoxine on anxiety-like behaviour and convulsions in BALB/cByJ and C57BL/6J mice: any relation to overexpression of central GABAA receptor beta2 subunits?

Dysfunction of GABAergic transmission related to abnormal expression of GABA(A) receptor subunits in specific brain regions underlies some pathological anxiety states. Besides involvement of the benzodiazepine recognition site of GABA(A) receptor in the expression of anxiety-like behaviour, the roles of the β(2)/β(3) subunits are not well characterized. To address this issue, the experimental design of this study utilized the GABAergic compound etifoxine (with a preferential effectiveness after binding to a specific site at β(2)/β(3) subunits) tested in two inbred mouse strains: BALB/cByJ and C57BL/6J mice using three behavioural paradigms (light/dark box, elevated plus maze and restraint stress-induced small intestinal transit inhibition) and the t-butylbicyclophosphorothionate-induced convulsions model. Etifoxine plasma and brain levels and β(2)/β(3) mRNAs and protein expression levels in various brain regions were compared between the two strains. The two mouse strains differed markedly in basal anxiety level. Etifoxine exhibited more pronounced anxiolytic and anticonvulsant effects in the BALB/cByJ mice compared to the C57BL/6J mice. The etifoxine brain/plasma ratios of the two strains were not different. Beta2 subunit mRNA and protein expression levels were around 25 and 10% higher respectively in the anterodorsal nucleus of the thalamus and the CA3 field of hippocampus of BALB/cByJ mice compared to C57BL/6J mice. Beta3 subunit mRNA and protein expression levels did not differ between the two strains. Based on these results, it is suggested that overexpression of GABA(A) receptor β(2) subunit in BALB/cByJ mice relative to C57BL/6j mice contributes to the dysfunction in GABA(A) transmission in regions of brain known to regulate responses to stress. The dysregulated GABA(A) function in BALB/cByJ mice may be corrected by the administration of etifoxine.

Using animal models to disentangle the role of genetic, epigenetic, and environmental influences on behavioral outcomes associated with maternal anxiety and depression

The etiology of complex psychiatric disorders results from both genetics and the environment. No definitive environmental factor has been implicated, but studies suggest that deficits in maternal care and bonding may be an important contributing factor in the development of anxiety and depression. Perinatal mood disorders such as postpartum depression occur in approximately 10% of pregnant women and can result in detriments in infant care and bonding. The consequences of impaired maternal-infant attachment during critical early brain development may lead to adverse effects on socioemotional and neurocognitive development in infants resulting in long-term behavioral and emotional problems, including increased vulnerability for mental illness. The exact mechanisms by which environmental stressors such as poor maternal care increase the risk for psychiatric disorders are not known and studies in humans have proven challenging. Two inbred mouse strains may prove useful for studying the interaction between maternal care and mood disorders. BALB/c (BALB) mice are considered an anxious strain in comparison to C57BL/6 (B6) mice in behavioral models of anxiety. These strain differences are most often attributed to genetics but may also be due to environment and gene by environment interactions. For example, BALB mice are described as poor mothers and B6 mice as good mothers and mothering behavior in rodents has been reported to affect both anxiety and stress behaviors in offspring. Changes in gene methylation patterns in response to maternal care have also been reported, providing evidence for epigenetic mechanisms. Characterization of these two mouse inbred strains over the course of pregnancy and in the postpartum period for behavioral and neuroendocrine changes may provide useful information by which to inform human studies, leading to advances in our understanding of the etiology of anxiety and depression and the role of genetics and the environment.