Candidate genes of anxiety-related behavior in HAB/LAB rats and mice: Focus on vasopressin and glyoxalase-I

Early Handling Exerts Anxiolytic Effects and Alters Brain Mitochondrial Dynamics in Adult High Anxiety Mice

Early handling (EH), the brief separation of pups from their mother during early life, has been shown to exert beneficial effects. However, the impact of EH in a high anxiety background as well as the role of brain mitochondria in shaping EH-driven responses remain elusive.Here, we used a high (HAB) vs. normal (NAB) anxiety-related behavior mouse model to study how EH affects pup and dam behavior in divergent anxiety backgrounds. We also investigated EH-induced effects at the protein and mRNA levels in adult male HAB mice in the hypothalamus, the prefrontal cortex, and the hippocampus by examining the same mitochondrial/energy pathways and mitochondrial dynamics mechanisms (fission, fusion, biogenesis, and mitophagy) in all three brain regions.EH exerts anxiolytic effects in adult HAB but not NAB male mice and does not affect HAB or NAB maternal behavior, although basal HAB vs. NAB maternal behaviors differ. In adult HAB male mice, EH does not impact oxidative phosphorylation (OXPHOS) and oxidative stress in any of the brain regions studied but leads to increased protein expression of glycolysis enzymes and a correlation of anxiety-related behavior with Krebs cycle enzymes in HAB mice in the hypothalamus. Intriguingly, EH alters mitochondrial dynamics by increasing hypothalamic DRP1, OPA1, and PGC1a protein levels. At the mRNA level, we observe altered, EH-driven mitochondrial dynamics mRNA signatures which predominantly affect the prefrontal cortex.Taken together, our results show that EH exerts anxiolytic effects in adulthood in high anxiety and modulates mitochondrial dynamics pathways in a brain region-specific manner.

Leveraging interindividual variability in threat conditioning of inbred mice to model trait anxiety

Trait anxiety is a major risk factor for stress-induced and anxiety disorders in humans. However, animal models accounting for the interindividual variability in stress vulnerability are largely lacking. Moreover, the pervasive bias of using mostly male animals in preclinical studies poorly reflects the increased prevalence of psychiatric disorders in women. Using the threat imminence continuum theory, we designed and validated an auditory aversive conditioning-based pipeline in both female and male mice. We operationalised trait anxiety by harnessing the naturally occurring variability of defensive freezing responses combined with a model-based clustering strategy. While sustained freezing during prolonged retrieval sessions was identified as an anxiety-endophenotype behavioral marker in both sexes, females were consistently associated with an increased freezing response. RNA-sequencing of CeA, BLA, ACC, and BNST revealed massive differences in phasic and sustained responders' transcriptomes, correlating with transcriptomic signatures of psychiatric disorders, particularly post-traumatic stress disorder (PTSD). Moreover, we detected significant alterations in the excitation/inhibition balance of principal neurons in the lateral amygdala. These findings provide compelling evidence that trait anxiety in inbred mice can be leveraged to develop translationally relevant preclinical models to investigate mechanisms of stress susceptibility in a sex-specific manner.

Vasopressin as Possible Treatment Option in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is rather common, presenting with prevalent early problems in social communication and accompanied by repetitive behavior. As vasopressin was implicated not only in salt-water homeostasis and stress-axis regulation, but also in social behavior, its role in the development of ASD might be suggested. In this review, we summarized a wide range of problems associated with ASD to which vasopressin might contribute, from social skills to communication, motor function problems, autonomous nervous system alterations as well as sleep disturbances, and altered sensory information processing. Beside functional connections between vasopressin and ASD, we draw attention to the anatomical background, highlighting several brain areas, including the paraventricular nucleus of the hypothalamus, medial preoptic area, lateral septum, bed nucleus of stria terminalis, amygdala, hippocampus, olfactory bulb and even the cerebellum, either producing vasopressin or containing vasopressinergic receptors (presumably V1a). Sex differences in the vasopressinergic system might underline the male prevalence of ASD. Moreover, vasopressin might contribute to the effectiveness of available off-label therapies as well as serve as a possible target for intervention. In this sense, vasopressin, but paradoxically also V1a receptor antagonist, were found to be effective in some clinical trials. We concluded that although vasopressin might be an effective candidate for ASD treatment, we might assume that only a subgroup (e.g., with stress-axis disturbances), a certain sex (most probably males) and a certain brain area (targeting by means of virus vectors) would benefit from this therapy.

Avoidance and inhibitory control are possible transdiagnostic traits? A systematic review in animal models

In clinical research, aberrant avoidance behavior and inhibitory control deficit have a high comorbidity in different psychopathological disorders. Therefore, avoidance and impulsive and/or compulsive behaviors might be classified as transdiagnostic traits, where the assessment through animal models could address evidence of their contribution as neurobehavioral mechanisms in psychopathology. The objective of the present review has been to assess the avoidance trait and the implication of inhibitory control behaviors, through studies using passive and active avoidance tests in rodents, and a preclinical model using selective breeding of high- or low-avoidance Roman rats (RHA, RLA). A systematic search strategy was carried out in the PubMed and Web of Science databases, where a total of 40 studies were accepted in the qualitative synthesis. The results of the different studies reviewed pointed to a relation between a reduced avoidance profile in passive avoidance (PA) with impulsive decision making and novelty-seeking behaviors; an increased avoidance profile in PA with compulsive drinking; a high active avoidance profile, including RHA rats, with different types of impulsivity and novelty- seeking behaviors; and regarding compulsivity depending on its measure, a low active avoidance profile, including RLA rats, has been associated with increased anxiety in the EPM and increased grooming, while a high active avoidance profile, including RHA rats, has been associated with increased rearing, compulsive drinking including alcohol, and cognitive inflexibility. The results have been discussed in terms of environmental factors and the underlying mechanisms between these possible transdiagnostic traits in psychopathology.

Understanding the Role of Oxidative Stress, Neuroinflammation and Abnormal Myelination in Excessive Aggression Associated with Depression: Recent Input from Mechanistic Studies

Aggression and deficient cognitive control problems are widespread in psychiatric disorders, including major depressive disorder (MDD). These abnormalities are known to contribute significantly to the accompanying functional impairment and the global burden of disease. Progress in the development of targeted treatments of excessive aggression and accompanying symptoms has been limited, and there exists a major unmet need to develop more efficacious treatments for depressed patients. Due to the complex nature and the clinical heterogeneity of MDD and the lack of precise knowledge regarding its pathophysiology, effective management is challenging. Nonetheless, the aetiology and pathophysiology of MDD has been the subject of extensive research and there is a vast body of the latest literature that points to new mechanisms for this disorder. Here, we overview the key mechanisms, which include neuroinflammation, oxidative stress, insulin receptor signalling and abnormal myelination. We discuss the hypotheses that have been proposed to unify these processes, as many of these pathways are integrated for the neurobiology of MDD. We also describe the current translational approaches in modelling depression, including the recent advances in stress models of MDD, and emerging novel therapies, including novel approaches to management of excessive aggression, such as anti-diabetic drugs, antioxidant treatment and herbal compositions.

Cross-Generational Impact of Epigenetic Male Influence on Physical Activity in Rat

The aim of this work was to study whether epigenetic events at conception influence the formation of behavioral features found in adult rats. First generational inheritance of activity level, anxiety like behavior, and learning ability was studied. To separate genetic and non-genetic inheritance, mating of males and females with average motor activity was carried out in the presence anesthetized or conscious males with high or low activity. Our results show that offspring of parents who mated in the presence of males with a high motor activity were significantly more active than offspring of parents that were paired in the presence of males with low activity. Anxiety like behavior and learning ability were not inherited in this way. It is possible that the phenomenon we discovered is important for maintaining a certain level of activity of specific populations of animals. It counteracts natural selection, which should lead to a constant increase in the activity of animals.

The Influence of HLA Alleles on the Affective Distress Profile

(1) Background: Affective distress can be triggered by aggressive stimuli with an unfavorable role for the individual. Some of the factors that lead to the development and evolution of a mental disorder can be genetic. The aim of this study is to determine some correlations between the human leukocyte antigen (HLA) genes and the affective distress profile (PDA). (2) Methods: A psychological assessment and testing tool for anxiety was applied to 115 people. The low-resolution HLA alleles of class I (HLA-A, HLA-B, and HLA-C) and class II (HLA-DRB1 and HLA-DQB1) were identified by the PCR technique after DNA extraction from the blood. Depending on the PDA, the subjects were divided into two groups: a group with a low PDA and another one with a medium and high PDA. The IBM SPSS software was used to compare the frequency of HLA alleles between the two groups. (3) Results: The univariate analysis revealed a significant association of the HLA-A locus (A*01, A*30), HLA-B (B*08), and HLA-DRB1 (DRB1*11) with the low PDA group and of the HLA-A locus (A*32), HLA-B (B*52), and HLA-C (C*12) with the medium and high PDA group. (4) Conclusions: The present study highlighted potential associations between HLA alleles and anxiety disorders.

Neuropeptide Y, calcitonin gene-related peptide, and neurokinin A in brain regions of HAB rats correlate with anxiety-like behaviours

Anxiety disorders are pervasive psychiatric disorders causing great suffering. The high (HAB) and low (LAB) anxiety-related behaviour rats were selectively bred to investigate neurobiological correlates of anxiety. We compared the level of neuropeptides relevant for anxiety- and depression-related behaviours in selected brain regions of HAB and LAB rats. Increased anxiety and depression-like behaviours of male and female HAB rats in the elevated plus-maze and forced swim tests were accompanied by elevated levels of neuropeptide Y (NPY) in the prefrontal (PFC), frontal (FC) and cingulate cortex (CCx), the striatum, and periaqueductal grey (PAG). Moreover, HAB rats displayed sex-dependent, elevated levels of calcitonin gene-related peptide (CGRP) in PFC, FC, CCx, hippocampus, and PAG. Higher neurokinin A (NKA) levels were detected in CCx, striatum, and PAG in HAB males and in CCx and hypothalamus in HAB females. Increased neurotensin was detected in CCx and PAG in HAB males and in hypothalamus in HAB females. Elevated corticotropin-releasing hormone (CRH) levels appeared in female HAB hypothalamus. Significant correlations were found between anxiety-like behaviour and NPY, CGRP, NKA, and neurotensin, particularly with NPY in CCx and striatum, CGRP in FC and hippocampus, and NKA in entorhinal cortex. This is the first report of NPY, CGRP, NKA, Neurotensin, and CRH measurements in brain regions of HAB and LAB rats, which showed widespread NPY and CGRP alterations in cortical regions, with NKA and neurotensin changes localised in sub-cortical areas. The results may contribute to elucidate pathophysiological mechanisms underlying anxiety and depression and should facilitate identifying novel therapeutic targets.

Epigenetic Modulation of Vasopressin Expression in Health and Disease

Vasopressin is a ubiquitous molecule playing an important role in a wide range of physiological processes thereby implicated in the pathomechanism of many disorders. Its effect is well characterized through V2 receptors, which regulates the water resorption in kidney, while its vasoconstrictory effect through V1a receptor also received a lot of attention in the maintenance of blood pressure during shock. However, the most striking is its central effect both through the V1b receptors in stress-axis regulation as well as through V1a receptors regulating many aspects of our behavior (e.g., social behavior, learning and memory). Vasopressin has been implicated in the development of depression, due to its connection with chronic stress, as well as schizophrenia because of its involvement in social interactions and memory processes. Epigenetic changes may also play a role in the development of these disorders. The possible mechanism includes DNA methylation, histone modification and/or micro RNAs, and these possible regulations will be in the focus of our present review.

Removal of vasopressin cells from the paraventricular nucleus of the hypothalamus enhances lipopolysaccharide-induced sickness behaviour in mice

Vasopressin (AVP) cells in the paraventricular nucleus of the hypothalamus (PVN) are activated during sickness and project to multiple nuclei responsible for the anxiety, social and motivated behaviours affected during sickness, suggesting that these cells may play a role in sickness behaviours, typically expressed as reduced mobility, increased anxiety, anhedonia and social withdrawal. In the present study, we selectively ablated AVP neurones in the PVN of male and female mice (Mus musculus) and induced sickness behaviour via injection of bacterial lipopolysaccharide (LPS). We found that PVN AVP ablation increased the effects of LPS, specifically by further decreasing sucrose preference in males and females and decreasing the social preference of males, monitored within 24 hours of LPS injection. These results suggest that PVN AVP contributes to the change in motivated behaviours during sickness and may help promote recovery from infection..

Pre-clinical models of reward deficiency syndrome: A behavioral octopus

Individuals with mood disorders or with addiction, impulsivity and some personality disorders can share in common a dysfunction in how the brain perceives reward, where processing of natural endorphins or the response to exogenous dopamine stimulants is impaired. Reward Deficiency Syndrome (RDS) is a polygenic trait with implications that suggest cross-talk between different neurological systems that include the known reward pathway, neuroendocrine systems, and motivational systems. In this review we evaluate well-characterized animal models for their construct validity and as potential models for RDS. Animal models used to study substance use disorder, major depressive disorder (MDD), early life stress, immune dysregulation, attention deficit hyperactivity disorder (ADHD), post traumatic stress disorder (PTSD), compulsive gambling and compulsive eating disorders are discussed. These disorders recruit underlying reward deficiency mechanisms in multiple brain centers. Because of the widespread and remarkable array of associated/overlapping behavioral manifestations with a common root of hypodopaminergia, the basic endophenotype recognized as RDS is indeed likened to a behavioral octopus. We conclude this review with a look ahead on how these models can be used to investigate potential therapeutics that target the underlying common deficiency.

Metabolomics in Psychiatric Disorders: What We Learn from Animal Models

Biomarkers are a recent research target within biological factors of psychiatric disorders. There is growing evidence for deriving biomarkers within psychiatric disorders in serum or urine samples in humans, however, few studies have investigated this differentiation in brain or cerebral fluid samples in psychiatric disorders. As brain samples from humans are only available at autopsy, animal models are commonly applied to determine the pathogenesis of psychiatric diseases and to test treatment strategies. The aim of this review is to summarize studies on biomarkers in animal models for psychiatric disorders. For depression, anxiety and addiction disorders studies, biomarkers in animal brains are available. Furthermore, several studies have investigated psychiatric medication, e.g., antipsychotics, antidepressants, or mood stabilizers, in animals. The most notable changes in biomarkers in depressed animal models were related to the glutamate-γ-aminobutyric acid-glutamine-cycle. In anxiety models, alterations in amino acid and energy metabolism (i.e., mitochondrial regulation) were observed. Addicted animals showed several biomarkers according to the induced drugs. In summary, animal models provide some direct insights into the cellular metabolites that are produced during psychiatric processes. In addition, the influence on biomarkers due to short- or long-term medication is a noticeable finding. Further studies should combine representative animal models and human studies on cerebral fluid to improve insight into mental disorders and advance the development of novel treatment strategies.

Sex differences in stress-related disorders: Major depressive disorder, bipolar disorder, and posttraumatic stress disorder

Stress-related disorders, such as mood disorders and posttraumatic stress disorder (PTSD), are more common in women than in men. This sex difference is at least partly due to the organizing effect of sex steroids during intrauterine development, while activating or inhibiting effects of circulating sex hormones in the postnatal period and adulthood also play a role. Such effects result in structural and functional changes in neuronal networks, neurotransmitters, and neuropeptides, which make the arousal- and stress-related brain systems more vulnerable to environmental stressful events in women. Certain brainstem nuclei, the amygdala, habenula, prefrontal cortex, and hypothalamus are important hubs in the stress-related neuronal network. Various hypothalamic nuclei play a central role in this sexually dimorphic network. This concerns not only the hypothalamus-pituitary-adrenal axis (HPA-axis), which integrates the neuro-endocrine-immune responses to stress, but also other hypothalamic nuclei and systems that play a key role in the symptoms of mood disorders, such as disordered day-night rhythm, lack of reward feelings, disturbed eating and sex, and disturbed cognitive functions. The present chapter focuses on the structural and functional sex differences that are present in the stress-related brain systems in mood disorders and PTSD, placing the HPA-axis in the center. The individual differences in the vulnerability of the discussed systems, caused by genetic and epigenetic developmental factors warrant further research to develop tailor-made therapeutic strategies.

Depression as a Neuroendocrine Disorder: Emerging Neuropsychopharmacological Approaches beyond Monoamines

Depression is currently recognized as a crucial problem in everyday clinical practice, in light of ever-increasing rates of prevalence, as well as disability, morbidity, and mortality related to this disorder. Currently available antidepressant drugs are notoriously problematic, with suboptimal remission rates and troubling side-effect profiles. Their mechanisms of action focus on the monoamine hypothesis for depression, which centers on the disruption of serotonergic, noradrenergic, and dopaminergic neurotransmission in the brain. Nevertheless, views on the pathophysiology of depression have evolved notably, and the comprehension of depression as a complex neuroendocrine disorder with important systemic implications has sparked interest in a myriad of novel neuropsychopharmacological approaches. Innovative pharmacological targets beyond monoamines include glutamatergic and GABAergic neurotransmission, brain-derived neurotrophic factor, various endocrine axes, as well as several neurosteroids, neuropeptides, opioids, endocannabinoids and endovanilloids. This review summarizes current knowledge on these pharmacological targets and their potential utility in the clinical management of depression.

The human hypothalamus in mood disorders: The HPA axis in the center

There are no specific structural neuropathological hallmarks found in the brain of mood disorders. Instead, there are molecular, functional and structural alterations reported in many brain areas. The neurodevelopmental underpinning indicated the presence of various genetic and developmental risk factors. The effect of genetic polymorphisms and developmental sequalae, some of which may start in the womb, result in functional changes in a network mediated by neurotransmitters and neuropeptides, which make the emotion- and stress-related brain systems more vulnerable to stressful events. This network of stress-related neurocircuits consists of, for instance, brainstem nuclei, the amygdala, habenula, prefrontal cortex and hypothalamus. Various nuclei of the hypothalamus form indeed one of the crucial hubs in this network. This structure concerns not only the hypothalamo-pituitary-adrenal (HPA) axis that integrate the neuro-endocrine-immune responses to stress, but also other hypothalamic nuclei and systems that play a key role in the symptoms of depression, such as disordered day-night rhythm, lack of reward feelings, disturbed eating, sex, and disturbed cognitive functions. The present review will focus on the changes in the human hypothalamus in depression, with the HPA axis in the center. We will discuss the inordinate network of neurotransmitters and neuropeptides involved, with the hope to find the most vulnerable neurobiological systems and the possible development of tailor-made treatments for mood disorders in the future.

Anxiolytic properties of compounds that counteract oxidative stress, neuroinflammation, and glutamatergic dysfunction: a review

Objective:

Anxiety disorders are highly prevalent and the efficacy of the available anxiolytic drugs is less than desired. Adverse effects also compromise patient quality of life and adherence to treatment. Accumulating evidence shows that the pathophysiology of anxiety and related disorders is multifactorial, involving oxidative stress, neuroinflammation, and glutamatergic dysfunction. The aim of this review was to evaluate data from animal studies and clinical trials showing the anxiolytic effects of agents whose mechanisms of action target these multiple domains.

Methods:

The PubMed database was searched for multitarget agents that had been evaluated in animal models of anxiety, as well as randomized double-blind placebo-controlled clinical trials of anxiety and/or anxiety related disorders.

Results:

The main multitarget agents that have shown consistent anxiolytic effects in various animal models of anxiety, as well in clinical trials, are agomelatine, N-acetylcysteine (NAC), and omega-3 fatty acids. Data from clinical trials are preliminary at best, but reveal good safety profiles and tolerance to adverse effects.

Conclusion:

Agomelatine, NAC and omega-3 fatty acids show beneficial effects in clinical conditions where mainstream treatments are ineffective. These three multitarget agents are considered promising candidates for innovative, effective, and better-tolerated anxiolytics.

Oxytocin Neurons Exhibit Extensive Functional Plasticity Due To Offspring Age in Mothers and Fathers

The needs of offspring change as they develop. Thus, parents should concomitantly change their investment based on the age-related needs of the offspring as they mature. Due to the high costs of parental care, it is optimal for parents to exhibit a shift from intense caregiving of young offspring to promoting independence in older offspring. Yet, the neural mechanisms that underlie shifts in parental behavior are poorly understood, and little is known about how the parental brain responds to offspring of different ages. To elucidate mechanisms that relate to shifts in parental behavior as offspring develop, we examined behavioral and neural responses of male and female prairie voles (Microtus ochrogaster), a biparental rodent, to interactions with offspring at different stages of development (ranging from neonatal to weaning age). Importantly, in biparental species, males and females may adjust their behavior differentially as offspring develop. Because the nonapeptides, vasopressin (VP) and oxytocin (OT), are well known for modulating aspects of parental care, we focused on functional activity of distinct VP and OT cell groups within the maternal and paternal brain in response to separation from, reunion (after a brief period of separation) with, or no separation from offspring of different ages. We found several differences in the neural responses of individual VP and OT cell groups that varied based on the age of pups and sex of the parent. Hypothalamic VP neurons exhibit similar functional responses in both mothers and fathers. However, hypothalamic and amygdalar OT neurons exhibit differential functional responses to being separated from pups based on the sex of the parent. Our results also reveal that the developmental stage of offspring significantly impacts neural function within OT, but not VP, cell groups of both mothers and fathers. These findings provide insight into the functional plastic capabilities of the nonapeptide system, specifically in relation to parental behavior. Identifying neural mechanisms that exhibit functional plasticity can elucidate one way in which animals are able to shift behavior on relatively short timescales in order to exhibit the most context-appropriate and adaptive behaviors.

Intranasal Oxytocin and Vasopressin Modulate Divergent Brainwide Functional Substrates

The neuropeptides oxytocin (OXT) and vasopressin (AVP) have been identified as modulators of emotional social behaviors and associated with neuropsychiatric disorders characterized by social dysfunction. Experimental and therapeutic use of OXT and AVP via the intranasal route is the subject of extensive clinical research. However, the large-scale functional substrates directly engaged by these peptides and their functional dynamics remain elusive. By using cerebral blood volume (CBV) weighted fMRI in the mouse, we show that intranasal administration of OXT rapidly elicits the transient activation of cortical regions and a sustained activation of hippocampal and forebrain areas characterized by high oxytocin receptor density. By contrast, intranasal administration of AVP produced a robust and sustained deactivation in cortico-parietal, thalamic and mesolimbic regions. Importantly, intravenous administration of OXT and AVP did not recapitulate the patterns of modulation produced by intranasal dosing, supporting a central origin of the observed functional changes. In keeping with this notion, hippocampal local field potential recordings revealed multi-band power increases upon intranasal OXT administration. We also show that the selective OXT-derivative TGOT reproduced the pattern of activation elicited by OXT and that the deletion of OXT receptors does not affect AVP-mediated deactivation. Collectively, our data document divergent modulation of brainwide neural systems by intranasal administration of OXT and AVP, an effect that involves key substrates of social and emotional behavior. The observed divergence calls for a deeper investigation of the systems-level mechanisms by which exogenous OXT and AVP modulate brain function and exert their putative therapeutic effects.

Amygdalar Endothelin-1 Regulates Pyramidal Neuron Excitability and Affects Anxiety

An abnormal neuronal activity in the amygdala is involved in the pathogenesis of anxiety disorders. However, little is known about the mechanisms. High-anxiety mice and low-anxiety mice, representing the innate extremes of anxiety-related behaviors, were first grouped according to their anxiety levels in the elevated plus maze test. We found that the mRNA for endothelin-1 (ET1) and ET1 B-type receptors (ETBRs) in the amygdala was down-regulated in high-anxiety mice compared with low-anxiety mice. Knocking down basolateral amygdala (BLA) ET1 expression enhanced anxiety-like behaviors, whereas over-expressing ETBRs, but not A-type receptors (ETARs), had an anxiolytic effect. The combined down-regulation of ETBR and ET1 had no additional anxiogenic effect compared to knocking down the ETBR gene alone, suggesting that BLA ET1 acts through ETBRs to regulate anxiety-like behaviors. To explore the mechanism underlying this phenomenon further, we verified that most of the ET1 and the ET1 receptors in the BLA were expressed in pyramidal neurons. The ET1–ETBR signaling pathway decreased the firing frequencies and threshold currents for the action potentials of BLA pyramidal neurons but did not alter BLA synaptic neurotransmission. Together, these results indicate that amygdalar ET1-ETBR signaling could attenuate anxiety-like behaviors by directly decreasing the excitability of glutamatergic neurons.

Genome-wide association study for behavior, type traits, and muscular development in Charolais beef cattle

Behavior, type traits, and muscular development are of interest for beef cattle breeding. Genome-wide association studies (GWAS) enable the identification of candidate genes, which enables gene-based selection and provides insight in the genetic architecture of these traits. The objective of the current study was to perform a GWAS for 3 behavior traits, 12 type traits, and muscular development in Charolais cattle. Behavior traits, including aggressiveness at parturition, aggressiveness during gestation period, and maternal care, were scored by farmers. Type traits, including udder conformation, teat, feet and legs, and locomotion, were scored by trained classifiers. Data used in the GWAS consisted of 3,274 cows with phenotypic records and genotyping information for 44,930 SNP. When SNP had a false discovery rate (FDR) smaller than 0.05, they were referred to as significant. When SNP had a FDR between 0.05 and 0.20, they were referred to as suggestive. Four significant and 12 suggestive regions were detected for aggressiveness during gestation, maternal care, udder balance, teat thinness, teat length, foot angle, foot depth, and locomotion. These 4 significant and 12 suggestive regions were not supported by other significant SNP in close proximity. No SNP with major effects were detected for behavior and type traits, and SNP associations for these traits were spread across the genome, suggesting that behavior and type traits were influenced by many genes, each explaining a small part of genetic variance. The GWAS identified 1 region on chromosome 2 significantly associated with muscular development, which included the myostatin gene (), which is known to affect muscularity. No other regions associated with muscular development were found. Results showed that the myostatin region associated with muscular development had pleiotropic effects on udder volume, teat thinness, rear leg, and leg angle.

Modelling depression in animals: at the interface of reward and stress pathways

RATIONALE

Despite substantial research efforts the aetiology of major depressive disorder (MDD) remains poorly understood, which is due in part to the heterogeneity of the disorder and the complexity of designing appropriate animal models. However, in the last few decades, a focus on the development of novel stress-based paradigms and a focus on using hedonic/anhedonic behaviour have led to renewed optimism in the use of animal models to assess aspects of MDD.

OBJECTIVES

Therefore, in this review article, dedicated to Athina Markou, we summarise the use of stress-based animal models for studying MDD in rodents and how reward-related readouts can be used to validate/assess the model and/or treatment.

RESULTS

We reveal the use and limitations of chronic stress paradigms, which we split into non-social (i.e. chronic mild stress), social (i.e. chronic social defeat) and drug-withdrawal paradigms for studying MDD and detail numerous reward-related readouts that are employed in preclinical research. Finally, we finish with a section regarding important factors to consider when using animal models.

CONCLUSIONS

One of the most consistent findings following chronic stress exposure in rodents is a disruption of the brain reward system, which can be easily assessed using sucrose, social interaction, food, drug of abuse or intracranial self-stimulation as a readout. Probing the underlying causes of such alterations is providing a greater understanding of the potential systems and processes that are disrupted in MDD.

Cellular and molecular mechanisms triggered by Deep Brain Stimulation in depression: A preclinical and clinical approach

Deep Brain Stimulation (DBS) was originally developed as a therapeutic approach to manage movement disorders, in particular Parkinson's Disease. However, DBS also seems to be an effective treatment against refractory depression when patients fail to respond satisfactorily to conventional therapies. Thus, DBS targeting specific brain areas can produce an antidepressant response that improves depressive symptomatology, these areas including the subcallosal cingulate region, nucleus accumbens, ventral capsule/ventral striatum, medial forebrain bundle, the inferior thalamic peduncle and lateral habenula. Although the efficacy and safety of this therapy has been demonstrated in some clinical trials and preclinical studies, the intrinsic mechanisms underlying its antidepressant effect remain poorly understood. This review aims to provide a comprehensive overview of DBS, focusing on the molecular and cellular changes reported after its use that could shed light on the mechanisms underpinning its antidepressant effect. Several potential mechanisms of action of DBS are considered, including monoaminergic and glutamatergic neurotransmission, neurotrophic and neuroinflammatory mechanisms, as well as potential effects on certain intracellular signaling pathways. Although future studies will be necessary to determine the key molecular events underlying the antidepressant effect of DBS, the findings presented provide an insight into some of its possible modes of action.

Vasopressinergic control of stress-related behavior: studies in Brattleboro rats

Vasopressin, a nonapeptide, signaling both as hormone in the blood and neuromodulator/neurotransmitter in the brain is considered to be causally involved in the pathological changes underlying anxiety and depression. In the present review we summarize experimental data obtained with Brattleboro rats as a model of congenital vasopressin-deficiency to test the hypothesis that central vasopressin signaling contributes to anxiety- and depression-like behavior. Male, female and lactating rats were studied. We focused on the paraventricular nucleus of the hypothalamus (PVN) and the septum, two brain areas in which vasopressin is proposed to control the endocrine and behavioral stress response, respectively. The presented data support the hypothesis that the behavioral changes seen in these rats are brought about by an altered vasopressin signaling at the brain level. Whereas vasopressin synthesized and released within the hypothalamus is primarily involved in endocrine regulation, vasopressin signaling in other brain areas may contribute to anxiety- and depression-like behavioral parameters. Further studies in this context might focus particularly on the interplay between extra-hypothalamic brain areas such as the septum and the medial amygdala.

Neuroendocrine Regulation of Anxiety: Beyond the Hypothalamic-Pituitary-Adrenal Axis

The central nervous system regulates and responds to endocrine signals, and this reciprocal relationship determines emotional processing and behavioural anxiety. Although the hypothalamic-pituitary-adrenal (HPA) axis remains the best-characterised system for this relationship, other steroid and peptide hormones are increasingly recognised for their effects on anxiety-like behaviour and reward. The present review examines recent developments related to the role of a number of different hormones in anxiety, including pregnane neurosteroids, gut peptides, neuropeptides and hormonal signals derived from fatty acids. Findings from both basic and clinical studies suggest that these alternative systems may complement or occlude stress-induced changes in anxiety and anxiety-like behaviour. By broadening the scope of mechanisms for depression and anxiety, it may be possible to develop novel strategies to attenuate stress-related psychiatric conditions. The targets for these potential therapies, as discussed in this review, encompass multiple circuits and systems, including those outside of the HPA axis.

What Can Ethobehavioral Studies Tell Us about the Brain's Fear System?

Foraging-associated predation risk is a natural problem all prey must face. Fear evolved due to its protective functions, guiding and shaping behaviors that help animals adapt to various ecological challenges. Despite the breadth of risky situations in nature that demand diversity in fear behaviors, contemporary neurobiological models of fear stem largely from Pavlovian fear conditioning studies that focus on how a particular cue becomes capable of eliciting learned fear responses, thus oversimplifying the brain's fear system. Here we review fear from functional, mechanistic, and phylogenetic perspectives where environmental threats cause animals to alter their foraging strategies in terms of spatial and temporal navigation, and discuss whether the inferences we draw from fear conditioning studies operate in the natural world.

Selective Mitochondrial Targeting Exerts Anxiolytic Effects In Vivo

Current treatment strategies for anxiety disorders are predominantly symptom-based. However, a third of anxiety patients remain unresponsive to anxiolytics highlighting the need for more effective, mechanism-based therapeutic approaches. We have previously compared high vs low anxiety mice and identified changes in mitochondrial pathways, including oxidative phosphorylation and oxidative stress. In this work, we show that selective pharmacological targeting of these mitochondrial pathways exerts anxiolytic effects in vivo. We treated high anxiety-related behavior (HAB) mice with MitoQ, an antioxidant that selectively targets mitochondria. MitoQ administration resulted in decreased anxiety-related behavior in HAB mice. This anxiolytic effect was specific for high anxiety as MitoQ treatment did not affect the anxiety phenotype of C57BL/6N and DBA/2J mouse strains. We furthermore investigated the molecular underpinnings of the MitoQ-driven anxiolytic effect and found that MitoQ treatment alters the brain metabolome and that the response to MitoQ treatment is characterized by distinct molecular signatures. These results indicate that a mechanism-driven approach based on selective mitochondrial targeting has the potential to attenuate the high anxiety phenotype in vivo, thus paving the way for translational implementation as long-term MitoQ administration is well-tolerated with no reported side effects in mice and humans.

Oxytocin Stimulates Extracellular Ca2+ Influx Through TRPV2 Channels in Hypothalamic Neurons to Exert Its Anxiolytic Effects

There is growing interest in anxiolytic and pro-social effects of the neuropeptide oxytocin (OXT), but the underlying intraneuronal mechanisms are largely unknown. Here we examined OXT-mediated anxiolysis in the hypothalamic paraventricular nucleus (PVN) of rats and effects of OXT administration on signaling events in hypothalamic primary and immortalized cells. In vivo, the application of SKF96365 prevented the anxiolytic activity of OXT in the PVN, suggesting that changes in intracellular Ca(2+) mediate the acute OXT behavioral effects. In vitro, mainly in the neurons with autonomous Ca(2+) oscillations, OXT increased intracellular Ca(2+) concentration and oscillation amplitude. Pharmacological intervention revealed OXT-dependent changes in Ca(2+) signaling that required activation of transient receptor potential vanilloid type-2 channel (TRPV2), mediated by phosphoinositide 3-kinase. TRPV2 induced the activation of the anxiolytic mitogen-activated protein kinase kinase (MEK1/2). In situ, immunohistochemistry revealed co-localization of TRPV2 and OXT in the PVN. Thus, functional and pharmacological analyses identified TRPV2 as a mediator of anxiolytic effects of OXT, conveying the OXT signal to MEK1/2 via modulation of intracellular Ca(2+).

Selective breeding for high anxiety introduces a synonymous SNP that increases neuropeptide S receptor activity

Neuropeptide S (NPS) has generated substantial interest due to its anxiolytic and fear-attenuating effects in rodents, while a corresponding receptor polymorphism associated with increased NPS receptor (NPSR1) surface expression and efficacy has been implicated in an increased risk of panic disorder in humans. To gain insight into this paradox, we examined the NPS system in rats and mice bred for high anxiety-related behavior (HAB) versus low anxiety-related behavior, and, thereafter, determined the effect of central NPS administration on anxiety- and fear-related behavior. The HAB phenotype was accompanied by lower basal NPS receptor (Npsr1) expression, which we could confirm via in vitro dual luciferase promoter assays. Assessment of shorter Npsr1 promoter constructs containing a sequence mutation that introduces a glucocorticoid receptor transcription factor binding site, confirmed via oligonucleotide pull-down assays, revealed increased HAB promoter activity-an effect that was prevented by dexamethasone. Analogous to the human NPSR1 risk isoform, functional analysis of a synonymous single nucleotide polymorphism in the coding region of HAB rodents revealed that it caused a higher cAMP response to NPS stimulation. Assessment of the behavioral consequence of these differences revealed that intracerebroventricular NPS reversed the hyperanxiety of HAB rodents as well as the impaired cued-fear extinction in HAB rats and the enhanced fear expression in HAB mice, respectively. These results suggest that alterations in the NPS system, conserved across rodents and humans, contribute to innate anxiety and fear, and that HAB rodents are particularly suited to resolve the apparent discrepancy between the preclinical and clinical findings to date.

The ups and downs of modelling mood disorders in rodents

The wide spectrum of disruptions that characterizes major depressive disorder (MDD) and bipolar disorder (BD) highlights the difficulties researchers are posed with as they try to mimic these disorders in the laboratory. Nonetheless, numerous attempts have been made to create rodent models of mood disorders or at least models of the symptoms of MDD and BD. Present antidepressants are all descendants of the serendipitous findings in the 1950s that the monoamine oxidase inhibitor iproniazid and the tricyclic antidepressant imipramine were effective antidepressants. Thus, the need for improved animal models to provide insights into the neuropathology underlying the disease is critical. Such information is in turn crucial for identifying new antidepressants and mood stabilisers. Currently, there is a shift away from traditional animal models to more focused research dealing with an endophenotype-style approach, genetic models, and incorporation of new findings from human neuroimaging and genetic studies. Such approaches are opening up more tractable avenues for understanding the neurobiological and genetic bases of these disorders. Further, such models promise to yield better translational animal models and hence more fruitful therapeutic targets. This overview focuses on such animal models and tests and how they can be used to assess MDD and BD in rodents.

Connecting Anxiety and Genomic Copy Number Variation: A Genome-Wide Analysis in CD-1 Mice

Genomic copy number variants (CNVs) have been implicated in multiple psychiatric disorders, but not much is known about their influence on anxiety disorders specifically. Using next-generation sequencing (NGS) and two additional array-based genotyping approaches, we detected CNVs in a mouse model consisting of two inbred mouse lines showing high (HAB) and low (LAB) anxiety-related behavior, respectively. An influence of CNVs on gene expression in the central (CeA) and basolateral (BLA) amygdala, paraventricular nucleus (PVN), and cingulate cortex (Cg) was shown by a two-proportion Z-test (p = 1.6 x 10^-31), with a positive correlation in the CeA (p = 0.0062), PVN (p = 0.0046) and Cg (p = 0.0114), indicating a contribution of CNVs to the genetic predisposition to trait anxiety in the specific context of HAB/LAB mice. In order to confirm anxiety-relevant CNVs and corresponding genes in a second mouse model, we further examined CD-1 outbred mice. We revealed the distribution of CNVs by genotyping 64 CD 1 individuals using a high-density genotyping array (Jackson Laboratory). 78 genes within those CNVs were identified to show nominally significant association (48 genes), or a statistical trend in their association (30 genes) with the time animals spent on the open arms of the elevated plus-maze (EPM). Fifteen of them were considered promising candidate genes of anxiety-related behavior as we could show a significant overlap (permutation test, p = 0.0051) with genes within HAB/LAB CNVs. Thus, here we provide what is to our knowledge the first extensive catalogue of CNVs in CD-1 mice and potential corresponding candidate genes linked to anxiety-related behavior in mice.

Intranasally applied neuropeptide S shifts a high-anxiety electrophysiological endophenotype in the ventral hippocampus towards a "normal"-anxiety one

The neurobiological basis of pathological anxiety and the improvement of its pharmacological treatment are a matter of intensive investigation. Here, using electrophysiological techniques in brain slices from animals of the high anxiety-related behavior (HAB) and normal anxiety-related behavior (NAB) mouse model, we show that basal neurotransmission at ventral hippocampal CA3-CA1 synapses is weaker in HAB compared to NAB mice. We further demonstrate that paired-pulse facilitation (PPF) and long-term potentiation (LTP) at these synapses are more pronounced in slices from HAB animals. Based on previous findings, we also examined whether intranasal delivery of neuropeptide S (NPS), which increasingly emerges as a potential novel treatment option for anxiety symptoms occurring in a variety of diseases like anxiety disorders, posttraumatic stress disorder, and major depression, impacts on the high-anxiety electrophysiological endophenotype in HAB mice. Strikingly, we detected enhanced basal neurotransmission and reduced PPF and LTP in slices from NPS-treated HAB animals. Collectively, our study uncovers a multifaceted high-anxiety neurophysiological endophenotype in the murine ventral hippocampus and provides the first evidence that an intranasally applied neuropeptide can shift such an endophenotype in an anxiety-regulating brain structure towards a “normal”-anxiety one.

Phobic Anxiety and Plasma Levels of Global Oxidative Stress in Women

BACKGROUND AND OBJECTIVES

Psychological distress has been hypothesized to be associated with adverse biologic states such as higher oxidative stress and inflammation. Yet, little is known about associations between a common form of distress - phobic anxiety - and global oxidative stress. Thus, we related phobic anxiety to plasma fluorescent oxidation products (FlOPs), a global oxidative stress marker.

METHODS

We conducted a cross-sectional analysis among 1,325 women (aged 43-70 years) from the Nurses' Health Study. Phobic anxiety was measured using the Crown-Crisp Index (CCI). Adjusted least-squares mean log-transformed FlOPs were calculated across phobic categories. Logistic regression models were used to calculate odds ratios (OR) comparing the highest CCI category (≥6 points) vs. lower scores, across FlOPs quartiles.

RESULTS

No association was found between phobic anxiety categories and mean FlOP levels in multivariable adjusted linear models. Similarly, in multivariable logistic regression models there were no associations between FlOPs quartiles and likelihood of being in the highest phobic category. Comparing women in the highest vs. lowest FlOPs quartiles: FlOP_360: OR=0.68 (95% CI: 0.40-1.15); FlOP_320: OR=0.99 (95% CI: 0.61-1.61); FlOP_400: OR=0.92 (95% CI: 0.52, 1.63).

CONCLUSIONS

No cross-sectional association was found between phobic anxiety and a plasma measure of global oxidative stress in this sample of middle-aged and older women.

Restoration of peripheral V2 receptor vasopressin signaling fails to correct behavioral changes in Brattleboro rats

Beside its hormonal function in salt and water homeostasis, vasopressin released into distinct brain areas plays a crucial role in stress-related behavior resulting in the enhancement of an anxious/depressive-like state. We aimed to investigate whether correction of the peripheral symptoms of congenital absence of AVP also corrects the behavioral alterations in AVP-deficient Brattleboro rats. Wild type (WT) and vasopressin-deficient (KO) male Brattleboro rats were tested. Half of the KO animals were treated by desmopressin (V2-receptor agonist) via osmotic minipump (subcutaneous) to eliminate the peripheral symptoms of vasopressin-deficiency. Anxiety was studied by elevated plus maze (EPM), defensive withdrawal (DW) and marble burying (MB) tests, while depressive-like changes were monitored in forced swimming (FS) and anhedonia by sucrose preference test. Cell activity was examined in septum and amygdala by c-Fos immunohistochemistry after 10 min FS. KO rats spent more time in the open arm of the EPM, spent less time at the periphery of DW and showed less burying behavior in MB suggesting a reduced anxiety state. KO animals showed less floating behavior during FS revealing a less depressive phenotype. Desmopressin treatment compensated the peripheral effects of vasopressin-deficiency without a significant influence on the behavior. The FS-induced c-Fos immunoreactivity in the medial amygdala was different in WT and KO rats, with almost identical levels in KO and desmopressin treated animals. There were no differences in central and basolateral amygdala as well as in lateral septum. Our data confirmed the role of vasopressin in the development of affective disorders through central mechanisms. The involvement of the medial amygdala in the behavioral alterations of vasopressin deficient animals deserves further attention.

Increased conditioned place preference for cocaine in high anxiety related behavior (HAB) mice is associated with an increased activation in the accumbens corridor

Anxiety disorders and substance use disorders are strongly associated in humans. Accordingly, a widely held but controversial concept in the addiction field, the so-called “self-medication hypothesis,” posits that anxious individuals are more vulnerable for drug dependence because they use drugs of abuse to alleviate their anxiety. We tested this hypothesis under controlled experimental conditions by quantifying the conditioned place preference (CPP) to 15 mg/kg i.p. cocaine given contingently (COCAINE) in CD1 mice selectively bred for high anxiety-related behavior (HAB) vs. normal anxiety-related behavior (NAB). Cocaine was conditioned to the initially non-preferred compartment in an alternate day design (cocaine vs. saline, four pairings each). HAB and NAB mice were also tested for the effects of non-contingent (NONCONT) cocaine administration. HAB mice showed a slightly higher bias for one of the conditioning compartments during the pretest than NAB mice that became statistically significant (p = 0.045) only after pooling COCAINE and NONCONT groups. Cocaine CPP was higher (p = 0.0035) in HAB compared to NAB mice. The increased cocaine CPP was associated with an increased expression of the immediate early genes (IEGs) c-Fos and Early Growth Related Protein 1 (EGR1) in the accumbens corridor, i.e., a region stretching from the anterior commissure to the interhemispheric border and comprising the medial nucleus accumbens core and shell, the major island of Calleja and intermediate part of the lateral septum, as well as the vertical limb of the diagonal band and medial septum. The cocaine CPP-induced EGR1 expression was only observed in D1- and D2-medium spiny neurons, whereas other types of neurons or glial cells were not involved. With respect to the activation by contingent vs. non-contingent cocaine EGR1 seemed to be a more sensitive marker than c-Fos. Our findings suggest that cocaine may be more rewarding in high anxiety individuals, plausibly due to an anxiolytic effect.

Effect of acute swim stress on plasma corticosterone and brain monoamine levels in bidirectionally selected DxH recombinant inbred mouse strains differing in fear recall and extinction

Stress-induced changes in plasma corticosterone and central monoamine levels were examined in mouse strains that differ in fear-related behaviors. Two DxH recombinant inbred mouse strains with a DBA/2J background, which were originally bred for a high (H-FSS) and low fear-sensitized acoustic startle reflex (L-FSS), were used. Levels of noradrenaline, dopamine, and serotonin and their metabolites 3,4-dihydroxyphenyacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) were studied in the amygdala, hippocampus, medial prefrontal cortex, striatum, hypothalamus and brainstem. H-FSS mice exhibited increased fear levels and a deficit in fear extinction (within-session) in the auditory fear-conditioning test, and depressive-like behavior in the acute forced swim stress test. They had higher tissue noradrenaline and serotonin levels and lower dopamine and serotonin turnover under basal conditions, although they were largely insensitive to stress-induced changes in neurotransmitter metabolism. In contrast, acute swim stress increased monoamine levels but decreased turnover in the less fearful L-FSS mice. L-FSS mice also showed a trend toward higher basal and stress-induced corticosterone levels and an increase in noradrenaline and serotonin in the hypothalamus and brainstem 30 min after stress compared to H-FSS mice. Moreover, the dopaminergic system was activated differentially in the medial prefrontal cortex and striatum of the two strains by acute stress. Thus, H-FSS mice showed increased basal noradrenaline tissue levels compatible with a fear phenotype or chronic stressed condition. Low corticosterone levels and the poor monoamine response to stress in H-FSS mice may point to mechanisms similar to those found in principal fear disorders or post-traumatic stress disorder.

Behavioral extremes of trait anxiety in mice are characterized by distinct metabolic profiles

No comprehensive metabolic profile of trait anxiety is to date available. To identify metabolic biosignatures for different anxiety states, we compared mice selectively inbred for ∼ 40 generations for high (HAB), normal (NAB) or low (LAB) anxiety-related behavior. Using a mass spectrometry-based targeted metabolomics approach, we quantified the levels of 257 unique metabolites in the cingulate cortex and plasma of HAB, NAB and LAB mice. We then pinpointed affected molecular systems in anxiety-related behavior by an in silico pathway and network prediction analysis followed by validation of in silico predicted alterations with molecular assays. We found distinct metabolic profiles for different trait anxiety states and detected metabolites with altered levels both in cingulate cortex and plasma. Metabolomics data revealed common candidate biomarkers in cingulate cortex and plasma for anxiety traits and in silico pathway analysis implicated amino acid metabolism, pyruvate metabolism, oxidative stress and apoptosis in the regulation of anxiety-related behavior. We report characteristic biosignatures for trait anxiety states and provide a network map of pathways involved in anxiety-related behavior. Pharmacological targeting of these pathways will enable a mechanism-based approach for identifying novel therapeutic targets for anxiety disorders.

Blunted HPA axis reactivity reveals glucocorticoid system dysbalance in a mouse model of high anxiety-related behavior

Depression and anxiety disorders are often characterized by altered hypothalamic-pituitary-adrenal (HPA) axis re-/activity. However, the presence of a molecular link between dysbalanced neuroendocrine regulation and psychopathologies is not yet fully established. Earlier, we reported that high (HAB), normal (NAB) and low (LAB) anxiety-related behavior mice express divergent anxiety-related and passive/active coping phenotypes. Here, we studied mechanisms that might contribute to the different HPA axis reactivity observed in HAB, NAB and LAB mice and their involvement in the regulation of anxiety-related behavior and passive/active coping style. We found that HAB mice respond with significantly reduced corticosterone (CORT) secretion to an acute stressful stimulus and a blunted response in the Dex/CRH test compared to NAB and LAB mice. At the molecular level, higher expression of the glucocorticoid receptor (GR/Nr3c1) and decreased corticotropin-releasing hormone receptor 1 (CRHR1) expression were observed in the pituitary of HAB mice. We further analyzed whether these stress mediators differed between the HAB, NAB and LAB lines in limbic system-associated brain regions and whether their interplay contributes to the phenotype. Interestingly, not only in the pituitary but also in almost all brain regions investigated, GR expression was significantly higher in HAB mice. In contrast, the amount of CORT in the brain structures analyzed was significantly lower in these animals. The expression of CRHR1 varied in the prefrontal cortex only. Since glucocorticoids regulate both GR and CRHR1, we treated HAB and NAB mice chronically with CORT. After 6 weeks of administration, reduced anxiety- and depression-like behaviors were observed in HAB mice, whereas increased anxiety was found in NABs. In both groups, GR, but not CRHR1, were significantly reduced. Taken together, our study proposes HAB mice as an animal model of simultaneous features of increased anxiety-related and depression-like behaviors with blunted HPA axis reactivity suggesting a dysregulated GR/CORT system as one key mechanism behind their phenotype.

Chronic unpredictable stress and long-term ovariectomy affect arginine-vasopressin expression in the paraventricular nucleus of adult female mice

Arginine-Vasopressin (AVP) may regulate the hypothalamic-pituitary-adrenal axis (HPA) and its effects on depressive responses. In a recent study, we demonstrated that Chronic Unpredictable Stress (CUS) depressive effects are enhanced by long-term ovariectomy (a model of post-menopause). In the present study, we investigated the effects of long-term ovariectomy and CUS on AVP expression in different subdivision of the paraventricular nucleus (PVN) of female mice. Both long-term ovariectomy and CUS affect AVP immunoreactivity in some of the PVN subnuclei of adult female mice. In particular, significant changes on AVP immunoreactivity were observed in magnocellular subdivisions, the paraventricular lateral magnocellular (PaLM) and the paraventricular medial magnocellular (PaMM), the 2 subnuclei projecting to the neurohypophysis for the hormonal regulation of body homeostasis. AVP immunoreactivity was decreased in the PaLM by both the long-term deprivation of ovarian hormones and the CUS. In contrast, AVP immunoreactivity was increased in the PaMM by CUS, whereas it was decreased by ovariectomy. Therefore, present results suggest morphological and functional differences among the PVN's subnuclei and complex interactions among CUS, gonadal hormones and AVP immunoreactivity.

Relationship of cortisol levels and genetic polymorphisms to antidepressant response to placebo and fluoxetine in patients with major depressive disorder: a prospective study

BACKGROUND

Increased cortisol levels and genetic polymorphisms have been related to both major depressive disorder and antidepressant treatment outcome. The aim of this study is to evaluate the relationship between circadian salivary cortisol levels, cortisol suppression by dexamethasone and genetic polymorphisms in some HPA axis-related genes to the response to placebo and fluoxetine in depressed patients.

METHODS

The diagnosis and severity of depression were performed using the Mini International Neuropsychiatric Interview (M.I.N.I.) and Hamilton depression scale (HAM-D17), respectively. Euthyroid patients were treated with placebo (one week) followed by fluoxetine (20 mg) (two months). Severity of depression was re-evaluated after placebo, three weeks and two months of fluoxetine treatments. Placebo response was defined as HAM-D17 score reductions of at least 25% and to < 15. Early response and response were reductions of at least 50% after three weeks and two months, and remission with ≤ 7 after two months. Plasma TSH, free-T4, circadian salivary cortisol levels and cortisol suppression by dexamethasone were evaluated. Seven genetic polymorphisms located in the Corticotrophin-releasing-hormone-receptor-1 (rs242939, rs242941, rs1876828), Corticotrophin-releasing-hormone-receptor-2 (rs2270007), Glucocorticoid-receptor (rs41423247), FK506-binding-protein-5 (rs1360780), and Arginine-vasopressin (rs3729965) genes were determined. Association analyses between response to placebo/fluoxetine and polymorphism were performed by chi-square or Fisher exact test. Cortisol levels were compared by t-test, ANOVA and the general linear model for repeated measures.

RESULTS

208 depressed patients were recruited, 187 of whom were euthyroid. Placebo responders, fluoxetine responders and remitters exhibited significantly lower circadian cortisol levels than those who did not respond (p-values of 0.014, 0.008 and 0.021 respectively). Patients who abandoned treatment before the third week also exhibited a trend to low cortisol levels (p = 0.057). The polymorphisms rs242939 (CRHR1) and rs2270007 (CRHR2) were not in Hardy-Weinberg equilibrium. Only the rs242939 polymorphism (CRHR1) exhibited association with early response (three weeks) to fluoxetine (p-value = 0.043). No other association between outcomes and polymorphisms was observed.

CONCLUSIONS

These results support the clinical relevance of low salivary cortisol levels as a predictor of antidepressant response, either to placebo or to fluoxetine. Only one polymorphism in the CRHR1 gene was associated with the early response. Other factors may be involved in antidepressant response, although further studies are needed to identify them.

Circadian abnormalities in a mouse model of high trait anxiety and depression

INTRODUCTION

Dysregulation of circadian rhythms is a key symptom of mood disorders, including anxiety disorders and depression. Whether the circadian abnormalities observed in depressed patients are cause or consequence of the disease remains elusive. Here we aimed to explore potential disturbances of circadian rhythms in a validated genetic animal model of high trait anxiety and co-morbid depression and examine its molecular correlates.

MATERIALS AND METHODS

Mice selectively bred for high (HAB) and normal (NAB) anxiety- and co-segregating depression-like behavior were subjected to analysis of circadian wheel-running activity to determine light-entrained (LD) and free-running circadian (DD) rhythms and a light-induced phase shift. Clock gene expression in HAB/NAB hippocampal tissue was analyzed by qRT-PCR and verified by Western blotting.

RESULTS

Compared to NABs, HAB mice were found to present with altered DD length of daily cycle, fragmented ultradiem rhythms, and a blunted phase shift response. Clock gene expression analysis revealed a selective reduction of Cry2 expression in hippocampal tissue of HAB mice.

DISCUSSION

We provide first evidence for a dysregulation of circadian rhythms in a mouse model of anxiety and co-morbid depression which suggests an association between depression and altered circadian rhythms at the genetic level and points towards a role for Cry2.

Environmental manipulations generate bidirectional shifts in both behavior and gene regulation in a crossbred mouse model of extremes in trait anxiety

Although gene-environment interactions are known to significantly influence psychopathology-related disease states, only few animal models cover both the genetic background and environmental manipulations. Therefore, we have taken advantage of the bidirectionally inbred high (HAB) and low (LAB) anxiety-related behavior mouse lines to generate HAB × LAB F1 hybrids that intrinsically carry both lines’ genetic characteristics, and subsequently raised them in three different environments—standard, enriched (EE) and chronic mild stress (CMS). Assessing genetic correlates of trait anxiety, we focused on two genes already known to play a role in HAB vs. LAB mice, corticotropin releasing hormone receptor type 1 (Crhr1) and high mobility group nucleosomal binding domain 3 (Hmgn3). While EE F1 mice showed decreased anxiety-related and increased explorative behaviors compared to controls, CMS sparked effects in the opposite direction. However, environmental treatments affected the expression of the two genes in distinct ways. Thus, while expression ratios of Hmgn3 between the HAB- and LAB-specific alleles remained equal, total expression resembled the one observed in HAB vs. LAB mice, i.e., decreased after EE and increased after CMS treatment. On the other hand, while total expression of Crhr1 remained unchanged between the groups, the relative expression of HAB- and LAB-specific alleles showed a clear effect following the environmental modifications. Thus, the environmentally driven bidirectional shift of trait anxiety in this F1 model strongly correlated with Hmgn3 expression, irrespective of allele-specific expression patterns that retained the proportions of basic differential HAB vs. LAB expression, making this gene a match for environment-induced modifications. An involvement of Crhr1 in the bidirectional behavioral shift could, however, rather be due to different effects of the HAB- and LAB-specific alleles described here. Both candidate genes therefore deserve attention in the complex regulation of anxiety-related phenotypes including environment-mediated effects.

Association of oxidative stress to the genesis of anxiety: implications for possible therapeutic interventions

Oxidative stress caused by reactive species, including reactive oxygen species, reactive nitrogen species, and unbound, adventitious metal ions (e.g., iron [Fe] and copper [Cu]), is an underlying cause of various neurodegenerative diseases. These reactive species are an inevitable by-product of cellular respiration or other metabolic processes that may cause the oxidation of lipids, nucleic acids, and proteins. Oxidative stress has recently been implicated in depression and anxiety-related disorders. Furthermore, the manifestation of anxiety in numerous psychiatric disorders, such as generalized anxiety disorder, depressive disorder, panic disorder, phobia, obsessive-compulsive disorder, and posttraumatic stress disorder, highlights the importance of studying the underlying biology of these disorders to gain a better understanding of the disease and to identify common biomarkers for these disorders. Most recently, the expression of glutathione reductase 1 and glyoxalase 1, which are genes involved in antioxidative metabolism, were reported to be correlated with anxiety-related phenotypes. This review focuses on direct and indirect evidence of the potential involvement of oxidative stress in the genesis of anxiety and discusses different opinions that exist in this field. Antioxidant therapeutic strategies are also discussed, highlighting the importance of oxidative stress in the etiology, incidence, progression, and prevention of psychiatric disorders.

Stress resilience: a low-anxiety genotype protects male mice from the consequences of chronic psychosocial stress

Chronic psychosocial stress is a risk factor for the development of affective as well as somatic disorders. However, vulnerability to adverse stress effects varies between individuals, with previous negative life events along with genetic predisposition playing a major role. In support, we previously showed that the consequences of chronic psychosocial stress induced by chronic subordinate colony housing (CSC, 19 days) can be amplified by pre-exposing mice to repeated maternal separation during early life. To test the significance of the genetic predisposition on the effects of CSC, mice selectively bred for high (mHAB) and low (mLAB) anxiety-related behavior and nonselected CD1 mice (mNAB) were exposed to CSC in the present study. In confirmation of our previous results, CSC mice of both mHAB and mNAB lines displayed chronic stress-related symptoms including increased adrenal weight, decreased adrenal in vitro ACTH sensitivity, lower plasma corticosterone to ACTH ratio, and increased interferon-γ secretion from isolated mesenteric lymph node cells compared with single-housed controls of the respective line. However, the CSC-induced anxiogenic effect found in mNAB was not confirmed in mHAB mice, possibly due to a ceiling effect in these highly anxious mice. Interestingly, mHAB were not more vulnerable to CSC than mNAB mice, whereas mLAB mice were resilient to CSC as indicated by all of the above mentioned parameters assessed. Taken together, our findings indicate that the genetic predisposition, in this case the innate anxiety of an individual, affects vulnerability to chronic psychosocial stress, with a low-anxiety phenotype mediating resilience to both affective and somatic consequences of CSC.

Neuropathology of stress

Environmental challenges are part of daily life for any individual. In fact, stress appears to be increasingly present in our modern, and demanding, industrialized society. Virtually every aspect of our body and brain can be influenced by stress and although its effects are partly mediated by powerful corticosteroid hormones that target the nervous system, relatively little is known about when, and how, the effects of stress shift from being beneficial and protective to becoming deleterious. Decades of stress research have provided valuable insights into whether stress can directly induce dysfunction and/or pathological alterations, which elements of stress exposure are responsible, and which structural substrates are involved. Using a broad definition of pathology, we here review the “neuropathology of stress” and focus on structural consequences of stress exposure for different regions of the rodent, primate and human brain. We discuss cytoarchitectural, neuropathological and structural plasticity measures as well as more recent neuroimaging techniques that allow direct monitoring of the spatiotemporal effects of stress and the role of different CNS structures in the regulation of the hypothalamic–pituitary–adrenal axis in human brain. We focus on the hypothalamus, hippocampus, amygdala, nucleus accumbens, prefrontal and orbitofrontal cortex, key brain regions that not only modulate emotions and cognition but also the response to stress itself, and discuss disorders like depression, post-traumatic stress disorder, Cushing syndrome and dementia.

50 years of hurdles and hope in anxiolytic drug discovery

Anxiety disorders are the most prevalent group of psychiatric diseases, and have high personal and societal costs. The search for novel pharmacological treatments for these conditions is driven by the growing medical need to improve on the effectiveness and the side effect profile of existing drugs. A huge volume of data has been generated by anxiolytic drug discovery studies, which has led to the progression of numerous new molecules into clinical trials. However, the clinical outcome of these efforts has been disappointing, as promising results with novel agents in rodent studies have very rarely translated into effectiveness in humans. Here, we analyse the major trends from preclinical studies over the past 50 years conducted in the search for new drugs beyond those that target the prototypical anxiety-associated GABA (γ-aminobutyric acid)-benzodiazepine system, which have focused most intensively on the serotonin, neuropeptide, glutamate and endocannabinoid systems. We highlight various key issues that may have hampered progress in the field, and offer recommendations for how anxiolytic drug discovery can be more effective in the future.

Maternal aggression in rodents: brain oxytocin and vasopressin mediate pup defence

The most significant social behaviour of the lactating mother is maternal behaviour, which comprises maternal care and maternal aggression (MA). The latter is a protective behaviour of the mother serving to defend the offspring against a potentially dangerous intruder. The extent to which the mother shows aggressive behaviour depends on extrinsic and intrinsic factors, as we have learned from studies in laboratory rodents. Among the extrinsic factors are the pups' presence and age, as well as the intruders' sex and age. With respect to intrinsic factors, the mothers' innate anxiety and the prosocial brain neuropeptides oxytocin (OXT) and arginine vasopressin (AVP) play important roles. While OXT is well known as a maternal neuropeptide, AVP has only recently been described in this context. The increased activities of these neuropeptides in lactation are the result of remarkable brain adaptations peripartum and are a prerequisite for the mother to become maternal. Consequently, OXT and AVP are significantly involved in mediating the fine-tuned regulation of MA depending on the brain regions. Importantly, both neuropeptides are also modulators of anxiety, which determines the extent of MA. This review provides a detailed overview of the role of OXT and AVP in MA and the link to anxiety.