Effects of chronic mild stress on sexual behavior, locomotor activity and consumption of sucrose and saccharine solutions

Do Behaviour Assessments in a Shelter Predict the Behaviour of Dogs Post-Adoption?

Simple Summary

In shelters it is usual to conduct standardised behaviour assessments on all incoming dogs. The information gathered from the assessment is used to identify dogs that are suitable for adoption and assist in matching dogs with suitable adopters. We investigated the predictive value of the standardised behaviour assessment protocol currently used in an Australian shelter for dog behaviour post-adoption. A total of 123 dogs, aged 1–10 years and housed in an animal care shelter, were assessed before they were adopted. The new owners of the dogs took part in a post-adoption survey conducted 1 month after adoption, which explored the behaviour of their dog in its new home. Regression analyses identified that friendly/social, fear and anxiousness identified in the shelter assessment significantly predicted corresponding behaviours post-adoption. However, behaviour problems, such as aggression, food guarding and separation-related behaviours, were not reliably predicted by the standardised behaviour assessment. We recommend that dog behaviour assessments in shelters are used only in conjunction with other monitoring tools to assess behaviour over the whole shelter stay, thus facilitating increased safety/welfare standards for dogs, shelters and the wider community.

Abstract

In shelters it is usual to conduct standardised behaviour assessments on admitted dogs. The information gathered from the assessment is used to identify dogs that are suitable for adoption and assist in matching the dog with suitable adopters. These assessments are also used to guide behaviour modification programs for dogs that display some unwanted behaviours. For some dogs, the results may indicate that they are unsuitable either for re-training or for adoption. In these circumstances the dogs may be euthanised. We investigated the predictive value of a standardised behaviour assessment protocol currently used in an Australian shelter for dog behaviour post-adoption. A total of 123 dogs, aged 1–10 years and housed in an animal care shelter, were assessed before they were adopted. The new owners of the dogs took part in a post-adoption survey conducted 1 month after adoption, which explored the behaviour of their dog after adoption. Ordinal regression analyses identified that friendly/social, fear and anxiousness identified in the shelter assessment significantly predicted corresponding behaviours post-adoption. However, behaviour problems, such as aggression, food guarding and separation-related behaviours, were not reliably predicted by the standardised behaviour assessment. The results suggest that further research is required to improve the predictability of behaviour assessment protocols for more specific behaviour problems, including different categories of aggression and separation-related problems. We recommend that dog behaviour assessments in shelters are used only in conjunction with other monitoring tools to assess behaviour over the whole shelter stay, thus facilitating increased safety/welfare standards for dogs, shelters and the wider community.

Intranasal delivery of icariin via a nanogel-thermoresponsive hydrogel compound system to improve its antidepressant-like activity

Although icariin has been reported to have antidepressant-like effects in different animal models, its poor oral bioavailability and low efficiency of delivery to the brain limit its application. In this study, icariin nanogels were prepared by reverse microemulsion methods to improve its poor water solubility. Then, we developed an icariin nanogel loaded self-assembled thermosensitive hydrogel system (icariin-NGSTH) to deliver icariin via a noninvasive, direct nose-to-brain delivery route for the treatment of depression. The in vivo distribution was investigated by fluorescence imaging with rhodamine B-labeled nanogels. The antidepressant efficacy of icariin-NGSTH was evaluated in behavioral despair tests and the chronic unpredictable mild stress (CUMS) model. The results showed that icariin-NGSTH had a zero-order kinetics release in the first 10 h. Icariin-NGSTH led to rapid brain distribution within 30 min. Icariin-NGSTH significantly reduced the duration of immobility in the tail suspension test (TST) and forced swim test (FST). Compared with oral administration, intranasally administered icariin-NGSTH had a fast-acting antidepressant effect in the TST and FST. Moreover, icariin-NGSTH increased body weight and sucrose preference, reversed abnormal plasma levels of testosterone, interleukin-6 (IL-6) and prostaglandin E₂ (PGE₂), and repaired neuronal damage in the hippocampi of CUMS rats. These results indicated that icariin-NGSTH at a low dose produced a significant antidepressant effect. As a complex drug delivery system, intranasally administered icariin-NGSTH is a rapid and effective treatment for depression, increasing the antidepressant-like activity of icariin.

Combined exposure to dinotefuran and chronic mild stress counteracts the change of the emotional and monoaminergic neuronal activity induced by either exposure singly despite corticosterone elevation in mice

Dinotefuran (DIN) belongs to the neonicotinoids (NNs), a class of globally applied pesticides originally developed to exhibit selective toxicity in insects. However, several reports have suggested that NNs also exert neurotoxic effects in mammals. We previously demonstrated neurobehavioral effects of DIN on mice under non-stressful conditions. For further toxicity assessments in the present study, we investigated the effects of DIN on mice exposed to stressful conditions. After subacutely administering a no-observed-effect-level (NOEL) dose of DIN and/or chronic unpredictable mild stress (CUMS) to mice, we conducted three behavioral tests (i.e., open field test [OFT], tail suspension test [TST] and forced swimming test [FST]). In addition, serotonin (5-HT) and tryptophan hydroxylase 2 (TPH2) of the dorsal raphe nuclei (DRN) and median raphe nuclei (MRN) and tyrosine hydroxylase (TH) of the ventral tegmental area and substantia nigra (SN) were evaluated immunohistochemically. A NOEL dose of DIN or CUMS alone increased of the total distance in OFT, decreased or increased the immobility time in TST or FST, respectively, and increased the positive intensity of 5-HT and TPH2 in the DRN/MRN, and TH in the SN. These changes were suppressed under the conditions of combined exposure to DIN and CUMS, though the blood corticosterone level was increased depending on the blood DIN values and the presence of CUMS. The present study suggests the multifaceted toxicity of the neurotoxin DIN.

Reverse translation of major depressive disorder symptoms: A framework for the behavioural phenotyping of putative biomarkers

BACKGROUND

Reverse translating putative biomarkers of depression from patients to animals is complex because Major Depressive Disorder (MDD) is a highly heterogenous condition. This review proposes an approach to reverse translation based on relating relevant bio-behavioural functions in laboratory rodents to MDD symptoms.

METHODS

This systematic review outlines symptom clusters assessed by psychometric tests of MDD and antidepressant treatment response including the Montgomery-Åsberg Depression Rating Scale, the Hamilton Depression Rating Scale, and the Beck Depression Inventory. Symptoms were related to relevant behavioural assays in laboratory rodents.

RESULTS

The resulting battery of tests includes passive coping, anxiety-like behaviours, sleep, caloric intake, cognition, psychomotor functions, hedonic reactivity and aversive learning. These assays are discussed alongside relevant clinical symptoms of MDD, providing a framework through which reverse translation of a biomarker can be interpreted.

LIMITATIONS

Certain aspects of MDD may not be quantified by tests in laboratory rodents, and their biological significance may not always be of clinical relevance.

CONCLUSIONS

Using this reverse translation approach, it is possible to clarify the functional significance of a putative biomarker in rodents and hence translate its contribution to specific clinical symptoms, or clusters of symptoms.

Can we and should we use animal models to study neurobehavioral comorbidities of epilepsy?

Animal systems have been widely used to examine mechanisms of neurobehavioral comorbidities of epilepsy and to help in developing their effective therapies. Despite the progress made in the field, animal studies have their limitations stemming both from issues with modeling neuropsychiatric disorders in the laboratory and from drawbacks of animal models of epilepsy themselves. This review discusses advantages and weaknesses of experimental paradigms and approaches used to model and to analyze neurobehavioral comorbidities of epilepsy, from the perspectives of their needs, interpretation, ways of improvement, and clinical relevance. Developmental studies are required to adequately address age-specific aspects of the comorbidities. The deployment of preclinical Common Data Elements (pCDEs) for epilepsy research should facilitate the standardization and the harmonization of studies in question, while the application of Research Domain Criteria (RDoC) to characterize neurobehavioral disorders in animals with epilepsy should help in closing the bench-to-bedside gap. Special Issue: Epilepsy & Behavior's 20th Anniversary.

The Sexual Motivation of Male Rats as a Tool in Animal Models of Human Health Disorders

Normal or dysfunctional sexual behavior seems to be an important indicator of health or disease. Many health disorders in male patients affect sexual activity by directly causing erectile dysfunction, affecting sexual motivation, or both. Clinical evidence indicates that many diseases strongly disrupt sexual motivation and sexual performance in patients with depression, addiction, diabetes mellitus and other metabolic disturbances with obesity and diet-related factors, kidney and liver failure, circadian rhythm disorders, sleep disturbances including obstructive sleep apnea syndrome, developmental and hormonal disorders, brain damages, cardiovascular diseases, and peripheral neuropathies. Preclinical studies of these conditions often require appropriate experimental paradigms, including animal models. Male sexual behavior and motivation have been intensively investigated over the last 80 years in animal rat model. Sexual motivation can be examined using such parameters as: anticipatory behavior and 50-kHz ultrasonic vocalizations reflecting the emotional state of rats, initiation of copulation, efficiency of copulation, or techniques of classical (pavlovian) and instrumental conditioning. In this review article, we analyze the behavioral parameters that describe the sexual motivation and sexual performance of male rats in the context of animal experimental models of human health disorders. Based on analysis of the parameters describing the heterogeneous and complex structure of sexual behavior in laboratory rodents, we propose an approach that is useful for delineating distinct mechanisms affecting sexual motivation and sexual performance in selected disease states and the efficacy of therapy in preclinical investigations.

Antidepressant effects of ketamine on depression-related phenotypes and dopamine dysfunction in rodent models of stress

Depression, the most prevalent psychiatric disorder, is characterized by increased negative affect (i.e. depressed mood) and reduced positive affect (i.e. anhedonia). Stress is a risk factor for depression in humans, and animal models of chronic stress are typically used to study neurobehavioral alterations relevant to depression. Common behavioral outcomes in rodent models of chronic stress include anhedonia, social dysfunction and behavioral despair. For example, chronically stressed rodents exhibit reduced reward preference, as measured by a loss of preference for sucrose solutions and time spent interacting with a novel conspecific, while also exhibiting less time struggling against inescapable stressors (e.g. forced swim, tail suspension). In both humans and rodents, anhedonia is associated with dysfunction of the dopamine (DA) system. Unlike traditional antidepressants, which are limited by inadequate efficacy and delayed therapeutic response, acute ketamine administration rapidly alleviates depressive symptoms in humans and reverses stress-induced changes in animal models. These effects are partially mediated via actions on the DA system. This review summarizes the clinical effects of ketamine, the neurobiological underpinnings of depression with a focus on DA dysfunction, as well as antidepressant effects of ketamine on depression-related endophenotypes (i.e. anhedonia, despair) and ventral tegmental area (VTA) activity in rodent models of repeated stress. Moreover, we discuss evidence regarding sex differences in ketamine's antidepressant effects, wherein females appear to be more sensitive to lower dose ketamine, as well as novel findings suggesting that ketamine has prophylactic effects with regard to protection against the neurobehavioral impact of future stressors.

Fluoxetine attenuates stress-induced depressive-like behavior through modulation of hippocampal GAP43 and neurogenesis in male rats

Based on the monoaminergic theory, Serotonin-Selective Reuptake Inhibitors (SSRIs) are used for treating depression. Recent hypotheses suggest that antidepressants may influence neurogenesis and synaptic plasticity. However, the mechanisms underlying these effects are still poorly understood. The aim of the present study was to evaluate the effect of fluoxetine, a widely used SSRI antidepressant, on the neurogenesis and the expression of Growth-Associated Protein 43 (GAP43), a synaptic protein, in the rat hippocampus exposed to Unpredictable Chronic Mild Stress (UCMS; the model of depressive-like behavior). We have analyzed the effects of chronic fluoxetine treatment on immobility behavior (forced swimming test), plasma interleukin-6 and corticosterone (enzyme-linked immunosorbent assay), BrdU-positive cells in the dentate gyrus and GAP43 expression in the CA3 region (Immunohistochemistry) of the hippocampus. This study provides evidence that fluoxetine is a potent enhancer of GAP-43, a protein related to the neuronal plasticity, in the hippocampus of the rat model of depression. Interestingly, our results showed that although fluoxetine significantly is effective in increasing BrdU positive cells, it is more effective in increasing the neurite formation compared with neurogenesis. The results support the idea that antidepressants can promote neuronal plasticity. We concluded that the increase of GAP-43- induced neurite formation may be an important mechanism by which fluoxetine augments hippocampal neuroplasticity and play its pivotal antidepressant role.

Anti-depressant like effects of quercetin 4'-O-glucoside from Allium cepa via regulation of brain oxidative stress and monoamine levels in mice subjected to unpredictable chronic mild stress

Objectives: Depression is a common neuropsychiatric disorder. The available pharmacotherapy is ineffective for a substantial proportion of patients and has numerous side effects. Therefore, finding safer drugs for the management of depression is of paramount importance. The present study was aimed to identify the compound responsible for anti-depressant like effects of Allium cepa outer scale extract (ACE) and to elucidate its mechanism of action. Methods:The anti-depressant compound from ACE was separated using bioactivity guided fractionation. Furthermore, mouse model of unpredictable chronic mild stress (UCMS) induced depressive behaviour was employed to investigate the anti-depressant like activity and potential mechanism of bioactive compound using behavioural tests (forced swim test (FST), sucrose preference test (SPT), open field test (OFT)) as well as by assessing brain oxidative stress, monoamine oxidase A and serotonin levels. Results:ACE and its ethylacetate fraction (EF) showed marked anti-depressant like effects in mice in the FST model. Chromatographic and spectroscopic studies of EF lead to the isolation of quercetin and quercetin 4'-O-glucoside (QG). Of these, QG (20 mg/kg) treated animals showed activity similar to that shown by fluoxetine in mice using FST. Thus, QG was tested for anti-depressant like activity against UCMS induced depressive behaviour in mice. Treatment of UCMS- exposed mice with QG (20 mg/kg) improved UCMS induced behaviour anomalies and restored brain biochemical parameters (oxidative stress, MAO-A activity and serotonin levels). Discussion:QG is responsible for anti-depressant like effects of ACE possibly via prevention of brain oxidative stress and restoring serotonin levels by inhibiting MAO-A activity.

The AT1 Receptor Antagonist Losartan Does Not Affect Depressive-Like State and Memory Impairment Evoked by Chronic Stressors in Rats

The present study investigated the effect of the treatment with the angiotensin II type 1 receptor (AT₁) antagonist losartan in the depressive-like state and memory impairment evoked by exposure to either homotypic (i.e., repeated exposure to the same type of stressor) or heterotypic (i.e., exposure to different aversive stimuli) chronic stressors in rats. For this, male Wistar rats were subjected to a 10 days regimen of repeated restraint stress (RRS, homotypic stressor) or chronic variable stress (CVS, heterotypic stressor) while being concurrently treated daily with losartan (30 mg/kg/day, p.o.). Depressive-like state was evaluated by analysis of the alterations considered as markers of depression (decreased sucrose preference and body weight and coat state deterioration), whereas cognitive non-emotional performance was tested using the novel object recognition (NOR) test. Locomotor activity was also evaluated in the open field test. Both RRS and CVS impaired sucrose preference and caused coat state deterioration, whereas only CVS impaired body weight gain. Besides, RRS impaired short-term memory (but not long-term memory) in the NOR test. Neither depressive-like state nor memory impairment evoked by the chronic stressors was affected by the treatment with losartan. Nevertheless, CVS increased the locomotion, which was inhibited by losartan. Taken together, these results provide evidence that the chronic treatment with losartan does not affect the depressive-like state and memory impairment evoked by either homotypic or heterotypic chronic stress regimens in rats.

Biological, Behavioral and Physiological Consequences of Drug-Induced Pregnancy Termination at First-Trimester Human Equivalent in an Animal Model

Given the significant physiological changes that take place during and resulting from pregnancy, as well as the relative absence of such information in relation to pregnancy termination, this study investigated the potential for developing a valid animal model to objectively assess the biological, physiological and behavioral consequences of drug-induced pregnancy termination. Female Long-Evans rats were divided into four groups (n = 19-21/group), controlling for drug [mifepristone (50 mg/kg/3 ml, i.g.)/misoprostol (0.3 mg/kg/ml, i.g.) or vehicle (1% Carboxymethylcellulose Sodium/0.2% Tween® 80 suspension, i.g.)] and pregnancy. Drug administration took place on days 12-14 of gestation (days 28-40 human gestational equivalent). Vehicle was administered to the controls on the same days. Parameters measured included rat body weight, food intake, vaginal impedance, sucrose consumption/preference, locomotor activity, forced swim test, and home-cage activity. At the termination of the study, rats were deeply anesthetized using urethane, and blood, brain, and liver were collected for biochemical analysis. Following drug/vehicle administration, only the pregnancy termination group (pregnant, drug) displayed a significant decrease in body weight, food intake, locomotor activity-related behaviors and home-cage activity relative to the control group (non-pregnant, vehicle). Additionally, the pregnancy termination group was the only group that displayed a significant reduction in sucrose consumption/preference during Treatment Week relative to Pre-Treatment Week. Vaginal impedance did not significantly decrease over time in parous rats in contrast to all other groups, including the rats in the pregnancy termination group. Biochemical analysis indicated putative drug- and pregnancy-specific influences on oxidative balance. Regression analysis indicated that pregnancy termination was a predictor variable for body weight, food intake and all locomotor activity parameters measured. Moreover, pertaining to body weight and food intake, the pregnancy termination group displayed significant changes, which were not present in a group of naturally miscarrying rats following pregnancy loss. Overall, our results appear to suggest negative biological and behavioral effects following pregnancy termination, that appear to also be distinct from natural miscarriage, and potential benefits of parity pertaining to fecundity. Thus, our findings indicate the importance for further objective investigation of the physiological and behavioral consequences of medical abortion, in order to provide further insight into the potential implications in humans.

Exploring the potential role of sonic hedgehog cell signalling pathway in antidepressant effects of nicotine in chronic unpredictable mild stress rat model

Nicotine is the most common and highly addictive drug of abuse, associated with several life-threatening diseases and high mortality. Nicotine abuse is the concerted effort to feel reward and fight depression in depressed individuals. The underlying mechanism of nicotine is to activate the brain reward system in the central nervous system and provide an antidepressant effect. Antidepressants provide their therapeutic effect by stimulating hippocampal neurogenesis, which can be correlated with brain derived neurotrophic factor (BDNF) expression in the hippocampus. BDNF interacts with Wnt/β-catenin and sonic hedgehog (Shh) signalling cascade to stimulate hippocampal neurogenesis. Shh is the marker of hippocampal neurogenesis and also involved in the neuropathology of depression. But knowledge in this area to identify the potential therapeutic target is limited. In our study, we explored the role of BDNF, Wnt/β-catenin and Shh signalling in depression and the involvement of these signalling pathways in providing an antidepressant effect by nicotine. Our investigations showed that chronic unpredictable mild stress induced depression results declined expression of BDNF, Wnt/β-catenin, Shh and its downstream transcription factors GLI1/2/3 and NKX2.2 in the hippocampus of male Wistar rat. Moreover, we also observed that nicotine administration increased the expression of these signalling molecules in providing the antidepressant effects.

Access to a high resource environment protects against accelerated maturation following early life stress: A translational animal model of high, medium and low security settings

Early life exposure to a low security setting, characterized by a scarcity of resources and limited food access, increases the risk for psychiatric illness and metabolic dysfunction. We utilized a translational rat model to mimic a low security environment and determined how this manipulation affected offspring behavior, metabolism, and puberty. Because food insecurity in humans is associated with reduced access to healthy food options the "low security" rat manipulation combined a Western diet with exposure to a limited bedding and nesting manipulation (WD-LB). In this setting, dams were provided with limited nesting materials during the pups' early life (P2-P10). This manipulation was contrasted with standard rodent caging (SD) and environmental enrichment (EE), to model "medium security" and "high security" environments, respectively. To determine if transitioning from a low to high security environment improved outcomes, some juvenile WD-LB offspring were exposed to EE. Maternal care was impacted by these environments such that EE dams engaged in high quality care when on the nest, but spent less time on the nest than SD dams. Although WD-LB dams excessively chased their tails, they were very attentive to their pups, perhaps to compensate for limited resources. Offspring exposed to WD-LB only displayed subtle changes in behavior. However, WD-LB exposure resulted in significant metabolic dysfunction characterized by increased body weight, precocious puberty and alterations in the hypothalamic kisspeptin system. These negative effects of WD-LB on puberty and weight regulation were mitigated by EE exposure. Collectively, these studies suggest that both compensatory maternal care and juvenile enrichment can reduce the impact of a low security environment. Moreover, they highlight how utilizing diverse models of resource (in)stability can reveal mechanisms that confer vulnerability and resilience to early life stress.

Social isolation and social support at adulthood affect epigenetic mechanisms, brain-derived neurotrophic factor levels and behavior of chronically stressed rats

Epigenetic modulation of brain-derived neurotrophic factor (BDNF) provides one possible explanation for the dysfunctions induced by stress, such as psychiatric disorders and cognitive decline. Interestingly, social support can be protective against some of these effects, but the mechanisms of social buffering are poorly understood. Conversely, early isolation exacerbates the responses to stressors, although its effects in adulthood remain unclear. This study investigated the effects of social isolation and social buffering on hippocampal epigenetic mechanisms, BDNF levels and behavioral responses of chronically stressed young adult rats. Male Wistar rats (3 months) were assigned to accompanied (paired) or isolated housing. After one-month half of each group was submitted to a chronic unpredictable stress (CUS) protocol for 18 days. Among accompanied animals, only one was exposed to stress. Behavioral analysis encompassed the Open field, plus maze and inhibitory avoidance tasks. Hippocampal H3K9 and H4K12 acetylation, HDAC5 expression and BDNF levels were evaluated. Isolated housing increased HDAC5 expression, decreased H3K9 and H4K12 acetylation, reduced BDNF levels, and impaired long-term memory. Stress affected weight gain, induced anxiety-like behavior and decreased AcK9H3 levels. Interactions between housing conditions and social stress were seen only for HDAC5 expression, which showed a further increase in the isolated + CUS group but remained constant in accompanied animals. In conclusion, social isolation at adulthood induced epigenetic alterations and exacerbated the effects of chronic stress on HDAC5. Notwithstanding, social support counteracted the adverse effects of stress on HDAC5 expression.

Investigating dopamine and glucocorticoid systems as underlying mechanisms of anhedonia

RATIONALE

Anhedonia, a deficit in reward processing, is an endophenotype of several neuropsychiatric conditions. Despite its prevalence and debilitating effects, treatments for anhedonia are lacking, primarily because its underlying mechanisms are poorly understood. Dopamine (DA) has been implicated in anhedonia through its role in reward-related learning; glucocorticoid systems may also be involved in that anhedonia is often preceded by chronic stress.

OBJECTIVE

This study investigated DA and glucocorticoid systems in anhedonia using a rat version of the probabilistic reward task (PRT).

METHODS

Adult male Wistar rats were trained on the PRT and then tested following: (1) activation or inhibition of DA activity induced by amphetamine (AMPH) or pramipexole (PRAMI) injections, (2) chronic mild stress (CMS), or (3) glucocorticoid system activation (dexamethasone (DEX)) or inhibition (mifepristone (MIFE)).

RESULTS

AMPH increased and PRAMI decreased response bias, pointing to enhanced and diminished reward responsiveness with DA agonism and antagonism, respectively. CMS reduced response bias but only in a subpopulation of rats. DEX also decreased response bias, suggesting that glucocorticoid processes contribute to anhedonia, although glucocorticoid inhibition (MIFE) had no effect. None of the manipulations altered the ability to detect and respond to reward-paired stimuli.

CONCLUSIONS

These results confirm a role of DA in anhedonia and elucidate the contribution of the glucocorticoid system to this effect. In addition, chronic stress may interfere with normal DA functioning, leading to impaired reward-related learning in some animals. These findings may direct future treatment of anhedonia by targeting DA and glucocorticoid systems, as well as a possible interaction between the two.

A companion to the preclinical common data elements on neurobehavioral comorbidities of epilepsy: a report of the TASK3 behavior working group of the ILAE/AES Joint Translational Task Force

The provided companion has been developed by the Behavioral Working Group of the Joint Translational Task Force of the International League Against Epilepsy (ILAE) and the American Epilepsy Society (AES) with the purpose of assisting the implementation of Preclinical Common Data Elements (CDE) for studying and for reporting neurobehavioral comorbidities in rodent models of epilepsy. Case Report Forms (CRFs) are provided, which should be completed on a per animal/per test basis, whereas the CDEs are a compiled list of the elements that should be reported. This companion is not designed as a list of recommendations, or guidelines for how the tests should be run-rather, it describes the different types of assessments, and highlights the importance of rigorous data collection and transparency in this regard. The tests are divided into 7 categories for examining behavioral dysfunction on the syndrome level: deficits in learning and memory; depression; anxiety; autism; attention deficit/hyperactivity disorder; psychosis; and aggression. Correspondence and integration of these categories into the National Institute of Mental Health (NIMH) Research Domain Criteria (RDoC) is introduced. Developmental aspects are addressed through the introduction of developmental milestones. Discussion includes complexities, limitations, and biases associated with neurobehavioral testing, especially when performed in animals with epilepsy, as well as the importance of rigorous data collection and of transparent reporting. This represents, to our knowledge, the first such resource dedicated to preclinical CDEs for behavioral testing of rodents.

[Signs of anhedonia and destructive changes in the ventral tegmental area of the midbrain in the model of the preclinical Parkinson's disease stage in experiment]

Parkinson's disease (PD) is one of incurable socially significant diseases. Success in the PD treatment is associated with the development of the technology of preclinical diagnosis and neuroprotective treatment of the disease. In the experimental model of the preclinical PD stage in rats created by intranasal administration of the proteasome inhibitor lactacystin, signs of depression as an anhedonia symptom were detected for the first time. Anhedonia was combined with the death of about one third of dopamine (DA)-ergic neurons in the ventral tegmental area of the midbrain and their axons in the ventral striatum; and a decrease of dopamine concentration in the ventral striatum (by 40%) and the tyrosine hydroxylase level in surviving DA-ergic neurons. The signs of depression may be an early marker of PD, signaling the onset of neurodegeneration in the mesolimbic brain system and increasing functional deficit of the DA-ergic transmission in the ventral striatum. The study results can be applied to the development of the technology of preclinical PD diagnosis and pathogenetic therapy.

Effects of stress on behavior and resting-state fMRI in rats and evaluation of Telmisartan therapy in a stress-induced depression model

BACKGROUND

The etiology of depression and its effective therapeutic treatment have not been clearly identified. Using behavioral phenotyping and resting-state functional magnetic resonance imaging (r-fMRI), we investigated the behavioral impact and cerebral alterations of chronic unpredictable mild stress (CUMS) in the rat. We also evaluated the efficacy of telmisartan therapy in this rodent model of depression.

METHODS

Thirty-two rats were divided into 4 groups: a control group(C group), a stress group(S group), a stress + telmisartan(0.5 mg/kg)group (T-0.5 mg/kg group) and a stress + telmisartan(1 mg/kg) group (T-1 mg/kg group). A behavioral battery, including an open field test (OFT), a sucrose preference test (SPT), and an object recognition test (ORT), as well as r-fMRI were conducted after 4 weeks of CUMS and telmisartan therapy. The r-fMRI data were analyzed using the amplitude of low-frequency fluctuations (ALFF) and regional homogeneity (ReHo) approach. The group differences in the behavior and r-fMRI test results as well as the correlations between these 2 approaches were examined.

RESULTS

CUMS reduced the number of rearings and the total moved distance in OFT, the sucrose preference in SPT, and novel object recognition ability in ORT. The telmisartan treatment (1 mg/kg) significantly improved B-A/B + A in the ORT and improved latency scores in the OFT and SPT. The S group exhibited a decreased ReHo in the motor cortex and pons, but increased ReHo in the thalamus, visual cortex, midbrain, cerebellum, hippocampus, hypothalamus, and olfactory cortex compared to the C group. Telmisartan (1 mg/kg)reversed or attenuated the stress-induced changes in the motor cortex, midbrain, thalamus, hippocampus, hypothalamus, visual cortex, and olfactory cortex. A negative correlation was found between OFT rearing and ReHo values in the thalamus. Two positive correlations were found between ORT B-A and the ReHo values in the olfactory cortexand pons.

CONCLUSIONS

Telmisartan may be an effective complementary drug for individuals with depression who also exhibit memory impairments. Stress induced widespread regional alterations in the cerebrum in ReHo measures while telmissartan can reverse part of theses alterations. These data lend support for future research on the pathology of depression and provide a new insight into the effects of telmisartan on brain function in depression.

Dopamine D2 receptors in the basolateral amygdala modulate erectile function in a rat model of nonorganic erectile dysfunction

Nonorganic erectile dysfunction is a problem with unknown central mechanisms. Changes in brain activity in the amygdala have been observed in human patients. This study aimed to investigate the dopamine system in the basolateral amygdala of male rats with nonorganic erectile dysfunction. We applied chronic mild stress to induce nonorganic erectile dysfunction. After exposure to chronic mild stress, the sucrose consumption test, sexual behaviour test and apomorphine test were used to select depression-like rats with erectile dysfunction as nonorganic erectile dysfunction model rats. The sexual behaviour of these rats after central infusion of a dopamine D1/D2 receptor agonist/antagonist was observed. The expression levels of dopamine D1/D2 receptors and tyrosine hydroxylase in the basolateral amygdala were also measured. The result of the sucrose consumption test, sexual behaviour test and apomorphine test indicated a successful nonorganic erectile dysfunction model. Central infusion of a dopamine D2 receptor agonist increased intromission ratio in model rats. Lower expression levels of tyrosine hydroxylase and the dopamine D2 receptor in the basolateral amygdala were observed in rats with nonorganic erectile dysfunction. These results suggest that impairment of the dopamine D2 receptor pathway in the basolateral amygdala may contribute to the development of nonorganic erectile dysfunction.

Making Sense of Rodent Models of Anhedonia

A markedly reduced interest or pleasure in activities previously considered pleasurable is a main symptom in mood disorder and psychosis and is often present in other psychiatric disorders and neurodegenerative diseases. This condition can be labeled as "anhedonia," although in its most rigorous connotation the term refers to the lost capacity to feel pleasure that is one aspect of the complex phenomenon of processing and responding to reward. The responses to rewarding stimuli are relatively easy to study in rodents, and the experimental conditions that consistently and persistently impair these responses are used to model anhedonia. To this end, long-term exposure to environmental aversive conditions is primarily used, and the resulting deficits in reward responses are often accompanied by other deficits that are mainly reminiscent of clinical depressive symptoms. The different components of impaired reward responses induced by environmental aversive events can be assessed by different tests or protocols that require different degrees of time allocation, technical resources, and equipment. Rodent models of anhedonia are valuable tools in the study of the neurobiological mechanisms underpinning impaired behavioral responses and in the screening and characterization of drugs that may reverse these behavioral deficits. In particular, the antianhedonic or promotivational effects are relevant features in the spectrum of activities of drugs used in mood disorders or psychosis. Thus, more than the model, it is the choice of tests that is crucial since it influences which facets of anhedonia will be detected and should be tuned to the purpose of the study.

Early maternal separation promotes alterations in the thermoregulatory profile of adult Wistar rats

Stressful lifelong events may influence psychiatric diseases, like depression and anxiety. Interestingly, depressed patients have dysfunction of thermoregulatory cooling mechanisms. Thus, understanding the mechanisms related to the thermoregulatory changes in stress-related pathologies is important to better understand the symptoms and treatments for those diseases. However, the influence of early-life stress on the thermoregulatory profile of adults is unknown. In this study, we aimed to evaluate the thermoregulatory profile of adult male Wistar rats submitted to early-life stress by maternal separation (MS). On postnatal days 2-14, rats were submitted daily to MS for 3 h per day. At 3-4 months of age, anxiety-like behavior was evaluated using the open field test and elevated plus maze, depression-like behavior was evaluated using the forced swim test and thermoregulatory profile were also evaluated. In the behavioral tests, MS animals exhibited anxiety- and depression-like behaviors, and had higher core body temperatures during dark period of the circadian cycle, when compared to controls. In addition, MS animals presented higher hyperthermic and vasoconstriction responses than control animals when exposed to the warmth environment, and engaged in cold-seeking behavior whenever possible to select their preferred ambient temperature. The results suggest that, besides emotional alterations, MS induces a change in the thermoregulatory profile of rats that persists into adulthood.

Persistent inflammatory pain alters sexually-motivated behavior in male rats

Urine from pro-œstrus female rodents evokes increased levels of sexually-motivated behaviors in males, including sniffing and scent marking of the urine spot as well as activation of brain reward regions. Stressors such as social defeat can adversely impact urine scent marking behavior in male rodents, an effect that can be mitigated with anti-depressant drugs. Persistent pain is also known to be a potent stressor, producing elevated levels of plasma corticosterone as well as reduced sucrose preference and reduced social interaction. However, the effect of persistent pain on sexually-motivated behavior is unknown. Here, we compared urine scent marking behavior in male rats for up to 3 weeks following intra-articular injection of Complete Freund’s Adjuvant (CFA) or sham injection. CFA-injected rats exhibited profound and ongoing deficits in static weight bearing capacity. CFA-induced persistent inflammatory pain increased plasma corticosterone levels and reduced urine scent marking behavior in male rats. Moreover, while the vast majority of injured rats showed decreased urine scent marking preference for the pro-œstrus female urine spot, male rats with higher baseline scent marking preference also exhibited higher post-injury scent marking preference, more sniffing behavior and lower levels of plasma corticosterone, compared to those with lower baseline scent marking preference. Overall, scent marking behavior may be an ethologically relevant behavioral predictor of persistent pain-induced stress in rats, representing a novel translational approach to understanding chronic pain comorbidities.

Single prolonged stress decreases sign-tracking and cue-induced reinstatement of cocaine-seeking

Exposure to prolonged, uncontrollable stress reduces reward-seeking behavior, resulting in anhedonia in neuropsychiatric disorders, such as posttraumatic stress disorder. However, it is unclear to what degree stressed subjects lose interest in rewards themselves or in reward-related cues that instigate reward-seeking behavior. In the present study, we investigated the effects of single prolonged stress (SPS) on cue-directed behavior in two different procedures: Pavlovian conditioned approach (PCA) and cue-induced reinstatement of cocaine-seeking. In Experiment 1, rats were exposed to SPS and tested for the acquisition of sign-tracking (cue-directed) and goal-tracking (reward-directed) behaviors during a PCA procedure. In Experiment 2, rats were exposed to SPS and tested for the expression of sign- and goal-tracking as well as cue-induced reinstatement of cocaine-seeking. Because dopaminergic activity in the nucleus accumbens is known to play a central role in many cue-directed behaviors, including both sign-tracking and cue-induced reinstatement, Experiment 3 used in vivo microdialysis to measure the effect of SPS on baseline and evoked dopamine levels in the nucleus accumbens. SPS decreased sign-tracking and increased goal-tracking during the acquisition of PCA behavior without affecting reward consumption. In addition, SPS decreased cue-induced reinstatement without affecting cocaine self-administration. Finally, SPS decreased evoked but not baseline levels of dopamine in the nucleus accumbens. These results suggest that SPS decreases the motivational, but not consummatory, aspects of reward-seeking behavior, which may result from long-term, SPS-induced reductions in dopamine release in the nucleus accumbens.

Consequences of a double hit of stress during the perinatal period and midlife in female rats: Mismatch or cumulative effect?

The interplay between experiences during critical developmental periods and later adult life is crucial in shaping individual variability in stress coping strategies. Exposure to stressful events in early life has strongly programs an individual's phenotype and adaptive capabilities. Until now, studies on programming and reversal strategies in early life stress animal models have been essentially limited to males. By using the perinatal stress (PRS) rat model (a model more sensitive to aging changes) in middle-aged females, we investigated the behavioral and endocrine responses following exposure in later life to an unpredictable chronic mild stress (uCMS) condition for six weeks. PRS by itself accelerated the ageing-related-disruption in the estrous cycle and led to reductions in the levels of estradiol. It also reduced motivational and risk-taking behavior in later life, with PRS females being characterized by a reduction in self-grooming in the splash test, in the exploration of the light compartment in the light/dark box test and in the time spent eating a palatable food in the novelty-induced suppression feeding test. PRS females showed impaired regulation of plasma glucose and insulin levels following a glucose challenge, with a hyperglycemic phenotype, and disrupted feedback of the HPA axis after acute stress with respect to controls. Remarkably, all PRS-induced alterations were modified by exposure to the uCMS procedure, thus resulting in a disease-dependent intervention; controls were not affected by uCMS, except for a slight and transient reduction in body weight, while PRS females displayed a reduced body weight gain for the entire duration of the uCMS procedure. Interestingly, the effects of uCMS on PRS females were still observed up to two months after its termination and the females displayed heightened rhythms of locomotor activity and enhanced sensitivity to reward with respect to controls exposed to uCMS. Our findings indicate that many parameters of the PRS female adult phenotype are shaped by both early and later life experiences in a non-additive way. As a consequence, early stressed individuals may be programmed with a more dynamic phenotype than non-stressed individuals.

The Impact and Mechanism of Methylated Metabotropic Glutamate Receptors 1 and 5 in the Hippocampus on Depression-Like Behavior in Prenatal Stress Offspring Rats

An increasing number of epidemiological investigations and animal models research suggest that prenatal stress (PS) could cause depression-like behavior in the offspring, which is sex specific. However, the underlying mechanisms remain to be elucidated. This study is to investigate the promoter methylation of metabotropic glutamate receptor 1 (mGluR1) and metabotropic Glutamate Receptor 5 (mGluR5) gene modification on PS induced depression-like behavior in offspring rats (OR). PS models were established, with or without 5-aza-2′-deoxycytidine (5-azaD, decitabine) treatment. Animal behavior was assessed by the sucrose preference test (SPT), forced swimming test (FST), and open field test (OFT). The mRNA and protein expression levels of mGluR1 and mGluR5 in the hippocampus of offspring were detected with quantitative real-time PCR and Western blot analysis, respectively. The promoter methylation in the hippocampus of mGluR1 and mGluR5 OR were also analyzed. SPT showed significantly reduced sucrose preference in PS induced OR. FST showed significantly prolonged immobility time in PS induced OR. OFT showed significantly reduced central residence time in PS induced OR and no significantly influence in rearing as well as in frequency of micturition. Moreover, the mRNA, protein expression levels, and gene promoter methylation level of mGluR1 and mGluR5 in the hippocampus were significantly increased in the PS induced male OR, while no significantly influence in the PS induced female OR. Furthermore, the PS induced effects in male OR could be reversed by the microinjection of 5-azaD. In conclusion, our results showed that the promoter methylation of mGluR1 and mGluR5 gene modification is only involved in PS induced depression-like behavior in male OR in a sex-specific manner. These findings might contribute to the understanding of the disease pathogenesis and clinical treatment in future.

Cardiovascular and metabolic consequences of the association between chronic stress and high-fat diet in rats

Obesity and chronic stress are considered independent risk factors for the development of cardiovascular diseases and changes in autonomic system activity. However, the cardiovascular consequences induced by the association between high-fat diet (HFD) and chronic stress are not fully understood. We hypothesized that the association between HFD and exposure to a chronic variable stress (CVS) protocol for four weeks might exacerbate the cardiovascular and metabolic disturbances in rats when compared to these factors singly. To test this hypothesis, male Wistar rats were divided into four groups: control-standard chow diet (SD; n = 8); control-HFD (n = 8); CVS-SD (n = 8); and CVS-HFD (n = 8). The CVS consisted of repeated exposure of the rats to different inescapable and unpredictable stressors (restraint tress; damp sawdust, cold, swim stress and light cycle inversion). We evaluated cardiovascular function, autonomic activity, dietary intake, adiposity and metabolism. The HFD increased body weight, adiposity and blood glucose concentration (∼15%) in both control and CVS rats. The CVS-HFD rats showed decreased insulin sensitivity (25%) compared to CVS-SD rats. The control-HFD and CVS-HFD rats presented increased intrinsic heart rate (HR) values (∼8%). CVS increased cardiac sympathetic activity (∼65%) in both SD- and HFD-fed rats. The HFD increased basal HR (∼10%). Blood pressure and baroreflex analyzes showed no differences among the experimental groups. In conclusion, the present data indicate absence of interaction on autonomic imbalance evoked by either CVS or HFD. Additionally, HFD increased HR and evoked metabolic disruptions which are independent of stress exposure.

JSH-23 prevents depressive-like behaviors in mice subjected to chronic mild stress: Effects on inflammation and antioxidant defense in the hippocampus

Nuclear factor-kappa B (NF-κB), which is reported to play an important role in the pathogenesis of depression, also has a central role in the genesis and progression of inflammation. Here, we have targeted the nuclear translocation of NF-κB using 4-methyl-N1-(3-phenyl-propyl)-benzene-1,2-diamine (JSH-23) to elucidate its role in depression. We investigated the antidepressant-like effects of JSH-23 in the chronic mild stress (CMS) mouse model, which is a valid, reasonably reliable, and useful model of depression. The antidepressant-like effects of JSH-23 were evaluated using the sucrose preference test (SPT) and the forced swimming test (FST). We also assessed inflammatory markers [interleukin (IL)-6 and tumor necrosis factor-α (TNF-α)] and components of antioxidant defense [superoxide dismutase (SOD) and nuclear factor erythroid-2-related factor 2 (Nrf 2)] in the hippocampus. Fluoxetine, a classical antidepressant, was used in this study as a positive control. Administration of JSH-23 significantly prevented the decreased sucrose preference in the SPT and prevented the increased immobility time in the FST caused by CMS, but had no effect on locomotor activity. Expression of NF-κB p65 protein in the hippocampus was decreased, and elevated levels of IL-6 and TNF-α were reduced, after JSH-23 administration. In addition to its anti-inflammatory effect, JSH-23 treatment increased the expression of SOD and Nrf 2 in the hippocampus, suggesting that it strengthens antioxidant defense. The current study demonstrated that inhibiting the NF-κB signaling cascade using JSH-23 prevented depressive-like behaviors by decreasing inflammation and improving antioxidant defense in the hippocampus. We concluded that NF-κB activation plays an important role in the pathophysiology of depression and that targeting NF-κB signaling may provide a novel and effective therapy for depression. Additional preclinical studies and clinical trials are, however, needed to further elucidate the effects of this therapeutic strategy.

H3K9 Acetylation of Tph2 Involved in Depression-like Behavior in Male, but not Female, Juvenile Offspring Rat Induced by Prenatal Stress

Increasing evidence has shown that prenatal stress (PS) could cause depression-like behavior in the offspring, which is sex-specific. However, the underlying mechanisms remain to be elucidated. This study is to investigate the involvement of tryptophan hydroxylase 2 (Tph2) H3K9 acetylation (H3K9ac) modification on PS-induced depression-like behavior in juvenile offspring rats (JOR). PS models were established, with or without trichostatin A (TSA) treatment. Animal behavior was assessed by the sucrose preference test (SPT) and forced swimming test (FST). The mRNA and protein expression levels of TPH2 in the dorsal raphenucleus (DRN), hippocampus, and prefrontal cortex were detected with quantitative real-time PCR and Western blot analysis, respectively. The Tph2 H3K9ac levels in the hippocampus were also analyzed. SPT and FST showed significantly reduced sucrose preference and significantly prolonged immobility in PS-induced male juvenile offspring rats (MJOR). Moreover, the mRNA and protein expression levels of TPH2 in the DRN and hippocampus were significantly declined, while the hippocampal Tph2 H3K9ac levels were significantly declined in the PS-induced MJOR. Furthermore, the PS-induced effects in MJOR could be reversed by the microinjection of TSA. However, no significant effects were observed for the female juvenile offspring rats (FJORs). In conclusion, our results showed that the Tph2 H3K9ac modification is only involved in PS-induced depression-like behavior in MJOR, in a sex-specific manner. These findings might contribute to the understanding of the disease pathogenesis and clinical treatment in future.

Rotational stress influences sensitized, but not habituated, exploratory behaviors in the woodlouse, Porcellio scaber

Terrestrial isopods (or woodlice), like the members of the other arthropod taxa, have a sophisticated nervous system that makes them sensitive to specific environmental factors. They can search for survival-related opportunities (e.g., approaching food sources or avoiding sunny areas). Two experiments examined how rotational stress could influence the propensity of common woodlice, Porcellio scaber to exhibit survival-related behaviors such as traveling and rearing up in a hostile environment. Experiment 1 assessed the behaviors of stressed and nonstressed woodlice exposed to a familiar or a novel environment without rewards. Experiment 2 assessed the effects of stress in woodlice given a free choice between a familiar and a novel environment without rewards. In the nonstressed individuals, the results showed a decrease in locomotor activity (habituation) and an increase in the time spent rearing up (sensitization) on the arena's walls over time. In the stressed individuals, repeated rotation had a detrimental effect on the time spent rearing up, but locomotion was decreased only in the stressed individuals that were not preexposed to the test environment beforehand. In addition, immobilization periods-as a plausible indicator of stress-were longer in the absence of preexposure. It is suggested that preexposure had some antistress protective effects on habituated but not on sensitized, exploratory behaviors in woodlice.

Chronic stress leads to long-lasting deficits in olfactory-guided behaviors, and to neuroplastic changes in the nucleus of the lateral olfactory tract

A recent study reported that the integrity of the nucleus of the lateral olfactory tract (nLOT) is required for normal olfaction and for the display of odor-driven behaviors that are critical for species survival and reproduction. In addition to being bi-directionally connected with a key element of the neural circuitry that mediates stress response, the basolateral nucleus of the amygdala, the nLOT is a potential target for glucocorticoids as its cells express glucocorticoid receptors. Herein, we have addressed this hypothesis by exploring, first, if chronic variable stress (CVS) disrupts odor detection and discrimination, and innate olfactory-driven behaviors, namely predator avoidance, sexual behavior and aggression in male rats. Next, we examined if CVS alters the nLOT structure and if such changes can be ascribed to stress-induced effects on the activity of the main output neurons, which are glutamatergic, and/or of local GABAergic interneurons. Finally, we analyzed if the stress-induced changes are transient or, conversely, persist after cessation of CVS exposure. Our data demonstrate that CVS leads to severe olfactory deficits with inability to detect and discriminate between odors and to innately avoid predator odors. No effects of CVS on sexual and aggressive behaviors were observed. Results also showed that CVS leads to somatic hypertrophy of pyramidal glutamatergic neurons, which likely results from neuronal disinhibition consequent to the loss of inhibitory inputs mediated by GABAergic interneurons. Most of the CVS-induced effects persist beyond a 4-week stress-free period, suggesting long-lasting effects of chronic stress on the structure and function of the olfactory system.

Methyl jasmonate attenuated lipopolysaccharide-induced depressive-like behaviour in mice

Depression is a recurrent neuropsychiatric disorder that affects millions of individuals worldwide and impact negatively on the patients' social functions and quality of life. Studies have shown that i.p injection of lipopolysaccharide (LPS) induces depressive-like behavior in rodents via induction of oxidative stress and neuroinflammation. Methyl jasmonate (MJ), an isolated compound from jasmine plant has gained reputation in aromatherapy for treatment of depression, nervousness and memory deficits. This study was designed to evaluate the effects of MJ on LPS-induced depressive-like behavior in mice. Mice were given MJ (5-20 mg/kg), imipramine (10 mg/kg) or vehicle (10 mL/kg) intraperitoneally for 7 consecutive days. On day 7, treatment was carried out 30 min prior to i.p injection of LPS (830 μg/kg). Twenty four hours after LPS administration, tail suspension, forced swim and sucrose preference tests were carried out. Thereafter, serum corticosterone levels were determined using ELISA. The levels of malondialdehyde (MDA), glutathione (GSH) and tumor necrosis factor-alpha (TNF-α) were determined in brain tissue homogenates. LPS significantly increased immobility time in the tail suspension and forced swim tests when compared with vehicle (p < 0.05), which indicates depressive-like syndromes. However, the increased immobility time was significantly reduced by MJ (5-20 mg/kg) when compared with LPS-treated group. LPS administration also altered the levels of MDA, GSH, corticosterone and TNF alpha in mice, which was significantly reversed by MJ. These findings suggest that attenuation of LPS-induced depressive-like behavior by MJ may be related to suppression of oxidative stress and release of TNF alpha.

Effects of CB1 receptor antagonism and stress exposures in adolescence on socioemotional behaviours, neuroendocrine stress responses, and expression of relevant proteins in the hippocampus and prefrontal cortex in rats

Little is known about the consequences of altered endocannabinoid signalling in adolescence. We hypothesized that CB1 receptor antagonism (AM251, 1 mg/kg) and stress exposures (1 h confinement stress) in adolescence (daily, postnatal days 30-44) would interact to increase neuroendocrine stress responses and anxiety when investigated a minimum of 24 h after drug and stress treatments; these treatment effects were independent of each other. Changes in homecage behaviour and in weight gain confirmed that both males and females were sensitive to the treatments. Nevertheless, in males, repeated AM251 administration was without effect on any of the measures investigated in days post-treatment. Males had reduced corticosterone release to the repeated stress and had increased GAD67 expression in the ventral hippocampus under baseline conditions. In females, AM251 also reduced weight gain and increased stereotypic behaviours in the homecage; these same females showed increased sociality, reduced CB1 receptor expression in the dorsal hippocampus, and increased GAD67 expression in the prefrontal cortex. Further, females exposed to repeated stress had enhanced recovery to baseline corticosterone concentrations after stress. The inclusion of a non-injected comparison group also revealed stress of injection effects in both sexes that otherwise would have been masked. Together, the findings demonstrate effects of CB1 receptor antagonism and stress that were more evident in females than males, suggesting that females may be more vulnerable to the consequences of disrupted endocannabinoid signalling during adolescence.

Developmental psychoneuroendocrine and psychoneuroimmune pathways from childhood adversity to disease

Childhood adversity has been repeatedly and robustly linked to physical and mental illness across the lifespan. Yet, the biological pathways through which this occurs remain unclear. Functioning of the inflammatory arm of the immune system and the hypothalamic-pituitary-adrenal (HPA)-axis are both hypothesized pathways through which childhood adversity leads to disease. This review provides a novel developmental framework for examining the role of adversity type and timing in inflammatory and HPA-axis functioning. In particular, we identify elements of childhood adversity that are salient to the developing organism: physical threat, disrupted caregiving, and unpredictable environmental conditions. We propose that existing, well-characterized animal models may be useful in differentiating the effects of these adversity elements and review both the animal and human literature that supports these ideas. To support these hypotheses, we also provide a detailed description of the development and structure of both the HPA-axis and the inflammatory arm of the immune system, as well as recent methodological advances in their measurement. Recommendations for future basic, developmental, translational, and clinical research are discussed.

Individual differences in circadian locomotor parameters correlate with anxiety- and depression-like behavior

Disrupted circadian rhythms are a core feature of mood and anxiety disorders. Circadian rhythms are coordinated by a light-entrainable master clock located in the suprachiasmatic nucleus. Animal models of mood and anxiety disorders often exhibit blunted rhythms in locomotor activity and clock gene expression. Interestingly, the changes in circadian rhythms correlate with mood-related behaviours. Although animal models of depression and anxiety exhibit aberrant circadian rhythms in physiology and behavior, it is possible that the methodology being used to induce the behavioral phenotype (e.g., brain lesions, chronic stress, global gene deletion) affect behavior independently of circadian system. This study investigates the relationship between individual differences in circadian locomotor parameters and mood-related behaviors in healthy rats. The circadian phenotype of male Lewis rats was characterized by analyzing wheel running behavior under standard 12h:12h LD conditions, constant dark, constant light, and rate of re-entrainment to a phase advance. Rats were then tested on a battery of behavioral tests: activity box, restricted feeding, elevated plus maze, forced swim test, and fear conditioning. Under 12h:12h LD conditions, percent of daily activity in the light phase and variability in activity onset were associated with longer latency to immobility in the forced swim test. Variability in onset also correlated positively with anxiety-like behavior in the elevated plus maze. Rate of re-entrainment correlated positively with measures of anxiety in the activity box and elevated plus maze. Lastly, we found that free running period under constant dark was associated with anxiety-like behaviors in the activity box and elevated plus maze. Our results provide a previously uncharacterized relationship between circadian locomotor parameters and mood-related behaviors in healthy rats and provide a basis for future examination into circadian clock functioning and mood.

Effects of chronic forced-swim stress on behavioral properties in rats with neonatal repeated MK-801 treatment

The two-hit hypothesis has been used to explain the onset mechanism of schizophrenia. It assumes that predisposition to schizophrenia is originally attributed to vulnerability in the brain which stems from genetic or early developmental factors, and that onset is triggered by exposure to later detrimental factors such as stress in adolescence or adulthood. Based on this hypothesis, the present study examined whether rats that had received neonatal repeated treatment with an N-methyl-d-aspartate (NMDA) receptor antagonist (MK-801), an animal model of schizophrenia, were vulnerable to chronic stress. Rats were treated with MK-801 (0.2mg/kg) or saline twice daily on postnatal days 7-20, and animals in the stress subgroups were subjected to 20days (5days/week×4weeks) of forced-swim stress in adulthood. Following this, behavioral tests (prepulse inhibition, spontaneous alternation, open-field, and forced-swim tests) were carried out. The results indicate that neonatal repeated MK-801 treatment in rats inhibits an increase in immobility in the forced-swim test after they have experienced chronic forced-swim stress. This suggests that rats that have undergone chronic neonatal repeated NMDA receptor blockade could have a reduced ability to habituate or adapt to a stressful situation, and supports the hypothesis that these rats are sensitive or vulnerable to stress.

Modeling hypohedonia following repeated social defeat: Individual vulnerability and dopaminergic involvement

Social defeat in rodents putatively can model hypohedonia. The present studies examined models for assessing hypohedonia-like behavior and tested the hypotheses that 1) individual differences in baseline reward sensitivity predict vulnerability, and 2) defeat elicits changes in pharmacological measures of striatal dopaminergic function. Male Wistar rats (n=142) received repeated defeat (3 "triad" blocks of 3 defeats) or control handling. To determine whether defeat influenced consumption of SuperSac (glucose-saccharin) over an isocaloric, less preferred, glucose solution, a 2-choice paradigm was used. To determine repeated defeat effects on the reinforcing efficacy of SuperSac, a progressive-ratio schedule of reinforcement was used. Amphetamine-induced locomotor activity (0.08mg/kg, s.c.) was determined as a measure sensitive to striatal dopaminergic function. Defeat reduced SuperSac consumption during the first two triads-an effect seen in the third triad only in defeated rats with High vs. Low baseline SuperSac intake. The characteristic escalation in PR breakpoint for SuperSac normally seen in controls was absent in defeated rats, leading to a significant difference by the third triad. Defeat-induced blunting of the escalation in PR performance was greater in rats with High antecedent PR breakpoints and persisted 2.5weeks post-defeat. Repeated defeat also blunted amphetamine-induced locomotion 13days post-defeat. Thus, hypohedonic-like effects of social defeat were detected and accompanied by persistently attenuated striatal dopamine function. Early effects were seen for consumption of differentially-palatable solutions, and persistent effects were seen for the "breakpoint" motivational measure. The results implicate initial reward sensitivity as a risk factor for stress-induced hypohedonia.

JIEYUANSHEN DECOCTION EXERTS ANTIDEPRESSANT EFFECTS ON DEPRESSIVE RAT MODEL VIA REGULATING HPA AXIS AND THE LEVEL OF AMINO ACIDS NEUROTRANSMITTER

Background:

Jieyuanshen decoction (JYAS-D) - a traditional Chinese medicine was invented by Professor Nie based on classic formulas, chaihu jia longgu muli decoction has been proved as having favorable curative effects on depression in clinical practices. The aim of this study was to investigate the antidepressant effects and its molecular mechanism of JYAS-D.

Materials and Methods:

The model of depression was established by Chronic Unpredictable Stress. Different doses (8.2 g/kg, 16.3 g/kg, 32.7 g/kg) of JYAS-D was orally administered; Fluoxetine was orally administered with 10mg/kg. All treatments lasted for 28 days. Sucrose preference and open-field tests were adopted to observe the behavior of rats. OPA (ortho-phthalaldehyde) derivatization method was used to detect the contents of amino acid neurotransmitter. RIA (Radiation immunity analysis) method was used to measure the serum concentrations of CORT (Corticosterone), ACTH (Adrenocorticotropic hormone) and CRH (Corticotropin-releasing hormone). ELISA (Enzyme linked immunosorbent assay) method was adopted to examine the contents of Glucocorticoid receptor (GR) and Mineralocorticoid receptor (MR) in hippocampus.

Results:

Compared with the model group, sucrose preference was increased in all treatment groups. The concentration of serum CORT was reduced in the middle dose of JYAS-D and control groups; the concentration of serum ACTH was reduced in the low and high-dose of JYAS-D; the concentration of serum CRH was reduced in the middle and high-dose of JYAS-D. The content of hippocampus GR was increased in the middle and high-dose of JYAS-D; the content of hippocampus Glu (Glutamic acid) was reduced among the low, middle and high-dose of JYAS-D and fluoxetine group, the ratio of Glu/γ-GABA (y-aminobutyric acid was reduced in the low and high-dose of JYAS-D.

Conclusion:

JYAS-D had a significant antidepressant-like effect on rat model through regulating serum concentration of CORT, ACTH and CRH, increasing the content of hippocampus GR and regulating the equilibrium of amino acids neurotransmitter.

Evaluation of 50-kHz ultrasonic vocalizations in animal models of mania: Ketamine and lisdexamfetamine-induced hyperlocomotion in rats

Drug-induced hyperlocomotion in rodents is frequently used as a behavioral model for mania. However, the use of locomotor activity as the single parameter in these animal models of mania may pose some limitations for developing new pharmacological treatments. Thus, alternative behavioral markers are required. Fifty-kHz ultrasonic vocalizations (USV), which are thought to represent positive affect, are increased by the administration of the psychostimulant d-amphetamine, an effect that can be prevented by lithium treatment, the gold standard antimanic drug for treating bipolar disorder. The aim of this study was to evaluate 50-kHz USV in two other pharmacological-induced animal models of mania: ketamine (KET)- and lisdexamfetamine (LDX)-induced hyperlocomotion. After systemic injection of LDX (10mg/kg, ip), racemic-ketamine (25mg/kg, ip) or S-ketamine (25mg/kg, ip), locomotor activity and 50-kHz USV emission were evaluated in rats. Furthermore, the effects of an antimanic treatment, namely lithium carbonate (100mg/kg, ip), on LDX-induced 50-kHz USV and hyperlocomotion were tested. Rats treated with racemic KET and S-KET showed increased locomotor activity, but these drug treatments did not significantly affect 50-kHz USV emission rates. On the other hand, LDX administration increased both locomotor activity and 50-kHz USV with both effects being reversed by lithium administration. The present findings suggest that 50-kHz USV can differentiate between drug-induced models of mania, which may represent different types of manic episodes. Thus, measuring 50-kHz USV might serve as an additional valuable behavioral variable to assess mania-like phenotypes in rat models.

Antidepressant-like effects of YL-IPA08, a potent ligand for the translocator protein (18 kDa) in chronically stressed rats

The present study aimed to examine the molecular and cellular mechanisms underlying the antidepressant-like effect of YL-IPA08, a novel TSPO ligand designed and synthesized at our institute. We firstly used the chronic unpredictable stress (CUS) procedure of rats, a well validated stress-related animal model of depression, to further determine the antidepressant-like of YL-IPA08. And we found that YL-IPA08 caused significant suppression of inhibiting of locomotor activity, reducing the sucrose preference and increasing the latency to eat induced by CUS. In addition, YL-IPA08 treatment increased the levels of progesterone and allopregnanolone in the hippocampus and prefrontal cortex of post- CUS rats. Furthermore, long-term YL-IPA08 administration reversed dendritic shrinkage, down-regulation of neurotrophic signaling pathway within the hippocampus, as well as HPA dysfunctions simultaneously observed in the CUS rats. Collectively, the evidence presented above supports the notion that binding to TSPO and the subsequent synthesis of neurosteroid, maintenance of hippocampal morphologic and functional plasticity, and preventing HPA axis dysfunction, may account for the profound molecular and cellular mechanism underlying the antidepressant-like effect of YL-IPA08.