A review on animal models for screening potential anti-stress agents

Posttraumatic anxiety-like behaviour in zebrafish is dose-dependently attenuated by the alpha-2A receptor agonist, guanfacine

Traumatic stress exposure increases noradrenaline (NA) release, which contributes to anxiety and impaired risk-appraisal. Guanfacine, a selective alpha-2A adrenergic receptor agonist, has been used to treat stress-related disorders characterised by impaired prefrontal cortex function. By acting on both presynaptic inhibitory autoreceptors and postsynaptic heteroreceptors, guanfacine attenuates stress reactivity and enhances cognition. However, its effectiveness in treating trauma-related anxiety and risk-taking behaviour remains unclear. Leveraging the advantages of zebrafish (Danio rerio ) as a sensitive and efficient preclinical model which is ideal for stress research, we explored the impact of traumatic stress exposure combined with varying concentrations of guanfacine in adult zebrafish. Zebrafish were evaluated for trauma-related anxiety using both the novel tank test (NTT) and a novel version of the open-field test (nOFT), the latter which was also used to investigate risk-taking behaviour. We found that (1) traumatic stress exposure led to heightened risk-taking behaviour in the nOFT, and (2) low-to-moderate concentrations of guanfacine (3-20 µg/L) attenuated anxiety-like, but not risk-taking behaviour, with the highest concentration (40 µg/L), showing no effect. These results highlight the complex role of NA in modulating dysregulated behaviours during traumatic events and indicate the potential of guanfacine for improving trauma-related anxiety and risk-taking behaviour.

Chronic stress and depression impact on tongue and major sublingual gland histology and the potential protective role of Thymus vulgaris: An animal study

OBJECTIVES

Reporting the histological effects of chronic stress on certain oral tissues, as well as the capacity of Thymus vulgaris (thyme) to protect tissues from stress and link both serum cortisol and serotonin levels.

METHODS

30 rats were randomly divided into a trio of groups: normal control (no treatment), stress group (chronic stress without treatment), and treatment group (chronic stress treated with thyme at a dose of 200 mg/kg BW orally via needle gavage daily for 21 days). At the end of the experiment, tongues and major sublingual glands (SLGs) were surgically removed and processed for histological and histochemical studies. Blood samples were taken shortly before scarification for the biochemical study of cortisol and serotonin serum levels.

RESULTS

Examination of tongue and SLG sections of the stress group indicated significant alterations in histology and changes in SLG secretion. An examination of tongue and SLG histological sections of the thyme-treated group are showed an improvement. Chronic stress raises cortisol serum levels and lowers serotonin serum levels.

CONCLUSIONS

Chronic stress causes alteration of the tongue and major SLG histology, as well as changes in SLG secretion. Thyme may protect tissues from stress, and there is a relation between cortisol and serotonin levels.

Phosphatidic acid is involved in regulation of autophagy in neurons in vitro and in vivo

Major depressive disorder (MDD) is a common and severe psychiatric disease, which does not only lead to variety of neuropsychiatric symptoms, but unfortunately in a relatively large proportion of cases also to suicide. The pathogenesis of MDD still requires definition. We have previously shown that ceramide is increased in the blood plasma of patients with MDD. In mouse models of MDD, which are induced by treatment with corticosterone or application of chronic unpredictable stress, increased blood plasma ceramide also increased and caused an inhibition of phospholipase D in endothelial cells of the hippocampus and reduced phosphatidic acid levels in the hippocampus. Here, we demonstrated that corticosterone treatment of PC12 cells resulted in reduced cellular autophagy, which is corrected by treatment with phosphatidic acid. In vivo, treatment of mice with corticosterone or chronic unpredictable stress also reduced autophagy in hippocampus neurons. Autophagy was normalized upon i.v. injection of phosphatidic acid in these mouse models of MDD. In an attempt to identify targets of phosphatidic acid in neurons, we demonstrated that corticosterone reduced levels of the ganglioside GM1 in PC-12 cells and the hippocampus of mice, which were normalized by treatment of cells or i.v. injection of mice with phosphatidic acid. GM1 application also normalized autophagy in cultured neurons. Phosphatidic acid and GM1 corrected stress-induced alterations in behavior, i.e., mainly anxiety and anhedonia, in experimental MDD in mice. Our data suggest that phosphatidic acid may regulate via GM1 autophagy in neurons.

Stress-induced premature senescence in high five cell cultures: a principal factor in cell-density effects

The Baculovirus Expression Vector System (BEVS) is highly valued in vaccine development, protein engineering, and drug metabolism research due to its biosafety, operational convenience, rapid scalability, and capacity for self-assembling virus-like particles. However, increasing cell density at the time of inoculation severely compromises the production capacity of BEVS, resulting in the "cell density effect". This study aimed to explore the mechanisms of the cell density effect through time-series analysis of transcriptomes and proteomes, with the goal of overcoming or alleviating the decline in productivity caused by increased cell density. The dynamic analysis of the omics of High Five cells under different CCI (cell density at infection) conditions showed that the impact of the "cell density effect" increased over time, particularly affecting genetic information processing, error repair, protein expression regulation, and material energy metabolism. Omics analysis of the growth stage of High Five cells showed that after 36 h of culture (cell density of about 1 × 106 cells/mL), the expression of ribosome-related proteins decreased, resulting in a rapid decrease in protein synthesis capacity, which was a key indicator of cell aging. Senescence verification experiments showed that cells began to show obvious early aging characteristics after 36 h, resulting in a decrease in the host cell's ability to resist stress. Overexpression and siRNA inhibition studies showed that the ndufa12 gene was a potential regulatory target for restricting the "cell density effect". Our results suggested that stress-induced premature senescence in High Five cell cultures, resulting in reduced energy metabolism and protein synthesis capabilities, was a critical factor contributing to cell density effects, and ultimately affecting virus production. In conclusion, this study provided new insights into managing virus production limitations due to cell density effects and offered innovative strategies to mitigate the adverse effects of cellular aging in biomanufacturing technologies.

Neuroprotective Effects of Thymol and p-Cymene in Immobilized Male rats through Alterations in Molecular, Biochemical, Histological, and Behavioral Parameters

The research was conducted to examine the neuroprotective effect of thymol and its precursor p-cymene on chronic immobility stress in adult male Wistar rats. The rats were subjected to 2.5 h of stress every day for 14 consecutive days by placing them inside a restrainer. Thymol (10 mg/kg) and p-cymene (50 mg/kg) were given to the rats during the same period. The results showed that thymol and p-cymene prevented the increase of MDA level, decline of GSH level, and decrease of SOD and GPx activity in the hippocampus of rats exposed to stress. These monoterpenes also prevented the increase in the expression of Tnfa, Il1b, Tlr4, and Nfkb, and the decrease in the expression of Nrf2, Ho1, and Bdnf. In addition, thymol and p-cymene inhibited the increase in the expression and activity of acetylcholinesterase in the hippocampus of animals exposed to immobility and enhanced the expression of A7nachr. They also reduced neuronal death in the CA1 region of stressed animals and improved their performance in the Morris water maze and elevated plus maze tests. Based on these findings, thymol and p-cymene may be effective in preventing neurodegenerative diseases as they reduce oxidative stress and neuroinflammation, strengthen ACh signaling, and stimulate Bdnf expression.

Unveiling the hidden pathways: Exploring astrocytes as a key target for depression therapy

Depressive disorders are widely debilitating psychiatric disease. Despite the considerable progress in the field of depression therapy, extensive research spanning many decades has failed to uncover pathogenic pathways that might aid in the creation of long-acting and rapid-acting antidepressants. Consequently, it is imperative to reconsider existing approaches and explore other targets to improve this area of study. In contemporary times, several scholarly investigations have unveiled that persons who have received a diagnosis of depression, as well as animal models employed to study depression, demonstrate a decrease in both the quantity as well as density of astrocytes, accompanied by alterations in gene expression and morphological attributes. Astrocytes rely on a diverse array of channels and receptors to facilitate their neurotransmitter transmission inside tripartite synapses. This study aimed to investigate the potential processes behind the development of depression, specifically focusing on astrocyte-associated neuroinflammation and the involvement of several molecular components such as connexin 43, potassium channel Kir4.1, aquaporin 4, glutamatergic aspartic acid transporter protein, SLC1A2 or GLT-1, glucocorticoid receptors, 5-hydroxytryptamine receptor 2B, and autophagy, that localized on the surface of astrocytes. The study also explores novel approaches in the treatment of depression, with a focus on astrocytes, offering innovative perspectives on potential antidepressant medications.

Emotional Stress Induces Adaptive Response in Rat Lymphocytes to Subsequent Ionizing Radiation Exposure

We studied the molecular mechanisms of cross-adaptation to ionizing radiation (1 Gy) of lymphocytes isolated from rats subjected to emotional stress. The effects of chronic (CES; various types of stress exposure) and acute (AES; forced swimming) emotional stress in rats on indicators of oxidative stress, cell death, and levels of NRF2 and NOX4 proteins involved in the development of the adaptive response were analyzed in isolated lymphocytes. It was found that stress induced an adaptive response in rat lymphocytes and triggered processes similar to the adaptive response induced by low doses of ionizing radiation: an increase in the level of oxidized DNA and cell death, as well as an increase in the content of NOX4 and NRF2 proteins. In animals subjected to emotional stress, suppressed DNA oxidation in response to irradiation, reduced levels of protective factor NRF2, as well as lymphocyte death were observed.

Anti-psychotic Nature of Antibiotics: Vancomycin and Omadacycline Combination Ameliorating Stress in a Zebrafish Model

Background Stress affects mental health significantly and is a ubiquitous feature of contemporary living. Among the possible antibiotics are omadacycline and vancomycin, whose anti-inflammatory properties have also been thoroughly documented in recent research. The goal of the current study was to examine their complex involvement in the brain's stress response circuits and how they modulate stress. An established model organism that provides a useful platform for examining stress-induced behaviors and possible therapeutic approaches is the zebrafish. To investigate how dopamine affects the stress response, we used a zebrafish model that was exposed to stress. Methodology For three minutes, zebrafish were continually subjected to chasing stress. They were then given antibiotic combinations of 50 µg/mL each of vancomycin and omadacycline at various ratios of 1:1, 3:1, and 3:1. Behavior alterations, including freezing bouts, top-bottom ratios, and latency periods, were analyzed and contrasted with control groups. ImageJ software was utilized to analyze the video footage of the fish. Results The study showed that the combination of omadacycline and vancomycin greatly reduced the behaviors in zebrafish caused by stress. They chose their concentration (50 µg/mL) according to the lethal concentration 50% result. By shortening the latency time and increasing the intensity of breezing sessions, these chemicals restored almost normal activity. There was statistical significance in the outcomes. The results show that the combination of vancomycin and omadacycline may have an anti-psychotic impact on zebrafish behaviors brought on by stress. Their control of stress reactions is consistent with their known roles in the reward and stress circuits of the brain. These results emphasize the complex interactions between neurotransmitter systems and the control of stress, highlighting the therapeutic potential of dopamine in the treatment of stress-related mental illnesses. Conclusions The combination of vancomycin and omadacycline has been shown to have anti-psychotic effects, which presents potential opportunities for the development of new treatment strategies for mental diseases associated with stress. To fully understand the specific processes underpinning their involvement in stress management and how they relate to mental illnesses in humans, more investigation is necessary.

Chemogenetic activation of CRF neurons as a model of chronic stress produces sex-specific physiological and behavioral effects

Trauma and chronic stress exposure are the strongest predictors of lifetime neuropsychiatric disease presentation. These disorders often have significant sex biases, with females having higher incidences of affective disorders such as major depression, anxiety, and PTSD. Understanding the mechanisms by which stress exposure heightens disease vulnerability is essential for developing novel interventions. Current rodent stress models consist of a battery of sensory, homeostatic, and psychological stressors that are ultimately integrated by corticotropin-releasing factor (CRF) neurons to trigger corticosteroid release. These stress paradigms, however, often differ between research groups in the type, timing, and duration of stressors utilized. These inconsistencies, along with the variability of individual animals' perception and response to each stressor, present challenges for reproducibility and translational relevance. Here, we hypothesized that a more direct approach using chemogenetic activation of CRF neurons would recapitulate the effects of traditional stress paradigms and provide a high-throughput method for examining stress-relevant phenotypes. Using a transgenic approach to express the Gq-coupled Designer Receptor Exclusively Activated by Designer Drugs (DREADD) receptor hM3Dq in CRF-neurons, we found that the DREADD ligand clozapine-N-oxide (CNO) produced an acute and robust activation of the hypothalamic-pituitary-adrenal (HPA) axis, as predicted. Interestingly, chronic treatment with this method of direct CRF activation uncovered a novel sex-specific dissociation of glucocorticoid levels with stress-related outcomes. Despite hM3Dq-expressing females producing greater corticosterone levels in response to CNO than males, hM3Dq-expressing males showed significant typical physiological stress sensitivity with reductions in body and thymus weights. hM3Dq-expressing females while resistant to the physiological effects of chronic CRF activation, showed significant increases in baseline and fear-conditioned freezing behaviors. These data establish a novel mouse model for interrogating stress-relevant phenotypes and highlight sex-specific stress circuitry distinct for physiological and limbic control that may underlie disease risk.

Assessment of the therapeutic potential of lutein and beta-carotene nanodispersions in a rat model of fibromyalgia

Fibromyalgia (FM) is a chronic disorder characterized by widespread musculoskeletal pain, fatigue, and cognitive impairment. Despite the availability of various treatment options, FM remains a challenging condition to manage. In the present study, we investigated the efficacy of formulated nanodispersions of lutein and beta-carotene in treating FM-related symptoms induced by reserpine in female Wistar rats. Several techniques have been implemented to assess this efficacy at various levels, including biochemical, bioelectrical, and behavioral. Namely, oxidative stress markers, monoamine levels, electrocorticography, pain threshold test, and open field test were conducted on control, FM-induced, and FM-treated groups of animals. Our results provided compelling evidence for the efficacy of carotenoid nanodispersions in treating FM-related symptoms. Specifically, we found that the dual action of the nanodispersion, as both antioxidant and antidepressant, accounted for their beneficial effects in treating FM. With further investigation, nano-carotenoids and particularly nano-lutein could potentially become an effective alternative treatment for patients with FM who do not respond to current treatment options.

Tarooneh extract relieves anxiety-like behaviors and cognitive deficits by inhibiting synaptic loss in the hippocampus and frontal cortex in rats subjected to chronic restraint stress

In traditional medicine, Tarooneh (a hardcover of the date palm; Phoenix dactylifera) has known as a sedative and relaxant medicine. In this study, we evaluated the protective effects of Tarooneh in the anxiety-like behavior, cognitive deficit, and neuronal damages in the CA1, CA3, and dentate gyrus (DG) regions of the hippocampus and frontal cortex neurons employing a rat model of chronic restraint stress. The animal received Tarooneh extract for 14 consecutive days in water, and chronic restraint stress was performed daily during this period. The results of the Barnes maze test showed that treatment with Tarooneh significantly improves spatial memory parameters such as latency time to find the target hole, number of errors, and distance traveling compared to the stress group. The EPM results showed that Tarooneh significantly increased the time spent in open arms and the percentage of entries into open arms and significantly decreased the frequency of head dipping behavior compared to animals in the stress group. Golgi-Cox staining indicates that loss of neural spine density in DG, CA1, CA3, and frontal cortex due to chronic restraint stress, was prevented with daily administration of Tarooneh. The results of cresyl-violet staining indicate that Tarooneh significantly increased the number of CV-positive neurons in the frontal cortex and CA1 region of the hippocampus compared to the stress group. Our results suggest that Tarooneh potentially prevented and improved effects in anxiety-like behavior, memory impairment, and synaptic plasticity loss in frontal and hippocampal neurons induced by chronic restraint stress. In conclusion, our results suggest that Tarooneh prevented and improved anxiety-like behavior, cognitive deficit, and neuronal damages in the CA1, CA3, and DG regions of the hippocampus and frontal cortex neurons induced by chronic restraint stress.

Exploring a shared genetic signature and immune infiltration between spontaneous intracerebral hemorrhage and Helicobacter pylori infection

BACKGROUND

Spontaneous intracerebral hemorrhage (ICH) is a devastating form of stroke with high morbidity, disability and mortality. Helicobacter pylori is a major pathogen responsible for chronic gastritis, leading to gastric ulcers and ultimately gastric cancer. Although it remains controversial whether H. pylori infection causes peptic ulcers under various traumatic stimuli, some related studies suggest that H. pylori infection may be an important factor in delaying peptic ulcer healing. However, the linking mechanism between ICH and H. pylori infection remain unclear. The purpose of this study was to examine the genetic features and pathways shared in ICH and H. pylori infection, and compare immune infiltration.

METHODS

We used microarray data for ICH and H. pylori infection from the Gene Expression Omnibus (GEO) database. Differential gene expression analysis was performed on both datasets using the R software and the limma package to find the common differentially expressed genes (DEGs). In addition, we performed functional enrichment analysis on DEGs, determined protein-protein interactions (PPIs), identified Hub genes using the STRING database and Cytoscape software, and constructed microRNA-messenger RNA (miRNA-mRNA) interaction networks. Additionally, immune infiltration analysis was performed with the R software and related R packages.

RESULTS

A total of 72 DEGs were identified between ICH and H. pylori infection, including 68 upregulated genes and 4 downregulated genes. Functional enrichment analysis revealed that multiple signaling pathways are closely linked to both diseases. In addition, the cytoHubba plugin identified 15 important hub genes, namely PLEK, NCF2, CXCR4, CXCL1, FGR, CXCL12, CXCL2, CD69, NOD2, RGS1, SLA, LCP1, HMOX1, EDN1, and ITGB3.Also, the correlation analysis of immune cell fractions revealed a limited link between their immune-related common genes and immune cells.

CONCLUSION

Through bioinformatics methods, this study revealed that there are common pathways and hub genes between ICH and H. pylori infection. Thus, H. pylori infection may have common pathogenic mechanisms with the development of peptic ulcer after ICH. This study provided new ideas for early diagnosis and prevention of ICH and H. pylori infection.

Understanding the relationships between physiological and psychosocial stress, cortisol and cognition

Stress is viewed as a state of real or perceived threat to homeostasis, the management of which involves the endocrine, nervous, and immune systems. These systems work independently and interactively as part of the stress response. The scientific stress literature, which spans both animal and human studies, contains heterogeneous findings about the effects of stress on the brain and the body. This review seeks to summarise and integrate literature on the relationships between these systems, examining particularly the roles of physiological and psychosocial stress, the stress hormone cortisol, as controlled by the hypothalamic-pituitary-adrenal (HPA) axis, and the effects of stress on cognitive functioning. Health conditions related to impaired HPA axis functioning and their associated neuropsychiatric symptoms will also be considered. Lastly, this review will provide suggestions of clinical applicability for endocrinologists who are uniquely placed to measure outcomes related to endocrine, nervous and immune system functioning and identify areas of intervention.

Prenatal restraint stress downregulates the hypothalamic kisspeptidergic system transcripts genes, reduces the estrogen plasma levels, delayed the onset of puberty, and reduced the sexual behavior intensity in female rats

AIMS

This study investigated the possible relationships between the expression of the Kiss1 and Gpr54 gene expressions and the pituitary-gonadal hormones with the female onset of puberty and sexual behavior. The Kiss1 and Gpr54 gene expressions were examined because they are critical to controlling the hypothalamic activation of GnRH neurons and, in turn, the pituitary-gonadal hormones related to the early onset of puberty and sexual behavior. Further, it was evaluated that the pituitary and gonadal hormones involved in the vaginal opening and the expression of sexual behavior.

METHODS

Pregnant rats exposed to PRS from gestation days 17 to 20 were evaluated for maternal and open-field behaviors. The maternal behavior was analyzed because it may alter brain sexual organization affecting the pups development. It was observed in female pups the physical and development and, in adult age, the open-field behavior, the anxiety-like behavior, the estrous cycle, the sexual behavior, the serum FSH, LH, estrogen, progesterone, and testosterone levels, and the gene expression of kisspeptin protein (Kiss1) and Gpr54 in the hypothalamus.

RESULTS

the maternal and open-field behaviors were unaffected. In the F1 generation, PRS reduced weight at weaning, delayed the day of the vaginal opening and reduced the intensity of lordosis, the estrogen levels, and the Kiss1 and Gpr54 gene expression. These effects were attributed to hypothalamic kisspeptidergic system downregulation of transcripts genes and the reduced estrogen levels affected by the PRS.

Knockout of IL-6 mitigates cold water-immersion restraint stress-induced intestinal epithelial injury and apoptosis

Background

Interleukin-6 (IL-6) is essential for maintaining intestinal epithelial homeostasis. Although cold water-immersion restraint (CWIR) stress is commonly used to induce in vivo gastric injury, it also affects intestinal epithelial permeability. Although IL-6 is increased in response to acute physiological and psychological stress, its exact effects on the pathophysiology of the intestinal epithelium in response to acute CWIR stress remain unknown.

Methods

We used IL-6 knockout (KO) mice with acute CWIR modeling to investigate the effect of IL-6 deficiency on intestinal epithelial morphology and pathological damage using histological staining assays under the acute stress. We detected jejunal epithelial apoptosis using TUNEL and standard molecular experiments.

Results

CWIR caused intestinal epithelial damage, which was alleviated by the absence of IL-6, as evidenced by morphological changes and goblet cell and intestinal permeability alteration. IL-6 KO also reduced CWIR-mediated inflammatory levels and improved stress defense. Meanwhile, IL-6 deficiency decreased the intestinal epithelial apoptosis induced by CWIR administration. This IL-6 KO-led effect depended more on mitochondrial AIF signaling rather than the traditional caspase pathway.

Conclusion

As a result, we concluded that acute CWIR-induced severe intestinal damage and jejunal epithelium apoptosis could be alleviated by IL-6 deficiency, implying a protective effect of IL-6 deficiency on the intestines under acute stress. The findings shed new light on treating CWIR-induced intestinal disorders by inhibiting IL-6 signaling.

Methylene Blue not Contraindicated in Treating Hemodynamic Instability in Pediatric and Neonate Patients

The present review was carried out to describe publications on the use of methylene blue (MB) in pediatrics and neonatology, discussing dose, infusion rate, action characteristics, and possible benefits for a pediatric patient group. The research was performed on the data sources PubMed, BioMed Central, and Embase (updated on Aug 31, 2020) by two independent investigators. The selected articles included human studies that evaluated MB use in pediatric or neonatal patients with vasoplegia due to any cause, regardless of the applied methodology. The MB use and 0 to 18-years-old patients with vasodilatory shock were the adopted criteria. Exclusion criteria were the use of MB in patients without vasoplegia and patients ≥ 18-years-old. The primary endpoint was the increase in mean arterial pressure (MAP). Side effects and dose were also evaluated. Eleven studies were found, of which 10 were case reports, and 1 was a randomized clinical study. Only two of these studies were with neonatal patients (less than 28 days-old), reporting a small number of cases (1 and 6). All studies described the positive action of MB on MAP, allowing the decrease of vasoactive amines in several of them. No severe side effects or death related to the use of the medication were reported. The maximum dose used was 2 mg/kg, but there was no consensus on the infusion rate and drug administration timing. Finally, no theoretical or experimental basis sustains the decision to avoid MB in children claiming it can cause pulmonary hypertension. The same goes for the concern of a possible deleterious effect on inflammatory distress syndrome.

Neural impact of neighborhood socioeconomic disadvantage in traumatically injured adults

Nearly 14 percent of Americans live in a socioeconomically disadvantaged neighborhood. Lower individual socioeconomic position (iSEP) has been linked to increased exposure to trauma and stress, as well as to alterations in brain structure and function; however, the neural effects of neighborhood SEP (nSEP) factors, such as neighborhood disadvantage, are unclear. Using a multi-modal approach with participants who recently experienced a traumatic injury (N = 185), we investigated the impact of neighborhood disadvantage, acute post-traumatic stress symptoms, and iSEP on brain structure and functional connectivity at rest. After controlling for iSEP, demographic variables, and acute PTSD symptoms, nSEP was associated with decreased volume and alterations of resting-state functional connectivity in structures implicated in affective processing, including the insula, ventromedial prefrontal cortex, amygdala, and hippocampus. Even in individuals who have recently experienced a traumatic injury, and after accounting for iSEP, the impact of living in a disadvantaged neighborhood is apparent, particularly in brain regions critical for experiencing and regulating emotion. These results should inform future research investigating how various levels of socioeconomic circumstances may impact recovery after a traumatic injury as well as policies and community-developed interventions aimed at reducing the impact of socioeconomic stressors.

The Effects of Furosemide on Behavioral and Hormonal Parameters in Male and Female Mice Subjected to Immobilization and Cold-Water Stress

Introduction

The diuretic agent furosemide (FUR, 25 and 50 mg/kg) has been shown in a single report to act as an anti-stressor agent in two models of acute stress in mice, viz. electric foot-shock stress and immobilization (IMS). The present work aimed to investigate the possible anti-stressor action of FUR on two models of acute stress in mice, cold-water stress (CWS) and IMS, and tried to determine whether gender has any impact on the effect of FUR.

Methods

FUR (40 mg/kg) was injected intraperitoneally, and after 30 minutes, mice were subjected to CWS (4°C for three minutes) or IMS (fixing movement for two and a half hrs using adhesive tape). Motor and exploratory activities, neuromuscular coordination, and thermal nociception were then tested. Blood was collected from the mice and used to measure the concentrations of three stress hormones (corticosterone, epinephrine and prolactin).

Results

Mice subjected to CWS and IMS had significantly reduced motor and exploratory activities, neuromuscular coordination, and increased nociception. CWS and IMS also significantly increased the plasma concentrations of the three hormones. FUR pretreatment significantly mitigated these stress-induced hormonal changes. There was no significant sex difference when CWS or IMS was applied.

Discussion

IMS and CWS stimuli in male and female mice caused significant elevations in the plasma concentrations of corticosterone, epinephrine, and prolactin, accompanied by a significant reduction of motor and exploratory activities, neuromuscular coordination, and thermal nociception. There were no sex differences when IMS was applied. In stressed mice, prior administration of FUR (40 mg/kg) significantly decreased the concentrations of stress hormones, and this effect significantly mitigated the stress-induced behavioural and motor changes.

Gonadotropin levels reduced in seven days immobilization stress-induced depressive-like behavior in female rats

OBJECTIVES

Reproduction is one of the physiological functions that are often negatively affected by chronic stress. We aimed to examine effects of two distinct 7-day chronic immobilization stress (IMO) models on gonadotropins levels and depression-like behaviors in female rats.

METHODS

Adult Wistar albino female rats were divided into three groups as follows (n=7 for each group): control, IMO-1 (45 min daily for 7-day) and IMO-2 (45 min twice a day for 7-day). Neuropsychiatric behaviors were determined by using forced swimming test (FST) and open field test (OFT). Gonadotropins were analyzed using ELISA tests.

RESULTS

In FST, swimming was lower, and immobility was higher in the IMO-1 group and IMO--2 group. Climbing score of the IMO-2 group was higher compared to the control group. In OFT, there was no significant alteration in the mean velocity, total distance, duration of time spent in the central area and duration of latency in the central area between the stress groups and the control group. Final body weight and percentage of body weight change were lower in both stress groups. The follicle-stimulating hormone level was lower only in the IMO-2 group, and the luteinizing hormone concentrations were significantly lower in the IMO-1 group and IMO-2 group.

CONCLUSIONS

Our results indicated that depression-like behaviors increased, and gonadotropins decreased in the female rats exposed to 7-day chronic IMO.

Investigation of Effects of Two Chronic Stress Protocols on Depression-Like Behaviors and Brain Mineral Levels in Female Rats: an Evaluation of 7-Day Immobilization Stress

We aimed to investigate the effects of two different chronic immobilization stress protocols on depression-related behaviors and brain mineral levels. Adult female Wistar albino rats were divided into 3 groups as follows (n = 10/group): control, immobilization stress-1 (45 min daily for 7 days), and immobilization stress-2 (45 min twice a day for 7 day). Stress-related behavior was evaluated by means of the forced swimming test (FST) and open field test (OFT). Minerals were analyzed using an inductively coupled plasma mass spectrometer. In the FST, swimming and immobility were significantly lower in the immobilization stress-1 and immobilization stress-2 groups. The climbing duration of the immobilization stress-2 group was higher than the control group. In the OFT, percentage of time spent in the central area was significantly lower in the immobilization stress-1 and immobilization stress-2 groups. Values of latency to center area, rearing, and grooming did not significantly differ between groups. In the immobilization stress-1 group, zinc was lower, and iron, copper, and manganese were higher than the control group. In the immobilization stress-2 group, copper and manganese were higher, and phosphate was lower than the control group. Our results showed that depression-related behaviors were more dominant in the immobilization stress-1 group. A decrease in the brain zinc level was valid only for the immobilization stress-1 group. These results point to the role of low brain zinc levels in the pathophysiology of depression.

Understanding stress: Insights from rodent models

Through incorporating both physical and psychological forms of stressors, a variety of rodent models have provided important insights into the understanding of stress physiology. Rodent models also have provided significant information with regards to the mechanistic basis of the pathophysiology of stress-related disorders such as anxiety disorders, depressive illnesses, cognitive impairment and post-traumatic stress disorder. Additionally, rodent models of stress have served as valuable tools in the area of drug screening and drug development for treatment of stress-induced conditions. Although rodent models do not accurately reproduce the biochemical or physiological parameters of stress response and cannot fully mimic the natural progression of human disorders, yet, animal research has provided answers to many important scientific questions. In this review article, important studies utilizing a variety of stress models are described in terms of their design and apparatus, with specific focus on their capabilities to generate reliable behavioral and biochemical read-out. The review focusses on the utility of rodent models by discussing examples in the literature that offer important mechanistic insights into physiologically relevant questions. The review highlights the utility of rodent models of stress as important tools for advancing the mission of scientific research and inquiry.

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Stressful life events may lead to the onset of severe psychopathologies in humans.

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Rodents may model many features of stress exposure in human populations.

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Induction of stress via pharmacological and psychological manipulations alter rodent behavior.

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Mechanistic rodent studies reveal key molecular targets critical for new therapeutic targets.

Chronic immobilization stress induces anxiety-related behaviors and affects brain essential minerals in male rats

Alterations of essential elements in the brain are associated with the pathophysiology of many neuropsychiatric disorders. It is known that chronic/overwhelming stress may cause some anxiety and/or depression. We aimed to investigate the effects of two different chronic immobilization stress protocols on anxiety-related behaviors and brain minerals. Adult male Wistar rats were divided into 3 groups as follows (n = 10/group): control, immobilization stress-1 (45 minutes daily for 7-day) and immobilization stress-2 (45 minutes twice a day for 7-day). Stress-related behaviors were evaluated by open field test and forced swimming test. In the immobilization stress-1 and immobilization stress-2 groups, percentage of time spent in the central area (6.38 ± 0.41% and 6.28 ± 1.03% respectively, p < 0.05) and rearing frequency (2.75 ± 0.41 and 3.85 ± 0.46, p < 0.01 and p < 0.05, respectively) were lower, latency to center area (49.11 ± 5.87 s and 44.92 ± 8.04 s, p < 0.01 and p < 0.01, respectively), were higher than the control group (8.65 ± 0.49%, 5.37 ± 0.44 and 15.3 ± 3.32 s, respectively). In the immobilization stress-1 group, zinc (12.65 ± 0.1 ppm, p < 0.001), magnesium (170.4 ± 1.7 ppm, p < 0.005) and phosphate (2.76 ± 0.1 ppm, p < 0.05) levels were lower than the control group (13.87 ± 0.16 ppm, 179.31 ± 1.87 ppm and 3.11 ± 0.06 ppm, respectively). In the immobilization stress-2 group, magnesium (171.56 ± 1.87 ppm, p < 0.05), phosphate (2.44 ± 0.07 ppm, p < 0.001) levels were lower, and manganese (373.68 ± 5.76 ppb, p < 0.001) and copper (2.79 ± 0.15 ppm, p < 0.05) levels were higher than the control group (179.31 ± 1.87 ppm, 3.11 ± 0.06 ppm, 327.25 ± 8.35 ppb and 2.45 ± 0.05 ppm, respectively). Our results indicated that 7-day chronic immobilization stress increased anxiety-related behaviors in both stress groups. Zinc, magnesium, phosphate, copper and manganese levels were affected in the brain.

Aging of the cells: Insight into cellular senescence and detection Methods

Cellular theory of aging states that human aging is the result of cellular aging, in which an increasing proportion of cells reach senescence. Senescence, from the Latin word senex, means "growing old," is an irreversible growth arrest which occurs in response to damaging stimuli, such as DNA damage, telomere shortening, telomere dysfunction and oncogenic stress leading to suppression of potentially dysfunctional, transformed, or aged cells. Cellular senescence is characterized by irreversible cell cycle arrest, flattened and enlarged morphology, resistance to apoptosis, alteration in gene expression and chromatin structure, expression of senescence associated- β-galactosidase (SA-β-gal) and acquisition of senescence associated secretory phenotype (SASP). In this review paper, different types of cellular senescence including replicative senescence (RS) which occurs due to telomere shortening and stress induced premature senescence (SIPS) which occurs in response to different types of stress in cells, are discussed. Biomarkers of cellular senescence and senescent assays including BrdU incorporation assay, senescence associated- β-galactosidase (SA-β-gal) and senescence-associated heterochromatin foci assays to detect senescent cells are also addressed.

The role of vitamin C in stress-related disorders

Stress-related disorders, such as depression and anxiety, present marked deficits in behavioral and cognitive functions related to reward. These are highly prevalent disabling conditions with high social and economic costs. Furthermore, a significant percentage of affected individuals cannot benefit from clinical intervention, opening space for new treatments. Although the literature data have reported limited and variable results regarding oxidative stress-related endpoints in stress-related disorders, the possible neuroprotective effect of antioxidant compounds, such as ascorbic acid (vitamin C), emerges as a possible therapy strategy for psychiatric diseases. Here, we briefly present background information on biological activity of ascorbic acid, particularly functions related to the CNS homeostasis. Additionaly, we reviewed the available information on the role of ascorbic acid in stress-related diseases, focusing on supplementation and depletion studies. The vitamin C deficiency is widely associated to stress-related diseases. Although the efficacy of this vitamin in anxiety spectrum disorders is less stablished, several studies showed that ascorbic acid supplementation produces antidepressant effect and improves mood. Interestingly, the modulation of monoaminergic and glutamatergic neurotransmitter systems is postulated as pivotal target for the antidepressant and anxiolytic effects of this vitamin. Given that ascorbic acid supplementation produces fast therapeutic response with low toxicity and high tolerance, it can be considered as a putative candidate for the treatment of mood and anxiety disorders, especially those that are refractory to current treatments. Herein, the literature was reviewed considering the potential use of ascorbic acid as an adjuvant in the treatment of anxiety and depression.

Chronic stress and endothelial dysfunction: mechanisms, experimental challenges, and the way ahead

Although chronic stress is an important risk factor for cardiovascular diseases (CVD) onset, the underlying mechanisms driving such pathophysiological complications remain relatively unknown. Here, dysregulation of innate stress response systems and the effects of downstream mediators are strongly implicated, with the vascular endothelium emerging as a primary target of excessive glucocorticoid and catecholamine action. Therefore, this review article explores the development of stress-related endothelial dysfunction by focusing on the following: 1) assessing the phenomenon of stress and complexities surrounding this notion, 2) discussing mechanistic links between chronic stress and endothelial dysfunction, and 3) evaluating the utility of various preclinical models currently employed to study mechanisms underlying the onset of stress-mediated complications such as endothelial dysfunction. The data reveal that preclinical models play an important role in our efforts to gain an increased understanding of mechanisms underlying stress-mediated endothelial dysfunction. It is our understanding that this provides a good foundation going forward, and we propose that further efforts should be made to 1) more clearly define the concept of stress and 2) standardize protocols of animal models with specific guidelines to better indicate the mental complications that are simulated.

Epigallocatechin-3-gallate protects immunity and liver drug-metabolism function in mice loaded with restraint stress

(-)-Epigallocatechin-3-gallate (EGCG) is the most abundant polyphenolic compound present in green tea and has been shown to possess bio-activities. In this study, we investigated the protective effects of EGCG against restraint stress (RS)-induced liver injury and immunosuppression. EGCG (10, 20 and 40 mg/kg) was orally administered to mice daily for 7 days before modeling the restraint stress. lood, liver and broncho-alveolar lavage fluid (BALF) samples were collected and tested. We found that EGCG significantly reduced the release of stress hormones to weak restraint stress response. EGCG effectively improved hepatic damage by decreas the serum levels of alanine aminotransaminase (ALT) and aspartate transaminase (AST) in restraint-challenged mice. Furthermore, EGCG also significantly prevented the release of H₂O₂, NOS and 8-isoprostane, and reduced the levels of interleukin (IL)-1β, IL-2,and IL-6 restrained mice. EGCG can normal the level of cytochrome P450 (CYP450) 1A2, 2D22, 2E1 and 3A11 that induced by restraint stress., the inhibition status of T cells subsets in serum and gA in BALF were significantly relieved EGCG pretreatment. Taken together, our data suggest that EGCG possesse hepatic- and immune-protective properties against restraint stress through its anti-oxidant, anti-inflammatory and immunomodulatory activities.

Involvement of the gabaergic, serotonergic and glucocorticoid mechanism in the anxiolytic-like effect of mastoparan-L

Mastoparan-L (mast-L) is a cell-penetrating tetradecapeptide and stimulator of monoamine exocytosis. In the present study, we evaluated the anxiolytic-like effect of mast-L. Preliminary pharmacological tests were conducted to determine the most appropriate route of administration, extrapolate dose and detect potential toxic effects of this peptide. Oral and intracerebroventricular administration of mast-L (0.1, 0.3 or 0.9 mg.kg^-1), diazepam (1 or 5 mg.kg^-1), buspirone (10 mg.kg^-1) or vehicle 10 mL.kg^-1 was carried out prior to the exposure of mice to the anxiety models: open field, light-dark box and elevated plus-maze. To characterize the mechanism underlying the antianxiety-like effect of mast-L, pharmacological antagonism, blood plasma analysis, molecular docking, and receptor binding assays were performed. The absence of a neurotoxic sign, animal's death as well as lack of significant changes in the relative organ weight, hematological and biochemical parameters suggest that mast-L is relatively safe. The anxiolytic-like effect of mast-L was attenuated by flumazenil (antagonist of benzodiazepine binding site) and WAY100635 (selective antagonist of 5-HT_1A receptors) pretreatments. Mast-L reduced plasma corticosterone and lowered the scoring function at GABA_A -18.48 kcal/mol (Ki = 155 nM), 5-HT_1A -22.39 kcal/mol (Ki = 130 nM), corticotropin-releasing factor receptor subtype 1 (CRF1) -11.95 kcal/mol (Ki = 299 nM) and glucocorticoid receptors (GR) -14.69 kcal/mol (Ki = 3552 nM). These data fit the binding affinity (Ki) and demonstrate the involvement of gabaergic, serotonergic and glucocorticoid mechanisms in the anxiolytic-like property of mast-L.

A psychological stressor conveyed by appetite-linked neurons

Mammals exhibit instinctive reactions to danger critical to survival, including surges in blood stress hormones. Hypothalamic corticotropin-releasing hormone neurons (CRHNs) control stress hormones but how diverse stressors converge on CRHNs is poorly understood. We used sRNA profiling to define CRHN receptors for neurotransmitters and neuromodulators and then viral tracing to localize subsets of upstream neurons expressing cognate receptor ligands. Unexpectedly, one subset comprised POMC (proopiomelanocortin)-expressing neurons in the arcuate nucleus, which are linked to appetite suppression. The POMC neurons were activated by one psychological stressor, physical restraint, but not another, a predator odor. Chemogenetic activation of POMC neurons induced a stress hormone response, mimicking a stressor. Moreover, their silencing markedly reduced the stress hormone response to physical restraint, but not predator odor. These findings indicate that POMC neurons involved in appetite suppression also play a major role in the stress hormone response to a specific type of psychological stressor.

Prenatal stress and later metabolic consequences: Systematic review and meta-analysis in rodents

BACKGROUND

Numerous rodent studies have evaluated the effects of maternal stress (MS) on later in life susceptibility to Metabolic Syndrome (MetS) intermediate phenotypes with varying results. The aim of this study was to quantitatively synthesize the available data on the effects of MS on offspring obesity, estimated indirectly by body mass (BM), body fat (BF) and plasma leptin; systolic blood pressure (SBP); plasma glucose (and insulin) and blood lipid concentrations.

METHODS

Literature was screened and summary estimates of the effect of MS outcomes were calculated by using random-effects models. Data on the effects of exogenous corticosteroid administration (or inhibition of 11β-HSD2) during pregnancy in rodents was analysed separately to characterize the direct phenotypic effects of prenatal corticosteroid excess (PCE).

RESULTS

We conducted 14 separate meta-analyses and synthesized relevant data on outcomes scarcely reported in literature. Both MS and PCE were associated with low birth weight without rapid catch-up growth resulting in decreased body mass later in life. Our analysis also revealed significant and contradictory effects on offspring adiposity. Little evidence was found for effects on glucose metabolism and blood lipids. We identified increased SBP in offspring exposed to PCE; however, there is not enough data to draw any conclusion about effects of MS on SBP.

CONCLUSIONS

Neonatal weight proved to be decreased in offspring prenatally exposed to stress or corticosteroids, but laboratory rodents in the absence of a challenging environment did not show catch-up growth. The available evidence is inconclusive regarding the effect on adiposity revealing clear methodological and knowledge gaps. This meta-analysis also confirmed a significant positive association between PCE and SBP. Nevertheless, additional studies should address the association with MS.

Short-term sleep deprivation in mice induces B cell migration to the brain compartment

Increasing evidence highlight the involvement of immune cells in brain activity and its dysfunction. The brain's immune compartment is a dynamic ensemble of cells that can fluctuate even in naive animals. However, the dynamics and factors that can affect the composition of immune cells in the naive brain are largely unknown. Here, we examined whether acute sleep deprivation can affect the brain's immune compartment (parenchyma, meninges, and choroid plexus). Using high-dimensional mass cytometry analysis, we broadly characterized the effects of short-term sleep deprivation on the immune composition in the mouse brain. We found that after 6 h of sleep deprivation, there was a significant increase in the abundance of B cells in the brain compartment. This effect can be accounted for, at least in part, by the elevated expression of the migration-related receptor, CXCR5, on B cells and its ligand, cxcl13, in the meninges following sleep deprivation. Thus, our study reveals that short-term sleep deprivation affects the brain's immune compartment, offering a new insight into how sleep disorders can affect brain function and potentially contribute to neurodegeneration and neuroinflammation.

Bidirectional cingulate-dependent danger information transfer across rats

Social transmission of freezing behavior has been conceived of as a one-way phenomenon in which an observer "catches" the fear of another. Here, we use a paradigm in which an observer rat witnesses another rat receiving electroshocks. Bayesian model comparison and Granger causality show that rats exchange information about danger in both directions: how the observer reacts to the demonstrator's distress also influences how the demonstrator responds to the danger. This was true to a similar extent across highly familiar and entirely unfamiliar rats but is stronger in animals preexposed to shocks. Injecting muscimol in the anterior cingulate of observers reduced freezing in the observers and in the demonstrators receiving the shocks. Using simulations, we support the notion that the coupling of freezing across rats could be selected for to more efficiently detect dangers in a group, in a way similar to cross-species eavesdropping.

Quercetin attenuates acute predator stress exposure-evoked innate fear and behavioral perturbation

Background Oxidative stress plays a pivotal role in the pathophysiology and pathogenesis of mental diseases, such as depression or anxiety. Psychological stress induced by predatory stimulus is one of the models that explain how induced affective behavior is manifested as a depression-like state. Quercetin is a flavonoid that exhibits potential pharmacological activity on mental diseases. Thus, the present study was designed to investigate the effect of quercetin on innate fear and affective behavior induced by repeated predator stress exposure on mice. Materials and methods ICR mice were exposed to predatory stress for 3 days. Quercetin at a dose of 50 mg/kg was given intraperitoneally along with stress induction. The freezing behavior during the stress induction was analyzed. The anxiety-like and depressive-like behaviors and cognitive and motor functions were examined on the last day of induction. Results Predatory stress increased the affective behaviors (anxiety-like and depressive-like behaviors) and produced freezing behavior without alterations in the cognitive function and exploratory behavior. Treatment with quercetin 50 mg/kg attenuated the freezing, anxiety-like and depressive-like behaviors. Conclusions Repeated predator stress exposure causes both innate fear and depression-like state for the prey animals. Quercetin may have a protective effect against depression and alleviates the fear of traumatic events.

Preliminary investigation of the effect of oral supplementation of Lactobacillus plantarum strain SNK12 on mRNA levels of neurotrophic factors and GABA receptors in the hippocampus of mice under stress-free and sub-chronic mild social defeat-stressing conditions

The effect of Lactobacillus plantarum SNK12 (CPLP) supplementation on mRNA levels of hippocampal neurotrophic factors and gamma aminobutyric acid receptors (GABA_R) was tested. In Experiment 1, stress-free, unsupplemented and CPLP (4 × 10⁸ cells/head)-supplemented male C57BL/6J (B6) mice were the experimental animals. In Experiment 2, intruder (male, B6) mice [negative control; unsupplemented, sub-chronic mild social defeat stress (sCSDS)-induced; and CPLP-supplemented, sCSDS-induced] were exposed to aggressor mice (adult male Slc:ICR). mRNA levels of neurotrophic factors and GABA_R in hippocampal samples of these mice were analyzed. In CPLP-supplemented mice of both experiments, mRNA levels of bdnf, nt-3, and GABA_R were upregulated. Moreover, a tendency toward the improvement of habituation ability (Experiment 1) and behavior (Experiment 2) was observed in mice, which may be associated with upregulated neurotrophic factors and GABA_R. We demonstrated that oral supplementation of CPLP to stress-free and stress-induced mice upregulated mRNA levels of hippocampal neurotrophic factors and GABA_R.

Oxidized Cell-Free DNA Role in the Antioxidant Defense Mechanisms under Stress

The present study focuses on the investigation of the oxidized cell-free DNA (cfDNA) properties in several experimental models, including cultured cerebellum cells, peripheral blood lymphocytes (PBL), plasma, and hippocampus under an acute and chronic unpredictable stress model in rats. Firstly, our study shows that Spectrum Green fluorescence-labeled oxidized cfDNA fragments were transferred into the cytoplasm of 80% of the cerebellum culture cells; meanwhile, the nonoxidized cfDNA fragments do not pass into the cells. Oxidized cfDNA stimulates the antioxidant mechanisms and induction of transcription factor NRF2 expression, followed by an activation of NRF2 signaling pathway genes-rise of Nrf2 and Hmox1 gene expression and consequently NRF2 protein synthesis. Secondly, we showed that stress increases plasma cfDNA concentration in rats corresponding with the duration of the stress exposure. At the same time, our study did not reveal any significant changes of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) level in PBL of rats under acute or chronic stress, probably due to the significantly increased Nrf2 expression, that we found in such conditions. 8-oxodG is one of the most reliable markers of DNA oxidation. We also found an increased level of 8-oxodG in the hippocampal homogenates and hippocampal dentate gyrus in rats subjected to acute and chronic stress. Taken together, our data shows that oxidized cfDNA may play a significant role in systemic and neuronal physiological mechanisms of stress and adaptation.

Medial prefrontal cortex exacerbates gastric dysfunction of rats upon restraint water‑immersion stress

Restraint water-immersion stress (RWIS) can induce a gastric mucosal lesions within a few hours. The medial prefrontal cortex (mPFC) is involved in the RWIS process. The present study investigated the modulatory effects and molecular mechanisms of the mPFC on gastric function under an RWIS state. Male Wistar rats were divided into four groups; namely, the control, RWIS 4 h (RWIS for 4 h only), sham-operated and bilateral-lesioned (bilateral-lesioned mPFC) groups. The gastric erosion index (EI) and gastric motility (GM) were determined, and the proteomic profiles of the mPFC were assessed by isobaric tags for relative and absolute quantitation (iTRAQ) coupled with two-dimensional liquid chromatography and tandem mass spectrometry. Additionally, iTRAQ results were verified by western blot analysis. Compared with the RWIS 4 h group and the sham-control group, the bilateral-lesioned group exhibited a significantly lower EI (P<0.01). In the bilateral-lesioned group, RWIS led to a significant decrease in EI and GM. When comparing the control and RWIS 4 h groups, 129 dysregulated proteins were identified, of which 88 were upregulated and 41 were downregulated. Gene Ontology functional analysis demonstrated that 29 dysregulated proteins, including postsynaptic density protein 95, were directly associated with axon morphology, axon growth and synaptic plasticity. Ingenuity pathway analysis revealed that the dysregulated proteins were mainly involved in neurological disease signaling pathways, including the NF-κB and ERK signaling pathways. These data indicated that the presence of the mPFC exacerbates gastric mucosal injury in awake rats during RWIS. Although the quantitative proteomic analysis elucidated the nervous system molecular targets associated with the production of gastric mucosal lesions, such as the role of PSD95. The underlying molecular mechanisms of synaptic plasticity need to be further elucidated.

Cardiovascular outcomes related to social defeat stress: New insights from resilient and susceptible rats

Stress exposure is an important risk factor for psychiatric and cardiovascular disorders. Two phenotypes related to coping with stress can be observed in rodents that experience chronic social defeat stress (SDS): susceptible, showing social avoidance and behavioral changes related to depression, and resilient, showing none of these alterations. Moreover, a strong correlation exists between depression and the development of or mortality due to cardiovascular diseases. Nevertheless, little is known about cardiovascular alterations related to SDS exposure in those phenotypes or their correlation with depressive-like behaviors. Using a chronic SDS protocol followed by the social interaction test, we identified Wistar rats as resilient or susceptible to SDS. Susceptible animals showed increased depressive-like behaviors with resting tachycardia and decreased heart rate variability (HRV) due to increased sympathetic tone in the heart and a less effective baroreflex. In contrast, resilient rats were protected from these alterations by increased vagal tone, resulting in greater HRV values. To our knowledge, our study is the first to indicate that harmful cardiovascular outcomes are related to depressive-like behaviors in susceptible rats and to suggest a mechanism by which resilient rats are protected from these changes. Also, our results suggest that enhanced HRV and vagal tone may be an important trait in resilient individuals.

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Cardiovascular alterations are correlated to depressive-like behaviors.

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Susceptible rats show increased sympathetic tone to the heart and lower HRV.

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Baroreflex effectiveness in susceptible rats is impaired.

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Resilient rats show an increased vagal tone to the heart and greater values of HRV.

Ammonium induced dysfunction of 5-HT2B receptor in astrocytes

Previously we reported that gene expression of astrocytic 5-HT_2B receptors was decreased in brains of depressed animals exposed to chronic mild stress (CMS) (Li et al., 2012) and of Parkinson's disease (Song et al., 2018). Depression is also one of the psychiatric symptoms in hyperammonemia, and astrocyte is a primary target of ammonium in brain in vivo. In the present study, we have used preparations of the brains of urease-treated mice and ammonium-treated astrocytes in culture to study gene expression and function of 5-HT_2B receptors. The urease-treated mice showed depressive behaviour. Both mRNA and protein of 5-HT_2B receptors were increased in the brains of urease-treated mice and in ammonium-treated cultured astrocytes. Further study revealed that mRNA and protein expression of adenosine deaminase acting on RNA 2 (ADAR2), an enzyme catalyze RNA deamination of adenosine to inosine was increased in the brains of urease-treated mice and in ammonium-treated cultured astrocytes. This increase in ADAR2 induced RNA editing of 5-HT_2B receptors. Cultured astrocytes treated with ammonium lost 5-HT induced Ca²⁺ signalling and ERK_1/2 phosphorylation, indicating dysfunction of 5-HT_2B receptors. This is in agreement with our previous observation that edited 5-HT_2B receptors no longer respond to 5-HT (Hertz et al., 2014). Ammonium effects are inhibited by ADAR2 siRNA in cultured astrocytes, suggesting that increased gene expression and editing and loss of function of 5-HT_2B receptors are results of increased activity of ADAR2. In summary, we have demonstrated that functional malfunction of astrocytic 5-HT_2B receptors occurs in animal models of major depression, Parkinson depression and hepatic encephalopathy albeit via different mechanisms. Understanding the role of astrocytic 5-HT_2B receptors in different pathological contexts may instigate development of novel therapeutic strategies for treating disease-specific depressive behaviour.

The Preventive and Curative Effects of Lactobacillus reuteri NK33 and Bifidobacterium adolescentis NK98 on Immobilization Stress-Induced Anxiety/Depression and Colitis in Mice

The gut dysbiosis by stressors such as immobilization deteriorates psychiatric disorders through microbiota-gut-brain axis activation. To understand whether probiotics could simultaneously alleviate anxiety/depression and colitis, we examined their effects on immobilization stress (IS)-induced anxiety/depression and colitis in mice. The probiotics Lactobacillus reuteri NK33 and Bifidobacterium adolescentis NK98 were isolated from healthy human feces. Mice with anxiety/depression and colitis were prepared by IS treatment. NK33 and NK98 potently suppressed NF-κB activation in lipopolysaccharide (LPS)-induced BV-2 cells. Treatment with NK33 and/or NK98, which were orally gavaged in mice before or after IS treatment, significantly suppressed the occurrence and development of anxiety/depression, infiltration of Iba1⁺ and LPS⁺/CD11b⁺ cells (activated microglia) into the hippocampus, and corticosterone, IL-6, and LPS levels in the blood. Furthermore, they induced hippocampal BDNF expression while NF-κB activation was suppressed. NK33 and/or NK98 treatments suppressed IS-induced colon shortening, myeloperoxidase activity, infiltration of CD11b⁺/CD11c⁺ cells, and IL-6 expression in the colon. Their treatments also suppressed the IS-induced fecal Proteobacteria population and excessive LPS production. They also induced BDNF expression in LPS-induced SH-SY5Y cells in vitro. In conclusion, NK33 and NK98 synergistically alleviated the occurrence and development of anxiety/depression and colitis through the regulation of gut immune responses and microbiota composition.

In Vivo Gastroprotective and Antidepressant Effects of Iridoids, Verbascoside and Tenuifloroside from Castilleja tenuiflora Benth

Stress is an important factor in the etiology of some illnesses such as gastric ulcers and depression. Castilleja tenuiflora Benth. (Orobanchaceae) is used in Mexican traditional medicine for the treatment of gastrointestinal diseases and nervous disorders. Previous studies indicated that organic extracts from C. tenuiflora had gastroprotective effects and antidepressant activity. In this study, we aimed to evaluate the gastroprotective and antidepressant activity of fractions and isolated compounds from the methanolic extract (MECt) of C. tenuiflora in stressed mice. Chromatographic fractionation of MECt produced four fractions (FCt-1, FCt-2, CFt-3, and FCt-4) as well as four bioactive compounds which were identified using TLC, HPLC and NMR analyses. The cold restraint stress (CRS)-induced gastric ulcer model followed by the tail suspension test and the forced swim test were used to evaluate the gastroprotective effect and antidepressant activity of the extract fractions. FCt-2 and FCt-3 at 100 mg/kg had significant gastroprotective and antidepressant effects. All isolated compounds (verbascoside, teniufloroside and mixture geniposide/ musseanoside) displayed gastroprotective effects and antidepressant activity at 1 or 2 mg/kg. The above results allow us to conclude that these polyphenols and iridoids from C. tenuiflora are responsible for the gastroprotective and antidepressant effects.

Behavioral, affective, and cognitive alterations induced by individual and combined environmental stressors in rats

OBJECTIVE

To evaluate whether exposing rats to individual or combined environmental stressors triggers endophenotypes related to mood and anxiety disorders, and whether this effect depends on the nature of the behavior (i.e., innate or learned).

METHODS

We conducted a three-phase experimental protocol. In phase I (baseline), animals subjected to mixed schedule of reinforcement were trained to press a lever with a fixed interval of 1 minute and a limited hold of 3 seconds. On the last day of phase I, an open-field test was performed and the animals were divided into four experimental groups (n=8/group). In phase II (repeated stress), each group was exposed to either hot air blast (HAB), paradoxical sleep deprivation (PSD) or both (HAB+PSD group) on alternate days over a 10-day period. Control group animals were not exposed to stressors. In phase III (post-stress evaluation), behavior was analyzed on the first (short-term effects), third (mid-term effects), and fifth (long-term effects) days after repeated stress.

RESULTS

The PSD group presented operant hyperactivity, the HAB group presented spontaneous hypoactivity and anxiety, and the HAB+PSD group presented spontaneous hyperactivity, operant hypoactivity, impulsivity, loss of interest, and cognitive impairment.

CONCLUSION

A combination of environmental stressors (HAB and PSD) may induce endophenotypes related to bipolar disorder.

Cotinine Plus Krill Oil Decreased Depressive Behavior, and Increased Astrocytes Survival in the Hippocampus of Mice Subjected to Restraint Stress

Restraint stress (RS) is a condition affecting millions of people worldwide. The investigation of new therapies to alleviate the consequences of prolonged RS is much needed. Cotinine, a nicotine-derivative, has shown to prevent the decrease in cerebral synaptic density, working memory deficits, anxiety, and depressive-like behavior after prolonged restraint stress (RS) in mice. Furthermore, post-treatment with cotinine reduced the adverse effects of chronic RS on astrocyte survival and architecture. On the other hand, the nutritional supplement krill oil (KO), has shown to be beneficial in decreasing depressive-like behavior and oxidative stress. In this study, in the search for effective preventative treatments to be used in people subjected to reduced mobility, the effect of co-treatment with cotinine plus KO in mice subjected to prolonged RS was investigated. The results show that cotinine plus KO prevented the loss of astrocytes, the appearance of depressive-like behavior and cognitive impairment induced by RS. The use of the combination of cotinine plus KO was more effective than cotinine alone in preventing the depressive-like behavior in the restrained mice. The potential use of this combination to alleviate the psychological effects of reduced mobility is discussed.

Protective effects of citrus based mixture drinks (CBMDs) on oxidative stress and restraint stress

In the current study investigated the protective effects of citrus based mixture drinks (CBMDs) using oxidative stress in human dermal fibroblast (HDF) cells and restraint-stressed rats. The CBMDs contained citrus bioflavonoids including narirutin and hesperidin. The cell viability of HDF cells treated with H₂O₂ was observed at 53.9% but treated with CBMD-1 and CBMD-2 (500 μg/mL) on H₂O₂ exposed HDF cells significantly increased the relative cell viability at 65.0 and 72.2%, respectively. In the treadmill test, the time spent on the electrode plate in the restraint-stressed group was analyzed 24.1 s, but restraint-stressed rats with administered CBMDs (300 mg/kg) had significantly decreased the time at 2.4 (CBMD-1) and 4.7 (CBMD-2) s, respectively. In addition, number of touches the electrode plate in restraint-stressed group was observed at 42.4 ea, but, restraint-stressed rats with administered CBMD-1 and CBMD-2 (300 mg/kg) were significantly decreased at 7.0 and 10.2 ea, respectively.

Effects of Isolation and Social Subchronic Stresses on Food Intake and Levels of Leptin, Ghrelin, and Glucose in Male Rats

Background:

Exposure to psychological stresses can be a reason for obesity. Therefore, identifying the effective nutritional mechanisms such as feeding markers is of high necessity for the psychological stress conditions. Hence, the present study investigates the effects of subchronic isolation and social stresses on food intake, body weight differences (BWD), and levels of leptin, ghrelin, and glucose in rats.

Materials and Methods:

Eighteen male rats were randomly allocated into three groups: control (Co), isolation stress (IS), and social stress (SS) groups. Rats were under stresses for 7 days. The food intake (for three continuous hours after 16–18 h of food deprivation), BWD, levels of ghrelin, leptin, and glucose were measured.

Results:

The results showed that the food intake significantly (P < 0.05) reduced during the 1^st h in the SS group compared to the Co group. At the 2^nd h, the food intake significantly (P < 0.001 and P < 0.01, respectively) decreased in the IS group compared to the Co and SS groups. The cumulative food intake and body weight were significantly (P < 0.05) reduced in the IS group compared to the Co group. The serum ghrelin level significantly reduced in the IS group compared to the Co group.

Conclusions:

The subchronic psychological stresses led to a reduction in food intake by the reduction of serum ghrelin levels. It seems that ghrelin might have a more fundamental role in the food intake with respect to the leptin and glucose levels in subchronic stress condition. Furthermore, the decreased body weight justified the reduction of food intake, particularly in subchronic isolation stress.

Current Status of Animal Models of Posttraumatic Stress Disorder: Behavioral and Biological Phenotypes, and Future Challenges in Improving Translation

Increasing predictability of animal models of posttraumatic stress disorder (PTSD) has required active collaboration between clinical and preclinical scientists. Modeling PTSD is challenging, as it is a heterogeneous disorder with ≥20 symptoms. Clinical research increasingly utilizes objective biological measures (e.g., imaging, peripheral biomarkers) or nonverbal behaviors and/or physiological responses to complement verbally reported symptoms. This shift toward more-objectively measurable phenotypes enables refinement of current animal models of PTSD, and it supports the incorporation of homologous measures across species. We reviewed >600 articles to examine the ability of current rodent models to probe biological phenotypes of PTSD (e.g., sleep disturbances, hippocampal and fear-circuit dysfunction, inflammation, glucocorticoid receptor hypersensitivity) in addition to behavioral phenotypes. Most models reliably produced enduring generalized anxiety-like or depression-like behaviors, as well as hyperactive fear circuits, glucocorticoid receptor hypersensitivity, and response to long-term selective serotonin reuptake inhibitors. Although a few paradigms probed fear conditioning/extinction or utilized peripheral immune, sleep, and noninvasive imaging measures, we argue that these should be incorporated more to enhance translation. Data on female subjects, on subjects at different ages across the life span, or on temporal trajectories of phenotypes after stress that can inform model validity and treatment study design are needed. Overall, preclinical (and clinical) PTSD researchers are increasingly incorporating homologous biological measures to assess markers of risk, response, and treatment outcome. This shift is exciting, as we and many others hope it not only will support translation of drug efficacy from animal models to clinical trials but also will potentially improve predictability of stage II for stage III clinical trials.

Static Magnetic Fields Modulate the Response of Different Oxidative Stress Markers in a Restraint Stress Model Animal

Stress is a state of vulnerable homeostasis that alters the physiological and behavioral responses. Stress induces oxidative damage in several organs including the brain, liver, kidney, stomach, and heart. Preliminary findings suggested that the magnetic stimulation could accelerate the healing processes and has been an effective complementary therapy in different pathologies. However, the mechanism of action of static magnetic fields (SMFs) is not well understood. In this study, we demonstrated the effects of static magnetic fields (0.8 mT) in a restraint stressed animal model, focusing on changes in different markers of oxidative damage. A significant increase in the plasma levels of nitric oxide (NO), malondialdehyde (MDA), and advanced oxidation protein products (AOPP), and a decrease in superoxide dismutase (SOD), glutathione (GSH), and glycation end products (AGEs) were observed in restraint stress model. Exposure to SMFs over 5 days (30, 60, and 240 min/day) caused a decrease in the NO, MDA, AGEs, and AOPP levels; in contrast, the SOD and GSH levels increased. The response to SMFs was time-dependent. Thus, we proposed that exposure to weak-intensity SMFs could offer a complementary therapy by attenuating oxidative stress. Our results provided a new perspective in health studies, particularly in the context of oxidative stress.