Weeks Of Chronic Unpredictable Stress Research Articles

Systemic administration of propranolol reduces bone resorption and inflammation in apical periodontitis of chronically stressed rats.

To evaluate the effect of systemic administration of propranolol on the severity of apical periodontitis (AP) in chronically stressed rats. Twenty-four 70-day-old male Wistar rats (Rattus norvegicus, albinus) were distributed into three groups (n = 8): rats with AP without stressful conditions (AP-Control), rats with AP and submitted to a chronic unpredictable stress (CUS) protocol (AP + S) and rats with AP and submitted to a CUS protocol treated with propranolol (AP + S + PRO). Stress procedures were applied daily until the end of the experiment. After 3 weeks of CUS, AP was induced in all groups by exposing the pulpal tissue of mandibular and maxillary first molars to the oral environment. Propranolol treatment was administered orally once a day for the entire period of the experiment. Rats were sacrificed at 42 days, and the blood was collected for stress biomarkers serum dosage by multiplex assay. Mandibles were removed and submitted to microtomography and histopathological analyses. Periapical tissue surrounding the upper first molar was homogenized and subjected to RT-PCR analysis to evaluate the mRNA expression of RANKL, TRAP and OPG. Parametric data were assessed using one-way ANOVA followed by Tukey's test while the nonparametric data were analysed by the Kruskal-Wallis followed by Dunn's test. Significance level was set at 5% (p < .05) for all assessed parameters. Micro-CT revealed statistically significant differences in bone resorption which was greater in the AP + S group (p < .05), but no differences were observed between the Control and AP + S + PRO groups (p > .05). The AP + S + PRO group had a lower intensity and extent of inflammatory infiltrate compared to the AP + S group with smaller areas of bone loss (p < 0.05). The gene expression of RANKL and TRAP was significantly higher in the stressed group AP + S compared to the control group (p < .05), and a significantly higher OPG expression was observed in AP + S + PRO compared to the AP + S group (p < .05). Oral administration of propranolol had a significant effect on the AP severity in stressed rats, suggesting an anti-inflammatory effect and a protective role on bone resorption of AP in stressed animals. Further research is necessary to fully comprehend the underlying mechanisms.

Running exercise improves astrocyte loss, morphological complexity and astrocyte-contacted synapses in the hippocampus of CUS-induced depression model mice

Although the antidepressant effects of running exercise have been widely reported, further research is still needed to determine the structural bases for these effects. Astrocyte processes physically contact many synapses and directly regulate the numbers of synapses, but it remains unclear whether running exercise can modulate astrocyte morphological complexity and astrocyte-contacted synapses in the hippocampus of the mice with depressive-like behavior. Male C57BL/6 J mice underwent four weeks of running exercise after four weeks of chronic unpredictable stress (CUS). The sucrose preference test (SPT), tail suspension test (TST) and forced swim test (FST) were used to assess anhedonia in mice. Western blotting was used to measure the expression of astrocyte- and synapse-related proteins. Immunofluorescence and 3D reconstruction were used to quantify the density and morphology of astrocytes, and astrocyte-contacted synapses in each hippocampal subregion. Four weeks of running exercise alleviated depressive-like symptoms in mice. The expression of astrocyte- and synapse-related proteins in the hippocampus; astrocyte process lengths, process numbers, and dendritic arborization; and the number of astrocyte-contacted PSD95 positive synapses in the CA2–3 and DG regions were significantly decreased in the mice with depressive-like behavior, and running exercise successfully reserved these changes. Running exercise improved the decreases in astrocyte morphological complexity and astrocyte-contacted PSD95 positive synapses in the CA2–3 and DG regions of the mice with depressive-like behavior, suggesting that the physical interactions between astrocytes and synapses can be increased by running exercise, which might be an important structural basis for the antidepressant effects of running exercise.

Astrocyte focal adhesion kinase reduces passive stress coping by inhibiting ciliary neurotrophic factor only in female mice

Astrocytes have been implicated in stress responses and produce ciliary neurotrophic factor (CNTF), which we have shown in the mouse medial amygdala (MeA) to promote passive stress coping response only in females. Pharmacological inhibition of focal adhesion kinase (FAK) upregulates CNTF expression. Here, we found that inducible knockout of FAK in astrocytes or systemic treatment with an FAK inhibitor increased passive coping behavior, i.e., immobility, in an acute forced swim stress test in female, but not male, mice. Strikingly, four weeks of chronic unpredictable stress (CUS) did not further increase passive coping in female astrocytic FAK knockout mice, whereas it exacerbated it in female wildtype mice and male mice of both genotypes. These data suggest that astrocyte FAK inhibition is required for chronic stress-induced passive coping in females. Indeed, CUS reduced phospho-FAK and increased CNTF in the female MeA. Progesterone treatment after ovariectomy activated amygdala FAK and alleviated ovariectomy-induced passive coping in wildtype, but not astrocytic FAK knockout females. This suggests that progesterone-mediated activation of FAK in astrocytes reduces female stress responses. Finally, astrocytic FAK knockout or FAK inhibitor treatment increased CNTF expression in the MeA of both sexes, although not in the hippocampus. As mentioned, MeA CNTF promotes stress responses only in females, which may explain the female-specific role of astrocytic FAK inhibition. Together, this study reveals a novel female-specific progesterone-astrocytic FAK pathway that counteracts CNTF-mediated stress responses and points to opportunities for developing treatments for stress-related disorders in women.

Nrf2 activation rescues stress-induced depression-like behaviour and inflammatory responses in male but not female rats

BackgroundMajor depressive disorder (MDD) is a recurring affective disorder that is two times more prevalent in females than males. Evidence supports immune system dysfunction as a major contributing factor to MDD, notably in a sexually dimorphic manner. Nuclear factor erythroid 2-related factor 2 (Nrf2), a regulator of antioxidant signalling during inflammation, is dysregulated in many chronic inflammatory disorders; however, its role in depression and the associated sex differences have yet to be explored. Here, we investigated the sex-specific antidepressant and cognitive effects of the potent Nrf2 activator dimethyl fumarate (DMF), as well as the associated gene expression profiles.MethodsMale and female rats were treated with vehicle or DMF (25 mg/kg) whilst subjected to 8 weeks of chronic unpredictable stress. The effect of DMF treatment on stress-induced depression- and anxiety-like behaviours, as well as deficits in recognition and spatial learning and memory were then assessed. Sex differences in hippocampal (HIP) gene expression responses were also evaluated.ResultsDMF treatment during stress exposure had antidepressant effects in male but not female rats, with no anxiolytic effects in either sex. Recognition learning and memory and spatial learning and memory were impaired in chronically stressed males and females, respectively, and DMF treatment rescued these deficits. Further, chronic stress elicited sex-specific alterations in HIP gene expression, many of which were normalized in animals treated with DMF. Of note, most of the differentially expressed genes in males normalized by DMF were related to antioxidant, inflammatory or immune responses.ConclusionsCollectively, these findings may support a greater role of immune processes in males than females in a rodent model of depression. This suggests that pharmacotherapies that target Nrf2 have the potential to be an effective sex-specific treatment for depression.

A mouse model of the 3-hit effects of stress: Genotype controls the effects of life adversities in females

Helplessness is a dysfunctional coping response to stressors associated with different psychiatric conditions. The present study tested the hypothesis that early and adult adversities cumulate to produce helplessness depending on the genotype (3-hit hypothesis of psychopathology). To this aim, we evaluated whether Chronic Unpredictable Stress (CUS) differently affected coping and mesoaccumbens dopamine (DA) responses to stress challenge by adult mice of the C57BL/6J (B6) and DBA/2J (D2) inbred strains depending on early life experience (Repeated Cross Fostering, RCF). Three weeks of CUS increased the helplessness expressed in the Forced Swimming Test (FST) and the Tail Suspension Test by RCF-exposed female mice of the D2 strain. Moreover, female D2 mice with both RCF and CUS experiences showed inhibition of the stress-induced extracellular DA outflow in the Nucleus Accumbens, as measured by in vivo microdialysis, during and after FST. RCF-exposed B6 mice, instead, showed reduced helplessness and increased mesoaccumbens DA release. The present results support genotype-dependent additive effects of early experiences and adult adversities on behavioral and neural responses to stress by female mice. To our knowledge, this is the first report of a 3-hit effect in an animal model. Finally, the comparative analyses of behavioral and neural phenotypes expressed by B6 and D2 mice suggest some translationally relevant hypotheses of genetic risk factors for psychiatric disorders.

Stress-induced myelin damage in the hippocampal formation in a rat model of depression

BackgroundAccording to previous studies, myelin damage may be involved in the occurrence of depression. However, to date, no study has quantitatively investigated the changes in myelinated fibers and myelin sheaths in the hippocampal formation (HF) and hippocampal subfields in the context of depression. Methods: Male Sprague-Dawley (SD) rats (aged 4–5 weeks) were evenly divided into the control group and chronic unpredictable stress (CUS) group. Behavioral tests were performed, and then changes in myelinated fibers and myelin ultrastructure in hippocampal subfields in depression model rats were investigated using modern stereological methods and transmission electron microscopy techniques. Results: After a four-week CUS protocol, CUS rats showed depressive-like and anxiety-like behaviors. The total length and total volume of myelinated fibers were reduced in the CA1 region and DG in the CUS group compared with the control group. The total volumes of myelin sheaths and axons in the CA1 region but not in the DG were significantly lower in the CUS group than in the control group. The decrease in the total length of myelinated nerve fibers in the CA1 region in CUS rats was mainly due to a decrease in the length of myelinated fibers with a myelin sheath thickness of 0.15 μm–0.20 μm. Limitations: The exact relationship between the degeneration of myelin sheaths and depression-like, anxiety-like behaviors needs to be further investigated. Conclusions: CUS induces depression- and anxiety-like behaviors, and the demyelination in the CA1 region induced by 4 weeks of CUS might be an important structural basis for these behaviors.

Lactobacillus paracasei CCFM1229 and Lactobacillus rhamnosus CCFM1228 Alleviated Depression- and Anxiety-Related Symptoms of Chronic Stress-Induced Depression in Mice by Regulating Xanthine Oxidase Activity in the Brain.

Depression is a common mood disorder that affects around 350 million people worldwide. We studied the effect of supplementation with Lactobacillus strains for the treatment of depression. Except for control group (n = 8), C57BL/6J mice were treated with Lactobacillus during six weeks of chronic unpredictable stress (depression group: n = 9, Lactobacillus intervention group: n = 7). L. paracasei CCFM1229 and L. rhamnosus CCFM1228 significantly reduced depressive behaviour in the forced swimming test and tail suspension test, significantly reduced anxiety behaviour in the open field test, and reduced anxiety behaviour in the marble burying test and light/dark box test. L. paracasei CCFM1229 and L. rhamnosus CCFM1228 significantly increased the brain serotonin and brain-derived neurotrophic factor concentrations, and CCFM1229 significantly decreased the serum corticosterone concentration, all of which are closely associated with the relief of depressive symptoms. Furthermore, CCFM1229 and CCFM1228 were shown to regulate purine metabolism in mice, as indicated by decreases in brain xanthine oxidase activity and an increase in liver adenosine deaminase activity. Anxiety- and depression-related indicators were significantly associated with xanthine oxidase activity in the cerebral cortex. The strains CCFM1229 and CCFM1228 reduced anxiety- and depression-related behaviour in a mouse model of chronic stress-induced depression, which may be achieved by regulating the activity of brain xanthine oxidase.

Microglia Loss and Astrocyte Activation Cause Dynamic Changes in Hippocampal [18F]DPA-714 Uptake in Mouse Models of Depression.

Major depression is a serious and chronic mental illness. However, its etiology is poorly understood. Although glial cells have been increasingly implicated in the pathogenesis of depression, the specific role of microglia and astrocytes in stress-induced depression remains unclear. Translocator protein (TSPO) has long been considered a marker of neuroinflammation and microglial activation. However, this protein is also present on astrocytes. Thus, it is necessary to explore the relationships between TSPO, microglia, and astrocytes in the context of depression. In this study, C57BL/6J male mice were subjected to chronic unpredictable stress (CUS) for 5 weeks. Subsequently, sucrose preference and tail suspension tests (TSTs) were performed to assess anhedonia and despair in these mice. [18F]DPA-714 positron emission tomography (PET) was adopted to dynamically assess the changes in glial cells before and 2, 4, or 5 weeks after CUS exposure. The numbers of TSPO+ cells, ionized calcium-binding adaptor molecule (Iba)-1+ microglial cells, TSPO+/Iba-1+ cells, glial fibrillary acidic protein (GFAP)+ astrocytes, TSPO+/GFAP+ cells, and TUNEL-stained microglia were quantified using immunofluorescence staining. Real-time PCR was used to evaluate interleukin (IL)-1β, IL-4, and IL-18 expression in the hippocampus. We observed that hippocampal [18F]DPA-714 uptake significantly increased after 2 weeks of CUS. However, the signal significantly decreased after 5 weeks of CUS. CUS significantly reduced the number of Iba-1+, TSPO+, and TSPO+/Iba-1+ cells in the hippocampus, especially in the CA1 and dentate gyrus (DG) subregions. However, this intervention increased the number of GFAP+ astrocytes in the CA2/CA3 subregions of the hippocampus. In addition, microglial apoptosis in the early stage of CUS appeared to be involved in microglia loss. Further, the expression of pro-inflammatory cytokines (IL-1β and IL-18) was significantly decreased after CUS. In contrast, the expression of the anti-inflammatory cytokine IL-4 was significantly increased after 2 weeks of CUS. These results suggested that the CUS-induced dynamic changes in hippocampal [18F]DPA-714 uptake and several cytokines may be due to combined microglial and astrocyte action. These findings provide a theoretical reference for the future clinical applications of TSPO PET.

Female-specific role of ciliary neurotrophic factor in the medial amygdala in promoting stress responses

Ciliary neurotrophic factor (CNTF) is produced by astrocytes which have been implicated in regulating stress responses. We found that CNTF in the medial amygdala (MeA) promotes despair or passive coping, i.e., immobility in an acute forced swim stress, in female mice, while having no effect in males. Neutralizing CNTF antibody injected into the MeA of wildtype females reduced activation of downstream STAT3 (Y705) 24 and 48 h later. In concert, the antibody reduced immobility in the swim test in females and only after MeA injection, but not when injected in the central or basolateral amygdala. Antibody injected into the male MeA did not affect immobility. These data reveal a unique role of CNTF in female MeA in promoting despair or passive coping behavior. Moreover, 4 weeks of chronic unpredictable stress (CUS) increased immobility in the swim test and reduced sucrose preference in wildtype CNTF+/+, but not CNTF−/− littermate, females. Following CUS, 10 min of restraint stress increased plasma corticosterone levels only in CNTF+/+ females. In males, the CUS effects were present in both genotypes. Further, CUS increased CNTF expression in the MeA of female, but not male, mice. CUS did not alter CNTF in the female hippocampus, hypothalamus and bed nucleus of stria terminalis. This suggests that MeA CNTF has a female-specific role in promoting CUS-induced despair or passive coping, behavioral anhedonia and neuroendocrine responses. Compared to CNTF+/+ mice, CNTF−/− mice did not show differences in CUS-induced anxiety-like behavior and sensorimotor gating function as measured by elevated T-Maze, open field and pre-pulse inhibition of the acoustic startle response. Together, this study reveals a novel CNTF-mediated female-specific mechanism in stress responses and points to opportunities for developing treatments for stress-related disorders in women.

Effects of Fatty Acid Amide Hydroxylase Inhibitor URB597 on the Catecholaminergic Activity of the Adrenal Medulla in Stressed Male and Female Rats

Introduction: The present study examined the effects of fatty acid amide hydrolase inhibitor URB597 on the level of plasma catecholamine and their content, synthesis, and degradation in the adrenal medulla of male and female rats subjected to chronic unpredictable stress (CUS). Material and Methods: Male and female Wistar rats were exposed to the 6 weeks of CUS and treated intraperitoneally with either 0.3 mg/kg/day of URB597 or vehicle in the last 2 weeks of stress protocol. Catecholamines’ plasma levels and catecholamines’ levels in adrenal medulla were examined using Elabscience ELISA kits. Western blot analysis was used to detect the protein in the medulla. Results: The results of our experiment showed that adrenal weights and catecholamine of unstressed control were higher in females and that CUS induced further enlargement of adrenal glands and catecholamine content and its synthesis compared to male rats. CUS caused an increase of plasma norepinephrine and depletion of norepinephrine content as well as unchanged synthesis and degradation of catecholamine in the adrenal medulla of male rats. URB597 reduced enlarged adrenals and catecholamine content and its synthesis in stressed female rats. URB597 reduces increased plasma norepinephrine and restores its content in the adrenal medulla, unchanging the expression of enzyme synthesis, while reduced protein levels of monoamine oxidase A in male rats are exposed to CUS. Discussion: Our results support the role of endocannabinoids as an antistress mechanism that inhibits elevated adrenomedullary activation and promotes its recovery to baseline in both male and female stressed rats.

Enriched environment mitigates depressive behavior by changing the inflammatory activation phenotype of microglia in the hippocampus of depression model rats

BackgroundInflammation mediated by microglia has been shown to be involved in the pathogenesis of depression. The enriched environment (EE) can improve depression-like behaviors and reduce inflammatory reactions, but it is unclear whether this is by changing the inflammatory activation phenotype of microglia. MethodA depression rat model was established using chronic unpredictable stress (CUS) for four weeks. The rats were then treated with EE or fluoxetine administration during the following three weeks. Behavior tests including sucrose preference, forced swimming and open field were applied to evaluate the depression-like behaviors of rats at the baseline period prior to CUS, the end of fourth week and at the end of the seventh week. Microglial activation and hippocampal neuro-inflammation were detected on postmortem using immunofluorescence, western blotting, and real-time polymerase reaction (PCR). ResultThe results showed that severe depressive-like behavior was induced by four weeks of CUS. Changes in peripheral blood inflammatory cytokines were detected by ELISA. Immunofluorescent staining showed the IBA-1 of microglia activation marker level significantly increased in affected rats. The hippocampal microglial activation state was determined by measuring the increased levels of iNOS an M1 marker and the decreased levels of CD206, an M2 marker. The activation of NF-κB upregulation of inflammatory cytokines in the hippocampus and factors such as IL-10 were decreased. This study showed that EE and chronic fluoxetine treatment alleviated the depressive-like behavior induced by chronic stress and significantly inhibited microglial activation, activated NF-κB inflammasome and increased pro-inflammatory cytokines. ConclusionEE can alleviate depression-like behavior by modulating the phenotype of microglia, inhibiting pro-inflammatory genes, and promoting anti-inflammatory genes. Furthermore, EE can effectively reduce the phosphorylation and expression levels of NF-κB.

Chronic unpredictable stress during adolescence protects against adult traumatic brain injury-induced affective and cognitive deficits

Pre-clinical early-life stress paradigms model early adverse events in humans. However, the long-term behavioral consequences of early-life adversities after traumatic brain injury (TBI) in adults have not been examined. In addition, endocannabinoids may protect against TBI neuropathology. Hence, the current study assessed the effects of adverse stress during adolescence on emotional and cognitive performance in rats sustaining a TBI as adults, and how cannabinoid receptor 1 (CB1) activation impacts the outcome. On postnatal days (PND) 30–60, adolescent male rats were exposed to four weeks of chronic unpredictable stress (CUS), followed by four weeks of no stress (PND 60–90), or no stress at any time (Control), and then anesthetized and provided a cortical impact of moderate severity (2.8 mm tissue deformation at 4 m/s) or sham injury. TBI and Sham rats (CUS and Control) were administered either arachidonyl-2′-chloroethylamide (ACEA; 1 mg/kg, i.p.), a CB1 receptor agonist, or vehicle (VEH; 1 mL/kg, i.p.) immediately after surgery and once daily for 7 days. Anxiety-like behavior was assessed in an open field test (OFT) and learning and memory in novel object recognition (NOR) and Morris water maze (MWM) tasks. No differences were revealed among the Sham groups in any behavioral assessment and thus the groups were pooled. In the ACEA and VEH-treated TBI groups, CUS increased exploration in the OFT, enhanced NOR focus, and decreased the time to reach the escape platform in the MWM, suggesting decreased anxiety and enhanced learning and memory relative to the Control group receiving VEH (p < 0.05). ACEA also enhanced NOR and MWM performance in the Control + TBI group (p < 0.05). These data suggest that 4 weeks of CUS provided during adolescence may provide protection against TBI acquired during adulthood and/or induce adaptive behavioral responses. Moreover, CB1 receptor agonism produces benefits after TBI independent of CUS protection.

Effect of chronic unpredictable stress on the progression of experimental apical periodontitis in rats.

To establish an experimental model combining chronic stress and apical periodontitis by assessing the development of periapical lesions in rats in three different time points. Forty-eight male Wistar rats were randomly assigned into two equal groups: Apical periodontitis (AP) and AP+Stress (AP+S). The animals of the AP group were not exposed to stressful conditions whereas the AP+S group were exposed to a variety of stressors on a daily basis until the end of the experiment. After three weeks of chronic unpredictable stress, apical periodontitis was induced in both groups by exposing the pulpal tissue of the mandibular first molar to the oral environment. Each group was further subdivided into three subgroups according to the euthanasia period: 14, 21 and 28days after pulp exposure. The animals were weighed, and the blood was collected for corticosterone serum dosage by radioimmunoassay. The mandibles were removed and submitted to histopathological and microtomography analyses to assess the inflammatory response and the progression of periapical lesions. Comparisons between the AP and AP+S groups were performed using Student's t-test and Mann-Whitney U-test for parametric and nonparametric data, respectively. The one-way anova test followed by Tukey's test (parametric data) and Kruskal-Wallis followed by Dunn's test (nonparametric data) were used for comparisons between the three time points within the same group (P<0.05). The AP+S group had a significantly lower average percentage of weight gain at 14days and 21days after AP induction (P<0.05). Significantly higher levels of corticosterone were found in the AP+S group at 21days (P<0.05). The AP+S group had a significantly greater intensity and extension of inflammatory infiltrate with larger areas of bone loss compared to the AP groups at 21days (P<0.05). The volume of the periapical lesions in the AP+S group was significantly larger than that of the AP group 21days following pulp exposure (P<0.05). The chronic unpredictable stress model applied for 6weeks exacerbated the inflammatory response and increased bone loss associated with AP, especially 21days after its induction. This model appears to be suitable for investigating the bidirectional relationship between apical periodontitis and chronic stress.

The Faster-Onset Antidepressant Effects of Hypidone Hydrochloride (YL-0919) in Monkeys Subjected to Chronic Unpredictable Stress.

Given the limited monkey models of depression available to date, as well as the procedural complexity and time investments that they involve, the ability to test the efficacy and time course of antidepressants in monkey models is greatly restricted. The present study attempted to build a simple and feasible monkey model of depression with chronic unpredictable stress (CUS) and evaluate the antidepressant effect and onset time of fluoxetine hydrochloride (FLX) and the new drug hypidone hydrochloride (YL-0919), a potent and selective 5-HT reuptake inhibitor, 5-HT1A receptor partial agonist and 5-HT6 receptor full agonist. Female cynomolgus monkeys with low social status in their colonies were selected and subjected to CUS for 8 weeks by means of food and water deprivation, space restriction, loud noise, strobe light, and intimidation with fake snakes. Huddling, self-clasping, locomotion and environmental exploration were monitored to evaluate behavioral changes. In addition, the window-opening test was used to evaluate the exploratory interest of the monkeys. The present results revealed that CUS-exposed monkeys displayed significant depression-like behaviors, including significant decreases in exploratory interest, locomotion, and exploration as well as significant increases in huddling and self-clasping behavior and the level of fecal cortisol after 8 weeks of CUS. Treatment with FLX (2.4 mg/kg, i. g.) or YL-0919 (1.2 mg/kg, i. g.) markedly reversed the depression-like behaviors caused by CUS, producing significant antidepressant effects. YL-0919 (once daily for 9 days) had a faster-onset antidepressant effect, compared with FLX (once daily for 17 days). In summary, the present study first established a CUS model using female cynomolgus monkeys with low social status and then successfully evaluated the onset time of 5-HTergic antidepressants. The results suggested that monkeys exposed to CUS displayed significant depression-like behaviors, and both FLX and YL-0919 produced antidepressant effects in this model. Moreover, YL-0919 appeared to act faster than FLX. The present study provides a promising prospect for the evaluation of fast-onset antidepressant drugs based on a CUS monkey model.

Effect of Voluntary Exercise Training on Corticosterone Level and Immobility Behavior Induced by Chronic Stress in Rats

Background: Depression is a common mood disorder that in the long-term impairs thoughts, behavior, feelings, and health. Chronic unpredictable stress is one of the factors that can cause depression. Objectives: To investigate the effect of voluntary exercise training on immobility behavior (caused by chronic unpredictable stress) and serum corticosterone concentration. Materials &amp; Methods: A total of 24 male rats were randomly and equally assigned to four groups of healthy-control, healthy-exercise, depressed-control, and depressed-exercise. Depressed-control and depressed-exercise groups were first exposed to three weeks of chronic unpredictable stress. After this period, the exercise groups performed four weeks of voluntary exercise training. Twentyfour hours after the last training session, a forced swim test was taken from the rats and their blood samples were taken 24 hours later. The obtained data were analyzed using a 2-way analysis of variance (significance level: P&lt;0.05). The Pearson correlation coefficient was used to examine the relationship between study variables. All statistical analyses were performed in SPSS v. 22. Results: Chronic stress increased immobility behavior (P=0.001) and serum corticosterone concentration (P=0.001). In contrast, exercise training reduced immobility behavior (P=0.001) and serum corticosterone (P=0.001). The immobility time (P=0.001) and serum corticosterone concentration in the depressed-exercise group were higher than those in the healthy-exercise group (P=0.001). There was a positive correlation between immobility behavior and serum corticosterone concentration (r=0.85 and P=0.001). Conclusion: While the chronic stress increases the immobility behavior and serum corticosterone concentration, voluntary exercise training can reduce immobility behavior and serum corticosterone and adjust some depression symptoms.

Low-Frequency Pulsed Magnetic Field Improves Depression-Like Behaviors and Cognitive Impairments in Depressive Rats Mainly via Modulating Synaptic Function.

Transcranial magnetic stimulation (TMS) has shown great promise as a medical treatment of depression. The effectiveness of TMS treatment at high frequency has been well investigated; however, low-frequency TMS in depression treatment has rarely been investigated in depression-induced cognitive deficits. Herein, this study was carried out to assess the possible modulatory role of low-frequency pulsed magnetic field (LFPMF) on reversing cognitive impairment in a model of depression induced by chronic unpredictable stress (CUS). Wistar rats were randomly allocated into four groups as follows: a control group (CON), a control applied with LFPMF (CON + LFPMF), a CUS group, and a CUS treated with LFPMF (CUS + LFPMF) group. During 8 weeks of CUS, compared to those in the CON group, animals not only gained less weight but also exhibited anhedonia, anxiety, and cognitive decline in behavioral tests. After 2-week treatment of LFPMF, a 20 mT, 1 Hz magnetic stimulation, it reversed the impairment of spatial cognition as well as hippocampal synaptic function including long-term potentiation and related protein expression. Thus, LFPMF has shown effectively improvements on depressant behavior and cognitive dysfunction in CUS rats, possibly via regulating synaptic function.

Abstract 2890: Paternal pre-conception stress as a potential risk factor for neuroblastoma

Abstract Neuroblastomas (NBs) are pediatric tumors that lack adequate treatment for their aggressive form, despite many efforts focusing on novel therapies. Although the disease is known to have a genetic background, its etiology cannot be explained solely by genetics. Yet, the role of environment in NB development is understudied. Thus, there are no established risk factors for NB aside from rare genetic predispositions and therefore no preventative measures. NBs arise due to defects in sympathetic neuron (SN) differentiation, which occurs in the fetus. Thus, we hypothesize that prenatal or pre-conception exposures may interfere with this process and promote NB. Maternal stress during pregnancy and paternal pre-conception stress induce neurodevelopmental defects in offspring by direct effects on fetal development or epigenetic changes, respectively. Indeed, we have previously shown that in a mouse model of NB prenatal stress interferes with SN differentiation in offspring, accelerating NB development and leading to its increased frequency and malignancy. The goal of the current study was to determine if a similar increase in risk of NB development can result from paternal pre-conception stress. To test the effect of paternal stress on NB, we subjected TH-MYCN males to 6 weeks of chronic unpredictable stress (CUS) prior to mating with wild type females and assessed the impact of stress on 1) miRNA content in the germline (RNAseq); 2) fertility and fetal survival; 3) NB frequency, latency, growth and metastasis in their hemizygous TH-MYCN offspring (periodic MRI, histological analyses). CUS resulted in significant changes in non-coding RNA content of the germline, including miRNAs and tsRNAs. Of particular interest was a stress-induced down-regulation of sperm miRNAs, including miR-200b and miR-128, which are involved in neuroblast differentiation, inhibit NB invasiveness and are inactivated in NB tumors. Paternal stress decreased the rate of successful pregnancies from 75% in controls to 37.5% and increased frequency of death in utero from 5.5% to 29.2% (p=0.02). Moreover, offspring of stressed fathers exhibited accelerated NB development (60% vs 0% of mice with tumors at 6 weeks of age for CUS and control groups, respectively; p=0.03) and growth (p=0.3), higher tumor frequency (60% vs 25% at 14 weeks of age, p=0.03), as well as a trend toward a more metastatic phenotype. However, these effects on NB formation and phenotype were observed solely in male offspring. In summary, our data provide the first evidence for the role of paternal preconception stress in NB development. If confirmed, our findings may open new avenues for NB prevention and identifying biomarkers of increased NB risk. Citation Format: Sung-Hyeok Hong, Susana Galli, Raquel Santana da Cruz, Lu Jin, Larissa Wetlisbach, Shiya Zhu, Abir Malik, Jason Tilan, Sonia de Assis, Joanna B. Kitlinska. Paternal pre-conception stress as a potential risk factor for neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2890.

The effect of depressive-like behavior and antidepressant therapy on social behavior and hierarchy in rats

BackgroundDepression is common and results in a significant morbidity and economic burden. Depression is associated with pervasive impairments in social functioning, and antidepressant treatments are highly variable in improving these impairments. The objectives of this study were to test the effects of depression on social organization and behavior in a rodent model of depression, and to study the effectiveness of antidepressant medication in improving both symptoms of depression and the social function of depressed animals. MethodsOne hundred-twenty male Sprague-Dawley rats were randomly and equally divided between the control group and depression group. After induction of depression by 5 weeks of chronic unpredictable stress, rats received either antidepressant treatment or placebo. In parallel with the initiation of drug therapy, 20 social groups of six rats were subjected to the complex diving-for-food situation to evaluate their social functioning. Four behavioral tests evaluated symptoms of depression and anxiety at 3 different time points. ResultsWe found that 1) depressed rats were significantly more active and aggressive in all parameters of social organization test compared with the control and antidepressant treatment groups, 2) depressed rats that received antidepressant treatment exhibited social behaviors like the control group, and 3) depression in the experimental groups was not accompanied by symptoms of anxiety. ConclusionsThese results suggest that depression can significantly alter the social behavior and hierarchy in the social group in rats. Investigations of complex social group dynamics offer novel opportunities for translational studies of mood and psychiatric disorders.

The effects of running exercise on oligodendrocytes in the hippocampus of rats with depression induced by chronic unpredictable stress

Running exercise has been shown to be associated with decreased symptoms of depression. However, the mechanisms underlying these antidepressant effects of running exercise remain relatively unclear. In the current study, we investigated the relationship between depressive symptoms in chronic unpredictable stress (CUS) model rats treated with running exercise and changes in oligodendrocytes in the hippocampus. After 4 weeks of CUS, the model group was randomly divided into a CUS standard group (18 rats) and a CUS running group (15 rats). Then, a 4-week treadmill running trial was performed with the CUS running group. In addition, the behavioral effects of exercise were investigated by means of a sucrose preference test (SPT) and an at the end of the 8th week. Immunohistochemical methods and modern stereological methods were used to precisely quantify the total number of 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase)-positive (CNPase+) oligodendrocytes in each hippocampal subregion. At the behavioral level, after four weeks of running, the CUS running group displayed significantly higher consumption of sucrose water in the SPT than the CUS standard group. Unbiased stereological analyses revealed significantly higher total numbers of CNPase+ cells in the hippocampal CA3 and dentate gyrus regions in the CUS running group than in the CUS standard group, whereas there was no significant difference between the groups in the number of CNPase+ cells in the hippocampal CA1 region. The present results further confirm that exercise can alleviate symptoms and protect hippocampal oligodendrocytes in depressed rats.

Differential effects of chronic stress in young-adult and old female mice: cognitive-behavioral manifestations and neurobiological correlates.

Stress-related psychopathology is highly prevalent among elderly individuals and is associated with detrimental effects on mood, appetite and cognition. Conversely, under certain circumstances repeated mild-to-moderate stressors have been shown to enhance cognitive performance in rodents and exert stress-inoculating effects in humans. As most stress-related favorable outcomes have been reported in adolescence and young-adulthood, this apparent disparity could result from fundamental differences in how aging organisms respond to stress. Furthermore, given prominent age-related alterations in sex hormones, the effect of chronic stress in aging females remains a highly relevant yet little studied issue. In the present study, female C57BL/6 mice aged 3 (young-adult) and 20-23 (old) months were subjected to 8 weeks of chronic unpredictable stress (CUS). Behavioral outcomes were measured during the last 3 weeks of the CUS protocol, followed by brain dissection for histological and molecular end points. We found that in young-adult female mice, CUS resulted in decreased anxiety-like behavior and enhanced cognitive performance, whereas in old female mice it led to weight loss, dysregulated locomotion and memory impairment. These phenotypes were paralleled by differential changes in the expression of hypothalamic insulin and melanocortin-4 receptors and were consistent with an age-dependent reduction in the dynamic range of stress-related changes in the hippocampal transcriptome. Supported by an integrated microRNA (miRNA)-mRNA expression analysis, the present study proposes that, when confronted with ongoing stress, neuroprotective mechanisms involving the upregulation of neurogenesis, Wnt signaling and miR-375 can be harnessed more effectively during young-adulthood. Conversely, we suggest that aging alters the pattern of immune activation elicited by stress. Ultimately, interventions that modulate these processes could reduce the burden of stress-related psychopathology in late life.