Chronic Unpredictable Stress Group Research Articles

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

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

Effects of oregano essential oil on brain TLR4 and TLR2 gene expression and depressive-like behavior in a rat model.

The aim of the present study was to evaluate the effects of oregano essential oil (OEO) on the hippocampus and prefrontal cortex TLR 2/4 gene expression and depressive like behavior induced by chronic unpredictable stress (CUS). Sucrose preference and forced swim tests were adopted to examine the antidepressant effect. Control (CON), OEO, CUS, and CUS + OEO groups were used. The OEO and CUS + OEO groups received OEO (0.2 mL/kg, i.p.), CON and CUS received saline (0.2 mL/kg, i.p.), and the positive drug groups of CUS rats received fluoxetine (10 mg/kg) and diazepam (3 mg/kg) once daily for 14 days. The expression of TLR 2/4 was determined using real time quantitative polymerase chain reaction with the SYBR green reporter dye. The compositions of the OEO were determined by gas chromatography-mass spectroscopy. The main constituents were thymol (20.72%), gamma-terpinene (8.83%), borneol (8.72%), cymene (6.83%), carvacrol (6.274%), alfa-terpinene (5.26%), and sabinene (4.92%). Administration of OEO significantly alleviated the depressive symptoms of CUS. A higher level of TLR2/4 mRNA was seen in the brain of CUS group (P < 0.05). The CUS-induced increases in the TLR2/4 levels were not reversed by OEO. According to the present study OEO may have the antidepressant-like activity but have no effect on the stress-induced TLR-2/4 upregulation.

Enriched environment combined with fluoxetine ameliorates depression-like behaviors and hippocampal SYP expression in a rat CUS model.

Effects of enriched environment (EE) combined with fluoxetine in a chronic unpredictable stress (CUS) rat model were examined in our study. Thirty male Sprague-Dawley rats were randomly divided into control group, CUS group, CUS+EE group, CUS+fluoxetine group, and CUS+EE+fluoxetine group (n=six per group). Rats in the CUS group were bred under conditions of CUS and separation for 6 weeks; Control group animals were bred in group cages (three rats per cage) under standard laboratory conditions for 6 weeks; Rats in CUS+EE group, CUS+fluoxetine group, and CUS+EE+fluoxetine groups were bred under the conditions of CUS and separation for 6 weeks and had an intervention of EE, an oral gavage of fluoxetine, and an intervention of EE+oral gavage of fluoxetine, respectively, every day for the final 3 weeks. Every rat underwent a behavioral assessment at the beginning of the 1st week, at the end of the 3rd week and at the end of the 6th week. Behavioral assessments included sucrose water consumption, weight measurement, and an open field test (measuring horizontal moving distance, rearing behavior, and defecation). Finally, the level of synaptophysin expressed in the hippocampus was measured with immunohistochemistry. We found that EE, fluoxetine, and EE+fluoxetine all reversed the depression-like behaviors of CUS rats. The effect of EE+fluoxetine appeared to be superior to EE or fluoxetine alone; the expression level of synaptophysin in CA1, CA3, and DG of the hippocampus was decreased in CUS rats, however, exposure to EE, fluoxetine, and EE+fluoxetine all reversed this decrease.

Effects of maternal deprivation on stress response and efficacy of escitalopram in adult rats

Objective To investigate the effects of maternal deprivation on chronic stress-induced depression behavior and its characteristics in adult rats, and to evaluate the effects of maternal deprivation on the efficacy of escitalopram. Methods Newborn SD male rats were randomly divided into control(C) group, maternal deprivation (MD) group, chronic unpredictable stress (CUPS) group, maternal deprivation and chronic unpredictable stress (MD+ CUPS) group. Rats in control group received no experimental handling.Rats in MD group and MD+ CUPS group received maternal deprivation from the lst day after birth for 14 days.Rats in CUPS group and MD+ CUPS group received chronic unpredictable stress from 10 th weeks after birth for 28 days. Screened the rats with depression behaviors and treated them with escitalopram for 4 weeks. Results The incidence of anhedonia was significantly different among 4 groups (χ2=143.24, P CUPS group (40.98%) > MD group (17.11%) >C group (4.17%), P<0.0083). The incidence of behavioral despair was significantly different among 4 groups (χ2=70.34, P<0.05). Pairwise comparison showed the incidence of behavioral despair in MD+ CUPS group (43.43%) and CUPS group (39.34%) were significantly higher than that in MD group (13.51%) and C group (3.33%), but no difference was observed between MD+ CUPS and CUPS group (P<0.0083). The incidence of behavioral despair in MD group was significant higher than that in C group. There was no significant efficacy of escitalopram on anhedonia and behavioral despair among 3 stressed models. However the recovery incidence from anhedonia (44/140) was significantly lower than that from behavioral despair (76/140) (χ2=14.93, P<0.05). Conclusion The maternal deprivation increases the stress sensitivity and the incidences of anhedonia in adult rats.The efficacy of escitalopram on behavioral despair is higher than that on anhedonia without influence from maternal deprivation. Key words: Maternal deprivation; Chronic unpredictable stress; Anhedonia; Behavioral despair; Escitalopram

Effect of XingPiJieYu decoction on spatial learning and memory and cAMP-PKA-CREB-BDNF pathway in rat model of depression through chronic unpredictable stress

BackgroundDepression is a mental disorder characterized by a pervasive low mood and loss of pleasure or interest in usual activities, and often results in cognitive dysfunction. The disturbance of cognitive processes associated with depression, especially the impairment of learning and memory, exacerbates illness and increases recurrence of depression. XingPiJieYu (XPJY) is one of the most widely clinical formulas of traditional Chinese medicine (TCM) and can improve the symptoms of depression, including learning and memory. However, its regulatory effects haven’t been comprehensively studied so far. Recently, some animal tests have indicated that the cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA)-cAMP response element-binding protein (CREB)-brain derived neurotrophic factor (BDNF) signaling pathway in hippocampus is closely related to depression and the pathogenesis of cognitive function impairments. The present study was performed to investigate the effect and mechanism of XPJY on depression and learning and memory in animal model.MaterialsThe rat model of depression was established by chronic unpredictable stress (CUS) for 21 days. The rats were randomly divided into six groups: control group, CUS group, CUS + XPJY (1.4 g/kg, 0.7 g/kg and 0.35 g/kg) groups, and CUS + sertraline (10 mg/kg) group. The sucrose preference, open field exploration and Morris water maze (MWM) were tested. The expression of cAMP, CREB, PKA and BDNF protein in hippocampus was examined with Elisa and Western Blot. The mRNA level of CREB and BDNF in hippocampus was measured with PCR.ResultsThe results demonstrated that rats subjected to CUS exhibited decreases in sucrose preference, total ambulation, percentage of central ambulation, rearing in the open field test and spatial performance in the MWM. CUS reduced the expression of cAMP, PKA, CREB and BDNF in hippocampus of model rats. These effects could be reversed by XPJY.ConclusionThe results indicated that XPJY can improve depression and related learning and memory and the effect of XPJY is partly exerted through the cAMP-PKA-CREB-BDNF signaling pathway.

The Role of Hippocampal Estradiol Receptor-α in a Perimenopausal Affective Disorders-Like Rat Model and Attenuating of Anxiety by Electroacupuncture.

Hormone replacement therapy is the principal treatment for perimenopausal affective disorders which can cause severe side effects. The present study compared the effects of electroacupuncture (EA) and estradiol treatment on perimenopausal affective disorders at the behavioral and cellular levels. In this randomized experimental in vivo study, adult female rats were divided into intact, ovariectomy, chronic unpredictable stress (CUS), and ovariectomy and CUS combination groups. After week 6, all groups were subdivided to three subgroups of control, EA, and estradiol treatment. The behavioral parameters in the open field and the elevated plus maze tests were assessed before and after treatments. Alterations of serum steroid hormones and changes of estradiol receptor-α (ER-α) immunofluorescence neurons in the hippocampus sections were evaluated. EA treatment caused more antianxiety effects than estradiol treatment in CUS group (P < 0.05). Notably, estradiol and EA treatments had better significant behavioral effects when the models were not estrogen-deficient. Importantly, within each group, compared to the control group, the numbers of ER-α-positive neurons were significantly larger in EA subgroups. Therefore, EA had antianxiety effects on perimenopausal affective disorders caused by CUS but not by estrogen deficiency and upregulation of hippocampus ER-α neurons may contribute to its mechanism of action.

Effects of ceftriaxone on depressive-like behavior and changes of hippocampal glutamate transporter-1 in depression model C57 mice

Objective To investigate the effects of ceftriaxone on depressive-like behavior and changes of hippocampal glutamate transporter-1(GLT-1) in C57 mice depression model, and to further explore the molecular mechanism of ceftriaxone on antidepressant action. Methods Thirty male C57 mice were randomly divided into control group(group A, n=10), CUS group(group B, n=10) and CUS+ ceftriaxone group(group C, n=10). The mice of the CUS group and the CUS+ ceftriaxone group were subjected to chronic unpredictable stress (CUS) for 2 sessions per day for 21 days. Then, the mice of the CUS+ ceftriaxone group were given ceftriaxone for 21 days. Behavioral changes were assessed by the sucrose preference test and open field test.The GLT-1 protein levels in the hippocampus were detected by Western blot analysis at the end of the ceftriaxone treatment. Results (1) Compared with the control group, the percentage of sucrose preference, the total traveled distance, the moved velocity, and the frequencies of rearing of the CUS group were significantly decreased(P<0.05) at the 21 days. However, the percentage of sucrose preference((78.74±3.54)%), the total traveled distance((6818.35±505.14)cm), the moved velocity((12.36±0.89)cm/s), and the frequencies of rearing(58.20±4.05) of the CUS+ ceftriaxone group at the end of the ceftriaxone treatment were improved significantly compared with the CUS group((59.46±2.75)%, (2931.71±271.89)cm, (5.84±0.42)cm/s, (26.20±2.62), P<0.05). (2) Western blot analysis indicated significant reductions of the GLT-1 protein levels in the hippocampus of CUS group (versus the control mice: P<0.05), and chronic ceftriaxone treatment reversed the CUS-induced decrease in the GLT-1 levels(P<0.05). Conclusion Ceftriaxone might significantly improve depressive-like behavior in C57 mice depression model. Chronic unpredictable stress (CUS) could down-regulate the GLT-1 protein levels in the hippocampus, which are reversed by ceftriaxone. These results further support the notion enhanced expression of the GLT-1 protein can be molecular mechanism of ceftriaxone on antidepressant action. Key words: Ceftriaxone; C57 mice; Chronic unpredictable stress; Glutamate transporter 1; Hippocampus; Depression

Antidepressant Effects of Ketamine Are Not Related to ¹⁸F-FDG Metabolism or Tyrosine Hydroxylase Immunoreactivity in the Ventral Tegmental Area of Wistar Rats.

Major depressive disorder (MDD) is an important health problem that is often associated to stress. One of the main brain regions related to MDD is the ventral tegmental area (VTA), a dopaminergic center, part of the reward and motivation circuitry. Recent studies show that changes to VTA dopaminergic neurons are associated with depression and treatment. Ketamine has recently shown a fast, potent antidepressant effect in acute, sub-anesthetic doses. Thus, our aims were to elucidate if ketamine would be able to revert depression-like behaviors induced by a chronic unpredictable stress (CUS) protocol and if it could cause alterations to metabolism and tyrosine hydroxylase (TH)-immunoreactivity in VTA. For this, 48 Wistar rats were divided into four groups: control + saline (CTRL + SAL), control + ketamine (CTRL + KET), CUS + saline (CUS + SAL), CUS + ketamine (CUS + KET). The CUS groups underwent 28 days of CUS protocol. Saline or ketamine (10 mg/kg) was administered intraperitonially once on day 28. The behavior was assessed by the sucrose preference test, the open field test, and the forced swim test. Glucose brain metabolism was assessed and quantified with microPET. TH-immunoreactivity was assessed by estimating neuronal density and regional and cellular optical densities. A decrease in sucrose intake in the CUS groups and an increase in immobility was rapidly reverted by ketamine (p < 0.05). No difference was observed in the open field test. There was no alteration to VTA metabolism and TH-immunoreaction. These results suggest that the depressive-like behavior induced by CUS and the antidepressant effects of ketamine are unrelated to changes in neuronal metabolism or dopamine production in VTA.

Cognitive Disorder as a Predisposing Factor for Mental Depression

There is a strong link between cognitive impairment and depression, but, it is not clear whether cognitive impairment may 'cause' depression or not. Therefore, this study examined the effect of cognitive impairment induced by permanent occlusion of common carotids, (2VO), on induction of chronic unpredictable stress (CUS) depression. Male Sprague-Dawley rats underwent 2VO or sham surgery. 60 days after 2VO, cognitive function was tested by the radial arm maze (RAM). All animals were randomly, divided into two subgroups:stressed and non-stressed. The stressed subgroups assigned to undergo 21 days of CUS. One week after the last stressor, depressive-like behaviors was assessed by the forced swim test (FST). Blood amino acid levels (glutamate, glutamine and glycine) were measured by high performance liquid chromatography (HPLC), plasma proinflammatory cytokine (interleukin 6) by enzyme-linked immunosorbent assay (ELISA) and CA1 neuronal damage by Nissl staining. 2VO surgery prior to CUS increased depressive-like behavior in 2VO+CUS group compared with rats exposed to CUS only (P=0.047). CUS and 2VO increased the plasma levels of glutamate, glycine and IL-6 and caused CA1 neuronal cell death. In addition, 2VO surgery before stress induction, intensified the effect of stress on IL- 6 (p=0.04 vs CUS), glutamate (p=0.019 vs CUS) and glycine (p=0.018 vs CUS) levels. Our findings showed that 2VO, as a widely-used animal model for induction of cognitive impairment, can induce degrees of biochemical and histological changes like what is seen in stressed animals, thus may, by itself, predispose the people to depression after stress exposure. we suggest that, primary cognitive impairment predispose depression.

Effect of chronic and unpredictable pre-gestational stress on the brain-derived neurotrophic factor-tyrosine protein kinase B signal transduction pathway in the brain of the offspring rats

Objective To investigate the effect of chronic and unpredictable pre-gestational stress on the serum cortisol level of the offspring, as well as the expressions of brain-derived neurotrophic factor (BDNF) and tyrosine protein kinase B (TrkB) in hippocampus when they were 2 month old. Methods Adult female SD rats were divided randomly into 2 groups: the control group and the chronic unpredictable stress(CUS) model group.All rats were tested in the open field test and sucrose intake test before and after CUS protocol.All offspring rats were sacrificed when 2-month old.Serum cortisol (COR) levels were determined by using a standard radioimmunoassay kit.The expressions of BDNF and TrkB in hippocampus were studied by immunoreactivity quantitative analysis. Results 1.After CUS procedure, CUS group showed decreasing activities in the open field test and decreasing sucrose consumption in sucrose intake test compared to the control group and before CUS procedure.2.The serum COR levels in the female offspring rats of CUS group(128.9±7.3) μg/L were higher than those of the control group(119.9±9.0) μg/L, as well as the male offspring of CUS group(116.5±10.9) μg/L compared with the control group(105.4±10.4) μg/L, but the body weight and brain weight between the offspring of 2 groups were not statistic significance.3.Immunoreactivity quantitative analysis showed that the gray values of BDNF in the female offspring of CUS group (36.1±8.5)decreased compared with the control group(42.4±6.9), as well as the male offspring of CUS(39.6±8.4)compared with the control group(43.7±6.4).4.The gray values of TrkB in the female offspring of CUS group (47.1±2.9)decreased than the control group(50.2±3.9), as well as the male offspring of CUS(46.5±6.7)compared with control group(50.5±5.4). Conclusion Pre-gestational stress reduced the expressions of BDNF and TrkB in hippocampus of the offspring which may relate to hypothalamic pituitary adrenal. Key words: Chronic unpredictable stress; Offspring; Cortisol; Brain-derived neurotrophic factor; Tyrosine protein kinase B

Pre-gestational stress alters stress-response of pubertal offspring rat in sexually dimorphic and hemispherically asymmetric manner

BackgroundThere is increasing evidence that maternal stress may have long-term effects on brain development in the offspring. In this study, we examined whether pre-gestational stress might affect offspring rats on the medial prefrontal cortical (mPFC) dopaminergic activity in response to acute stress in puberty and if so, whether such effects exhibited hemispheric asymmetry or sexual dimorphism.ResultsWe used behavioral tests to assess the model of chronic unpredictable stress (CUS). We found that the activity in the open field test and sucrose intake test were lower for maternal rats in the CUS group than those in the control group. Offspring rats in the CUS group floated more and swam or climbed less as compared to the offsprings in the control group in the forced swimming test. The floating time was longer and swimming or climbing time was shorter in the female offspring rats than those in the males. Serum corticosterone and corticotrophin-releasing hormone levels were significantly higher for CUS maternal rats and their offsprings than the respective controls. The ratio of dihydroxy-phenyl acetic acid (DOPAC) to dopamine (DA), DA transporter (DAT), norepinephrine transporter (NET) were lower in the mPFC of offspring rats in the CUS group than the control group. Levels of catechol-O-methyltransferase (COMT) in the left mPFC of female offspring rats and in the right mPFC of both female and male offspring rats were lower in the CUS group than those in the controls, but there was no difference in the left mPFC of male offspring between the CUS and control groups. DOPAC, the ratio of DOPAC to DA, NET and COMT were lower in the right mPFC than in the left mPFC of offspring rats in the CUS group. The ratio of DOPAC to DA in the right mPFC was lower in the female offspring rats than male offspring rats in the CUS group. The NET and COMT levels in both left and right mPFC were lower in the female offspring rats than those of the male offsprings in the CUS group.ConclusionOur data provide evidence that the effect of pre-gestational stress on the mPFC dopaminergic activity in response to acute stress exhibited hemispheric asymmetry and sexual dimorphism in the pubertal offspring rats.

The effects of quetiapine on the improvement of behavior and expression of pERK1/2 in the hippocampus of chronic unpredictable stress model rats

Objective To investigate the effect of quetiapine on the behavior and expression of pERK1/2 in chronic unpredictable stress(CUS) model rats. Methods 32 adult male Sprague Dawley rats were randomly divided into four groups(n=8 for each group): control group, CUS group, CUS+ QUE(5 mg/kg, L)group and CUS+ QUE(10 mg/kg, M)group. The rats in control group were left undisturbed in their home cage for 28 days and the other groups were exposed to 28 consecutive days of CUS, then the rats in control group and CUS group were treated with 1% DMSO in saline(5 ml/kg, intraperitoneal injection), the rats in CUS+ QUE(L)group and CUS+ QUE(M)group respectively treated with quetiapine(5 mg/kg)or quetiapine(10 mg/kg) for consecutive 7 days.The weight data of each group were recorded, and the behavioral changes in these rats were analyzed by open field test and forced swimming test; and the expression of pERK1/2 was measured by Western blot. Results (1) Compared with control group, quetiapine (10 mg/kg) ameliorated the inhibition of body weight gain that induced by chronic unpredictable stress (P 0.05). (3)The expression of pERK1/2 in CUS group showed significant decrease when compared with control group or CUS+ QUE(M)group, but showed no significant difference with CUS+ QUE(L)group(F=6.641, P<0.01). Conclusion Quetiapine can ameliorate depressive-like behaviors induced by chronic unpredictable stress, and this effect may be carried out by up-regulation the expression of pERK1/2 in the hippocampus. Key words: Qutiapine; Chronic unpredictable stress; Phosphorylated extracellular signal-regulated protein kinase; Rat; Hippocampus

Pre-gestational stress reduces the ratio of 5-HIAA to 5-HT and the expression of 5-HT1A receptor and serotonin transporter in the brain of foetal rat

BackgroundMany studies have found that stress before or during pregnancy is linked to an increased incidence of behavioural disorders in offspring. However, few studies have investigated hypothalamic-pituitary-adrenal (HPA) axis activity and the serotonergic system as a consequence of pregestational stress. In the present study, we investigated the effect of pre-gestational stress on HPA axis activity in maternal rats and their foetuses and examined whether changes in HPA axis activity of maternal rats produced functional changes in the serotonergic system in the brain of foetuses.ResultsWe used the behavioural tests to assess the model of chronic unpredictable stress (CUS) in maternal rats. We found the activity in the open field and sucrose consumption was lower for rats with CUS than for the controls. Body weight but not brain weight was higher for control foetuses than those from the CUS group. Serum corticosterone and corticotrophin-releasing hormone levels were significantly higher for mothers with CUS before pregnancy and their foetuses than for the controls. Levels of 5-hydroxytryptamine (5-HT) were higher in the hippocampus and hypothalamus of foetuses in the CUS group than in the controls, and 5-hydroxyindoleacetic acid (5-HIAA) levels were lower in the hippocampus in foetuses in the CUS group than in the control group. Levels of 5-HIAA in the hypothalamus did not differ between foetuses in the CUS group and in the control group. The ratio of 5-HIAA to 5-HT was significantly lower for foetuses in the CUS group than in the control group. Levels of 5-HT1A receptor were significantly lower in the foetal hippocampus in the CUS group than in the control group, with no significant difference in the hypothalamus. The levels of serotonin transporter (SERT) were lower in both the foetal hippocampus and foetal hypothalamus in the CUS group than in the control group.ConclusionsOur data demonstrate that pre-gestational stress alters HPA axis activity in maternal rats and their foetuses, which is associated with functional changes in 5-HT activity (5-HT, 5-HIAA and ratio of 5-HIAA to 5-HT), as well as the levels of the 5-HT1A receptor and SERT in the hippocampus and hypothalamus of foetuses.

Different pattern of changes in calcium binding proteins immunoreactivity in the medial prefrontal cortex of rats exposed to stress models of depression

Reductions in the number and size of neurons in the medial prefrontal cortex (mPFC) have been documented in many post-mortem studies of depressed patients and animals exposed to stress. Here, we examined the effect of chronic unpredictable stress (CUS) and chronic mild stress (CMS) on specific populations of neurons in the rat mPFC. Antibodies directed against parvalbumin (PV), calbindin D-28K (CB) and active caspase-3 have been used to quantify the numerical density of PV-immunoreactive (PV-ir), CB-ir and active caspase-3-ir cells, and to measure the relative optical density of neuropil. CUS decreased the density of CB-ir neurons and the optical density of CB-ir neuropil. In turn, CMS increased the densities of both CB-ir neurons and neuropil, while PV-ir neurons and PV-ir neuropil were not changed. The frequency distribution of neuronal surface areas was significantly different only for PV-ir neurons, and only between the control and CUS group. CMS reduced the density of active caspase-3-ir cells while CUS did not. We concluded that the mPFC reveals a different pattern of changes in neurons containing calcium binding proteins and active caspase-3 immunoreactivity in response to CUS and CMS.

Chronic Unpredictable Stress Before Pregnancy Reduce the Expression of Brain-Derived Neurotrophic Factor and N-Methyl-D-Aspartate Receptor in Hippocampus of Offspring Rats Associated with Impairment of Memory

To investigate the effect of stress before pregnancy on memory function and serum corticosterone (COR) levels, as well as the expression of brain-derived neurotrophic factor (BDNF), N-methyl-D-aspartate (NMDA) 2A (NR2A) and 2B (NR2B) receptors in the hippocampus of the offspring rats when they were 2 months postnatally. Adult female Sprague-Dawley (SD) rats were divided randomly into two groups: control group (n = 8) and chronic unpredictable stress (CUS) group (n = 12). All rats were tested in the open field test and sucrose intake test before and after CUS. The memory function of their offspring were tested in the Morris water maze. Serum COR levels were determined by using a standard radioimmunoassay kit. The expression of BDNF, NR2A and NR2B in the hippocampus of the offspring rats were studied by immunoreactivity quantitative analysis and real-time RT-PCR. (1) Following CUS, reduced open field test activity and decreased sucrose consumption were observed relative to controls. (2) The Morris water maze task demonstrated increased escape latency in the offspring rats of CUS group relative to controls (P < 0.01). No-platform probe testing showed reduced crossings for offspring of CUS relative to controls (P < 0.05). (3) CUS induced a significant increase in serum COR levels of the offspring rats (P < 0.01), but no difference was observed in the body or brain weight between the offspring of the two groups. (4) Immunoreactivity quantitative analysis shows that BDNF and NR2B in the offspring of CUS group was decreased in the CA3 and DG regions of the hippocampus compared to the control group offspring, but NR2A levels were not altered between the offspring of the two groups. (5) Real-time RT-PCR demonstrated that BDNF and NR2B mRNAs were significantly decreased in the offspring of the CUS group compared with the control group (P < 0.01). No significant difference in the levels of NR2A mRNA was detected between offspring of CUS and offspring of control groups. In our study, pregestational stress can increase serum corticosterone levels and reduce the expression of BDNF and NR2B in the hippocampus of offspring. These alterations are associated with impairment of memory in the adult offspring. These data suggest that, stress before pregnancy might have a profound influence on brain development of offspring, that may persist into and be manifested in adulthood.

Differential expression of MAPKs subgroup in the hippocampus of rats exposed to chronic unpredictable stress

Objective To examine the cognitive function and the differential expression of mitogen-activated protein kinase (MAPK) subgroup in the hippocampus of rats exposed to chronic unpredictable stress. Methods Thirty-two SD rats were divided into chronic unpredictable stress (CUS) group and controls. CUS rats were exposed to 21 days chronic unpredictable stressors,and the controls were stress-free. Immediately after the last stressor,the cognitive function was tested using Morris water maze,and the protein levels of MAPK subgroup in hippocampus were detected by immunohistochemistry and western blot. Results The latencies of CUS and control rats differed significantly on the first 5 trial (F=5.258～10.225,P 0.05),and the number of times that rats crossed the removed hidden platform in CUS group was significantly fewer than that in the control group (1.8±0.5 VS 7.0±3.9,t=3.741,P<0.05). Immunohistochemistry showed that the labeling index of P-CREB was reduced in the dentate gyrus in CUS group compared with that in the control group. Western blot showed that CREB,ERK1/2,P-ERK1/2,P38,P-P38 and JNK levels had no statistical difference in hippocampus between the two groups. However,CUS significantly decreased P-CREB level [(13.6±8.3) % VS (36.0±14.5)%,t=3.792,P<0.05] and P-JNK level [(30.8±7.8) % VS (113.8±55.3) %,t=4.204,P<0.05] in the hippocampus. Conclusions Abnormal JNK-CREB cascade played important roles in the CUS,and the spatial memory of the CUS rats was reduced compared to control rats,but can be restored to the comparable level through training. Key words: Chronic unpredictable stress (CUS); Mitogen-activated protein kinase (MAPK); cAMP response element-binding protein (CREB); Hippocampus