Fluoxetine during development reverses the effects of prenatal stress on depressive-like behavior and hippocampal neurogenesis in adolescence

Depression during pregnancy and the postpartum period is a growing health problem, which affects up to 20% of women. Currently, selective serotonin reuptake inhibitor (SSRIs) medications are commonly used for treatment of maternal depression. Unfortunately, there is very little research on the long-term effect of maternal depression and perinatal SSRI exposure on offspring development. Therefore, the aim of this study was to determine the role of exposure to fluoxetine during development on affective-like behaviors and hippocampal neurogenesis in adolescent offspring in a rodent model of maternal depression. To do this, gestationally stressed and non-stressed Sprague-Dawley rat dams were treated with either fluoxetine (5 mg/kg/day) or vehicle beginning on postnatal day 1 (P1). Adolescent male and female offspring were divided into 4 groups: 1) prenatal stress+fluoxetine exposure, 2) prenatal stress+vehicle, 3) fluoxetine exposure alone, and 4) vehicle alone. Adolescent offspring were assessed for anxiety-like behavior using the Open Field Test and depressive-like behavior using the Forced Swim Test. Brains were analyzed for endogenous markers of hippocampal neurogenesis via immunohistochemistry. Results demonstrate that maternal fluoxetine exposure reverses the reduction in immobility evident in prenatally stressed adolescent offspring. In addition, maternal fluoxetine exposure reverses the decrease in hippocampal cell proliferation and neurogenesis in maternally stressed adolescent offspring. This research provides important evidence on the long-term effect of fluoxetine exposure during development in a model of maternal adversity.     

强制运动促进成年大鼠海马齿状回神经发生并提高学习能力

为了探讨强制运动对成年大鼠海马齿状回（dentate gyrus,DG）神经发生的影响,强制大鼠在马达驱动的转轮中跑步,用5-溴-2-脱氧尿苷（5-bromo-2-deoxyuridine,BrdU）标记增殖细胞,巢蛋白（neuroepthelial stem cell protein,nestin）标记神经干细胞／前体细胞,然后用免疫细胞化学技术检测大鼠DG中BrdU及nestin阳性细胞。为了解强制运动后DG增殖细胞的功能意义,采用Y-迷宫检测大鼠的学习能力。结果表明,强制运动组DG中BrdU及nestin阳性细胞数均日月显多于对照组（P〈0．05）：强制运动对DG神经发生的效应有强度依赖性。Y-迷宫检测结果显示,强制运动能明显改善大鼠的学习能力。结果提示,在转轮中进行强制跑步能促进成年火鼠DG的神经发生,并改善学习能力。     

Running throughout middle-age improves memory function, hippocampal neurogenesis, and BDNF levels in female C57BL/6J mice

Age-related memory loss is considered to commence at middle-age and coincides with reduced adult hippocampal neurogenesis and neurotrophin levels. Consistent physical activity at midlife may preserve brain-derived neurotrophic factor (BDNF) levels, new cell genesis, and learning. In the present study, 9-month-old female C57Bl/6J mice were housed with or without a running wheel and injected with bromodeoxyuridine (BrdU) to label newborn cells. Morris water maze learning, open field activity and rotarod behavior were tested 1 and 6 months after exercise onset. Here we show that long-term running improved retention of spatial memory and modestly enhanced rotarod performance at 15 months of age. Both hippocampal neurogenesis and mature BDNF peptide levels were elevated after long-term running. Thus, regular exercise from the onset and during middle-age may maintain brain function.     

Perinatal supplementation of 4-phenylbutyrate and glutamine attenuates endoplasmic reticulum stress and improves colonic epithelial barrier function in rats born with intrauterine growth restriction

Intrauterine growth restriction (IUGR) can affect the structure and function of the intestinal barrier and increase digestive disease risk in adulthood. Using the rat model of maternal dietary protein restriction (8% vs. 20%), we found that the colon of IUGR offspring displayed decreased mRNA expression of epithelial barrier proteins MUC2 and occludin during development. This was associated with increased mRNA expression of endoplasmic reticulum (ER) stress marker XBP1s and increased colonic permeability measured in Ussing chambers. We hypothesized that ER stress contributes to colonic barrier alterations and that perinatal supplementation of dams with ER stress modulators, phenylbutyrate and glutamine (PG) could prevent these defects in IUGR offspring. We first demonstrated that ER stress induction by tunicamycin or thapsigargin increased the permeability of rat colonic tissues mounted in Ussing chamber and that PG treatment prevented this effect. Therefore, we supplemented the diet of control and IUGR dams with PG during gestation and lactation. Real-time polymerase chain reaction and histological analysis of colons from 120-day-old offspring revealed that perinatal PG treatment partially prevented the increased expression of ER stress markers but reversed the reduction of crypt depth and goblet cell number in IUGR rats. In dextran sodium sulfate-induced injury and recovery experiments, the colon of IUGR rats without perinatal PG treatment showed higher XBP1s mRNA levels and histological scores of inflammation than IUGR rats with perinatal PG treatment. In conclusion, these data suggest that perinatal supplementation with PG could alleviate ER stress and prevent epithelial barrier dysfunction in IUGR offspring.     

Sensitiveness to social stress in female rats with alteration of the pituitary-adrenal axis stress reactivity

The sensitiveness of female rats to social stress induced by increasing group density, was investigated. It was shown that female rats were housed in groups of 9-10 animala per cage in pubertal period and demonstrated significant alteration of oestrous cycle duration and anxiety level. This housing condition increased basal level of corticostcrone in prenatal stressed female rats who have high stress reactivity of the hypothalamic-pituitary-adrenal axis, as well as a more profound effect on anxiety level and oestrous cycle. Prenatal stressed rats retained impairment of oestrous cycle and behavior after optimization of housing condition, whereas control rats demonstrated normalization of oestrous cycle duration and anxiety level. These data suggest that high stress reactivity females rats are more sensitive to crowding-induced stress.     

The effects of social environment on adult neurogenesis in the female prairie vole

In the mammalian brain, adult neurogenesis has been found to occur primarily in the subventricular zone (SVZ) and dentate gyrus of the hippocampus (DG) and to be influenced by both exogenous and endogenous factors. In the present study, we examined the effects of male exposure or social isolation on neurogenesis in adult female prairie voles (Microtus ochrogaster). Newly proliferated cells labeled by a cell proliferation marker, 5-bromo-2'-deoxyuridine (BrdU), were found in the SVZ and DG, as well as in other brain areas, such as the amygdala, hypothalamus, neocortex, and caudate/putamen. Two days of male exposure significantly increased the number of BrdU-labeled cells in the amygdala and hypothalamus in comparison to social isolation. Three weeks later, group differences in BrdU labeling generally persisted in the amygdala, whereas in the hypothalamus, the male-exposed animals had more BrdU-labeled cells than did the female-exposed animals. In the SVZ, 2 days of social isolation increased the number of BrdU-labeled cells compared to female exposure, but this difference was no longer present 3 weeks later. We have also found that the vast majority of the BrdU-labeled cells contained a neuronal marker, indicating neuronal phenotypes. Finally, group differences in the number of cells undergoing apoptosis were subtle and did not seem to account for the observed differences in BrdU labeling. Together, our data indicate that social environment affects neuron proliferation in a stimulus- and site-specific manner in adult female prairie voles.     

Influence of intrauterine growth restriction on renal function in the adult rat

Intrauterine growth restriction (IUGR) has been shown to influence renal development and lead to fewer nephrons. Data on long term renal function after IUGR are limited. We studied the effect on renal function of IUGR in aging rats. IUGR was induced using a model of bilateral uterine artery ligation in pregnant Wistar rats. Renal function was studied at the age of 18 months. In male IUGR rats, estimated glomerular filtration rate was significantly decreased compared to male control rats [1.1 (SD 0.3) 1.7 (SD 0.3) ml x min(-1), p<0.05]. Female IUGR rats showed an increased urinary protein excretion compared with female control rats [84 (SD 73) vs. 12 (SD 13) mg x 24h(-1), p<0.01]. All male rats showed heavy proteinuria (p<0.01 vs. female rats from same experimental group), with no significant differences between the groups. Tubular reabsorption of phosphorus was lower in females, but showed no differences between the experimental groups. In conclusion, IUGR impairs renal function in the rat. It is suggested that a low nephron endowment leads to proteinuria as a sign of glomerular damage, and ends with a decrease in glomerular filtration rate as a sign of glomerular loss.     

The effects of long-term estradiol treatment on social behavior and gene expression in adult female rats

This study tested the effects of long-term estradiol (E₂) replacement on social behavior and gene expression in brain nuclei involved in the regulation of these social behaviors in adult female rats. We developed an ultrasonic vocalization (USV) test and a sociability test to examine communications, social interactions, and social preference, using young adult female cagemates. All rats were ovariectomized (OVX) and implanted with a Silastic capsule containing E₂ or vehicle, and housed in same-treatment pairs for a 3-month period. Then, rats were behaviorally tested, euthanized, and 5 nuclei in the brain's social decision-making circuit were selected for neuromolecular profiling by a multiplex qPCR method. Our novel USV test proved to be a robust tool to measure numbers and types of calls emitted by cagemates that had been reintroduced after a 1-week separation. Results also showed that E₂-treated OVX rats had profoundly decreased numbers of USV calls compared to vehicle-treated OVX rats. In a test of sociability, in which a female was allowed to choose between her cagemate or a same-treatment novel rat, we found few effects of E₂ compared to vehicle, although interestingly, rats chose the cagemate over an unfamiliar conspecific. Gene expression results revealed that the supraoptic nucleus had the greatest number of gene changes caused by E₂: Oxt, Oxtr and Avp were increased, and Drd2, Htr1a, Grin2b, and Gabbr1 were decreased, by E₂. No genes were affected in the prefrontal cortex, and 1–4 genes were changed in paraventricular nucleus (Pgr), bed nucleus of the stria terminalis (Oxtr, Esr2, Dnmt3a), and medial amygdala (Oxtr, Ar, Foxp1, Tac3). Thus, E₂ changes communicative interactions between adult female rats, together with selected expression of genes in the brain, especially in the supraoptic nucleus.     

Effect of digoxin imprinting in adolescence on the sexual behavior of adult rats

Four-time 3 micrograms digoxin treatment of male rats at puberty (in six weeks old rats) significantly increased the libido of rats (number of intromissions) and reduced the number of ejaculations, two months after the treatments (in three and a half months old rats). In female rats the Meyerson index and lordosis quotient were not significantly decreased. The experiment calls attention to the wide-ranging imprinting effect of digoxin which was also demonstrated earlier after prenatal (maternal) treatment. The experiment also supports the male sexual potency influencing effect of digoxin treatment, previously supposed in men.     

Social instability in adolescence differentially alters dendritic morphology in the medial prefrontal cortex and its response to stress in adult male and female rats

Adolescence is an important period for HPA axis development and synapse maturation and reorganization in the prefrontal cortex (PFC). Thus, stress during adolescence could alter stress‐sensitive brain regions such as the PFC and may alter the impact of future stressors on these brain regions. Given that women are more susceptible to many stress‐linked psychological disorders in which dysfunction of PFC is implicated, and that this increased vulnerability emerges in adolescence, stress during this time could have sex‐dependent effects. Therefore, we investigated the effects of adolescent social instability stress (SIS) on dendritic morphology of Golgi‐stained pyramidal cells in the medial PFC of adult male and female rats. We then examined dendritic reorganization following chronic restraint stress (CRS) with and without a rest period in adult rats that had been stressed in adolescence. Adolescent SIS conferred long‐term alterations in prelimbic of males and females, whereby females show reduced apical length and basilar thin spine density and males show reduced basilar length. CRS in adulthood failed to produce immediate dendritic remodeling in SIS rats. However, CRS followed by a rest period reduced apical dendritic length and increases mushroom spine density in adolescently stressed adult males. Conversely, CRS followed by rest produced apical outgrowth and decreased mushroom spine density in adolescently stressed adult females. These results suggest that stress during adolescence alters development of the PFC and modulates stress‐induced dendritic changes in adulthood.     

Transgenerational effects of social stress on social behavior,corticosterone, oxytocin,and prolactin in rats

Social stressors such as depressed maternal care and family conflict are robust challenges which can have long-term physiological and behavioral effects on offspring and future generations. The current study investigates the transgenerational effects of an ethologically relevant chronic social stress on the behavior and endocrinology of juvenile and adult rats. Exposure to chronic social stress during lactation impairs maternal care in F0 lactating dams and the maternal care of the F1 offspring of those stressed F0 dams. The overall hypothesis was that the male and female F2 offspring of stressed F1 dams would display decreased social behavior as both juveniles and adults and that these behavioral effects would be accompanied by changes in plasma corticosterone, prolactin, and oxytocin. Both the female and male F2 offspring of dams exposed to chronic social stress displayed decreased social behavior as juveniles and adults, and these behavioral effects were accompanied by decreases in basal concentrations of corticosterone in both sexes, as well as elevated juvenile oxytocin and decreased adult prolactin in the female offspring. The data support the conclusion that social stress has transgenerational effects on the social behavior of the female and male offspring which are mediated by changes in the hypothalamic–pituitary–adrenal axis and hypothalamic–pituitary–gonadal axis. Social stress models are valuable resources in the study of the transgenerational effects of stress on the behavioral endocrinology of disorders such as depression, anxiety, autism, and other disorders involving disrupted social behavior.     

Exposure to alcohol in utero alters the adult patterns of luteinizing hormone secretion in male and female rats

Luteinizing hormone (LH) secretory patterns were characterized in adult male and female rats exposed to ethanol during the last week of fetal life. Gonadectomized fetal alcohol exposed (FAE) males and females had significantly reduced plasma LH titers as compared to those of pair-fed (PF) controls. The phasic afternoon LH secretory response to estrogen and progesterone priming was also significantly reduced in FAE females. These differences do not appear to be a result of altered pituitary sensitivity to luteinizing hormone releasing hormone (LHRH), since the infusion of LHRH resulted in an equal response in PF and FAE females. Subsequent characterization of the episodic pattern of LH secretion in FAE males revealed significantly reduced mean LH level as well as a decreased pulse amplitude and frequency when compared to PF males. Taken together, these data indicate that some of the central mechanisms controlling pituitary LH secretion are altered by prenatal exposure to alcohol.     

Prenatal stress differentially affects habituation of corticosterone responses to repeated stress in adult male and female rats

Environmental factors operating early in life have long-lasting and important consequences for the mental and physical health of the adult organism. In particular, prenatal exposure to stress represents one category of adverse early environmental events that are associated with development of depression and schizophrenia in adulthood. In the present studies, we examined whether prenatal stress alters the habituation of hypothalamic-pituitary-adrenal (HPA) activity that occurs with repeated stress exposure in adulthood. We compared corticosterone responses to the first vs. the eighth restraint, with lower responses to the eighth vs. the first considered evidence of habituation. In males, prenatal stress prevented the habituation of corticosterone responses to repeated restraint that was observed in non-prenatally stressed rats. Limited evidence of habituation was seen in either group of females and prenatally stressed females did not exhibit the enhanced corticosterone response during recovery from the eighth restraint that was seen in non-prenatally stressed females. Together, these results suggest a sex-specific interaction between prenatal stress and adult chronic stress on HPA activity.     

Electroacupuncture attenuates the decrease of hippocampal progenitor cell proliferation in the adult rats exposed to chronic unpredictable stress

The present study was designed to investigate whether electroacupuncture (EA) was beneficial to extenuate the behavioral deficit in a rat model of depression induced by chronic unpredictable stress (CUS) and to observe the effect of EA on progenitor cell proliferation in the dentate gyrus (DG) of hippocampus. EA was performed on acupoints "Bai-Hui" (Du 20) and unilateral "An-Mian" (EX 17) once daily for 3 consecutive weeks, 2 weeks post CUS procedure. Open field test and forced swimming test were employed to evaluate the behavioral activity during a stress period or EA treatment. The results revealed that exposure to CUS resulted in a decrease of behavioral activity, whilst a daily session of EA treatment significantly reversed the behavioral deficit of these depression model rats. Moreover, as shown by 5-bromo-2-deoxyuridine (BrdU) labeling immunohistochemistry, hippocampal progenitor cell proliferation was decreased in the DG of depression model rats. Intriguingly, EA treatment effectively blocked this decrease. The study demonstrated a potential antidepressant-like effect of EA treatment on CUS induced depression model rats, which might be mediated by up-regulating the hippocampal progenitor cell proliferation.     

Aggressive behavior in female golden hamsters: development and the effect of repeated social stress

In male golden hamsters, agonistic behavior matures during puberty, changing from play fighting to adult-like aggression. In addition, this transition is accelerated by repeated social subjugation early in puberty. However, little is known about the development of agonistic behavior in females. In the present study, we compared the development of agonistic behavior in male and female golden hamsters. Furthermore, we also tested the effects of repeated social subjugation on the development of agonistic behavior during puberty. Hamsters were tested for agonistic behavior in the presence of a smaller intruder at different intervals during puberty. Several observations were made. First, the frequency of attacks remained stable in females, while varying in males. Second, the transition from play fighting to adult-like aggression occurred at earlier time periods in females than in males. Finally, a clear transitional period marked by attacks focused on the flanks was observable in males around mid-puberty. However, this transitional period was not apparent in females. In addition, juvenile females were exposed to aggressive adult males or females. In both cases, repeated exposure to stress had no statistically significant effect on the development of agonistic behavior. After 2 weeks of subjugation, exposure to aggressive adults had no effect on serum cortisol levels, indicating that juvenile females habituate to repeated social stress. These data show significant sex differences in the development of agonistic behavior and adaptation to repeated stress in juvenile golden hamsters.     

Effects of early life social stress on endocrinology,maternal behavior,and lactation in rats

Exposure to early life stress is a predictor of mental health disorders, and two common forms of early life stress are social conflict and impaired maternal care, which are predominant features of postpartum mood disorders. Exposure of lactating female rats to a novel male intruder involves robust social conflict and induces deficits in maternal care towards the F1 offspring. This exposure is an early life social stressor for female F1 pups that induces inefficient lactation associated with central changes in oxytocin (OXT), prolactin (PRL), and arginine vasopressin (AVP) gene expression in adult F1 females.     

Postnatal growth velocity modulates alterations of proteins involved in metabolism and neuronal plasticity in neonatal hypothalamus in rats born with intrauterine growth restriction

Intrauterine growth restriction (IUGR) due to maternal protein restriction is associated in rats with an alteration in hypothalamic centers involved in feeding behaviour. In order to gain insight into the mechanism of perinatal maternal undernutrition in the brain, we used proteomics approach to identify hypothalamic proteins that are altered in their expression following protein restriction in utero. We used an animal model in which restriction of the protein intake of pregnant rats (8% vs. 20%) produces IUGR pups which were randomized to a nursing regimen leading to either rapid or slow catch-up growth. We identified several proteins which allowed, by multivariate analysis, a very good discrimination of the three groups according to their perinatal nutrition. These proteins were related to energy-sensing pathways (Eno 1, E(2)PDH, Acot 1 and Fabp5), redox status (Bcs 1L, PrdX3 and 14-3-3 protein) or amino acid pathway (Acy1) as well as neurodevelopment (DRPs, MAP2, Snca). In addition, the differential expressions of several key proteins suggested possible shunts towards ketone-body metabolism and lipid oxidation, providing the energy and carbon skeletons necessary to lipogenesis. Our results show that maternal protein deprivation during pregnancy only (IUGR with rapid catch-up growth) or pregnancy and lactation (IUGR with slow postnatal growth) modulates numerous metabolic pathways resulting in alterations of hypothalamic energy supply. As several of these pathways are involved in signalling, it remains to be determined whether hypothalamic proteome adaptation of IUGR rats in response to different postnatal growth rates could also interfere with cerebral plasticity or neuronal maturation.     

The polymethoxylated flavone,Tangeretin improves cognitive memory in rats experiencing a single episode of prolonged post-traumatic stress

Post-traumatic stress disorder (PTSD) is a stress-related psychiatric/mental condition. Tangeretin (TAN), a major polymethoxylated flavone of citrus plants, exhibits anti-inflammatory and neuroprotective activities. However, whether TAN leads to cognitive improvement in PTSD patients remains unclear. In the present study, we explored whether TAN improved cognitive impairment induced in rats by single prolonged stress (SPS episode mimicking PTSD induction) and determined whether TAN reversed reductions in dopamine (DA) and serotonin (5-HT) levels. Rats were intraperitoneally injected with TAN for 14 consecutive days after the SPS, which had induced cognitive deficits evident in the object recognition task and the Morris water maze test; the impairments were improved by TAN (100?mg/kg). TAN rescued the neurochemical abnormalities and the SPS-induced decreases in DA and 5-HT levels in the hippocampus and amygdala. These effects may be attributable in part to induction of hippocampal genes encoding tyrosine hydroxylase and tryptophan hydroxylase-1. Our results support the idea that rats with PTSD exhibit changes in DAergic and serotonergic transmission and in memory impairment. Thus, TAN mediated reversal of memory-related behavioral dysfunction associated with traumatic stress may be a useful therapeutic intervention in PTSD patients.