Glucocorticoids, hippocampal damage and the glutamatergic synapse

ClassIIb histone deacetylase participates in perioperative neurocognitive disorders in elderly mice via HSP90/GR signaling pathway

OBJECTIVE

Multiple factors contribute to the development of perioperative neurocognitive disorders (PND). This study was designed to investigate whether Histone Deacetylase 6 (HDAC6) was involved in the formation of postoperative cognitive dysfunction in elderly mice by regulating the degree of acetylation of heat shock protein (HSP90) and related protein functions and quantities.

METHODS

C57BL/6 J male mice were randomly divided into six groups: control naive (group Control), anesthesia (group Anesthesia), splenectomy surgery (group Surgery), splenectomy surgery plus dissolvent (group Vehicles), splenectomy surgery plus the inhibitor ACY-1215 (group Ricolinostat), and splenectomy surgery plus the inhibitor RU-486(group Mifepristone). After the mice were trained for Morris Water Maze (MWM) test for five days, anesthesia and operational surgery were carried out the following day. Cognitive function was assessed on the 1st, 3rd and 7th days post-surgery. The hippocampi were harvested on days 1, 3, and 7 post-surgeries for Western blots and ELISA assays.

RESULTS

Mice with the splenectomy surgery displayed the activation of the hypothalamic-pituitary-adrenal axis (HPA-axis), marked an increase in adrenocorticotropic hormone (ACTH), glucocorticoid, mineralocorticoid at the molecular level and impaired spatial memory in the MWM test. The hippocampus of surgical groups showed a decrease in acetylated HSP90, a rise in glucocorticoid receptor (GR)-HSP90 association, and an increase in GR phosphorylation and translocation. HDAC6 was increased after the surgical treated. Using two specific inhibitors, HDAC6 inhibitor Ricolinostat (ACY-1215) and GR inhibitor Mifepristone (RU-486), can partially mitigate the effects caused by surgical operation.

CONCLUSIONS

Abdominal surgery may impair hippocampal spatial memory, possibly through the HDAC6-triggered increase in the function of HSP90, consequently strengthening the negative role of steroids in cognitive function. Targeting HDAC6- HSP90/GR signaling may provide a potential avenue for the treatment of the impairment of cognitive function after surgery.

Mapping pathways to neuronal atrophy in healthy, mid-aged adults: From chronic stress to systemic inflammation to neurodegeneration?

Growing evidence implicates systemic inflammation in the loss of structural brain integrity in natural ageing and disorder development. Chronic stress and glucocorticoid exposure can potentiate inflammatory processes and may also be linked to neuronal atrophy, particularly in the hippocampus and the human neocortex. To improve understanding of emerging maladaptive interactions between stress and inflammation, this study examined evidence for glucocorticoid- and inflammation-mediated neurodegeneration in healthy mid-aged adults. N = 169 healthy adults (mean age = 39.4, 64.5% female) were sampled from the general population in the context of the ReSource Project. Stress, inflammation and neuronal atrophy were quantified using physiological indices of chronic stress (hair cortisol (HCC) and cortisone (HEC) concentration), systemic inflammation (interleukin-6 (IL-6), high-sensitive C-reactive protein (hs-CRP)), the systemic inflammation index (SII), hippocampal volume (HCV) and cortical thickness (CT) in regions of interest. Structural equation models were used to examine evidence for pathways from stress and inflammation to neuronal atrophy. Model fit indices indicated good representation of stress, inflammation, and neurological data through the constructed models (CT model: robust RMSEA = 0.041, robust χ2 = 910.90; HCV model: robust RMSEA <0.001, robust χ2 = 40.95). Among inflammatory indices, only the SII was positively associated with hair cortisol as one indicator of chronic stress (β = 0.18, p < 0.05). Direct and indirect pathways from chronic stress and systemic inflammation to cortical thickness or hippocampal volume were non-significant. In exploratory analysis, the SII was inversely related to mean cortical thickness. Our results emphasize the importance of considering the multidimensionality of systemic inflammation and chronic stress, with various indicators that may represent different aspects of the systemic reaction. We conclude that inflammation and glucocorticoid-mediated neurodegeneration indicated by IL-6 and hs-CRP and HCC and HEC may only emerge during advanced ageing and disorder processes, still the SII could be a promising candidate for detecting associations between inflammation and neurodegeneration in younger and healthy samples. Future work should examine these pathways in prospective longitudinal designs, for which the present investigation serves as a baseline.

Does a steroid dementia syndrome really exist? A brief narrative review of what the literature highlights about the relationship between glucocorticoids and cognition

Glucocorticoids (GCs) may cause cognitive impairment through complex pathways involving specific receptors. In the human brain, hippocampal CA1 neurons exhibit the highest level of GCs receptors. Even the elderly expressed these receptors. The purpose of this brief review is to concentrate on the relationship between GCs and cognition in order to discuss the effects of the so-called steroid dementia in routine clinical practice.

Spatial Learning Is Impaired in Male Pubertal Rats Following Neonatal Daily but Not Randomly Spaced Maternal Deprivation

Severe early life stress has long been associated with neuropsychological disorders in adulthood, including depression, schizophrenia, post-traumatic stress disorder, and memory dysfunction. To some extent, all of these conditions involve dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and reduced negative feedback inhibition of cortisol release in adulthood. However, the time course for mental health and hormonal outcomes across life stages and the attributes of early life stress that direct the behavioral and biological alterations is not fully understood. We designed our studies to compare outcomes of the two most common maternal deprivation schedules on cognitive ability prior to adulthood. We exposed rat pups to daily or randomly spaced maternal separation bouts within the first 3 weeks of life and examined cognitive performance, neurotrophic signaling, and stress and immune system markers during puberty. We found that the daily separation schedule impaired spatial learning while the randomly spaced schedule did not alter maze performance relative to normally reared control animals. Animals that underwent daily separation showed a tendency for reduced body weight compared to the randomly spaced condition, but there were no differences in adrenal weight. Thymus weight normalized by body weight was increased following daily separation compared to random separation and control conditions. Plasma corticosterone levels measured after behavior testing did not differ amongst experimental groups and there was no impact of TrKB receptor inhibition. Combined, the results show that different early life stress schedules produce different behavioral and biological outcomes when measured at puberty. Combined with prior findings from more mature animals, the results presented here suggest that daily neonatal stress produces varied alterations in spatial cognition at different life stages with a transient learning deficit at puberty preceding a more persistent and a progressive memory impairment through adulthood and into aging.

Biochemical Mechanisms and Translational Relevance of Hippocampal Vulnerability to Distant Focal Brain Injury: The Price of Stress Response

Focal brain injuries (in particular, stroke and traumatic brain injury) induce with high probability the development of delayed (months, years) cognitive and depressive disturbances which are frequently comorbid. The association of these complications with hippocampal alterations (in spite of the lack of a primary injury of this structure), as well as the lack of a clear dependence between the probability of depression and dementia development and primary damage severity and localization served as the basis for a new hypothesis on the distant hippocampal damage as a key link in the pathogenesis of cognitive and psychiatric disturbances. According to this hypothesis, the excess of corticosteroids secreted after a focal brain damage, in particular in patients with abnormal stress-response due to hypothalamic-pituitary-adrenal axis (HPAA) dysfunction, interacts with corticosteroid receptors in the hippocampus inducing signaling pathways which stimulate neuroinflammation and subsequent events including disturbances in neurogenesis and hippocampal neurodegeneration. In this article, the molecular and cellular mechanisms associated with the regulatory role of the HPAA and multiple functions of brain corticosteroid receptors in the hippocampus are analyzed. Functional and structural damage to the hippocampus, a brain region selectively vulnerable to external factors and responding to them by increased cytokine secretion, forms the basis for cognitive function disturbances and psychopathology development. This concept is confirmed by our own experimental data, results of other groups and by prospective clinical studies of post-stroke complications. Clinically relevant biochemical approaches to predict the risks and probability of post-stroke/post-trauma cognitive and depressive disturbances are suggested using the evaluation of biochemical markers of patients' individual stress-response. Pathogenetically justified ways for preventing these consequences of focal brain damage are proposed by targeting key molecular mechanisms underlying hippocampal dysfunction.

Fetal exposure to high levels of maternal glucocorticoids alters reelin signaling in the prefrontal cortex of rat pups

Maternal stress (MS) is associated with various neuropsychiatric disorders and cognitive impairment in the offspring. However, it is unclear how early life stress alters the pup's brain development and how it contributes to the pathology of neuropsychiatric disorders later in life. Reelin is a large extracellular matrix glycoprotein that plays essential roles in early brain development such as neural migration, synaptic development, and maturation. Dysregulation of reelin and its signaling proteins is associated with the emergence of neuropsychiatric disorders in adulthood. This study examined the effect of repeated maternal Carbenoxolone (CBX) injection during late gestation on reelin signaling in the prefrontal cortex (PFC) of rat pups. CBX is a selective 11β-HSD2 enzyme inhibitor that promotes the direct transfer of maternal corticosteroids (CORT) to the fetus. Therefore, treatment with CBX can mimic the animal model of early life exposure to high levels of maternal stress hormone. In this study, pregnant rats were injected daily with either saline or CBX during gestation day (GD) 14-21, and the levels of reelin and its signaling proteins were examined in the PFC of rat pups at different postnatal age from P0-P21. The main result of this study is the repeated maternal CBX injections during GD14-21 acutely increase reln mRNA and protein expression in the PFC of rat pups at birth (P0) and follow by a significant decrease during P7-P14. The treatment also causes long term decreases in the amount of VLDLR and Dab1 which are the downstream signaling proteins for the reelin pathway, at least until P21. Our results indicated that fetal exposure to high levels of maternal CORT interferes with reelin signaling which might have profound effects on cortical development associated with neuropsychiatric disorders later in life.

Delirium pathophysiology: An updated hypothesis of the etiology of acute brain failure

BACKGROUND

Delirium is the most common neuropsychiatric syndrome encountered by clinicians dealing with older adults and the medically ill and is best characterized by 5 core domains: cognitive deficits, attentional deficits, circadian rhythm dysregulation, emotional dysregulation, and alteration in psychomotor functioning.

DESIGN

An extensive literature review and consolidation of published data into a novel interpretation of known pathophysiological causes of delirium.

RESULTS

Available data suggest that numerous pathological factors may serve as precipitants for delirium, each having differential effects depending on patient-specific patient physiological characteristics (substrate). On the basis of an extensive literature search, a newly proposed theory, the systems integration failure hypothesis, was developed to bring together the most salient previously described theories, by describing the various contributions from each into a complex web of pathways-highlighting areas of intersection and commonalities and explaining how the variable contribution of these may lead to the development of various cognitive and behavioral dysfunctions characteristic of delirium. The specific cognitive and behavioral manifestations of the specific delirium picture result from a combination of neurotransmitter function and availability, variability in integration and processing of sensory information, motor responses to both external and internal cues, and the degree of breakdown in neuronal network connectivity, hence the term acute brain failure.

CONCLUSIONS

The systems integration failure hypothesis attempts to explain how the various proposed delirium pathophysiologic theories interact with each other, causing various clinically observed delirium phenotypes. A better understanding of the underlying pathophysiology of delirium may eventually assist in designing better prevention and management approaches.

CA3 hippocampal field: Cellular changes and its relation with blood nitro-oxidative stress reveal a balancing function of CA3 area in rats exposed to repetead restraint stress

Rats exposed to repeated restraint stress exhibit structural and functional deficits in hippocampus that are similar to those observed in patients with depressive illnesses. Blood corticosterone concentrations are proportionally increased with catalase and glutathione-peroxidase activity and are inversely proportional with 3-nitrotyrosine concentrations.Cytochrome c oxidase, adenosin tryphosphatase and monoamine oxidase activities of CA3 hippocampal field mark a stress-time dependent decrease. Acridine-orange labeling of the CA3 field reveals an enhancing green fluorescence of glyocites in stress conditions. After three days of restraint stress, the secretory activity of CA3 neurons did not show significant decrease, and neurons appeared with normal shapes and distribution. CA3 neurons after seven days of restraint stress have marked a slight decrease of secretory activity. In contrast to a well-preserved histological appearance of the CA3 neurons, local and blood stress-related reactions are observed. CA3-glial activation and disturbance of blood oxidative homeostasis are tandem processes during three and seven days of RS. This study depicts the balancing role of CA3 area in time-varying stress conditions.

Longitudinal Evidence for Smaller Hippocampus Volume as a Vulnerability Factor for Perceived Stress

Hippocampal volume has been found to be smaller in individuals with stress-related disorders, but it remains unclear whether smaller volume is a consequence of stress or rather a vulnerability factor. Here, we examined this issue by relating stress levels to hippocampal volumes in healthy participants examined every 5 years in a longitudinal population-based study. Based on scores of 25- to 60-year–old participants on the perceived stress questionnaire, we defined moderately to high (n = 35) and low (n = 76) stress groups. The groups were re-examined after 5 years (at the 6th study wave). Historical data on subjective stress were available up to 10 years prior to Wave 5. At the first MRI session, the moderately to high stress group had a significantly smaller hippocampal volume, as measured by FreeSurfer (version 5.3), compared with the low-stress group. At follow-up, group differences in stress levels and hippocampal volume remained unchanged. In retrospective analyses of subjective stress, the observed group difference in stress was found to be stable. The long-term stability of group differences in perceived stress and hippocampal volume suggests that a small hippocampal volume may be a vulnerability factor for stress-related disorders.

The Role of Lactate-Mediated Metabolic Coupling between Astrocytes and Neurons in Long-Term Memory Formation

Long-term memory formation, the ability to retain information over time about an experience, is a complex function that affects multiple behaviors, and is an integral part of an individual's identity. In the last 50 years many scientists have focused their work on understanding the biological mechanisms underlying memory formation and processing. Molecular studies over the last three decades have mostly investigated, or given attention to, neuronal mechanisms. However, the brain is composed of different cell types that, by concerted actions, cooperate to mediate brain functions. Here, we consider some new insights that emerged from recent studies implicating astrocytic glycogen and glucose metabolisms, and particularly their coupling to neuronal functions via lactate, as an essential mechanism for long-term memory formation.

Stress-induced remodeling of hippocampal CA3 pyramidal neurons

The discovery of steroid hormone receptors in brain regions that mediate virtually every aspect of brain function has broadened the definition of 'neuroendocrinology' to include the reciprocal communication between the brain and the body via hormonal and neural pathways. The brain is the central organ of stress and adaptation to stress because it perceives and determines what is threatening, as well as determining the behavioral and physiological responses to the stressor. The adult and developing brain possess remarkable structural and functional plasticity in response to stress, including neurogenesis leading to neuronal replacement, dendritic remodeling, and synapse turnover. Stress causes an imbalance of neural circuitry subserving cognition, decision-making, anxiety and mood that can alter expression of those behaviors and behavioral states. The two Brain Research papers noted in this review played an important role in triggering these advances. This article is part of a Special Issue entitled SI:50th Anniversary Issue.

60 YEARS OF NEUROENDOCRINOLOGY: Redefining neuroendocrinology: stress, sex and cognitive and emotional regulation

The discovery of steroid hormone receptors in brain regions that mediate every aspect of brain function has broadened the definition of 'neuroendocrinology' to include the reciprocal communication between the brain and the body via hormonal and neural pathways. The brain is the central organ of stress and adaptation to stress because it perceives and determines what is threatening, as well as the behavioral and physiological responses to the stressor. The adult and developing brain possess remarkable structural and functional plasticity in response to stress, including neuronal replacement, dendritic remodeling, and synapse turnover. Stress causes an imbalance of neural circuitry subserving cognition, decision-making, anxiety and mood that can alter expression of those behaviors and behavioral states. This imbalance, in turn, affects systemic physiology via neuroendocrine, autonomic, immune and metabolic mediators. In the short term, as for increased fearful vigilance and anxiety in a threatening environment, these changes may be adaptive. But, if the danger passes and the behavioral state persists along with the changes in neural circuitry, such maladaptation may need intervention with a combination of pharmacological and behavioral therapies, as is the case for chronic anxiety and depression. There are important sex differences in the brain responses to stressors that are in urgent need of further exploration. Moreover, adverse early-life experience, interacting with alleles of certain genes, produce lasting effects on brain and body over the life-course via epigenetic mechanisms. While prevention is most important, the plasticity of the brain gives hope for therapies that take into consideration brain-body interactions.

Actions and interactions of estradiol and glucocorticoids in cognition and the brain: Implications for aging women

Menopause involves dramatic declines in estradiol production and levels. Importantly, estradiol and the class of stress hormones known as glucocorticoids exert countervailing effects throughout the body, with estradiol exerting positive effects on the brain and cognition, glucocorticoids exerting negative effects on the brain and cognition, and estradiol able to mitigate negative effects of glucocorticoids. Although the effects of these hormones in isolation have been extensively studied, the effects of estradiol on the stress response and the neuroprotection offered against glucocorticoid exposure in humans are less well known. Here we review evidence suggesting that estradiol-related protection against glucocorticoids mitigates stress-induced interference with cognitive processes. Animal and human research indicates that estradiol-related mitigation of glucocorticoid damage and interference is one benefit of estradiol supplementation during peri-menopause or soon after menopause. The evidence for estradiol-related protection against glucocorticoids suggests that maintaining estradiol levels in post-menopausal women could protect them from stress-induced declines in neural and cognitive integrity.

The effect of chronic phenytoin administration on single prolonged stress induced extinction retention deficits and glucocorticoid upregulation in the rat medial prefrontal cortex

RATIONALE

Post-traumatic stress disorder (PTSD) is a chronic, debilitating disorder. Only two pharmacological agents are approved for PTSD treatment, and they often do not address the full range of symptoms nor are they equally effective in all cases. Animal models of PTSD are critical for understanding the neurobiology involved and for identification of novel therapeutic targets. Using the rodent PTSD model, single prolonged stress (SPS), we have implicated aberrant excitatory neural transmission and glucocorticoid receptor (GR) upregulation in the medial prefrontal cortex (mPFC) and hippocampus (HPC) in fear memory abnormalities associated with PTSD.

OBJECTIVE

The objective of this study is to examine the potential protective effect of antiepileptic phenytoin (PHE) administration on SPS-induced extinction retention deficits and GR expression.

METHODS

Forty-eight SPS-treated male Sprague Dawley rats or controls were administered PHE (40, 20 mg/kg, vehicle) for 7 days following SPS stressors; then, fear conditioning, extinction, and extinction retention were tested.

RESULTS

Fear conditioning and extinction were unaffected by SPS or PHE, but SPS impaired extinction retention, and both doses of PHE rescued this impairment. Similarly, SPS increased GR expression in the mPFC and dorsal HPC, and PHE prevented SPS-induced GR upregulation in the mPFC.

CONCLUSIONS

These data demonstrate that PHE administration can prevent the development of extinction retention deficits and upregulation of GR. PHE exerts inhibitory effects on voltage-gated sodium channels and decreases excitatory neural transmission via glutamate antagonism. If glutamate hyperactivity in the days following SPS contributes to SPS-induced deficits, then these data may suggest that the glutamatergic system constitutes a target for secondary prevention.

Different patterns of morphological changes in the hippocampus and dentate gyrus accompany the differential expression of disability following nerve injury

Physical and psychological trauma which results in mood disorders and the disruption of complex behaviours is associated with reductions in hippocampal volume. Clinical evaluation of neuropathic pain reveals mood and behavioural change in a significant number of patients. A rat model of neuropathic injury results in complex behavioural changes in a subpopulation (~30%) of injured rats; these changes are co-morbid with a range of other 'disabilities'. The specific objective of this study was to determine in rats the morphology of the hippocampus and dentate gyrus in individuals with and without complex behavioural disruptions following a constriction injury of the sciatic nerve, and to determine whether rats that develop disabilities following nerve injury have a reduced hippocampal volume compared with injured rats with no disabilities. The social behaviours of nerve-injured rats were evaluated before and after nerve injury. The morphology of the hippocampus of rats with and without behavioural disruptions was compared in serial histological sections. Single-housing and repeated social-interaction testing had no effect on the morphology of either the hippocampus or the dentate gyrus. Rats with transient or ongoing disability identified by behavioural disruption following sciatic nerve injury, show bilateral reductions in hippocampal volume, and lateralised reduction in the dentate gyrus (left side). Disabled rats display a combination of behavioural and physiological changes, which resemble many of the criteria used clinically to diagnose mood disorders. They also show reductions in the volume of the hippocampus similar to people with clinically diagnosed mood disorders. The sciatic nerve injury model reveals a similarity to the human neuropathic pain presentation presenting an anatomically specific focus for the investigation of the neural mechanisms underpinning the co-morbidity of chronic pain and mood disorder.

Neuropathogenesis of delirium: review of current etiologic theories and common pathways

Delirium is a neurobehavioral syndrome caused by dysregulation of neuronal activity secondary to systemic disturbances. Over time, a number of theories have been proposed in an attempt to explain the processes leading to the development of delirium. Each proposed theory has focused on a specific mechanism or pathologic process (e.g., dopamine excess or acetylcholine deficiency theories), observational and experiential evidence (e.g., sleep deprivation, aging), or empirical data (e.g., specific pharmacologic agents' association with postoperative delirium, intraoperative hypoxia). This article represents a review of published literature and summarizes the top seven proposed theories and their interrelation. This review includes the "neuroinflammatory," "neuronal aging," "oxidative stress," "neurotransmitter deficiency," "neuroendocrine," "diurnal dysregulation," and "network disconnectivity" hypotheses. Most of these theories are complementary, rather than competing, with many areas of intersection and reciprocal influence. The literature suggests that many factors or mechanisms included in these theories lead to a final common outcome associated with an alteration in neurotransmitter synthesis, function, and/or availability that mediates the complex behavioral and cognitive changes observed in delirium. In general, the most commonly described neurotransmitter changes associated with delirium include deficiencies in acetylcholine and/or melatonin availability; excess in dopamine, norepinephrine, and/or glutamate release; and variable alterations (e.g., either a decreased or increased activity, depending on delirium presentation and cause) in serotonin, histamine, and/or γ-aminobutyric acid. In the end, it is unlikely that any one of these theories is fully capable of explaining the etiology or phenomenologic manifestations of delirium but rather that two or more of these, if not all, act together to lead to the biochemical derangement and, ultimately, to the complex cognitive and behavioral changes characteristic of delirium.

Kai-xin-san, a chinese herbal decoction containing ginseng radix et rhizoma, polygalae radix, acori tatarinowii rhizoma, and poria, stimulates the expression and secretion of neurotrophic factors in cultured astrocytes

Kai-xin-san (KXS), a Chinese herbal decoction prescribed by Sun Simiao in Beiji Qianjin Yaofang about 1400 years ago, contains Ginseng Radix et Rhizoma, Polygalae Radix, Acori Tatarinowii Rhizoma, and Poria. In China, KXS has been used to treat stress-related psychiatric diseases with the symptoms of depression and forgetfulness. Although animal study has supported the antidepression function of KXS, the mechanism in cellular level is still unknown. Here, a chemically standardized water extract of KXS was applied onto cultured astrocytes in exploring the action mechanisms of KXS treatment, which significantly stimulated the expression and secretion of neurotrophic factors, including NGF, BDNF, and GDNF, in a dose-dependent manner: the stimulation was both in mRNA and protein levels. In addition, the water extracts of four individual herbs did not significantly stimulate the expression of neurotrophic factors, which could explain the optimized effect of KXS in a herbal decoction. The KXS-induced expression of neurotrophic factors did not depend on signaling mediated by estrogen receptor or protein kinase. The results suggested that the antidepressant-like action of KXS might be mediated by an increase of expression of neurotrophic factors in astrocytes, which fully supported the clinical usage of this decoction.

Limbic brain responses in mothers with post-traumatic stress disorder and comorbid dissociation to video clips of their children

Maternal dissociative symptoms which can be comorbid with interpersonal violence-related post-traumatic stress disorder (IPV-PTSD) have been linked to decreased sensitivity and responsiveness to children's emotional communication. This study examined the influence of dissociation on neural activation independently of IPV-PTSD symptom severity when mothers watch video-stimuli of their children during stressful and non-stressful mother-child interactions. Based on previous observations in related fields, we hypothesized that more severe comorbid dissociation in IPV-PTSD would be associated with lower limbic system activation and greater neural activity in regions of the emotion regulation circuit such as the medial prefrontal cortex and dorsolateral prefrontal cortex (dlPFC). Twenty mothers (of children aged 12-42 months), with and without IPV-PTSD watched epochs showing their child during separation and play while undergoing functional magnetic resonance imaging (fMRI). Multiple regression indicated that when mothers diagnosed with IPV-PTSD watched their children during separation compared to play, dissociative symptom severity was indeed linked to lowered activation within the limbic system, while greater IPV-PTSD symptom severity was associated with heightened limbic activity. Concerning emotion regulation areas, there was activation associated to dissociation in the right dlPFC. Our results are likely a neural correlate of affected mothers' reduced capacity for sensitive responsiveness to their young child following exposure to interpersonal stress, situations that are common in day-to-day parenting.

Glucocorticoids and preterm hypoxic-ischemic brain injury: the good and the bad

Fetuses at risk of premature delivery are now routinely exposed to maternal treatment with synthetic glucocorticoids. In randomized clinical trials, these substantially reduce acute neonatal systemic morbidity, and mortality, after premature birth and reduce intraventricular hemorrhage. However, the overall neurodevelopmental impact is surprisingly unclear; worryingly, postnatal glucocorticoids are consistently associated with impaired brain development. We review the clinical and experimental evidence on how glucocorticoids may affect the developing brain and highlight the need for systematic research.

Fisetin prevents fluoride- and dexamethasone-induced oxidative damage in osteoblast and hippocampal cells

Fluoride intoxication and dexamethasone treatment produce deleterious effects in bone and brain. The aim of this study was to evaluate the effect of fluoride (F) and dexamethasone (Dex) co-exposure on oxidative stress and apoptosis in osteoblast-like MC3T3-E1 and hippocampal HT22 cell lines. Co-exposure to F and Dex resulted in a concentration-dependent decrease in cell viability, induction of apoptosis and increased generation of reactive oxygen species (ROS) and nitric oxide (NO) following 72 h of incubation. Fluoride-induced apoptosis in MC3T3-E1 and HT22 cells was attenuated by catalase and L-NNMA, indicating a role for H2O2 and NO as mediators of cytotoxicity. Dexamethasone-induced apoptosis was associated with H2O2 generation in both cell lines and it was attenuated during co-incubation with catalase. These data indicate that co-exposure to F and Dex amplifies their respective cytotoxicity in H2O2- and NO-dependent manner. As flavonoid fisetin prevented F- and Dex-induced cytotoxicity the potential role of this product in pharmacology and diet may be considered.

A double-blind randomized controlled trial to study the efficacy of topiramate in a civilian sample of PTSD

OBJECTIVE

To evaluate the efficacy and tolerability of topiramate in patients with posttraumatic stress disorder (PTSD).

METHOD

We conducted a 12-week double-blind, randomized, placebo-controlled study comparing topiramate to placebo. Men and women aged 18-62 years with diagnosis of PTSD according to DSM-IV were recruited from the outpatient clinic of the violence program of Federal University of São Paulo Hospital (Prove-UNIFESP), São Paulo City, between April 2006 and December 2009. Subjects were assessed for the Clinician-Administered Posttraumatic Stress Scale (CAPS), Clinical Global Impression, and Beck Depression Inventory (BDI). After 1-week period of washout, 35 patients were randomized to either group. The primary outcome measure was the CAPS total score changes from baseline to the endpoint.

RESULTS

82.35% of patients in the topiramate group exhibited improvements in PTSD symptoms. The efficacy analysis demonstrated that patients in the topiramate group exhibited significant improvements in reexperiencing symptoms: flashbacks, intrusive memories, and nightmares of the trauma (CAPS-B; P= 0.04) and in avoidance/numbing symptoms associated with the trauma, social isolation, and emotional numbing (CAPS-C; P= 0.0001). Furthermore, the experimental group demonstrated a significant difference in decrease in CAPS total score (topiramate -57.78; placebo -32.41; P= 0.0076). Mean topiramate dose was 102.94 mg/d. Topiramate was generally well tolerated.

CONCLUSION

Topiramate was effective in improving reexperiencing and avoidance/numbing symptom clusters in patients with PTSD. This study supports the use of anticonvulsants for the improvement of symptoms of PTSD.

Adult Hippocampal Neurogenesis: A Possible Way how Physical Exercise Counteracts Stress

It was considered that neurogenesis only occurred during the embryonic and developmental stage. This view has greatly changed since the discovery of adult neurogenesis in two brain regions: the hippocampus and the olfactory bulb. Recently, it is suggested that altered hippocampal neurogenesis is related to pathophysiology of mood disorders and mechanism of antidepressant treatments. Accumulating knowledge about the effects of physical exercise on brain function suggests a special role of adult hippocampal neurogenesis in cognitive and mental health, even though the functional significance of adult neurogenesis is still debated. The beneficial effects of running correlating with increased adult neurogenesis may provide a hint that newborn neurons may be involved, at least in part, in the counteractive mechanism of physical exercise on stress-related disorders, like depression. The present review provides an overview of recent findings to emphasize the possible involvement of hippocampal neurogenesis in mediating the beneficial effects of physical exercise on counteracting stress.

Corticosterone decreases the activity of rat glutamate transporter type 3 expressed in Xenopus oocytes

Glucocorticoids can increase the extracellular concentrations of glutamate, the major excitatory neurotransmitter. We investigated the effects of corticosterone on the activity of a glutamate transporter, excitatory amino acid carrier 1 (EAAC1; also called excitatory amino acid transporter type 3 [EAAT3]), and the roles of protein kinase C (PKC) and phosphatidylinositol 3-kinase (PI3K) in regulating these effects. Rat EAAC1 was expressed in Xenopus oocytes by injecting mRNA. L-Glutamate (30 μM)-induced membrane currents were measured using the two-electrode voltage clamp technique. Exposure of these oocytes to corticosterone (0.01-1 μM) for 72 h decreased EAAC1 activity in a dose-dependent fashion, and this inhibition was incubation time-dependent. Corticosterone (0.01 μM for 72 h) significantly decreased the V(max), but not the K(m), of EAAC1 for glutamate. Furthermore, pretreatment of oocytes with staurosporine, a PKC inhibitor, significantly decreased EAAC1 activity (1.00±0.06 to 0.70±0.05 μC; P<0.05). However, no statistical differences were observed between oocytes treated with staurosporine, corticosterone, or corticosterone plus staurosporine. Similar patterns of responses were achieved by chelerythrine or calphostin C, other PKC inhibitors. Phorbol-12-myristate-13-acetate (PMA), a PKC activator, inhibited corticosterone-induced reduction in EAAC1 activity. Pretreating oocytes with wortmannin or LY294002, PI3K inhibitors, also significantly reduced EAAC1 activity, but no difference was observed between oocytes treated with wortmannin, corticosterone, or wortmannin plus corticosterone. The above results suggest that corticosterone exposure reduces EAAC1 activity and this effect is PKC- and PI3K-dependent.

Restraint stress increases neuroinflammation independently of amyloid β levels in amyloid precursor protein/PS1 transgenic mice

Both hypercortisolemia and hippocampal damage are features found in patients diagnosed of Alzheimer's disease (AD) and epidemiological evidence supports a role for stress as a risk factor for AD. It is known that immobilization stress is followed by accumulation of oxidative/nitrosative mediators in brain after the release of proinflammatory cytokines, nuclear factor kappa B activation, nitric oxide synthase-2 and cyclooxygenase-2 expression. Long-term exposure to elevated corticosteroid levels is known to affect the hippocampus which plays a central role in the regulation of the hypothalamic-pituitary-adrenal axis. We therefore studied the effect of chronic immobilization stress on amyloid precursor protein/PS1 mice. Stress exposure increased AD-induced neuroinflammation characterized by astrogliosis, increased inflammatory gene transcription and lipid peroxidation. Importantly, immobilization stress did not increase the soluble or insoluble amyloid β levels suggesting that increased cortisol levels lower the threshold for a neuroinflammatory response, independently from amyloid β. Since inflammation may act as a factor that contributes disease progression, the stress-inflammation relation described here may be relevant to understand the initial mechanisms in underlying the risk enhancing action of stress on AD.

Chewing under restraint stress inhibits the stress-induced suppression of cell birth in the dentate gyrus of aged SAMP8 mice

To investigate the mechanisms underlying impaired hippocampal function resulting from masticatory dysfunction, we examined the effects of the molarless condition on cell proliferation and the effect of the administration of metyrapone, which suppresses the stress-induced rise in plasma corticosterone levels, on cell proliferation in the hippocampal dentate gyrus (DG) of aged senescence-accelerated prone (SAMP8) mice. In addition, we examined whether chewing under restraint stress prevents the stress-induced suppression of cell proliferation. In aged mice, the molarless condition suppressed cell proliferation in the hippocampal DG. Vehicle-injected molarless mice had significantly higher plasma corticosterone levels than vehicle-injected control and metyrapone-injected molarless mice, in association with decreased cell proliferation in the hippocampal DG. Pretreatment with metyrapone inhibited the increase in plasma corticosterone levels induced by the bite-raised condition, and also attenuated the reduction in cell proliferation. Immobilization stress suppressed cell proliferation in the hippocampal DG, but chewing under restraint stress blocked the stress-induced suppression of cell proliferation in the DG. These results suggest that the morphologic deficits induced by the molarless condition in aged SAMP8 mice are a result of increased plasma corticosterone levels, and that chewing under restraint stress prevents the stress-induced suppression of cell birth in the DG.

Hypothalamo-pituitary-adrenocortical axis, glucocorticoids, and neurologic disease

Neurologic diseases are often accompanied by significant life stress and consequent increases in stress hormone levels. Glucocorticoid stress hormones are known to have deleterious interactions with neurodegenerative processes, and are hypersecreted in neurologic disorders as well as in comorbid psychiatric conditions, such as depression. This article highlights the state of our knowledge on mechanisms controlling activation and inhibition of glucocorticoid secretion, outlines signaling mechanisms used by these hormones in neural tissue, and describes how endogenous glucocorticoids can mediate neuronal damage in various models of neurologic disease. The article highlights the importance of controlling stress and consequent stress hormone secretion in the context of neurologic disease states.

Effects of voluntary and forced exercise on plaque deposition, hippocampal volume, and behavior in the Tg2576 mouse model of Alzheimer's disease

We examined the effects of voluntary (16 weeks of wheel running) and forced (16 weeks of treadmill running) exercise on memory-related behavior, hippocampal volume, thioflavine-stained plaque number, and soluble Abeta levels in brain tissue in the Tg2576 mouse model of Alzheimer's disease (AD). Voluntary running animals spent more time investigating a novel object in a recognition memory paradigm than all other groups. Also, voluntary running animals showed fewer thioflavine S stained plaques than all other groups, whereas forced running animals showed an intermediate number of plaques between voluntary running and sedentary animals. Both voluntary and forced running animals had larger hippocampal volumes than sedentary animals. However, levels of soluble Abeta-40 or Abeta-42 did not significantly differ among groups. The results indicate that voluntary exercise may be superior to forced exercise for reducing certain aspects of AD-like deficits - i.e., plaque deposition and memory impairment, in a mouse model of AD.

Repeated immobilization stress alters rat hippocampal and prefrontal cortical morphology in parallel with endogenous agmatine and arginine decarboxylase levels

Agmatine, an endogenous amine derived from decarboxylation of L-arginine catalyzed by arginine decarboxylase, has been proposed as a neurotransmitter or neuromodulator in the brain. In the present study, we examined whether agmatine has neuroprotective effects against repeated immobilization-induced morphological changes in brain tissues and possible effects of immobilization stress on endogenous agmatine levels and arginine decarboxylase expression in rat brains. Sprague-Dawley rats were subjected to 2h immobilization stress daily for 7 days. This paradigm significantly increased plasma corticosterone levels, and the glutamate efflux in the hippocampus as measured by in vivo microdialysis. Immunohistochemical staining with beta-tubulin III showed that repeated immobilization caused marked morphological alterations in the hippocampus and medial prefrontal cortex that were prevented by simultaneous treatment with agmatine (50mg/kg/day), i.p.). Likewise, endogenous agmatine levels measured by high-performance liquid chromatography in the prefrontal cortex, hippocampus, striatum and hypothalamus were significantly increased by immobilization, as compared to controls. The increased endogenous agmatine levels, ranging from 92 to 265% of controls, were accompanied by a significant increase of arginine decarboxylase protein levels in the same regions. These results demonstrate that the administration of exogenous agmatine protects the hippocampus and medial prefrontal cortex against neuronal insults caused by repeated immobilization. The parallel increase in endogenous brain agmatine and arginine decarboxylase protein levels triggered by repeated immobilization indicates that the endogenous agmatine system may play an important role in adaptation to stress as a potential neuronal self-protection mechanism.

Parental alcohol use and brain volumes in early- and late-onset alcoholics

BACKGROUND

Studies have shown that alcoholics have smaller brain volumes than non-alcoholic cohorts, but an effect of family history (FH) of heavy drinking on brain volume has not been demonstrated. We examined the relationship between an FH of heavy drinking and both brain shrinkage as measured by the ratio of brain volumes to intracranial volume (ICV) as well as maximal brain growth as measured by ICV in early-onset and late-onset alcoholics.

METHODS

With T1-weighted resonance imaging, we measured ICV, brain volume, and white and gray matter volume in adult treatment-seeking late-onset and early-onset alcoholics with either a positive or a negative FH of heavy alcohol use, and in healthy control subjects. We also calculated brain shrinkage using a ratio of soft tissue volumes to ICV.

RESULTS

The FH positive alcoholic patients had significantly smaller ICVs than FH negative patients, suggesting smaller premorbid brain growth. Brain shrinkage did not correlate with FH. Late-onset alcoholics showed a greater difference in ICV between FH positive and FH negative patients than early-onset alcoholics. Late-onset FH positive patients also had significantly lower IQ scores than late-onset FH negative patients, and IQ scores were correlated with ICV.

CONCLUSIONS

These data provide evidence that parental alcohol use might increase risk for alcoholism in offspring in part by a genetic and/or environmental effect that might be related to reduced brain growth.

Neuroprotective effects of agmatine against cell damage caused by glucocorticoids in cultured rat hippocampal neurons

In the present study the neuroprotective effects of agmatine against neuronal damage caused by glucocorticoids were examined in cultured rat hippocampal neurons. Spectrophotometric measurements of lactate dehydrogenase activities, beta-tubulin III immunocytochemical staining, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick-end-labeling assay (TUNEL) labeling and caspase-3 assays were carried out to detect cell damage or possible involved mechanisms. Our results show that dexamethasone and corticosterone produced a concentration-dependent increase of lactate dehydrogenase release in 12-day hippocampal cultures. Addition of 100 microM agmatine into media prevented the glucocorticoid-induced increase of lactate dehydrogenase release, an effect also shared with the specific N-methyl-D-aspartate receptor antagonist MK801 and glucocorticoid receptor antagonists mifepristone and spironolactone. Arcaine, an analog of agmatine with similar structure as agmatine, also blocked glucocorticoid-induced increase of lactate dehydrogenase release. Spermine and putrescine, the endogenous polyamine and metabolic products of agmatine without the guanidino moiety of agmatine, have no appreciable effect on glucocorticoid-induced injuries, indicating a structural relevance for this neuroprotection. Immunocytochemical staining with beta-tubulin III confirmed the substantial neuronal injuries caused by glucocorticoids and the neuroprotective effects of agmatine against these neuronal injuries. TUNEL labeling demonstrated that agmatine significantly reduced TUNEL-positive cell numbers induced by exposure of cultured neurons to dexamethasone. Moreover, exposure of hippocampal neurons to dexamethasone significantly increased caspase-3 activity, which was inhibited by co-treatment with agmatine. Taken together, these results demonstrate that agmatine can protect cultured hippocampal neurons from glucocorticoid-induced neurotoxicity, through a possible blockade of the N-methyl-D-aspartate receptor channels or a potential anti-apoptotic property.

A 24 h corticosterone exposure exacerbates excitotoxic insult in rat hippocampal slice cultures independently of glucocorticoid receptor activation or protein synthesis

Elevations in circulating concentrations of glucocorticoids (GC) may increase the expression and/or sensitivity of ionotropic transmitter receptors in brain. For example, recent evidence suggests that acute and chronic GC exposure may alter the number and/or function of N-methyl-D-aspartate (NMDA)-type glutamate receptors, effects that may sensitize the brain to excitotoxic insults. The present studies examined the ability of short-term (24 h) corticosterone (CORT) exposure to potentiate NMDA-induced cytotoxicity in rat hippocampal slice cultures. Additional studies evaluated the role of mineralocorticoid (MR) and glucocorticoid receptor (GR) function, as well as de novo protein synthesis, in potentiation of toxicity by corticosterone exposure. Hippocampal slice cultures were exposed to NMDA (20 microM) for 24 h with cytotoxicity assessed by fluorescent detection of propidium iodide uptake. Exposure to NMDA caused significant propidium iodide uptake in each hippocampal region, while 24 h CORT (0.001-1 microM) exposure alone did not significantly increase propidium iodide uptake. Co-exposure of cultures to CORT and NMDA synergistically increased propidium iodide uptake in each hippocampal region, effects that were prevented by co-exposure to a non-toxic concentration of MK-801 (20 microM). In contrast, 24 h exposure with the MR antagonist spironolactone (1-10 microM), the GR antagonist RU-486 (1-10 microM), or the protein synthesis inhibitor cycloheximide (1 microM) failed to reduce the significant increase in propidium iodide uptake. These data suggest that relatively brief elevations in CORT levels may sensitize the hippocampus to injury independently of GC receptor activity and protein synthesis.

Differential adaptive responses to chronic stress of maternally stressed male mice offspring

It is well established that stress in early life can alter the activity of the hypothalamus-pituitary-adrenal (HPA) axis, but most studies to date have focused on HPA reactivity in response to a single acute stress. The present study addressed whether stress in pregnant mice could influence the adaptive responses of their offspring to chronic stress. Male offspring were exclusively used in this study. Elevated plus maze tests revealed that 14 d of repeated restraint stress (6 h per day; from postnatal d 50-63) significantly increased anxiety-like behavior in maternally stressed mice. NBI 27914, a CRH receptor antagonist, completely eliminated anxiety-related behaviors in a dose-dependent manner, indicating an involvement of a hyperactive CRH system. In accordance with increased anxiety, CRH contents in the hypothalamus and amygdala were significantly higher in these mice. Despite an increased basal activity of the CRH-ACTH system, the combination of chronic prenatal and postnatal stress resulted in a significant reduction of basal plasma corticosterone level, presumably because of a defect in adrenal function. Along with alterations in hypothalamic and hippocampal corticosteroid receptors, it was also demonstrated that a dysfunction in negative feedback inhibition of the HPA axis could be deteriorated by chronic stress in maternally stressed male mice. Taken together, these results indicate that exposure to maternal stress in the womb can affect an animal's coping capacity to chronic postnatal stress.

Transient early postnatal corticosterone treatment of rats leads to accelerated aquisition of a spatial radial maze task and morphological changes in the septohippocampal region

In the present study new-born rats were treated with corticosterone (CORT) between postnatal days 1 and 12. At the age of 16-20 weeks, these animals were tested for spatial learning capacity using an eight-arm radial maze. After behavioral testing, density of cholinergic fibers and sizes of the mossy fiber terminal fields in the hippocampus and number of cholinergic and GABAergic neurons in the septal area were quantified. In the radial arm maze CORT-treated animals initially showed better working memory performance than controls. However, control animals showed a significant improvement of spatial working memory in the last trials and reached similar working memory scores as compared to treated animals. At neither day of training differences in reference memory errors were found between groups. In the diagonal band of Broca, both numbers of cholinergic and GABAergic neurons were increased after corticosterone treatment. The fiber systems in hippocampus showed no significant differences between groups. In conclusion, early postnatal stress induced by CORT administration in neonatal rats results in mild, yet significant morphological and behavioral changes in later life.

BDNF in schizophrenia, depression and corresponding animal models

Understanding the etiology and pathogenesis schizophrenia and depression is a major challenge facing psychiatry. One hypothesis is that these disorders are secondary to a malfunction of neurotrophic factors. Inappropriate neurotrophic support during brain development could lead to structural disorganisation in which neuronal networks are established in a nonoptimal manner. Inadequate neurotrophic support in adult individuals could ultimately be an underlying mechanism leading to decreased capacity of brain to adaptive changes and increased vulnerability to neurotoxic damage. Brain-derived neurotrophic factor (BDNF) is a mediator involved in neuronal survival and plasticity of dopaminergic, cholinergic, and serotonergic neurons in the central nervous system (CNS). In this review, we summarize findings regarding altered BDNF in schizophrenia and depression and animal models, as well as the effects of antipsychotic and antidepressive treatments on the expression of BDNF.

Corticotropin-releasing hormone (CRH) in psychiatry: from stress to psychopathology

Corticotropin-releasing hormone (CRH) plays a central role in the adaptation of the organism to stress. It serves as the main regulating hormone of the hypothalamic pituitary adrenal (HPA) axis, which is activated within seconds after exposure to acute stress. Furthermore, it acts as a neurotransmitter in numerous other brain regions. Globally, CRH leads to a number of metabolic, neuroendocrine and autonomic adaptations, which are vitally important for an adequate reaction to acute stress, but can lead to pathological somatic and psychological effects in chronic stress situations. The adequate functioning of CRH is a delicate equilibrium, which can be permanently disturbed by early experiences of physical or sexual abuse, leading to psychopathology in adulthood. This review discusses the physiological functions of CRH as the stress response hormone. Subsequently, the emerging data on the disruptive effects of early trauma on the CRH system are summarized. The third part is devoted to CRH and HPA axis abnormalities in major depression and other psychiatric disorders. This rapidly accumulating evidence will change our understanding of psychopathology, and might challenge the established classification of psychiatric disorders.

CRH, Stress, and Major Depression: A Psychobiological Interplay

Major depressive disorder (MDD) is a complex disease and is one of the leading causes of disability in our society. The provoking factors are multiple; acute and chronic psychological stress, severe early trauma experiences, somatic disease, and genetic factors all play a role. This review focuses on hyperdrive of corticotropin-releasing hormone (CRH) as the fundamental neurobiological correlate of MDD. CRH plays a key role in the adaptation to acute stress, but chronic CRH hyperdrive leads to a number of disadvantageous emotional and somatic effects. The evidence that the HPA axis is hyperactive in MDD, probably as a result of a primary hyperdrive of CRH, comes from multiple sources: biochemical studies, functional HPA axis tests, neuroimaging and postmortem studies, and clinical trials with HPA axis-related compounds. The liability to develop CRH hyperdrive is probably partly genetic. For a number of relevant genes, transgenic animal studies and human association studies indicate a role in HPA axis regulation and the liability to develop CRH hyperdrive. These data are reviewed. Finally, early adverse experience can produce a lasting effect on HPA axis regulation as well, probably leading to a lifelong tendency to develop chronic CRH hyperdrive in response to stress. This has been shown in a number of animal studies, and recently some data in humans with early trauma have become available as well. Taken together, these findings allow formulating an integrative hypothesis, with CRH hyperdrive at the core, bridging the old dichotomy between biology and psychology in our thinking about MDD.

Neurotrophic factors and CNS disorders: findings in rodent models of depression and schizophrenia

Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are proteins involved in neuronal survival and plasticity of dopaminergic, cholinergic and serotonergic neurons in the central nervous system (CNS). Loss of neurons in specific brain regions has been found in depression and schizophrenia, and this chapter summarizes the findings of altered neurotrophins in animal models of those two disorders under baseline condition and following antidepressive and antipsychotic treatments. In a model of depression (Flinders sensitive line/Flinders resistant line; FSL/FRL rats), increased NGF and BDNF concentrations were found in frontal cortex of female, and in occipital cortex of male 'depressed' FSL compared to FRL control rats. Using the same model, the effects of electroconvulsive stimuli (ECS) and chronic lithium treatment on brain NGF, BDNF and glial cell line-derived neurotrophic factors were investigated. ECS and lithium altered the brain concentrations of neurotrophic factors in the hippocampus, frontal cortex, occipital cortex and striatum. ECS mimic the effects of electroconvulsive therapy (ECT) that is an effective treatment for depression and also schizophrenia. Since NGF and BDNF may also be changed in the CNS of animal models of schizophrenia, we investigated whether treatment with antipsychotic drugs (haloperidol, risperidone, and olanzapine) affects the constitutive levels of NGF and BDNF in the CNS. Both typical and atypical antipsychotic drugs altered the regional brain levels of NGF and BDNF. Other studies also demonstrated that these drugs differentially altered neurotrophin mRNAs. Overall, these studies indicate that alteration of brain level of NGF and BDNF could constitute part of the biochemical alterations induced by antipsychotic drugs.

Effects of dexamethasone on K(+)-evoked glutamate release from rat hippocampal slices

Dexamethasone (DEX) at physiologically elevated (stress) concentration (1 microM) decreased K(+)-evoked glutamate release from rat hippocampal slices under superfusion in the presence of Ca2+. On the contrary 10 microM DEX increased this K(+)-evoked glutamate release while 0.1 microM DEX had no effect. The glucocorticoid antagonist for the "classic" receptor, RU 486, completely reversed the effect of 1 microM DEX. Actinomycin D had no effect. Dexamethasone at 1 microM had no effect on the Ca2(+)-independent (10 mM Mg2+ replacing 1 mM Ca2+) K(+)-evoked glutamate release. Dexamethasone at 1 microM or 10 microM had no effect on the phosphate-activated glutaminase--the key enzyme for the biosynthesis of neurotransmitter glutamate. These results suggest that the effect of DEX on K(+)-evoked glutamate release: (i) depends on its concentration; (ii) is exerted on the Ca2(+)-dependent (neurotransmitter release), at least at physiological stress concentrations; and (iii) is exerted via the classical receptor but is nongenomic.

Amygdalar atrophy in panic disorder patients detected by volumetric magnetic resonance imaging

It has been suggested that the pathophysiology of panic disorder (PD) may involve abnormalities in several brain structures, including the amygdala. To date, however, no study has used quantitative structural neuroimaging techniques to examine amygdalar anatomy in this disorder. Volumetric magnetic resonance imaging (MRI) studies of the amygdalas, hippocampi, and temporal lobes were conducted in 12 drug-free, symptomatic PD patients (six females and six males), and 12 case-matched healthy comparison subjects. Volumetric MRI data were normalized for brain size. PD patients were found to have smaller left-sided and right-sided amygdalar volumes than controls. No differences were found in either hippocampi or temporal lobes. These findings provide new evidence of changes in amygdalar structure in PD and warrant further anatomical and MRI brain studies of patients with this disorder.

Glucocorticoid exposure at the dose used clinically alters cytoskeletal proteins and presynaptic terminals in the fetal baboon brain

Glucocorticoids have been used for 30 years to accelerate fetal lung maturation in human pregnancy at risk of preterm delivery. Exposure to inappropriate levels of steroid, however, leads to altered maturation of the cardiovascular, metabolic and central nervous systems. The effects of betamethasone on neuronal development and function were determined in the fetal baboon brain by examination of cytoskeletal microtubule associated proteins (MAPs) and the presynaptic marker protein synaptophysin. At 0.73 gestation, commencing 28 weeks of gestation, pregnant baboons received four doses of saline (n = 8) or 87.5 microg (kg body weight)(-1) betamethasone I.M. (n = 7) 12 h apart. This dose is equivalent to 12 mg betamethasone administered daily over two consecutive days to a 70 kg woman. Baboons underwent Caesarean section 12 h after the last injection. Paraffin sections of the fetal neocortex and the underlying white matter were labelled immunohistochemically against MAP1B, MAP2abc, MAP2ab and synaptophysin and stained histochemically with hematoxylin-eosin and silver. Tissue staining was quantified morphometrically. Betamethasone exposure resulted in decreased immunoreactivity (IR) of MAP1B by 34.3 % and MAP2abc by 34.1 % (P < 0.05). Loss of MAP2 IR was due to loss of IR of the juvenile isoform MAP2c (P < 0.05). MAP1B and MAP2c are involved in neuritogenesis and neuronal plasticity. Synaptophysin IR was reduced by 51.8 % (P < 0.01). These changes might reflect functional neuronal disturbances because they were not accompanied by an alteration of the density of neurofibrils or neuronal necrosis. These results are in agreement with earlier findings of alterations of cytoskeletal proteins and presynaptic terminals in the fetal sheep brain after betamethasone infusion directly to the fetus and support a common effect of inappropriate fetal exposure to glucocorticoids on neuronal cytoskeleton and synapses in mammalian species.

Victimization and Substance Abuse among Women: Contributing Factors, Interventions, and Implications

Although the literature indicates that there is an association of victimization with substance abuse, there has been limited research focused on understanding and synthesizing the factors that have been identified as contributing to victimization and substance abuse and on interventions designed to address these contributing factors. The purposes of this article are to (a) review the literature on factors related to victimization and substance abuse, (b) review interventions and outcomes, and (c) discuss clinical implications for interventions and research. Results suggest that there is a high rate of co-occurrence of victimization and substance abuse among women, that the factors contributing to victimization and substance abuse are complex, and that there is a lack of treatment models addressing victimization and substance abuse.

Psychological stress and environmental adaptation in enriched vs. impoverished housed rats

In this study, we report differential behavioural and cognitive effects, as assessed in the open-field and the Morris water maze, following psychological stress in enriched vs. impoverished housed rats. Three stress conditions were evaluated: nonstress, mild stress and powerful stress. Mild stress consisted of exposure to an avoidance box but without shock, while in the powerful stress condition animals were exposed to an electric shock. The results revealed distinct effects in the differentially housed animals. Prior exposure to a mild stress enhanced escape performance in the water maze in enriched but not impoverished animals. However, preexposure to powerful stress negatively affected animals from both housing conditions in the water maze task, but with the enriched animals less affected than impoverished animals. In the open-field test, stress preexposure reduced locomotion counts in both the differentially housed animals. In addition, the results showed that the enrichment effect on emotional reactivity in the open-field is long-lasting and persists even after extensive training and housing in standard laboratory conditions. The results are discussed in relation to the nature of the behavioural and learning differences between the differentially housed animals.

Stress activation of glutamate neurotransmission in the prefrontal cortex: implications for dopamine-associated psychiatric disorders

In most psychiatric disorders, stress is the major nongenomic factor that contributes to the expression or exacerbation of acute symptoms, recurrence or relapse after a period of remission, and treatment outcome. Delineation of mechanisms by which stress contributes to these processes is fundamental to understanding the disease process and for improving outcome. In this article, evidence is reviewed to indicate that many central aspects of stress response, including activation of the hypothalmic-pituitary-adrenal (HPA) axis and dopamine neurotransmission, are modulated, and in some cases mediated, by glutamate neurotransmission in the prefrontal cortex (PFC). It is suggested that activation of glutamatergic neurotransmission in the PFC presents a common mechanism by which stress influences normal and abnormal processes that sustain affect and cognition. Although monoamines, in particular dopamine, have been considered the major culprits in the adverse effects of stress in disorders such as addiction and schizophrenia, it is likely that in a vulnerable brain with an underlying PFC pathophysiology, abnormal stress-activated monoaminergic neurotransmission is secondary to anomalies in cortical glutamate neurotransmission. Thus, understanding the contribution of glutamate-mediated processes to stress response through the use of experimental models that involve disrupted PFC function can provide insights to the fundamental pathophysiology of stress-sensitive psychiatric disorders and lead to novel strategies for treatment and prevention.

Early exclusive use of the affected forelimb after moderate transient focal ischemia in rats : functional and anatomic outcome

BACKGROUND AND PURPOSE

Previous work by researchers in our laboratory has shown that in the rat, the exclusive use of the affected forelimb during an early critical period exaggerates lesion volume and retards functional recovery after electrolytic lesions of the forelimb sensorimotor cortex. In the present study, we examined the effects of exclusive use of the affected forelimb after middle cerebral artery occlusion (MCAO).

METHODS

Ischemia of moderate severity was produced in male Long-Evans rats through 45 minutes of occlusion of the left middle cerebral and both common carotid arteries. Exclusive use of either the affected or unaffected forelimb was forced through immobilization of either the ipsilateral (MCAO+ipsi) or contralateral (MCAO+contra) forelimb, respectively, for 10 days in a plaster cast, or the animal was left uncasted (MCAO+nocast). Sham surgeries were performed, and animals were also casted for 10 days or left uncasted. Sensorimotor testing was performed during days 17 to 38. At the end of sensorimotor testing, cognitive performance was tested with use of the Morris water maze. In a separate experiment, temperatures and corticosterone levels were measured during the 10-day period after 45-minute ischemia and casting.

RESULTS

The MCAO+ipsi group performed worse on sensorimotor tasks than the MCAO+contra, MCAO+nocast, and sham groups. Infarct volume was significantly larger in the MCAO+ipsi group than in the sham and MCAO+contra groups but not in the MCAO+nocast group. No group differences were found with the Morris water maze, and no group differences were found in either temperature or plasma corticosterone level.

CONCLUSIONS

The exclusive use of the affected forelimb immediately after focal ischemia has detrimental effects on sensorimotor function that cannot be attributed to hyperthermia or stress.

Chronic social stress reduces dendritic arbors in CA3 of hippocampus and decreases binding to serotonin transporter sites

Male rats housed in mixed-sex groups in a visible burrow system (VBS) form a dominance hierarchy in which subordinate animals show stress-related changes in behavior, endocrine function and neurochemistry. Dominants also appear to be moderately stressed compared to controls, although these animals do not develop the more pronounced behavioral and physiological deficits seen in the subordinates. In the present study, we examined the effects of chronic psychosocial stress on the morphology of Golgi-impregnated CA3 pyramidal neurons. In addition, since serotonin has been implicated in the mechanisms mediating the dendritic remodeling seen with other chronic stress regimens, we used quantitative autoradiography to measure binding to the serotonin transporter (5HTT) in hippocampus and dorsal and median raphe. Chronic social stress led to a decrease in the number of branch points and total dendritic length in the apical dendritic trees of CA3 pyramidal neurons in dominant animals compared to unstressed controls; subordinates also had a decreased number of dendritic branch points. [(3)H]paroxetine binding to the 5HTT was decreased in Ammon's horn in both dominants and subordinates compared to controls, while 5HTT binding remained unchanged in dentate gyrus and raphe. The similarity of the changes in 5HTT binding and dendritic arborization between both groups of VBS animals, despite apparent differences in stressor severity, suggests that these changes may be part of the normal adaptive response to chronic social stress. The mechanisms underlying dendritic remodeling in CA3 pyramidal neurons are likely to involve stress-induced changes in glucocorticoids and in 5HT and other transmitters.