Decrease in cortisol reverses human hippocampal atrophy following treatment of Cushing's disease

Overview of the brain polyamine-stress-response: regulation, development, and modulation by lithium and role in cell survival

An early transient increase in brain polyamine (PA) metabolism, termed the PA-stress-response (PSR), is a common reaction to stressful stimuli, including physical, emotional, and hormonal stressors, with a magnitude related to the stress intensity. In the extreme, traumatic injury can result in an incomplete PSR, with persistent accumulation of putrescine and eventual reduction in the concentrations of the higher polyamines (PAs), spermidine and spermine. Chronic intermittent application of stressors causes a recurrence of the brain PSR, but, in contrast, it leads to habituation of the response in the periphery (liver). Severe continuous stress, however, may lead to accumulation of brain PAs. Long-term inhibition of PA synthesis depletes brain PAs and can result in altered emotional reactivity to stressors. Furthermore, the brain PSR, in contrast to the periphery, can be blocked by a long-term, but not by short-term, treatment with lithium, the most efficacious treatment of manic-depressive illness. The brain PSR is developmentally regulated, and the switch to the mature pattern coincides with the cessation of the "stress hyporesponsive period" in the hypothalamic-pituitary-adrenocortical (HPA) system. In contrast to the brain and liver, the PSR in the adrenal and thymus is down-regulated by acute stressors. Transient up-regulation of the PSR, as in the brain and liver, is implicated in cell survival while its down-regulation is implicated in cell death. Taken together, the findings indicate that the PSR is a dynamic process that varies with the type, intensity, and duration of stressors, and implicate this response as an adaptive mechanism in the reaction to stressful events. Under persistent stressful conditions, however, the PSR may be maladaptive as may be reflected by PA accumulation. This raises the hypothesis that proper regulation of brain PSR may be critical for neuronal function and for an appropriate behavioral response to stressors.

Antidepressant treatment with tianeptine reduces apoptosis in the hippocampal dentate gyrus and temporal cortex

BACKGROUND

Recent clinical and preclinical studies suggest that major depression may be related to impairments of structural plasticity. Consequently, antidepressants may act by restoring altered rates of cell birth or death. Here, we investigated whether the antidepressant tianeptine would affect apoptosis in an animal model of depression, the psychosocially stressed tree shrew.

METHODS

Animals were subjected to a 7-day period of psychosocial stress before the onset of daily administration of tianeptine. Stress continued throughout the 28-day treatment period. In situ end labeling was used to detect apoptosis in hippocampus and adjacent temporal cortex.

RESULTS

Both stress and tianeptine treatment had a region-specific effect. Stress increased apoptosis in the temporal cortex, while it reduced it in the Ammons Horn. No significant effect was observed in the dentate gyrus. Interestingly, tianeptine treatment significantly reduced apoptosis in the temporal cortex and dentate gyrus, both in control and stressed animals, but had no effect in the Ammons Horn. Parallel Fluoro-Jade staining indicated that this apoptosis most likely represents non-neuronal cells.

CONCLUSIONS

This is the first report showing an anti-apoptotic effect of tianeptine in hippocampal subfields and temporal cortex. These findings are consistent with current theories that ascribe enhanced general cell survival to antidepressant action.

Life Stress, Genes, and Depression: Multiple Pathways Lead to Increased Risk and New Opportunities for Intervention

Major depression is a common, severe, chronic, and often life-threatening illness. There is a growing appreciation that, far from being a disease with purely psychological manifestations, major depression is a systemic disease with deleterious effects on multiple organ systems. Stressful life events have a substantial causal association with depression, and there is now compelling evidence that even early life stress constitutes a major risk factor for the subsequent development of depression. The emerging evidence suggests that the combination of genetics, early life stress, and ongoing stress may ultimately determine individual responsiveness to stress and the vulnerability to psychiatric disorders, such as depression. It is likely that genetic factors and life stress contribute not only to neurochemical alterations, but also to the impairments of cellular plasticity and resilience observed in depression. Recent preclinical and clinical studies have shown that signaling pathways involved in regulating cell plasticity and resilience are long-term targets for the actions of antidepressant agents. Agents capable of reversing the hypothesized impairments of cellular resilience, reductions in brain volume, and cell death or atrophy in depression have the potential of becoming new therapeutic classes of antidepressant drugs. Novel cellular targets include agents targeting neurotrophic pathways, glucocorticoid signaling, phosphodiesterase activity, and glutamatergic throughput. The future development of treatments that more directly target molecules in critical CNS (central nervous system) signaling pathways that regulate cellular plasticity thus hold promise as novel, improved long-term treatments for major depression.

Hippocampal volume, spectroscopy, cognition, and mood in patients receiving corticosteroid therapy

BACKGROUND

Hippocampal volume reduction, declarative memory deficits, and cortisol elevations are reported in persons with major depressive disorder; however, data linking cortisol elevations with hippocampal atrophy are lacking. Prescription corticosteroid-treated patients offer an opportunity to examine corticosteroid effects on hippocampal volume and biochemistry and memory in humans.

METHODS

Seventeen patients on long-term prescription corticosteroid therapy and 15 controls of similar age, gender, ethnicity, education, height, and medical history were assessed with magnetic resonance imaging and proton magnetic resonance spectroscopy, the Rey Auditory Verbal Learning Test, Stroop Color Word Test and other neurocognitive measures, the Hamilton Rating Scale for Depression, Young Mania Rating Scale, and Brief Psychiatric Rating Scale.

RESULTS

Compared with controls, corticosteroid-treated patients had smaller hippocampal volumes and lower N-acetyl aspartate ratios, lower scores on the Rey Auditory Verbal Learning Test and Stroop Color Word Test, and higher Hamilton Rating Scale for Depression and Brief Psychiatric Rating Scale scores.

CONCLUSIONS

Patients receiving chronic corticosteroid therapy have smaller hippocampal volumes, lower N-acetyl aspartate ratios, and declarative memory deficits compared with controls. These findings support the idea that corticosteroid exposure appears to be associated with changes in hippocampal volume and functioning in humans.

Progress and controversy in the study of posttraumatic stress disorder

Research on posttraumatic stress disorder (PTSD) has been notable for controversy as well as progress. This article concerns the evidence bearing on the most contentious issues in the field of traumatic stress: broadening of the definition of trauma, problems with the dose-response model of PTSD, distortion in the recollection of trauma, concerns about "phony combat vets," psychologically toxic guilt as a traumatic stressor, risk factors for PTSD, possible brain-damaging effects of stress hormones, recovered memories of childhood sexual abuse, and the politics of trauma.

Stress and plasticity in the limbic system

The adult nervous system is not static, but instead can change, can be reshaped by experience. Such plasticity has been demonstrated from the most reductive to the most integrated levels, and understanding the bases of this plasticity is a major challenge. It is apparent that stress can alter plasticity in the nervous system, particularly in the limbic system. This paper reviews that subject, concentrating on: a) the ability of severe and/or prolonged stress to impair hippocampal-dependent explicit learning and the plasticity that underlies it; b) the ability of mild and transient stress to facilitate such plasticity; c) the ability of a range of stressors to enhance implicit fear conditioning, and to enhance the amygdaloid plasticity that underlies it.

Association of depression with medical illness: does cortisol play a role?

Elevated cortisol in a subset of depressed patients is an enduring and well-replicated finding. Much interest has focused on the possible effects of depression on the hippocampus; however, an emerging body of evidence suggests an association between depression and non-central nervous system illnesses. In this review, data on the effects of depression on the brain and other organ systems sensitive to elevated cortisol are discussed. From searches of the MEDLINE, PSYCHINFO, and Current Contents databases, and other sources, articles were found specifically related to depression and physical changes or medical conditions associated with corticosteroid excess in patients with Cushing's disease, including cognitive impairment, hippocampal atrophy, increased waist-to-hip ratio, bone loss, hypertension, diabetes, peptic ulcers, and hyperlipidemia. Data are strongest for a relationship between elevated cortisol and depression, hippocampal atrophy, cognitive impairment, abdominal obesity, and loss of bone density. Some evidence suggests an association between depression and hypertension, peptic ulcers, and diabetes. Depression does not appear to be associated with hyperlipidemia. The data provide some support for similar health effects in depressed patients and patients with Cushing's disease or the metabolic syndrome; however, additional studies are needed relating systemic effects of depression to cortisol. Limitations of the current literature, treatment implications, and possible directions for future research are discussed.

Relationship between hippocampal volume and memory ability in healthy individuals across the lifespan: review and meta-analysis

Poor memory ability and small hippocampal volume measurements in magnetic resonance images co-occur in neurological patients. Numerous studies have examined the relationship between memory performance and hippocampal volumes in participants without neurological or psychiatric disorders, with widely varying results. Three hypotheses about volume-memory relationships in the normal human brain are discussed: "bigger is always better", a neuropsychological view that volume decreases due to normal aging are accompanied by memory decline, and a developmental perspective that regressive events in development may result in negative correlations between hippocampal volume and memory ability. Meta-analysis of results from 33 studies led to little support for the bigger-is-better hypothesis. A negative relationship between hippocampal volume and memory (smaller is better) was significant for studies with children, adolescents, and young adults. For studies with older adults, the most striking observation was extreme variability: the evidence for a positive relationship between hippocampal size and episodic memory ability in older adults was surprisingly weak. Some of the variability in results from older adults was associated with statistical methods of normalizing for age and head size, which are discussed.

Neurobiology of antidepressant withdrawal: implications for the longitudinal outcome of depression

Inappropriate discontinuation of drug treatment and noncompliance are a leading cause of long-term morbidity during treatment of depression. Increasing evidence supports an association between depressive illness and disturbances in brain glutamate activity, nitric oxide synthesis, and gamma-amino butyric acid. Animal models also confirm that suppression of glutamate N-methyl-D-aspartate receptor activity or inhibition of the nitric oxide-cyclic guanosine monophosphate pathway, as well as increasing brain levels of gamma-amino butyric acid, may be key elements in antidepressant action. Imaging studies demonstrate, for the most part, decreased hippocampal volume in patients with depression, which may worsen with recurrent depressive episodes. Preclinical models link this potentially neurodegenerative pathology to continued stress-evoked synaptic remodeling, driven primarily by the release of glucocorticoids, glutamate, and nitric oxide. These stress-induced structural changes can be reversed by antidepressant treatment. In patients with depression, antidepressant withdrawal after chronic administration is associated with a stress response as well as functional and neurochemical changes. Preclinical data also show that antidepressant withdrawal evokes a behavioral stress response that is associated with increased hippocampal N-methyl-D-aspartate receptor density, with both responses dependent on N-methyl-D-aspartate receptor activation. Drawing from both clinical and preclinical studies, this article proposes a preliminary molecular perspective and hypothesis on the neuronal implications of adherence to and discontinuation of antidepressant medication.

Differential effects of learning on neurogenesis: learning increases or decreases the number of newly born cells depending on their birth date

The hippocampal formation, to which new neurons are added on a daily basis throughout life, is important in spatial learning. Surviving de novo produced cells integrate into the functional circuitry, where they can influence both normal and pathological behaviors. In this study, we examined the effect of the water-maze (a hippocampal-dependent spatial task) on neurogenesis. Learning in this task can be divided into two phases, an early phase during which performance improves rapidly, and a late phase during which asymptotic levels of performance are reached. Here we demonstrate that the late phase of learning has a multifaceted effect on neurogenesis depending on the birth date of new neurons. The number of newly born cells increased contingently with the late phase and a large proportion of these cells survived for at least 4 weeks and differentiated into neurons. In contrast, late-phase learning decreased the number of newly born cells produced during the early phase. This decline in neurogenesis was positively correlated with performance in the water-maze. Thus, rats with the highest de novo cell number were less able to acquire and use spatial information than those with low numbers of new cells. These results show that learning has a complex effect on hippocampal neurogenesis, and reveals a novel mechanism through which neurogenesis may influence normal and pathological behaviors.

Long-term treatment with paroxetine increases verbal declarative memory and hippocampal volume in posttraumatic stress disorder

BACKGROUND

Animal studies have shown that stress is associated with damage to the hippocampus, inhibition of neurogenesis, and deficits in hippocampal-based memory dysfunction. Studies in patients with posttraumatic stress disorder (PTSD) found deficits in hippocampal-based declarative verbal memory and smaller hippocampal volume, as measured with magnetic resonance imaging (MRI). Recent preclinical evidence has shown that selective serotonin reuptake inhibitors promote neurogenesis and reverse the effects of stress on hippocampal atrophy. This study assessed the effects of long-term treatment with paroxetine on hippocampal volume and declarative memory performance in PTSD.

METHODS

Declarative memory was assessed with the Wechsler Memory Scale-Revised and Selective Reminding Test before and after 9-12 months of treatment with paroxetine in PTSD. Hippocampal volume was measured with MRI. Of the 28 patients who started the protocol, 23 completed the full course of treatment and neuropsychological testing. Twenty patients were able to complete MRI imaging.

RESULTS

Patients with PTSD showed a significant improvement in PTSD symptoms with treatment. Treatment resulted in significant improvements in verbal declarative memory and a 4.6% increase in mean hippocampal volume.

CONCLUSIONS

These findings suggest that long-term treatment with paroxetine is associated with improvement of verbal declarative memory deficits and an increase in hippocampal volume in PTSD.

Effects of aging and stress on hippocampal structure and function

Aging is often simply defined as the decline in various body systems and functions (eg, endocrine, cognitive, motor, etc) that occur with the passage of time, although the degree of deterioration can vary greatly across individuals. Increases in average life span have brought a greater focus on brain aging. There is an emphasis on understanding how aging contributes to a decline in brain functions (eg, cognition) because such a decline adversely affects the quality of life. The hippocampus is a key brain structure for cognition and the feedback control of the stress response. Herein we describe how the hippocampus changes with age and we examine the idea that age-related changes in the secretory patterns of the hypothalamic-pituitary adrenal (HPA) axis can contribute to hippocampal aging. We also examine the proposal that cumulative stress, perhaps due to compromised HPA axis function, can contribute to hippocampal aging by subjecting it to exposure to excessive levels of glucocorticoids. The aging hippocampus does not appear to suffer a generalized loss of cells or synapses, although atrophy of the structure may occur in humans. Thus, age-related cognitive impairments are likely related to other neurobiological alterations that could include changes in the signaling, information encoding, and plastic, electrophysiological, or neurochemical properties of neurons or glia. Dysfunction of the HPA axis sometimes occurs with aging, and while excessive glucocorticoids can disrupt cognition as well as hippocampal neuronal integrity, these are not an inevitable consequence of aging. The general preservation of cells and the plastic potential of the hippocampus provide a focus for the development of pharmacological, nutritional, or life-style strategies to combat age-related declines.

Endocrine, cognitive and hippocampal/cortical 5HT 1A/2A receptor changes evoked by a time-dependent sensitisation (TDS) stress model in rats

Post traumatic stress disorder (PTSD) is characterised by hyperarousal, anxiety and amnesic symptoms. Deficits in explicit memory recall have been causally related to volume reductions of the hippocampus and prefrontal cortex. While stress-related glucocorticoid secretion appears involved in this apparent atrophy, there is also evidence for low plasma cortisol in PTSD. Prior exposure to trauma is an important risk factor for PTSD, suggesting a role for sensitisation. Using Sprague-Dawley rats, we studied the effects of a time-dependent sensitisation (TDS) model of stress on spatial memory deficits, 1 week post-stress, using the Morris water maze. Basal and 7-day post-stress plasma corticosterone levels were also determined. Due to the putative role of serotonin in anxiety and stress, and in the treatment of PTSD, hippocampal 5HT(1A) and prefrontal cortex 5HT(2A) radioligand binding studies were performed. TDS stress evoked a marked deficit in spatial memory on day 7 post TDS stress, coupled with significantly depressed plasma corticosterone levels. Cognitive and endocrine changes at day 7 post stress were associated with a significant increase in receptor density (B(max)) and a significant decrease in receptor affinity (K(d)) for hippocampal 5HT(1A) receptors. The B(max) of prefrontal cortex 5HT(2A) receptors were unaffected, but K(d) was significantly increased. We conclude that TDS stress evokes cognitive and endocrine changes characteristic of PTSD. Moreover, TDS stress induces diverse adaptive 5HT receptor changes in critical brain areas involved in emotion and memory that may underlie the effect of stress on cognitive function.

Chronic social stress: effects on limbic brain structures

Different types of stressors are known to activate distinct neuronal circuits in the brain. Acute physiological stimuli that are life threatening and require immediate reactions lead to a rapid stimulation of brainstem and hypothalamus to activate efferent visceral pathways. In contrast, psychological stressors activate higher-order brain structures for further interpretations of the perceived endangerment. Common to the later multimodal stressors is that they need cortical processing and, depending on previous experience or ongoing activation, the information is assembled within limbic circuits connecting, e.g., the hippocampus, amygdala and prefrontal cortex to induce neuroendocrine and behavioral responses. In view of the fact that stressful life events often contribute to the etiology of psychopathologies such as depressive episodes, several animal models have been developed to study central nervous mechanisms that are induced by stress. The present review summarizes observations made in the tree shrew chronic psychosocial stress paradigm with particular focus on neurotransmitter systems and structural changes in limbic brain regions.

Mood disorders and allostatic load

The brain controls both the physiologic and the behavioral coping responses to daily events as well as major stressors, and the nervous system is itself a target of the mediators of those responses through circulating hormones. The amygdala and hippocampus interpret what is stressful and regulate appropriate responses. The amygdala becomes hyperactive in posttraumatic stress disorder (PTSD) and depressive illness, and hypertrophy of amygdala nerve cells is reported after repeated stress in an animal model. The hippocampus expresses adrenal steroid receptors. It undergoes atrophy in several psychiatric disorders and responds to repeated stressors with decreased dendritic branching and reduction in number of neurons in the dentate gyrus. Stress promotes adaptation ("allostasis"), but a perturbed diurnal rhythm or failed shutoff of mediators after stress ("allostatic state") leads, over time, to wear and tear on the body ("allostatic load"). Neural changes mirror the pattern seen in the cardiovascular, metabolic, and immune systems, that is, short-term adaptation versus long-term damage. Allostatic load leads to impaired immunity, atherosclerosis, obesity, bone demineralization, and atrophy of nerve cells in brain. Allostatic load is seen in major depressive illness and may also be expressed in other chronic anxiety disorders such as PTSD and should be documented.

Gedächtnisleistung im Alter:

Zusammenfassung. Das höhere Lebensalter ist durch zahlreiche Veränderungen des Hormonsystems charakterisiert. Besonders markant ist die Abnahme der Sexualsteroidhormone (Östradiol, Progesteron, Testosteron, DHEA), während die basalen Spiegel des “Stresshormons“ Cortisol stabil bleiben oder leicht ansteigen. Die vorliegende Übersichtsarbeit diskutiert die Relevanz dieser hormonellen Veränderungen für Funktion und Struktur des Gehirns am Beispiel der Gedächtnisleistung im höheren Lebensalter. Bei älteren Frauen wurden wiederholt gedächtnisverbessernde und neuroprotektive Effekte von Östradiol berichtet. Inwieweit und in welche Richtung Progesteron die Östrogeneffekte moduliert, ist noch unklar, da sowohl synergistische als auch antagonistische Effekte berichtet wurden. Die Rolle des Testosterons für die Gedächtnisleistung des alternden Mannes ist bisher kaum untersucht. Mehrere Studien haben hingegen gezeigt, dass DHEA bei gesunden älteren Männern und Frauen keine positiven Effekte auf die Gedächtnisleistung ausübt. Das Nebennierenrindenhormon Cortisol verschlechtert akut Leistungen des Arbeitsgedächtnisses und des deklarativen Gedächtnisses. Darüber hinaus gibt es vermehrt Hinweise darauf, dass erhöhte basale Cortisolspiegel im Alter sowohl zu einer Verschlechterung der Gedächtnisleistung als auch zu einer Verringerung des Hippocampusvolumens führen. Zusammengenommen verdeutlichen diese Befunde, dass Steroidhormone die Struktur und Funktion des menschlichen zentralen Nervensystems nachhaltig beeinflussen.

Chronic administration of corticosterone impairs spatial reference memory before spatial working memory in rats

Corticosterone (CORT), the predominant glucocorticoid in rodents, elevated for 21 days damages hippocampal subregion CA3. We tested the hypothesis that CORT would impair spatial memory, a hippocampal function. In each of the three experiments, rats received daily, subcutaneous injections of either CORT (26.8 mg/kg body weight in sesame oil) or sesame oil vehicle alone (VEH). CORT given for 21 or 56 days effectively attenuated body weight gain and reduced selective organ and muscle weights. All behavioral testing was done on tasks that are minimally stressful and avoid deprivation. For each experiment, testing commenced 24h after the last injection. CORT given for 21 days did not impair spatial working memory in the Y-maze (Experiments 1 and 2). After 56-day administration of CORT, spatial working memory was impaired in the Y-maze (Experiment 2). CORT given for 21 days also failed to impair spatial working memory in the Barnes maze (Experiment 3). However, in trials that depended solely on reference memory, the VEH group improved in performance, whereas the CORT group did not. In conclusion, CORT elevated over a period of 21 days did not impair spatial working memory, but impaired the formation of a longer-term form of memory, most likely reference memory. Impairments in spatial working memory are seen only after longer durations of CORT administration.

HPA axis and memory

The hormones of the hypothalamus-pituitary-adrenal (HPA) axis influence memory in situations of acute and chronic stress. The present review tries to summarize the current state of knowledge by describing the enhancing as well as the impairing effects of stress or glucocorticoid (GC) treatment documented in animals and humans. GCs secreted during the acquisition of a stressful task facilitate consolidation. However, acute stress (or GC treatment) unrelated to the task impairs performance. The effects of acute stress are additionally modulated by gender, age and the emotional valence of the learning material. Chronic stress in rodents has mostly impairing effects on memory and hippocampal integrity. However, other regions of the brain, such as the prefrontal cortex, are also sensitive to stress. In humans, similar observations have been reported in several patient populations as well as in older subjects. The potential to reverse these effects using behavioural or pharmacological approaches needs to be explored.

Enhancing neuronal plasticity and cellular resilience to develop novel, improved therapeutics for difficult-to-treat depression

There is growing evidence from neuroimaging and ostmortem studies that severe mood disorders, which have traditionally been conceptualized as neurochemical disorders, are associated with impairments of structural plasticity and cellular resilience. It is thus noteworthy that recent preclinical studies have shown that critical molecules in neurotrophic signaling cascades (most notably cyclic adenosine monophosphate [cAMP] response element binding protein, brain-derived neurotrophic factor, bcl-2, and mitogen activated protein [MAP] kinases) are long-term targets for antidepressant agents and antidepressant potentiating modalities. This suggests that effective treatments provide both trophic and neurochemical support, which serves to enhance and maintainnormal synaptic connectivity, thereby allowing the chemical signal to reinstate the optimal functioning of critical circuits necessary for normal affective functioning. For many refractory patients, drugs mimicking "traditional" strategies, which directly or indirectly alter monoaminergic levels, may be of limited benefit. Newer "plasticity enhancing" strategies that may have utility in the treatment of refractory depression include N-methyl-D-aspartate antagonists, alpha-amino-3-hydroxy-5-methylisoxazole propionate (AMPA) potentiators, cAMP phosphodiesterase inhibitors, and glucocorticoid receptor antagonists. Small-molecule agents that regulate the activity f growth factors, MAP kinases cascades, and the bcl-2 family of proteins are also promising future avenues. The development of novel, nonaminergic-based therapeutics holds much promise for improved treatment of severe, refractory mood disorders.

The role of insulin resistance in the pathogenesis of Alzheimer's disease: implications for treatment

An emerging body of evidence suggests that an increased prevalence of insulin abnormalities and insulin resistance in Alzheimer's disease may contribute to the disease pathophysiology and clinical symptoms. It has long been known that insulin is essential for energy metabolism in the periphery. In the past 2 decades, convergent findings have begun to demonstrate that insulin also plays a role in energy metabolism and other aspects of CNS function. Investigators reported 20 years ago that insulin and insulin receptors were densely but selectively expressed in the brain, including the medial temporal regions that support the formation of memory. It has recently been demonstrated that insulin-sensitive glucose transporters are localised to the same regions supporting memory and that insulin plays a role in memory functions. Collectively, these findings suggest that insulin may contribute to normal cognitive functioning and that insulin abnormalities may exacerbate cognitive impairments, such as those associated with Alzheimer's disease. Insulin may also play a role in regulating the amyloid precursor protein and its derivative beta-amyloid (Abeta), which is associated with senile plaques, a neuropathological hallmark of Alzheimer's disease. It has been proposed that insulin can accelerate the intracellular trafficking of Abeta and interfere with its degradation. These findings are consistent with the notion that insulin abnormalities may potentially influence levels of Abeta in the brains of patients with Alzheimer's disease. The increased occurrence of insulin resistance in Alzheimer's disease and the numerous mechanisms through which insulin may affect clinical and pathological aspects of the disease suggest that improving insulin effectiveness may have therapeutic benefit for patients with Alzheimer's disease. The thiazolidinedione rosiglitazone has been shown to have a potent insulin-sensitising action that appears to be mediated through the peroxisome proliferator-activated receptor-gamma (PPAR-gamma). PPAR-gamma agonists, such as rosiglitazone, also have anti-inflammatory effects that may be of therapeutic benefit in patients with Alzheimer's disease. This review presents evidence suggesting that insulin resistance plays a role in the pathophysiology and clinical symptoms of Alzheimer's disease. Based on this evidence, we propose that treatment of insulin resistance may reduce the risk or retard the development of Alzheimer's disease.

Improvement in learning associated with increase in hippocampal formation volume

BACKGROUND

Patients with spontaneous Cushing's syndrome are exposed to elevated levels of endogenous cortisol for months to years. We previously reported that hippocampal formation volume (HFV) increased in such patients after treatment lowered cortisol to normal concentrations. In the present study, we examined whether the structural increase was associated with improvement in cognition.

METHODS

Twenty-four patients with Cushing's disease were studied before treatment and following treatment. Magnetic resonance imaging was used to measure HFV and caudate head volume. Neuropsychologic tests of verbal cognition, learning, and memory were also administered.

RESULTS

Patients showed variability in improvement on neuropsychologic test performance. After partialing out age, education, duration of illness, and time since surgical treatment, greater improvement in word list learning, as measured by the Selective Reminding Test was associated with greater increase in HFV (r =.59, p <.02). There were no significant associations between improvement in paragraph or paired-word learning or memory tasks and increase in HFV. Improvement in other verbal tasks not strongly dependent on the hippocampus were not significantly associated with increase in HFV.

CONCLUSIONS

After cortisol levels decline to normal concentrations, structural volumetric increase in HFV is accompanied by functional improvement in learning of unrelated words.

Acute and chronic restraint stress alter the incidence of social conflict in male rats

Stress and elevated stress hormone levels are known to alter cognition, learning, memory, and emotional responses. Three weeks of chronic stress or glucocorticoid exposure is reported to alter neuronal morphology in the hippocampus, the amygdala, and the prefrontal cortex, and to decrease neurogenesis in the dentate gyrus. Here we examine the effects of acute and chronic restraint stress exposure on the incidence of emotional responses throughout a 3-week period among adult rat conspecifics. Our data indicate that acute restraint stress (i.e., a single 6-h exposure) results in a significant reduction in aggressive conflicts among stressed males compared to experimental controls. In contrast, on Days 14 and 21, repeatedly restrained rats exhibited significantly more aggressive behaviors than controls. Blood samples taken 18 h after the last restraint session indicate that plasma concentrations of the stress hormone corticosterone (CORT) in stressed rats were equivalent to those of unstressed rats; however, the number of individually initiated aggressive acts observed positively correlated with plasma CORT measures taken at the end of the study. In contrast to studies of psychosocial stress or intruder paradigms, here we observe spontaneous emotional responses to an uncontrollable stressor in the homecage. This study provides a novel examination of the effects of chronic restraint stress on emotional responses in the home environment among cagemates. These results indicate that acute and chronic restraint stress alter the incidence of aggression, and emphasize the relevance of this model of chronic stress to studies of stress-responsive disorders characterized by aggressive behavior.

Recent developments in the psychobiology and pharmacotherapy of depression: optimising existing treatments and novel approaches for the future

Effective antidepressants include monoamine oxidase inhibitors and tricyclic antidepressants, selective serotonin re-uptake inhibitors and novel agents, including serotonin and noradrenaline re-uptake inhibitors. Although effective, current treatments most often produce partial symptomatic improvement (response) rather than symptom resolution and optimal functioning (remission). While current pharmacotherapies target monoaminergic systems, different symptoms of major depressive disorder (MDD) may have distinct neurobiological underpinnings and other neurobiological systems are likely involved in the pathogenesis of MDD. In this article a review of current pharmacotherapeutic options for MDD, current understanding of the neurobiology and pathogenesis of MDD and a review of new and promising directions in pharmacological research will be provided. It is generally accepted that no single neurotransmitter or system is responsible for the dysregulation found in MDD. While agents that affect monoaminergic systems will likely continue to be first-line treatments for MDD for the foreseeable future, a number of new and novel agents, including corticotropin-releasing factor antagonists, substance P antagonists and antiglucocorticoids show considerable promise for refining treatment options. In order to better understand the neurobiology and treatment response of MDD, it is probable that more sophisticated theory-driven typologies of MDD will have to be developed.

Corticosteroids: sculptors of the hippocampal formation

The influence of corticosteroids on hippocampus-dependent learning and memory processes is now indisputable. On the other hand, closer scrutiny of early studies together with interpretations from newer studies would suggest that the proposition that corticosteroid-induced hippocampal cell death accounts fully for the associated cognitive deficits is only partially correct. Firstly, it is now clear that a specific sub-population of hippocampal neurons, the granule cells of the dentate gyrus, is more sensitive to changes in the corticosteroid environment; this fact raises the interesting question of what might be the unique properties of granule cells that render them more vulnerable to these hormones, since virtually all hippocampal cells express corticosteroid receptors. Secondly, from a critical analysis of the available data, the picture that emerges is that corticosteroids, by acting through two distinct receptors, influence not only cell birth and death, but probably also cell differentiation. Mineralocorticoid receptor (MR) occupation appears to be essential for the survival of existing and newly generated granule neurons. In contrast, while glucocorticoid receptors (GR) can induce loss of neurons in the absence of MR activation, it appears that their occupation usually results in less drastic effects involving only dendritic atrophy and loss of synaptic contacts. This revised scheme of corticosteroid actions on hippocampal structure should explain earlier observations that many of the cognition- impairing effects of corticosteroids are reversible.

Prednisone induces cognitive dysfunction, neuronal degeneration, and reactive gliosis in rats

BACKGROUND

High glucocorticoid serum levels and prednisone (PDN) therapy have been associated with depression, posttraumatic stress disorder, and some types of cognitive dysfunction in humans.

OBJECTIVE

The aim of this study was to assess whether chronic (90 days) PDN administration produces disturbance in learning and memory retention associated with neuronal degeneration and cerebral glial changes.

METHODS

Male Wistar rats were studied. Controls received 0.1 ml distilled water vehicle orally. The PDN group was treated orally with 5 mg/kg/d PDN, which is equivalent to moderate doses used in clinical settings. Learning and memory retention were assessed with the Morris water maze. The index of degenerated neurons as well as the number and cytoplasmic transformation of astrocytes and microglia cells were evaluated in the prefrontal cortex and the CA1 hippocampus.

RESULTS

PDN-treated rats showed a significant delay of 20% in learning and memory retention as compared with controls. In addition, in the PDN group, the neuronal degeneration index was two times higher in the prefrontal cortex, and approximately 10 times higher in the CA1 hippocampus, than in control animals. The number and cytoplasmic transformation of astrocytes were also significantly higher in the PDN group than in control animals. In the PDN-treated group, isolectin-B4-labeled microglia cells were higher in the prefrontal cortex but not in the hippocampus.

CONCLUSION

These results suggest that chronic exposure to PDN produces learning and memory impairment, reduces neural viability, and increases glial reactivity in cerebral regions with these cognitive functions.

Salivary cortisol day profiles in elderly with mild cognitive impairment

It is unknown whether hypothalamus-pituitary-adrenal (HPA) axis dysfunction is associated with the memory impairments observed among elderly participants with mild cognitive impairment (MCI), a group considered at increased risk for Alzheimer's disease (AD). Therefore, salivary cortisol levels were measured at six points over the course of the day while at-home in MCI participants (n=16), normal elderly (n=28), and young controls (n=14). Results revealed that MCI participants did not show elevated salivary cortisol levels. The 9 a.m. cortisol level of the MCI group was significantly lower than the 9 a.m. level of the young controls, but did not differ from those of the normal elderly group. In contrast to the other two groups, within the MCI group mean cortisol levels were inversely related to immediate recall of paragraphs. No association was observed between mean cortisol levels and performance in paired associates and digit span. Whether cortisol levels, in conjunction with other factors, such as hippocampal volume, will lead to improved prediction of future decline to AD in participants with MCI remains to be established in longitudinal studies.

Neural and behavioral substrates of mood and mood regulation

A review of behavioral and neurobiological data on mood and mood regulation as they pertain to an understanding of mood disorders is presented. Four approaches are considered: 1) behavioral and cognitive; 2) neurobiological; 3) computational; and 4) developmental. Within each of these four sections, we summarize the current status of the field and present our vision for the future, including particular challenges and opportunities. We conclude with a series of specific recommendations for National Institute of Mental Health priorities. Recommendations are presented for the behavioral domain, the neural domain, the domain of behavioral-neural interaction, for training, and for dissemination. It is in the domain of behavioral-neural interaction, in particular, that new research is required that brings together traditions that have developed relatively independently. Training interdisciplinary clinical scientists who meaningfully draw upon both behavioral and neuroscientific literatures and methods is critically required for the realization of these goals.

Chronic stress induces contrasting patterns of dendritic remodeling in hippocampal and amygdaloid neurons

The hippocampus and the amygdala are essential components of the neural circuitry mediating stress responses. The hippocampus, which provides negative feedback regulation of the stress response, is particularly vulnerable to degenerative changes caused by chronic stress. Unlike the hippocampus, relatively little is known about how stress affects the amygdala and the nature of its role in the stress response. Hence, we examined the effects of two different models of chronic stress on hippocampal and amygdaloid neuronal morphology in rats. In agreement with previous reports, chronic immobilization stress (CIS) induced dendritic atrophy and debranching in CA3 pyramidal neurons of the hippocampus. In striking contrast, pyramidal and stellate neurons in the basolateral complex of the amygdala exhibited enhanced dendritic arborization in response to the same CIS. Chronic unpredictable stress (CUS), however, had little effect on CA3 pyramidal neurons and induced atrophy only in BLA bipolar neurons. These results indicate that chronic stress can cause contrasting patterns of dendritic remodeling in neurons of the amygdala and hippocampus. Moreover, CIS, but not CUS, reduced open-arm activity in the elevated plus-maze. These findings raise the possibility that certain forms of chronic stress, by affecting specific neuronal elements in the amygdala, may lead to behavioral manifestations of enhanced emotionality. Thus, stress-induced structural plasticity in amygdala neurons may provide a candidate cellular substrate for affective disorders triggered by chronic stress.

Penetration of endogenous steroid hormones corticosterone, cortisol, aldosterone and progesterone into the brain is enhanced in mice deficient for both mdr1a and mdr1b P-glycoproteins

Numerous investigations have confirmed an important role for multidrug-resistance gene 1-type P-glycoproteins (MDR1-type P-gps) in the blood-brain barrier, protecting the brain against the accumulation of a wide range of toxic xenobiotics and drugs. Several studies have provided evidence in vitro that certain steroid hormones are transported by MDR1-type P-gps; however, the question of whether this might also apply to the situation in vivo still remained to be determined. We used mice deficient for both murine mdr1a and mdr1b P-gps [mdr1a/1b(-/-)] to determine the uptake of [3H]-cortisol, [3H]-corticosterone, [3H]-aldosterone and [3H]-progesterone into the plasma, brain, testes, liver, spleen, pituitary and adrenal glands. We provide evidence that the access of the endogenous steroid hormones corticosterone, cortisol and aldosterone is regulated by MDR1-type P-gps in vivo. As peripherally administered steroid hormones accumulate in the brain of mice deficient for MDR1-type P-gps, mdr1a/1b proteins are likely to transport these hormones out of the brain, providing a kinetic barrier to their entry. Intracerebral progesterone concentrations are influenced by MDR1-type P-gp function as well; however, the effects are only small. In addition, all four endogenous glucocorticoid hormones accumulated in the testes of mdr1a/1b(-/-) mice. Our findings underline the importance of MDR1-type P-gps as an endogenous barrier system controlling the access of endogenous steroid hormones at the blood-brain barrier to maintain homeostatic control and to protect central nervous system neurones.

Morphological brain changes in depression: can antidepressants reverse them?

Structural neuroimaging and postmortem histopathological studies of the brain have revealed morphological changes in cortical and subcortical regions in individuals diagnosed with depression. Moreover, these regions are known to be functionally altered in mood disorders. This indicates that the morphological changes might be directly involved in the pathophysiology of depression, and implies that antidepressants may be able to regulate or reverse the detected structural abnormalities. Work with animal models has shown that antidepressants are capable of inducing structural alterations in dendrites and axons and changes in the numbers of neural cells. However, there have been no studies in the human brain that have directly addressed whether antidepressant treatment can reverse or regulate the depression-related structural changes. Nevertheless, experience with lithium in bipolar disorder and antipsychotics in schizophrenia suggests that treatment with psychotropic drugs can result in structural changes that are consistent with reversion towards normal values. Clearly, ascertaining the role of the reversal of structural changes in the therapeutic actions of antidepressants will require further longitudinal studies and careful comparisons between those patients with mood disorder who are treated with antidepressants and those who are not.

Stress-induced dynamic changes in mouse brain polyamines. Role in behavioral reactivity

Recent findings indicate that rapid and transient changes in polyamine metabolism, termed the polyamine-stress-response, may occur repeatedly in the brain after chronic intermittent stress. Here, we sought to examine the effects of chronic intermittent restraint stress, or of daily intraperitoneal dexamethasone injections on polyamine concentrations in the hippocampus of adult male C57BL/6 mice. Additionally, we studied the effects of alpha-difluoromethylornithine, an irreversible ornithine decarboxylase inhibitor, on stress-induced changes in polyamines and on behavioral reactivity to novelty stress measured in an open-field arena. As previously observed, following a single stress episode putrescine concentration increased transiently, but the polyamines spermidine and spermine remained unchanged. Following chronic restraint stress, putrescine concentration was increased after each daily stress episode with the largest increase observed after the 4th episode, while spermidine was increased just after the 2nd and 4th episodes and spermine only after the 4th daily episode. In contrast, all polyamine concentrations were increased after 10 injections of either dexamethasone or vehicle (0.9% NaCl). A 14-day course of alpha-difluoromethylornithine treatment resulted in a complete putrescine depletion and over 50% reduction in polyamines, and led to changes in open field activity indicative of altered emotional behavior.

CONCLUSIONS

(a) while putrescine concentration increases in the hippocampus after each restraint stress episode, spermidine and spermine undergo a delayed but transient increase; (b) in contrast, chronic dexamethasone treatment may lead to a permanent increase in the concentrations of all polyamines and; (c) chronic alpha-difluoromethylornithine treatment reduces brain polyamine concentrations and modulates emotional reactivity to novelty stress. The study indicates that the brain polyamine-stress-response is a dynamic process that varies with the type, intensity and length of stressful stimuli, and implicates this response as an adaptive mechanism in the reaction to stressors.

The neurobiology and neuroendocrinology of stress. Implications for post-traumatic stress disorder from a basic science perspective

Stress is a condition of the mind and a factor in the expression of disease that differs among individuals. In post-traumatic stress disorder (PTSD), traumatic events can create a long-lasting state of physiologic reactivity that amplifies and exacerbates the effects of daily life events. The elevated activities of physiologic systems lead to wear and tear, called "allostatic load." It reflects not only the impact of life experiences but also of genes, individual life-style habits (e.g., diet, exercise, and substance abuse), and developmental experiences that set life-long patterns of behavior and physiologic reactivity. Hormones associated with stress and allostatic load protect the body in the short run and promote adaptation, but in the long run allostatic load causes changes in the body that lead to disease.

The stressed hippocampus, synaptic plasticity and lost memories

Stress is a biologically significant factor that, by altering brain cell properties, can disturb cognitive processes such as learning and memory, and consequently limit the quality of human life. Extensive rodent and human research has shown that the hippocampus is not only crucially involved in memory formation, but is also highly sensitive to stress. So, the study of stress-induced cognitive and neurobiological sequelae in animal models might provide valuable insight into the mnemonic mechanisms that are vulnerable to stress. Here, we provide an overview of the neurobiology of stress memory interactions, and present a neural endocrine model to explain how stress modifies hippocampal functioning.

Residual symptoms in depression an emerging therapeutic concept

Cushing's syndrome is due to chronic glucocorticoid excess that may have various etiologies. The most common endogenous form is pituitary-dependent bilateral adrenal hyperplasia, which is termed Cushing's disease. Major depression occurs in more than half of the cases. The presence of depressive symptoms connotes severity of clinical presentation and, in patients with hypothalamic-pituitary forms, entails prognostic value. Medical treatment may be used while awaiting more definitive solutions for the illness by surgery. The inhibitors of steroid production (e.g., ketoconazole, metyrapone and aminoglutethimide), rather than antidepressant drugs, are generally successful in lifting depression as well as other disabling symptoms. Since central serotonergic regulation could have a role in the course of Cushing's disease, serotonin antagonists (e.g., cyproheptadine, ritanserin and ketanserin) have been employed. Findings related to the pharmacological response of depression in Cushing's disease were found to have implications for the pathophysiology of depression and the potential involvement of the hypothalamic-pituitary-adrenal axis (HPA axis) in resistance and tolerance to antidepressant drugs. The use of serotonergic drugs in Cushing's disease may yield important insights in the understanding of serotonergic regulation both in Cushing's disease and in the HPA axis in nonendocrine major depression.

Depression: perspectives from affective neuroscience

Depression is a disorder of the representation and regulation of mood and emotion. The circuitry underlying the representation and regulation of normal emotion and mood is reviewed, including studies at the animal level, human lesion studies, and human brain imaging studies. This corpus of data is used to construct a model of the ways in which affect can become disordered in depression. Research on the prefrontal cortex, anterior cingulate, hippocampus, and amygdala is reviewed and abnormalities in the structure and function of these different regions in depression is considered. The review concludes with proposals for the specific types of processing abnormalities that result from dysfunctions in different parts of this circuitry and offers suggestions for the major themes upon which future research in this area should be focused.

Persistent cognitive impairment following surgical treatment of Cushing's syndrome

Chronic exposure to elevated glucocorticoid (GC) levels in Cushing's syndrome (CS) is associated with deficits in cognitive function. It has already been shown that CS patients scored significantly lower than controls on several aspects of cognitive function (J. Int. Neuropsychol. Soc. 6 (2000) 20). In the present study, 13 subjects who presented with CS were investigated one year after surgical treatment to determine the extent to which the effects of hypercortisolism on cognitive function are reversible. Subjects were evaluated with a battery of tasks, similar to the original battery of a year earlier and including tests of attention, visuospatial processing, memory, reasoning and verbal fluency. Except for one task of visual organization, the results showed little change in performance, suggesting that prolonged exposure to high levels of GC can cause long-lasting deleterious effects on cognitive function. The data suggest that correction of hypercortisolism is not necessarily correlated with short-term improvement in cognitive function.

Psychiatric disorders associated with Cushing's syndrome. Epidemiology, pathophysiology and treatment

Cushing's syndrome is caused by a chronic excess of glucocorticoids. A number of psychiatric and psychological disturbances may be associated with the condition, regardless of its aetiology. Major depression is the most common comorbid disorder. Other psychopathological aspects of Cushing's syndrome in adults include mania, anxiety disorders and cognitive dysfunction. The presence of depression connotes a severe clinical presentation and, in patients with hypothalamic-pituitary forms of Cushing's syndrome, is prognostically useful. Inhibitors of corticosteroid production (e.g. ketoconazole, metyrapone, aminoglutethimide), rather than antidepressant drugs, are generally successful in relieving depressive symptoms, as well as other disabling symptoms. These drugs can be used to control symptoms prior to surgical treatment of Cushing's syndrome. Long-standing hypercortisolism may cause some degree of irreversible pathological damage and induce highly individualised affective responses based on each patient's psychological assets and liabilities. As a result, upon normalisation of cortisol levels, treatment may still be required, and should encompass both psychotherapeutic strategies (particularly cognitive-behavioural therapies that have been found to be effective in affective disorders) and psychotropic drug treatment [antidepressants such as tricyclic agents and selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitors]. In patients with severe anxiety, benzodiazepines (e.g. clonazepam in small doses) may also be helpful.

Chronic psychosocial stress impairs learning and memory and increases sensitivity to yohimbine in adult rats

BACKGROUND

It is well known that intense and prolonged stress can produce cognitive impairments and hippocampal damage and increase noradrenergic activity in humans. This study investigated the hypothesis that chronic psychosocial stress would affect behavior, drug sensitivity, and hippocampal-dependent learning and memory in rats. The work provides a novel connection between animal and human studies by evaluating the effects of stress on a rat's response to yohimbine, an alpha(2) adrenergic receptor antagonist.

METHODS

Rats were exposed to a cat for 5 weeks and randomly housed with a different group of cohorts each day (psychosocial stress). The effects of the stress manipulations were then assessed on open field behavior, spatial learning and memory in the radial arm water maze and the behavioral response to a low dose of yohimbine (1.5 mg/kg).

RESULTS

Stressed rats displayed impaired habituation to a novel environment, heightened anxiety, and increased sensitivity to yohimbine. In addition, the stressed rats exhibited impaired learning and memory.

CONCLUSIONS

There are commonalities between the current findings on stressed rats and from studies on traumatized people. Thus, psychosocial stress manipulations in rats may yield insight into the basis of cognitive and neuroendocrine disturbances that commonly occur in people with anxiety disorders.

Stress, memory, and the hippocampus: can't live with it, can't live without it

Since the 1968s discovery of receptors for stress hormones (corticosteroids) in the rodent hippocampus, a tremendous amount of data has been gathered on the specific and somewhat isolated role of the hippocampus in stress reactivity. The hippocampal sensitivity to stress has also been extended in order to explain the negative impact of stress and related stress hormones on animal and human cognitive function. As a consequence, a majority of studies now uses the stress-hippocampus link as a working hypothesis in setting up experimental protocols. However, in the last decade, new data were gathered showing that stress impacts on many cortical and subcortical brain structures other than the hippocampus. The goal of this paper is to summarize the four major arguments previously used in order to confirm the stress-hippocampus link, and to describe new data showing the implication of other brain regions for each of these previously used arguments. The conclusion of this analysis will be that scientists should gain from extending the impact of stress hormones to other brain regions, since hormonal functions on the brain are best explained by their modulatory role on various brain structures, rather than by their unique impact on one particular brain region.

Metyrapone reveals that previous chronic stress differentially impairs hippocampal-dependent memory

Chronic stress facilitates fear conditioning in rats with hippocampal neuronal atrophy and in rats in which the atrophy is prevented with tianeptine, a serotonin re-uptake enhancer. The purpose of this study was to determine whether the lack of dissociation between fear conditioning performance and hippocampal integrity was masked by the presence of endogenous corticosteroids during training. As in previous studies, rats were stressed by daily restraint (6 h/day for 21 days), trained in the conditioning chamber (day 23), and then assessed for conditioned fear (day 25) at a time when hippocampal dendritic atrophy persists. On the training day, half of the control and stressed rats were. injected with metyrapone to reduce corticosterone release. Two hours later, two paired or unpaired presentations of tone and footshock were delivered. Although metyrapone reduced conditioned fear in all rats, only stressed rats showed dissociated fear conditioning (i.e. tone conditioning was reduced while contextual conditioning was eliminated). Chronically stressed rats, regardless of metyrapone treatment displayed more rearing in the open field when tested immediately after the completion of fear conditioning. These data support the hypothesis that increased emotionality and enhanced fear conditioning exhibited by chronically stressed rats maybe due to endogenous corticosterone secretion at the time of fear conditioned training. Moreover,these data suggest that chronic stress impairs hippocampal-dependent processes more robustly than hippocampal-independent processes after metyrapone to reduce corticosterone secretion during aversive training.

PET measurement of the influence of corticosteroids on serotonin-1A receptor number

BACKGROUND

The hypothalamic-pituitary-adrenal (HPA) axis and serotonergic system interact functionally. The modulatory effect of corticosteroids on 5-HT(1A) receptor number and function has been repeatedly demonstrated in preclinical studies suggesting that raised corticosteroid levels decrease 5-HT(1A) receptor number and function in the hippocampus.

METHODS

We used positron emission tomography (PET) to quantify the number of 5-HT(1A) receptors in two studies, the first in normal subjects given a single dose of hydrocortisone using a random-order, double-blind, placebo-controlled design and second in patients treated long-term with corticosteroids.

RESULTS

We did not find that exposure to elevated levels of corticosteroids in either the short or long term alters 5-HT(1A) receptor binding in the hippocampus or other brain regions examined.

CONCLUSIONS

This study does not support the hypothesis that corticosteroids exert a major inhibitory regulatory control over the 5-HT(1A) receptor binding in the human brain.

Neither major depression nor glucocorticoid treatment affects the cellular integrity of the human hippocampus

In major depression, decreased hippocampal volume has been attributed to hypercortisolemia, a frequent sign of the disorder, because in animals an excess of corticosteroids has led to dendritic atrophy, astrogliosis and loss of neurons in this brain region. The present study is the first to investigate the structural integrity of the human hippocampus in major depression and following glucocorticoid treatment. Post-mortem hippocampal tissue from 15 patients who had had major depression or bipolar affective disorder, 10 patients who had been treated with glucocorticoids and 16 controls was assessed using haematoxylin-eosin, Nissl and Bodian staining. The patterns of reactive astrogliosis (glial fibrillary acidic protein, GFAP), synaptic density (synaptophysin), synaptic reorganization (growth-associated protein B-50) and early signs of Alzheimer's disease (Alz-50) were examined immunocytochemically. Multivariate analysis, with the patients' age, tissue fixation time and postmortem delay as covariates, was performed. There was no evidence of neuronal cell loss or other major morphological alterations in any of the groups, nor was there a significant change in the distribution pattern of synaptophysin or Alz-50. Changes in B-50 and GFAP staining were observed in the steroid-treated and depressed patients in areas CA1 and CA2 only. The human hippocampus in major depression and after glucocorticoid treatment does not reveal any major morphological changes or signs of neuronal cell death, but does show subtle alterations in B-50 and GFAP expression in selected parts of the pyramidal cell layer.

Elevated cortisol levels in Cushing's disease are associated with cognitive decrements

OBJECTIVE

The objective of this study was to use Cushing's disease as a unique human model to elucidate the cognitive deficits resulting from exposure to chronic stress-level elevations of endogenous cortisol.

METHODS

Forty-eight patients with a first episode of acute, untreated Cushing's disease and 38 healthy control subjects were studied.

RESULTS

Scores for four of five verbal IQ subtests were significantly lower in patients with Cushing's disease; their scores were significantly lower for only one nonverbal performance IQ subtest (block design). Verbal, but not visual, learning and delayed recall at 30 minutes were significantly decreased among patients with Cushing's disease. Although verbal delayed recall was significantly lower in these patients, the retention index (percentage), which compares the amount of initially learned material to that recalled after the delay, was not significantly decreased. There was no significant association between depression scores and cognitive performance. A higher degree of cortisol elevation was associated with poorer performance on several subtests of learning, delayed recall, and visual-spatial ability.

CONCLUSIONS

Chronically elevated levels of glucocorticoids have deleterious effects on particular domains of cognition. Verbal learning and other verbal functions seem more vulnerable than nonverbal functions. The results suggest that both the neocortex and hippocampus are affected.

Stress-induced changes in cerebral metabolites, hippocampal volume, and cell proliferation are prevented by antidepressant treatment with tianeptine

Stress-induced structural remodeling in the adult hippocampus, involving debranching and shortening of dendrites and suppression of neurogenesis, provides a cellular basis for understanding the impairment of neural plasticity in the human hippocampus in depressive illness. Accordingly, reversal of structural remodeling may be a desirable goal for antidepressant therapy. The present study investigated the effect of tianeptine, a modified tricyclic antidepressant, in the chronic psychosocial stress model of adult male tree shrews (Tupaia belangeri), a model with high validity for research on the pathophysiology of major depression. Animals were subjected to a 7-day period of psychosocial stress to elicit stress-induced endocrine and central nervous alterations before the onset of daily oral administration of tianeptine (50 mg/kg). The psychosocial stress continued throughout the treatment period of 28 days. Brain metabolite concentrations were determined in vivo by proton magnetic resonance spectroscopy, cell proliferation in the dentate gyrus was quantified by using BrdUrd immunohistochemistry, and hippocampal volume was measured post mortem. Chronic psychosocial stress significantly decreased in vivo concentrations of N-acetyl-aspartate (-13%), creatine and phosphocreatine (-15%), and choline-containing compounds (-13%). The proliferation rate of the granule precursor cells in the dentate gyrus was reduced (-33%). These stress effects were prevented by the simultaneous administration of tianeptine yielding normal values. In stressed animals treated with tianeptine, hippocampal volume increased above the small decrease produced by stress alone. These findings provide a cellular and neurochemical basis for evaluating antidepressant treatments with regard to possible reversal of structural changes in brain that have been reported in depressive disorders.

Action of glucocorticoids on survival of nerve cells: promoting neurodegeneration or neuroprotection?

Extensive studies during the past decades provided compelling evidence that glucocorticoids (GCs) have the potential to affect the development, survival and death of neurones. These observations, however, reflect paradoxical features of GCs, as they may be critically involved in both neurodegenerative and neuroprotective processes. Hence, we first address different aspects of the complex role of GCs in neurodegeneration and neuroprotection, such as concentration dependent actions of GCs on neuronal viability, anatomical diversity of GC-mediated mechanisms in the brain and species and strain differences in GC-induced neurodegeneration. Second, the modulatory action of GCs during development and ageing of the central nervous system, as well as the contribution of altered GC balance to the pathogenesis of neurodegenerative disorders is considered. In addition, we survey recent data as to the possible mechanisms underlying the neurodegenerative and neuroprotective actions of GCs. As such, two major aspects will be discerned: (i) GC-dependent offensive events, such as GC-induced inhibition of glucose uptake, increased extracellular glutamate concentration and concomitant elevation of intracellular Ca(2+), decrease in GABAergic signalling and regulation of local GC concentrations by 11 beta-hydroxysteroid dehydrogenases; and (ii) GC-related cellular defence mechanisms, such as decrease in after-hyperpolarization, increased synthesis and release of neurotrophic factors and lipocortin-1, feedback regulation of Ca(2+) currents and induction of antioxidant enzymes. The particular relevance of these mechanisms to the neurodegenerative and neuroprotective effects of GCs in the brain is discussed.