Glucocorticoid-biogenic amine interactions in relation to mood and behavior

Corticosterone injection into the basolateral amygdala before and after memory reactivation impairs the subsequent expression of fear memory in rats: An interaction of glucocorticoids and β-adrenoceptors

Glucocorticoid administration, before or after fear memory reactivation, impairs subsequent fear memory expression, but the underlying mechanisms are not well understood. The present study examined the role of basolateral amygdala (BLA) β-adrenoceptors in the effects of intra-BLA corticosterone injection on fear memory in rats. Bilateral cannulae were implanted in the BLA of Wistar male rats. The rats were trained and tested using an inhibitory avoidance task (1 mA footshock for 3 s). Forty-eight hours after training, corticosterone (CORT, 5, 10, or 20 ng/0.5 µl/side) and the β2-adrenoceptor agonist clenbuterol (CLEN, 10 or 20 ng/0.5 µl/side) or the β-adrenoceptor antagonist propranolol (PROP, 250 or 500 ng/0.5 µl/side) were injected into the BLA before or right after memory reactivation (retrieval, Test 1). We performed subsequent tests 2 (Test 2), 5 (Test 3), 7 (Test 4), and 9 (Test 5) days after Test 1. The results demonstrated that CORT injection before Test 1 disrupted memory retrieval and reduced fear expression in Tests 2-5, possibly due to enhanced extinction or impaired reconsolidation. CORT injection after Test 1 also impaired reconsolidation and reduced fear expression in Tests 2-5. CLEN prevented, but PROP exacerbated, the effects of CORT on fear expression. The reminder shock did not recover fear memory in CORT-treated animals, suggesting that reconsolidation, not extinction, was affected. These results indicate that glucocorticoids and β-adrenoceptors in the BLA jointly modulate fear memory reconsolidation and expression. Comprehending the neurobiology of stress and the impact of glucocorticoids on fear memory may lead to new treatments for stress and trauma-induced disorders such as PTSD.

Early-Life Maternal Deprivation Predicts Stronger Sickness Behaviour and Reduced Immune Responses to Acute Endotoxaemia in a Pig Model

Early-life adversity may have programming effects on neuroendocrine and immune adaptation mechanisms in humans and socially living animals. Using a pig model, we investigated the effect of daily 2-h maternal and littermate deprivation from postnatal days 2–15, either alone (DA) or in a group of littermates (DG) on the neuroendocrine, immunological and behavioural responses of piglets challenged with the bacterial endotoxin lipopolysaccharide (LPS) on day 42. LPS increased plasma concentrations of cortisol, tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and interleukin-10 (IL-10) and induced typical signs of sickness in all piglets. DA+DG piglets showed stronger signs of sickness compared to control (C) piglets. Plasma TNF-α concentrations were significantly lower in DA+DG males. In addition, the TNF-α/IL-10 ratio was significantly lower in DA than in DG and C males. Gene expression analyses showed lower hypothalamic TNF-α mRNA expression and diminished mRNA expression of the mineralocorticoid receptor (MR) and IL-10 in the amygdala of DA+DG piglets in response to LPS. Interestingly, males showed a higher MR- and a lower IL-10 mRNA expression in the amygdala than females. The present data suggest that repeated maternal deprivation during early life may alter neuroendocrine and immune responses to acute endotoxaemia in a sex-specific manner.

Sex differences in the hypothalamic-pituitary-adrenal axis: An obstacle to antidepressant drug development?

Hypothalamic-pituitary-adrenal (HPA) axis dysfunction has long been implicated in the pathophysiology of depression, and HPA axis-based compounds have served as potential new therapeutic targets, but with no success. This review details sex differences from animal and human studies in the function of HPA axis elements (glucocorticoids, corticotropin releasing factor, and vasopressin) and related compounds tested as candidate antidepressants. We propose that sex differences contribute to the failure of novel HPA axis-based drugs in clinical trials. Compounds studied preclinically in males were tested in clinical trials that recruited more, if not exclusively, women, and did not control, but rather adjusted, for potential sex differences. Indeed, clinical trials of antidepressants are usually not stratified by sex or other important factors, although preclinical and epidemiological data support such stratification. In conclusion, we suggest that clinical testing of HPA axis-related compounds creates an opportunity for targeted, personalized antidepressant treatments based on sex. LINKED ARTICLES: This article is part of a themed section on The Importance of Sex Differences in Pharmacology Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.21/issuetoc.

Drug-Induced Glucocorticoids and Memory for Substance Use

The biological stress response of the body forms one of the foundations of adaptive behavior, including promoting (and impairing) different forms of memory. This response transcends stressful experiences and underlies reactions to challenges and even reinforcers such as addictive substances. Nevertheless, drug-induced stress responses are rarely incorporated into models of addiction. We propose here that drug-induced stress responses (particularly glucocorticoids) play a crucial role in addictive behavior by modulating the formation of memories for substance-use experiences. We review the contributions of amygdala-, striatum-, and hippocampus-based memory systems to addiction, and reveal common effects of addictive drugs and acute stress on these different memories. We suggest that the contributions of drug-induced stress responses to memory may provide insights into the mechanisms driving addictive behavior.

Limbic brain structures and burnout-A systematic review

More profound understanding of the relationship between the burnout and the limbic system function can provide better insight into brain structures associated with the burnout syndrome. The objective of this review is to explore all evidence of limbic brain structures associated with the burnout syndrome. In total, 13 studies were selected. Four of them applied the neuroimaging technology to investigate the sizes/volumes of the limbic brain structures of burnout patients. Six other studies were to investigate the hypothalamus-pituitary-adrenal (HPA) axis of burnout patients. Based on the results of the studies on the HPA-axis and neuroimaging of the limbic brain structures, one can see great impact of the chronic occupational stress on the limbic structures in terms of HPA dysregulation, a decrease of BDNF, impaired neurogenesis and limbic structures atrophy. It can be concluded that chronic stress inhibits the feedback control pathway in the HPA axis, causes the decrease of brain-derived neurotrophic factor (BDNF), then impaired neurogenesis and eventually neuron atrophy.

Molecular Mechanisms of Stress-Induced Increases in Fear Memory Consolidation within the Amygdala

Stress can significantly impact brain function and increase the risk for developing various psychiatric disorders. Many of the brain regions that are implicated in psychiatric disorders and are vulnerable to the effects of stress are also involved in mediating emotional learning. Emotional learning has been a subject of intense investigation for the past 30 years, with the vast majority of studies focusing on the amygdala and its role in associative fear learning. However, the mechanisms by which stress affects the amygdala and amygdala-dependent fear memories remain unclear. Here we review the literature on the enhancing effects of acute and chronic stress on the acquisition and/or consolidation of a fear memory, as measured by auditory Pavlovian fear conditioning, and discuss potential mechanisms by which these changes occur in the amygdala. We hypothesize that stress-mediated activation of glucocorticoid receptors (GR) and norepinephrine release within the amygdala leads to the mobilization of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors to the synapse, which underlies stress-induced increases in fear memory. We discuss the implications of this hypothesis for evaluating the effects of stress on extinction and for developing treatments for anxiety disorders. Understanding how stress-induced changes in glucocorticoid and norepinephrine signaling might converge to affect emotional learning by increasing the trafficking of AMPA receptors and enhancing amygdala excitability is a promising area for future research.

Behavioral epigenetics and the developmental origins of child mental health disorders

Advances in understanding the molecular basis of behavior through epigenetic mechanisms could help explain the developmental origins of child mental health disorders. However, the application of epigenetic principles to the study of human behavior is a relatively new endeavor. In this paper we discuss the 'Developmental Origins of Health and Disease' including the role of fetal programming. We then review epigenetic principles related to fetal programming and the recent application of epigenetics to behavior. We focus on the neuroendocrine system and develop a simple heuristic stress-related model to illustrate how epigenetic changes in placental genes could predispose the infant to neurobehavioral profiles that interact with postnatal environmental factors potentially leading to mental health disorders. We then discuss from an 'Evo-Devo' perspective how some of these behaviors could also be adaptive. We suggest how elucidation of these mechanisms can help to better define risk and protective factors and populations at risk.

Steroid psychosis: a review for neurosurgeons

Steroids are beneficial in neurological illness, but have many serious side effects. Having observed several patients with severe steroid psychoses, which greatly prolonged their hospitalizations, the authors sought to improve understanding of this entity. A literature review was conducted. The incidence of severe psychiatric symptoms was estimated in a meta-analysis of 2,555 patients to be 5.7 % and the incidence of any psychiatric symptoms was 18.6 % in patients receiving >80 mg/day of prednisone (12 mg/day dexamethasone). Dose is not predictive of time of onset, severity, type, or duration of symptoms. Symptoms can develop rapidly following exposure to even low doses and with oral, epidural, or intra-articular administration. Glucocorticoid effects on the brain fall into three categories: genomic, non-genomic, and neurotrophic/neurotoxic and can be permanent. Excessive glucocorticoid exposure may result in decreased production of endogenous neurosteroid molecules, resulting in unopposed glucocorticoid effects. Treatment includes early recognition, steroid withdrawal when appropriate, reduction in stimulation, and medication. Atypical antipsychotics like olanzapine and risperidone may cause fewer dystonic reactions and extrapyramidal symptoms than typical antipsychotics like haloperidol, and therefore, are often recommended as first line treatment. Steroids are powerful medications with many undesirable side effects. They should be used with caution. More research is needed on their effects on the human central nervous system.

Regulation of corticoid and serotonin receptor brain system following early life exposure of glucocorticoids: long term implications for the neurobiology of mood

Potent glucocorticoids (GC) administered early in life have improved premature infant survival dramatically. However, these agents may increase the risk for physical, neurological and behavior alterations. Anxiety, depression and attention difficulties are commonly described in adolescent and young adult survivors of prematurity. In the present study we administered vehicle, dexamethasone, or hydrocortisone to Sprague-Dawley rat pups on postnatal days 5 and 6, mimicking a short term clinical protocol commonly used in human infants. Two systems that are implicated in the regulation of stress and behavior were assessed: the limbic-hypothalamic-pituitary-adrenal axis [LHPA; glucocorticoid and mineralocorticoid receptors within] and the Serotonin (5-HT) system. We found that as adults, male Sprague-Dawley pups treated with GC showed agent specific altered growth, anxiety-related behavior, changes in corticoid response to novelty and gene expression changes within LHPA and 5-HT-related circuitry. The data suggest that prolonged GC-receptor stimulation during the early neonatal period can contribute to the development of individual differences in stress response and anxiety-related behavior later in life.

Depression gets old fast: do stress and depression accelerate cell aging?

Depression has been likened to a state of "accelerated aging," and depressed individuals have a higher incidence of various diseases of aging, such as cardiovascular and cerebrovascular diseases, metabolic syndrome, and dementia. Chronic exposure to certain interlinked biochemical pathways that mediate stress-related depression may contribute to "accelerated aging," cell damage, and certain comorbid medical illnesses. Biochemical mediators explored in this theoretical review include the hypothalamic-pituitary-adrenal axis (e.g., hyper- or hypoactivation of glucocorticoid receptors), neurosteroids, such as dehydroepiandrosterone and allopregnanolone, brain-derived neurotrophic factor, excitotoxicity, oxidative and inflammatory stress, and disturbances of the telomere/telomerase maintenance system. A better appreciation of the role of these mediators in depressive illness could lead to refined models of depression, to a re-conceptualization of depression as a whole body disease rather than just a "mental illness," and to the rational development of new classes of medications to treat depression and its related medical comorbidities.

Children of addicted women

The purpose of this article was to review follow up studies of children with prenatal drug exposure from preschool through adolescence. Specifically, the authors focus on the effects of prenatal exposure to cocaine, methamphetamine, and opiates on behavior and development. The largest number of studies have examined cocaine-exposed children. The authors identified 42 studies that suggest that there are unique effects of prenatal cocaine exposure on 4- to 13-year-old children, particularly in the areas of behavior problems, attention, language, and cognition. In addition, studies make reasonable attempts to control for possible confounding factors. Systematic research on the long-term effects of prenatal methamphetamine exposure is just beginning but seems to be showing similar effects to that of cocaine. The literature on the on the long-term effects of children with prenatal opiate exposure is more substantial than the methamphetamine literature but it is still relatively sparse and surprising in that there is little recent work. Thus, there are no studies on the current concerns with opiates used for prescription mediation. There is a growing literature using neuroimaging techniques to study the effects of prenatal drug exposure that holds promise for understanding brain/behavior relationships. In addition to pharmacological and teratogenic effects, drugs can also be viewed from a prenatal stressor model. The author discuss this "fetal origins" approach that involves fetal programming and the neuroendocrine system and the potential implications for adolescent brain and behavioral development.

Glucocorticoids. Mood, memory, and mechanisms

Elevated circulating levels of glucocorticoids are associated with psychiatric symptoms across several different conditions. It remains unknown if this hormonal abnormality is a cause or an effect of the psychiatric conditions. For example, the hypercortisolemia observed in a subset of patients with depression may have a direct impact on the symptoms of depression, but it is also possible that the hypercortisolemia merely reflects the stress associated with depression. Further, rather than causing depression, hypercortisolemia could represent a homeostatic attempt to overcome glucocorticoid resistance. Each of these possibilities will be considered, and correlational and causal evidence will be reviewed. This article will focus on the relationships between glucocorticoids and psychiatric symptoms in Cushing's syndrome, major depression, and steroid psychosis/steroid dementia, as well as the effects of exogenously administered glucocorticoids in normal volunteers. Similarities and differences in the relationship of glucocorticoid hormones to psychiatric symptoms in these conditions will be reviewed. Possible mediators of glucocorticoid effects on the brain and behavior, as well as possible "pro-aging" effects of glucocorticoids in certain cells of the body, will be reviewed. The article concludes with a conceptual model of glucocorticoid actions in the brain that may lead to novel therapeutic opportunities.

Individual differences in the effects of chronic prazosin hydrochloride treatment on hippocampal mineralocorticoid and glucocorticoid receptors

The aim of this study was to investigate the noradrenergic regulation of mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs) in high responder (HR) and low responder (LR) male rats, an animal model of individual differences in hypothalamo-pituitary-adrenal axis activity and vulnerability to drugs of abuse. The effects of a chronic treatment with the noradrenergic alpha(1) antagonist (1-[4-amino-6,7-dimethoxy-2-quinazolinyl]-4-[2-furanylcarbonyl] piperazine) hydrochloride (prazosin) (0.5 mg/kg, i.p., 35 days) were assessed on stress-induced corticosterone (CORT) secretion and on hippocampal MRs and GRs in adrenally intact rats. In order to ascertain whether the effects of chronic prazosin treatment on hippocampal MRs and GRs were direct or indirect, through prazosin-induced CORT secretion, we also assessed the effects of the same treatment on adrenalectomized rats with CORT substitutive therapy. When compared with LR rats, HR rats exhibited a delayed return to the basal level of CORT following acute restraint stress; this was associated with a lower binding of MRs and GRs in HR rats than in LR rats. Chronic prazosin treatment had no effect in HR animals but markedly reduced hippocampal MRs and GRs, and increased stress-induced CORT secretion in LR rats. In LR adrenalectomized rats, prazosin reduced hipppocampal MRs but did not change GRs. Our results provide evidence of a differential regulation by noradrenaline of hippocampal MRs and GRs in HR and LR rats. These data could have clinical implications in terms of individual differences in the resistance to antidepressant treatments and individual differences in drug abuse.

Glucocorticoids interact with emotion-induced noradrenergic activation in influencing different memory functions

Extensive evidence from rat and human studies indicates that glucocorticoid hormones influence cognitive performance. Posttraining activation of glucocorticoid-sensitive pathways dose-dependently enhances the consolidation of long-term memory. Glucocorticoid effects on memory consolidation rely on noradrenergic activation of the basolateral amygdala and interactions of the basolateral amygdala with other brain regions. Glucocorticoids interact with the noradrenergic system both at a postsynaptic level, increasing the efficacy of the beta-adrenoceptor-cyclic AMP/protein kinase A system, as well as presynaptically in brainstem noradrenergic cell groups that project to the basolateral amygdala. In contrast, memory retrieval and working memory performance are impaired with high circulating levels of glucocorticoids. Glucocorticoid-induced impairment of these two memory functions also requires the integrity of the basolateral amygdala and the noradrenergic system. Such critical interactions between glucocorticoids and noradrenergic activation of the basolateral amygdala have important consequences for the role of emotional arousal in enabling glucocorticoid effects on these different memory functions.

Antidepressants reverse corticosterone-mediated decrease in brain-derived neurotrophic factor expression: differential regulation of specific exons by antidepressants and corticosterone

Earlier studies have implicated brain-derived neurotrophic factor in stress and in the mechanism of action of antidepressants. It has been shown that antidepressants upregulate, whereas corticosterone downregulates, brain-derived neurotrophic factor expression in rat brain. Whether various classes of antidepressants reverse corticosterone-mediated downregulation of brain-derived neurotrophic factor is unclear. Also not known is how antidepressants or corticosterone regulates brain-derived neurotrophic factor expression. To clarify this, we examined the effects of various classes of antidepressants and corticosterone, alone and in combination, on the mRNA expression of total brain-derived neurotrophic factor and of individual brain-derived neurotrophic factor exons, in rat brain. Normal or corticosterone pellet-implanted (100 mg, 21 days) rats were injected with different classes of antidepressants, fluoxetine, desipramine, or phenelzine, intraperitoneally for 21 days and killed 2 h after the last injection. mRNA expression of total brain-derived neurotrophic factor and of exons I-IV was measured in frontal cortex and hippocampus. Given to normal rats, fluoxetine increased total brain-derived neurotrophic factor mRNA only in hippocampus, whereas desipramine or phenelzine increased brain-derived neurotrophic factor mRNA in both frontal cortex and hippocampus. When specific exons were examined, desipramine increased expression of exons I and III in both brain areas, whereas phenelzine increased exon I in both frontal cortex and hippocampus but exon IV only in hippocampus. On the other hand, fluoxetine increased only exon II in hippocampus. Corticosterone treatment of normal rats decreased expression of total brain-derived neurotrophic factor mRNA in both brain areas, specifically decreasing exons II and IV. Treatment with desipramine or phenelzine of corticosterone pellet-implanted rats reversed the corticosterone-induced decrease in total brain-derived neurotrophic factor expression in both brain areas; however, fluoxetine reversed the decrease only partially in hippocampus. Interestingly, antidepressant treatment of corticosterone pellet-implanted rats increased only those specific exons that are increased during treatment of normal rats with each particular antidepressant. We found that although corticosterone and antidepressants both modulate brain-derived neurotrophic factor expression, and antidepressants reverse the corticosterone-induced brain-derived neurotrophic factor decrease, antidepressants and corticosterone differ in how they regulate the expression of brain-derived neurotrophic factor exon(s).

Dopaminergic contribution to the regulation of emotional perception

Dopamine (DA) acts as a key neurotransmitter in the brain. Numerous studies have shown its regulatory role in motor and cognitive function. However, the impairment of emotional processes in neurologic and psychiatric pathologies involving the dopaminergic system (Parkinson disease, schizophrenia, autism, Attention Deficit Hyperactivity Disorder, Huntington disease, frontal lobe lesions), as well as the influence that administration of dopaminergic agonists/antagonists exert on the processing of emotion, suggest a role for DA in emotional processes. Moreover, emotional processes are dependent upon a variety of structures, the majority of which form part of the limbic system and are subject to DA innervation. In reviewing the literature, the amygdala emerges as a brain structure critical for emotional processing. It may also be implicated in deficits in emotional recognition found in two major disorders where DA's implication is clear: Parkinson disease and schizophrenia. In addition, the amygdala's response to emotional tasks is likely to be altered by the administration of both agonist and antagonist dopaminergic drugs. Experimental studies reinforce the idea of a dopaminergic contribution to emotional response, as suggested by biochemical, pharmacologic, and lesion experiments. Although the implication of the dopaminergic system in emotional processing appears to be clearly documented, the contribution of specific DA receptor subtypes, or of the DA cotransmitters cholecystokinin and neurotensin, or even glutamate, is, however, still unclear. Altogether, these observations suggest that DA has, undoubtedly, a direct and/or indirect role in the full emotional process.

Glucocorticoid effects on memory retrieval require concurrent noradrenergic activity in the hippocampus and basolateral amygdala

Previous findings indicate that administration of abeta-adrenoceptor antagonist systemically blocks glucocorticoid impairment of memory retrieval. Here, we report that beta-adrenoceptor activation in the hippocampus and the basolateral complex of the amygdala (BLA) is implicated in the impairing effects of glucocorticoids on memory retrieval. The specific glucocorticoid receptor (GR) agonist 11beta,17beta-dihydroxy-6,21-dimethyl-17alpha-pregna-4,6-trien-20yn-3-one (RU 28362) (15 ng) infused into the hippocampus of male Sprague Dawley rats 60 min before water maze retention testing, 24 hr after training, impaired probe trial retention performance, as assessed by quadrant search time and initial latency to cross the platform location. Because we found previously that RU 28362 infused into the hippocampus does not affect water maze acquisition or immediate recall, the findings suggest that the GR agonist-induced retention impairment was attributable to a selective influence on long-term memory retrieval. Likewise, systemic injections of the beta1-adrenoceptor partial agonist xamoterol (3.0 or 10.0 mg/kg, s.c.) 60 min before the probe trial dose-dependently impaired retention performance. The beta-adrenoceptor antagonist propranolol (2.0 mg/kg) administered subcutaneously before retention testing did not affect retention performance alone, but blocked the memory retrieval impairment induced by concurrent intrahippocampal infusions of RU 28362. Pretest infusions of the beta1-adrenoceptor antagonist atenolol into either the hippocampus (1.25 microg in 0.5 microl) or the BLA (0.5 microg in 0.2 microl) also prevented the GR agonist-induced memory retrieval impairment. These findings suggest that glucocorticoids impair retrieval of long-term spatial memory by facilitating noradrenergic mechanisms in the hippocampus, and additionally, that norepinephrine-mediated BLA activity is critical in enabling hippocampal glucocorticoid effects on memory retrieval.

A systemically administered β-adrenoceptor antagonist blocks corticosterone-induced impairment of contextual memory retrieval in rats

Several studies have reported that glucocorticoids impair memory retrieval. The present study examined in male Sprague-Dawley rats the effects of systemically administered corticosterone on retrieval of memory for inhibitory avoidance training. Corticosterone (3.0mg/kg, s.c.) injected 30min before retention testing, 48h after training, significantly impaired retention performance, as compared to vehicle treatment, of rats tested in the training context. In contrast, corticosterone administration did not impair retrieval when rats were tested for retention in a different context. Corticosterone did also not impair retention performance of rats given a mild-intensity footshock that resulted in only weak, non-contextual memory. These findings strongly suggest that corticosterone selectively impaired retrieval of contextual information associated with the training context. The centrally acting beta-adrenoceptor antagonist propranolol (2.0mg/kg), co-administered in a dose that did not affect retention performance alone, blocked the impairment in contextual memory retrieval induced by corticosterone. These findings provide evidence for the view that glucocorticoids interact with noradrenergic mechanisms in influencing memory retrieval.

The basolateral amygdala interacts with the medial prefrontal cortex in regulating glucocorticoid effects on working memory impairment

Previous findings indicate that the basolateral complex of the amygdala (BLA) interacts with other brain regions in regulating stress hormone effects on memory functions. Lesions of the BLA or infusions of a beta-adrenoceptor antagonist into the BLA block glucocorticoid effects on both memory consolidation and retrieval when administered either systemically or directly into the hippocampus. The present experiments examined BLA and beta-adrenoceptor involvement in regulating glucocorticoid effects on spatial working memory, a task that depends on the medial prefrontal cortex (mPFC). Male Sprague Dawley rats with bilateral sham- or NMDA-induced lesions of the BLA received either corticosterone (1.0 or 3.0 mg/kg, i.p.) systemically or the specific glucocorticoid receptor agonist 11beta,17beta-dihydroxy-6,21-dimethyl-17alpha-pregna-4,6-trien-20yn-3-one (RU 28362; 3.0 or 10.0 ng in 0.5 microl) into the mPFC shortly before testing on a delayed alternation task in a T-maze. Both glucocorticoid treatments induced comparable impairments in working memory performance in sham-lesioned controls. Although lesions of the BLA alone did not affect working memory, BLA lesions blocked the impairment induced by either corticosterone or RU 28362. Likewise, systemic injections of the centrally acting beta-adrenoceptor antagonist propranolol (2.0 mg/kg, i.p.) given before testing prevented corticosterone-induced working memory impairment. These findings indicate that BLA activity is essential for enabling glucocorticoid effects in the mPFC on working memory and suggest that stress hormone-induced modulation of working memory involves noradrenergic activation.

Systems mediating acute glucocorticoid effects on memory consolidation and retrieval

It is well established that glucocorticoid hormones, secreted by the adrenal cortex after a stressful event, influence cognitive performance. This article reviews recent findings from this laboratory on the acute effects of glucocorticoids in rats on specific memory phases, i.e., memory consolidation and memory retrieval. Posttraining activation of glucocorticoid-sensitive pathways involving glucocorticoid receptors (GRs) enhances memory consolidation in a dose-dependent manner. Glucocorticoid influences on memory consolidation depend on noradrenergic activation of the basolateral complex of the amygdala (BLA) and interactions of the BLA with other brain regions. By contrast, memory retrieval processes are usually impaired with high circulating levels of glucocorticoids or following infusions of GR agonists into the hippocampus. Although the BLA does not appear to be a site of glucocorticoid action in influencing memory retrieval, an intact BLA is required for enabling glucocorticoid effects on memory retrieval. The BLA appears to be a key structure in a memory-modulatory system that regulates, in concert with other brain regions, stress and glucocorticoid effects on both memory consolidation and memory retrieval.

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.

Role of the basolateral amygdala in memory consolidation

Memories of emotionally arousing events tend to be more vivid and to persist longer than do memories of neutral or trivial events. Moreover, memories of emotionally influenced information may endure after a single experience. Recent findings strongly suggest that the influence of emotional arousal on memory consolidation is mediated by the release of adrenal stress hormones (epinephrine and glucocorticoids) and neurotransmitters that converge in modulating the noradrenergic system within the amygdala. Considerable evidence also indicates that amygdala activation influences memory by regulating consolidation in other brain regions. The findings suggest further that this memory-modulatory system may be involved in the formation of traumatic memories and posttraumatic stress disorder in human subjects.

The alerting effects of dexamethasone

The purpose of this study was to characterize the level of sleepiness/alertness following the nocturnal administration of dexamethasone. Thirteen healthy men participated in this study. Following the initial screening, dexamethasone (4 mg) or placebo was administered at 22:30 hr in a randomized double-blind procedure. Subjects were given nap opportunities at 23:00, 1:00, 3:00, 4:30, 5:30, 7:30, 9:30, 11:30, 13:30, 15:30, 17:30, and 19:30 hr. The administration of dexamethasone resulted in an overall lengthening of sleep latency. Although the two groups displayed comparable latencies to stage 1 for the 23:00-7:30 hr nap opportunities, the administration of dexamethasone resulted in significantly longer latencies on the 9:30-19:30 hr nap opportunities. Consistent with these results, participants reported significantly greater levels of alertness on the Stanford Sleepiness Scale. The results of this study revealed greater levels of daytime alertness following the nocturnal administration of dexamethasone.

Acute changes in cerebrospinal fluid 5-HIAA following oral paroxetine challenge in healthy humans

A number of studies have reported decreased human lumbar cerebrospinal fluid (CSF) concentrations of the major serotonin metabolite, 5-hydroxyindoleacetic acid (5-HIAA), following chronic administration of selective serotonin reuptake inhibitors (SSRIs). This decrease has been thought to be a consequence of elevated extracellular serotonin and to be mediated through terminal autoreceptor feedback inhibition of serotonin turnover. We wished to study the previously unexamined acute effects of SSRI administration on human CSF 5-HIAA. A serial lumbar puncture (LP) procedure was used to collect CSF samples before and after a single oral 40 mg dose of the SSRI paroxetine (PAR) or matching placebo in eight healthy adult humans in a randomized, double-blind fashion. CSF 5-HIAA concentrations did not change following placebo, but showed a statistically significant 27% mean increase 3 h following PAR. Our findings stand in contrast to the decreases reported for CSF 5-HIAA after chronic SSRI treatment in humans and the decreases seen in brain extracellular 5-HIAA after acute or chronic administration of SSRIs to animals.

Stress-induced subsensitivity to modafinil and its prevention by corticosteroids

Brain alpha(1)-adrenoceptors are known to be necessary for motor activity in rodents and have been shown to be altered by stress and corticosteroids but only in biochemical experiments. To determine if the behaviorally coupled receptors are also affected by stress, the present study examined the effect of stress and corticosteroids treatment on the motor activity response to modafinil, a putative alpha(1)-adrenoceptor agonist, which is unique in that it elicits extremely high levels of activity via these receptors. Mice were subjected to various schedules of restraint stress for 1-6 days and were subsequently tested for either modafinil-induced or dopaminergically induced behavioral activity in the home cage using videotape recording. In experiments on corticosteroid treatment, mice received exogenous corticosterone or dexamethasone in the drinking water before and during the stress and were tested for modafinil-induced activity as above. It was found that the stress significantly reduced the response to the drug by the third daily session. Motor responses to dopaminergic agents including apomorphine, amphetamine, dihydrexidine and quinpirole were either not altered or were increased at this time. Treatment of animals with corticosterone or dexamethasone prior to and during stress prevented the behavioral subsensitivity to modafinil. Corticosterone pretreatment markedly suppressed the plasma corticosterone response to the stress. The present results provide further support for the hypothesis that stress produces a selective desensitization or inhibition of motor-related brain alpha(1)-adrenoceptors and that this effect can be prevented by corticosteroid treatment.

The role of alpha-adrenoceptors in the amnestic effect of intracerebroventricular dexamethasone

Corticosteroids exert dual enhancing or impairing effects on cognitive functions. While their memory-enhancing effects have been well investigated, the mechanisms involved in their amnestic effects are not completely understood. Thus, we examined the role of alpha-adrenoceptors on dexamethasone-induced amnesia using step-through passive avoidance test in rat. Intracerebroventricular (i.c.v.) injection of dexamethasone (5 and 10 microg per rat) decreased the retention latencies. Likewise, intraperitoneal administration of alpha(2)-adrenoceptor agonist clonidine (0.1-0.3 mg kg(-1)) but not alpha(2)-adrenoceptor antagonist yohimbine (0.5-2 mg kg(-1)) decreased the retention latency. Yohimbine pre-treatment decreased the amnestic effects of dexamethasone or dexamethasone plus clonidine. On the other hand, intraperitoneal administration of alpha(1)-adrenoceptor agonist phenylephrine (0.5-2 mg kg(-1)) per se increased, while prazosin at 2 mg kg(-1) decreased the retention latency. Administration of phenylephrine before dexamethasone completely reversed the amnestic effect of the latter, while prozosin did not affect dexamethasone-induced amnesia. These data suggest that dexamethasone may induce its amnestic effect through activation of alpha(2)-adrenoceptors, leading to decreased alpha(1)-adrenergic activity.

Double-blind antiglucocorticoid treatment in schizophrenia and schizoaffective disorder: a pilot study

BACKGROUND

Antiglucocorticoids, such as ketoconazole, have been investigated as antidepressant agents in major depression and other conditions. Despite evidence that a significant number of patients with schizophrenia and schizoaffective disorder are both hypercortisolemic and depressed, the antidepressant effects of antiglucocorticoids have never been assessed in these populations.

METHODS

Fifteen symptomatic patients with diagnoses of schizophrenia or schizoaffective disorder, who were at least partially treatment-resistant, were treated with ketoconazole, up to 800 mg/day, (n = 8) or placebo (n = 7) for four weeks in a double-blind manner. The study medication was added to a pre-stabilized antipsychotic and/or antidepressant medication regimen.

RESULTS

Ketoconazole treatment, compared to placebo, was associated with significant improvements in observer-rated depression, but not in subjectively rated depression, positive or negative psychotic symptom ratings, or cognitive performance scores.

CONCLUSIONS

These pilot data partially support the hypothesis that antiglucocorticoids reduce depressive symptoms in patients with schizophrenia and schizoaffective disorder, although objective and subjective ratings may not be similarly affected during a four-week course of treatment. Further studies with larger sample sizes, more extensive endocrine assessments and longer duration of drug administration seem warranted.

Chronic psychosocial stress regulates the expression of both GR and MR mRNA in the hippocampal formation of tree shrews

A persistent hyperactivity of the hypothalamic-pituitary-adrenal axis and thus elevated glucocorticoid levels are main neuroendocrine features of depressive symptomatology in humans. The broad range of effects that are set off by glucocorticoids is mediated by glucocorticoid receptors (GRs) and mineralocorticoid receptors (MRs), which themselves are subject to autoregulation. In order to investigate the impact of long-lasting psychological stress on corticosteroid receptor mRNA expression in the hippocampal formation, we employed the psychosocial stress paradigm in male tree shrews (Tupaia belangeri). By in situ hybridization studies and semiquantitative evaluation of stress-induced changes of GR and MR mRNA expression at the single-cell level, brain tissue from subordinate animals which were exposed to 27 days (1 h/day) of social confrontation was compared to that of nonstressed animals. Four weeks of stress exposure resulted in a downregulation of GR mRNA in the dentate gyrus and hippocampal subfields CA1 and CA3 of subordinate male tree shrews compared to controls. The MR mRNA content in these subfields of the anterior hippocampus was also clearly reduced. On the contrary, in a more posterior location on the longitudinal axis of the tree shrew hippocampus, the MR message was increased in subfields CA1 and CA3 and in the dentate gyrus. These results suggest a relevance of the stress-induced regulation of both corticosteroid receptor subtype mRNAs in a naturalistic challenging situation. Moreover, the differential regulation of MR mRNA along the rostrocaudal axis of the hippocampus adds another feature to the heterogenous composition of this structure.

Glucocorticoids interact with the basolateral amygdala beta-adrenoceptor--cAMP/cAMP/PKA system in influencing memory consolidation

Infusion of a beta-adrenoceptor antagonist into the basolateral nucleus of the amygdala (BLA) blocks memory enhancement induced by systemic or intra-BLA administration of a glucocorticoid receptor (GR) agonist. As there is evidence that glucocorticoids interact with the noradrenergic signalling pathway in activating adenosine 3prime prime or minute,5prime prime or minute-cyclic monophosphate (cAMP), the present experiments examined whether glucocorticoids influence the beta-adrenoceptor--cAMP system in the BLA in modulating memory consolidation. Male, Sprague--Dawley rats received bilateral infusions of atenolol (a beta-adrenoceptor antagonist), prazosin (an alpha1-adrenoceptor antagonist) or Rp-cAMPS (a protein kinase A inhibitor) into the BLA 10 min before inhibitory avoidance training and immediate post-training intra-BLA infusions of the GR agonist, RU 28362. Atenolol and Rp-cAMPS, but not prazosin, blocked 48-h retention enhancement induced by RU 28362. A second series of experiments investigated whether a GR antagonist alters the effect of noradrenergic activation in the BLA on memory consolidation. Bilateral intra-BLA infusions of the GR antagonist, RU 38486, administered 10 min before inhibitory avoidance training completely blocked retention enhancement induced by alpha1-adrenoceptor activation and attenuated the dose--response effects of post-training intra-BLA infusions of clenbuterol (a beta-adrenoceptor agonist). However, the GR antagonist did not alter retention enhancement induced by post-training intra-BLA infusions of 8-Br-cAMP (a synthetic cAMP analogue). These findings suggest that glucocorticoids influence the efficacy of noradrenergic stimulation in the BLA on memory consolidation via an interaction with the beta-adrenoceptor--cAMP cascade, at a locus between the membrane-bound beta-adrenoceptor and the intracellular cAMP formation site.

Defining the neuromolecular action of myo-inositol: application to obsessive-compulsive disorder

Dietary inositol is incorporated into neuronal cell membranes as inositol phospholipids where it serves as a key metabolic precursor in G protein-coupled receptors. In the brain, several subtypes of adrenergic, cholinergic, serotonergic and metabotropic glutamatergic receptors are coupled to the hydrolysis of phosphoinositides (PI) with myo-inositol (MI) crucial to the resynthesis of PI and the maintenance and effectiveness of signalling. Despite a mode of action that remains illusive, MI has demonstrated therapeutic efficacy in obsessive-compulsive disorder (OCD), putative OCD-spectrum disorders, as well as panic and depression. Behavioural and biochemical studies indicate that this efficacy does not involve simply the replenishing of the membrane PI pool. In addition to its precursory role in cell signalling, inositol lipids alter receptor sensitivity, can direct membrane trafficking events, and have been found to modulate an increasing array of signalling proteins. These effects may afford MI an ability to modulate the interaction between neurotransmitters, drugs, receptors and signalling proteins. This paper reviews the neuromolecular and genetic aspects of OCD in terms of the PI-linked 5HT receptor subtypes and relates these to the behavioural and therapeutic effects of MI. Since OCD often is poorly responsive to current drug treatment, understanding the neuropharmacology of MI holds great promise for understanding the neuropathology of this and other MI-responsive disorders.

Mice with targeted mutations of glucocorticoid and mineralocorticoid receptors: models for depression and anxiety?

Impaired corticosteroid receptor signaling is a key mechanism in the pathogenesis of stress-related psychiatric disorders such as depression and anxiety. Since in vivo expression and functional studies of corticosteroid receptors are not feasible in the human central nervous system, such analyses have to be done in animal models. Transgenic mice with mutations of corticosteroid receptors are promising tools, which allow us to investigate the role of these proteins in the pathogenesis of symptoms characteristic for depression and anxiety. This review summarizes the neuroendocrinological and behavioral findings that have been obtained in six different mouse strains with specific mutations that influence the expression or the function of the glucocorticoid or the mineralocorticoid receptor (MR). The analyses of these mice helped to define molecular concepts of how corticosteroid receptors regulate the activity of the hypothalamic-pituitary-adrenal (HPA) system. Furthermore, some of these mutant mice exhibited characteristic alterations in behavioral tests for anxiety and despair. However, so far, none of the mouse strains described here can be viewed as an animal model of a specific psychiatric disease defined by common diagnostic criteria. Using high throughput technologies for the identification of genes regulated by glucocorticoid receptor (GR) and MR in brain areas responsible for specific symptoms of stress-related disorders will yield potential new drug targets for the treatment of depression and anxiety.

Glucocorticoid programming of pituitary-adrenal function: mechanisms and physiological consequences

Increasing epidemiological evidence supports the notion that adverse events in fetal life permanently alter the structure and physiology of the adult offspring, a phenomenon dubbed 'fetal programming'. In particular, low weight or thinness at birth in humans is associated with an increased risk of cardiovascular and metabolic disorders as well as neuroendocrine dysfunction in adult life. Glucocorticoid administration during pregnancy is well-documented to both reduce offspring birth weight and alter the maturation of organs (hence their use to accelerate fetal lung maturation in premature labour). Here data are reviewed which show, in rodents and other models, that antenatal exposure to endogenous or exogenous glucocorticoids reduces offspring birth weight and produces permanent hypertension, hyperglycaemia, hyperinsulinaemia, altered behaviour and neuroendocrine responses throughout the lifespan. Processes underlying fetal programming include determination of the 'set point' of the hypothalamic-pituitary-adrenal (HPA) axis and of tissue glucocorticoid receptor (GR) expression. Similar HPA axis hyperreactivity occurs in lower birth weight humans and may be an early manifestation of the 'low birth weight' phenotype.

Stress hormone-related psychopathology: pathophysiological and treatment implications

Stress is commonly associated with a variety of psychiatric conditions, including major depression, and with chronic medical conditions, including diabetes and insulin resistance. Whether stress causes these conditions is uncertain, but plausible mechanisms exist by which such effects might occur. To the extent stress-induced hormonal alterations (e.g., chronically elevated cortisol levels and lowered dehydroepiandrosterone [DHEA] levels) contribute to psychiatric and medical disease states, manipulations that normalize these hormonal aberrations should prove therapeutic. In this review, we discuss mechanisms by which hormonal imbalance (discussed in the frameworks of "allostatic load" and "anabolic balance") might contribute to illness. We then review certain clinical manifestations of such hormonal imbalances and discuss pharmacological and behavioural treatment strategies aimed at normalizing hormonal output and lessening psychiatric and physical pathology.

Depressive symptoms modulate the subjective and physiological response to cocaine in humans

The goal of this study was to examine the relationship between the presence of subclinical depressive symptoms and physiological and subjective responses to smoked cocaine in humans. Cocaine users without major depression, who participated in various inpatient studies, received a single 0.4 mg/kg of smoked cocaine. When the relationship between the Beck Depression Inventory (BDI) scores and various subjective and physiological responses to cocaine was examined, similar trends were found. Low BDI scores of 0-7 were associated with a smaller physiological and subjective cocaine response. In contrast, BDI ranges of 8-13 were associated with enhanced cocaine response which plateaued or declined in the higher (> 14) BDI group. These group differences were not explained by sex or body weight differences among groups. The implication of these results is that the presence of depressive symptoms may affect cocaine use behavior partly by being associated with an enhanced response to cocaine.

Corticosteroids in relation to fear, anxiety and psychopathology

Corticosteroids play extremely important roles in fear and anxiety. The mechanisms by which corticosteroids exert their effects on behavior are often indirect, because, although corticosteroids do not regulate behavior, they induce chemical changes in particular sets of neurons making certain behavioral outcomes more likely in certain contexts as a result of the strengthening or weakening of particular neural pathways. The timing of corticosteroid increase (before, during or after exposure to a stressor) determines whether and how behavior is affected. The present review shows that different aspects of fear and anxiety are affected differentially by the occupation of the mineralocorticoid receptor (MR) or glucocorticoid receptor (GR) at different phases of the stress response. Corticosteroids, at low circulating levels, exert a permissive action via brain MRs on the mediation of acute freezing behavior and acute fear-related plus-maze behavior. Corticosteroids, at high circulating levels, enhance acquisition, conditioning and consolidation of an inescapable stressful experience via GR-mechanisms. Brain GR-occupation also promotes processes underlying fear potentiation. Fear potentiation can be seen as an adjustment in anticipation of changing demands. However, such feed-forward regulation may be particularly vulnerable to dysfunction. MR and/or GR mechanisms are involved in fear extinction. Brain MRs may be involved in the extinction of passive avoidance, and GRs may be involved in mediating the extinction of active avoidance. In the developing brain, corticosteroids play a facilitatory role in the ontogeny of freezing behavior, probably via GRs in the dorsal hippocampus, and their influence on the development of the septo-hippocampal cholinergic system. Corticosteroids can exert maladaptive rather than adaptive effects when their actions via MRs and GRs are chronically unbalanced due to chronic stress. Both mental health of humans and animal welfare is likely to be seriously threatened after psychosocial stress, prolonged stress, prenatal stress or postnatal stress, especially when maternal care or social support is absent, because these can chronically dysregulate the central MR/GR balance. In such circumstances the normally adaptive corticosteroid responses can become maladaptive.

Corticosteroid receptor mRNA expression in the brains of patients with epilepsy

The effects of corticosteroids in the brain are mediated through the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR). We used a sensitive competitive RT-PCR assay to quantify the amounts of GR and MR mRNA in human brain tissue specimens from patients with focal epilepsies. GR and MR mRNAs were expressed at approximately the same levels in the temporal lobe, frontal lobe, and hippocampus as compared to tissues with high glucocorticoid/mineralocorticoid receptor expression (liver/kidney). GR and MR mRNA concentrations in the temporal lobe increased markedly during childhood and reached adult levels at puberty. GR and MR mRNA expression was significantly higher in the temporal lobe and frontal lobe cortex of women than in those of men. In women, MR and GR mRNA concentrations were markedly lower in hippocampal tissue than in frontal and temporal lobe cortex tissue. In conclusion, our data demonstrate sex- and site-dependent expression of corticosteroid receptor mRNA in the human brain.

Adult brain neurogenesis and psychiatry: a novel theory of depression

Neurogenesis (the birth of new neurons) continues postnatally and into adulthood in the brains of many animal species, including humans. This is particularly prominent in the dentate gyrus of the hippocampal formation. One of the factors that potently suppresses adult neurogenesis is stress, probably due to increased glucocorticoid release. Complementing this, we have recently found that increasing brain levels of serotonin enhance the basal rate of dentate gyrus neurogenesis. These and other data have led us to propose the following theory regarding clinical depression. Stress-induced decreases in dentate gyrus neurogenesis are an important causal factor in precipitating episodes of depression. Reciprocally, therapeutic interventions for depression that increase serotonergic neurotransmission act at least in part by augmenting dentate gyrus neurogenesis and thereby promoting recovery from depression. Thus, we hypothesize that the waning and waxing of neurogenesis in the hippocampal formation are important causal factors, respectively, in the precipitation of, and recovery from, episodes of clinical depression.

1999 Curt P. Richter award. Glucocorticoids and the regulation of memory consolidation

This paper summarizes recent findings on the amygdala's role in mediating acute effects of glucocorticoids on memory consolidation in rats. Posttraining activation of glucocorticoid-sensitive pathways involving glucocorticoid receptors (GRs or type II) enhances memory consolidation in a dose-dependent inverted-U fashion. Selective lesions of the basolateral nucleus of the amygdala (BLA) or infusions of beta-adrenoceptor antagonists into the BLA block the memory-modulatory effects of systemic injections of glucocorticoids. Additionally, posttraining infusions of a specific GR agonist administered directly into the BLA enhance memory consolidation, whereas those of a GR antagonist impair. These findings indicate that glucocorticoid effects on memory consolidation are mediated, in part, by an activation of GRs in the BLA and that the effects require beta-adrenergic activity in the BLA. Other findings indicate that the BLA interacts with the hippocampus in mediating glucocorticoid-induced modulatory influences on memory consolidation. Lesions of the BLA or inactivation of beta-adrenoceptors within the BLA also block the memory-modulatory effects of intrahippocampal administration of a GR agonist or antagonist. These findings are in agreement with the general hypothesis that the BLA integrates hormonal and neuromodulatory influences on memory consolidation. However, the BLA is not a permanent locus of storage for this information, but modulates consolidation processes for explicit/associative memories in other brain regions, including the hippocampus.

Genetic approaches to studying norepinephrine function: knockout of the mouse norepinephrine transporter gene

Norepinephrine is an important chemical messenger in the nervous system. It regulates affective states, learning and memory, endocrine and autonomic functions. It has been implicated in depression, aggression, and addiction, as well as cardiac and thermal dysregulation. The norepinephrine transporter functions by uptaking norepinephrine back into the cell for cyclic use, and is a direct target of a number of antidepressants and psychostimulants. Functional deletion (knockout) of monamine transporters results in increases in extracellular levels of neurotransmitters, thereby prolonging their actions. For the norepinephrine transporter knockout mice, this altered state of the norepinephrine system should simulate the therapeutic effects of norepinephrine selective antidepressants and some of the effects of psychostimulants. Careful use of such an animal model can hopefully provide valuable insight into the multiple roles norepinephrine plays in normal and pathological physiology.

Alpha-1-noradrenergic neurotransmission, corticosterone, and behavioral depression

BACKGROUND

Impaired brain alpha-1 noradrenergic neurotransmission has been implicated in some of the symptoms of depressive illness but has been difficult to investigate experimentally because of the insensitivity of current animal models of depression. The present experiment addressed this problem by examining the effects of pharmacologic blockade and corticosteroid-induced desensitization of alpha-1 receptors on two newer, more sensitive models in mice: the inhibition of nest-leaving and the tail suspension tests (TST).

METHODS

Male mice were administered either prazosin, betaxolol, atipamezole, corticosterone, or repeated restraint stress prior to measurement of either nest-leaving or TST. General behavioral function was assessed in horizontal wire, swim, and latency to escape footshock tests.

RESULTS

Prazosin increased depressive behavior in the nest-leaving and TSTs, whereas corticosterone and restraint stress did so only in the more sensitive nest-leaving test. Betaxolol also reduced nest-leaving, suggestive of an alpha-1 beta-1 receptor synergy. The effects of these agents could not be attributed to hypotension, sedation, or general behavioral impairment.

CONCLUSIONS

The fact that a reduction in alpha-1 noradrenergic neurotransmission increases depressive behavior, coupled with the fact that this change can result from elevated corticosteroid secretion, provides further support for a role of this factor in depressive illness. As not all alpha-1 functions are reduced in depression, it is likely that only a subgroup or specific locality of alpha-1 receptors are affected.

Treatment of depression with antiglucocorticoid drugs

OBJECTIVE

The theoretical and empirical rationales for the potential therapeutic use of antiglucocorticoid agents in the treatment of depression are reviewed.

METHOD

Individual case reports, case series, open-label, and double-blind, controlled trials of the usage of cortisol-lowering treatments in Cushing's syndrome and major depression are evaluated and critiqued.

RESULTS

In each of the 28 reports of antiglucocorticoid treatment of Cushing's syndrome, antidepressant effects were noted in some patients; the largest two series document a response rate of 70% to 73%. Full response, however, was at times erratic and delayed. Across the 11 studies of antiglucocorticoid treatment of major depression, some degree of antidepressant response was noted in 67% to 77% of patients. Antidepressant or antiobsessional effects of antiglucocorticoid augmentation of other psychotropic medications have also been noted in small studies of patients with treatment-resistant depression, obsessive-compulsive disorder, and schizoaffective disorder or schizophrenia.

CONCLUSIONS

These promising results with antiglucocorticoid treatment must be interpreted cautiously because of the small sample sizes and heterogeneity of the studies reviewed, the bias favoring publication of positive results, and the open-label nature of most of the studies. Although definitive controlled trials remain to be conducted, there is a consistent body of evidence indicating that cortisol-lowering treatments may be of clinical benefit in select individuals with major depression and other hypercortisolemic conditions.

Repeated administration of dexamethasone increases phosphoinositide-specific phospholipase C activity and mRNA and protein expression of the phospholipase C beta 1 isozyme in rat brain

Altered hypothalamic-pituitary-adrenal (HPA) function has been shown to be associated with changes in mood and behavior. The enzyme phosphoinositide-specific phospholipase C (PI-PLC), an important component of the PI signal transduction system, plays a major role in mediating various physiological functions. In the present study, we investigated the effects of a single dose and of repeated administration (0.5 or 1.0 mg/kg for 10 days) of dexamethasone (DEX), a synthetic glucocorticoid, on PI-PLC activity and on expression of PLC isozymes (beta1, delta1, and gamma1) in rat brain. Repeated administration of DEX (1.0 mg/kg) caused a significant increase in PI-PLC activity and in protein expression of the PLC beta1 isozyme in both membrane and cytosol fractions of cortex and hippocampus; however, the repeated administration of a smaller dose of DEX (0.5 mg/kg) caused these changes only in hippocampus but not in cortex. The increase in PLC beta1 protein was associated with an increase in its mRNA level, as measured by competitive RT-PCR. A single administration of DEX (0.5 or 1.0 mg/kg) to rats had no significant effects on PI-PLC activity or on the protein expression of PLC isozymes. These results suggest that DEX up-regulates PI-PLC in rat brain, which presumably is due to a selective increase in expression of the PLC beta1 isozyme, and that these changes in PI-PLC may be related to HPA axis-mediated changes in mood and behavior.

Serotonin 1A receptor messenger RNA regulation in the hippocampus after acute stress

BACKGROUND

When rats are subjected to chronic stress for 2 weeks, a significant decrease in hippocampal serotonin (5-HT)1A messenger RNA (mRNA) is observed. We wanted to investigate whether stress, administered for shorter periods of time, would result in decreases in 5-HT1A gene expression in hippocampus.

METHODS

In one experiment, rats were either stressed daily for 1 week or implanted with two corticosterone pellets to produce elevated corticosterone levels. In another experiment, rats were subjected to a severe acute stressor and sacrificed 1 day or 1 week after the stressor.

RESULTS

We found that 24 hours after the acute stress, rats showed a significant decrease in 5-HT1A mRNA levels in CA1 and the dentate gyrus compared to controls. No significant changes in 5-HT1A mRNA levels were detected in any of the other groups.

CONCLUSIONS

Although 1 week of chronic stress is not sufficient to cause significant decreases in hippocampal 5-HT1A mRNA levels, a severe and prolonged acute stress is capable of down-regulating, at least transiently, 5-HT1A mRNA gene expression in hippocampus.

Glucocorticoid receptor activation in the rat nucleus of the solitary tract facilitates memory consolidation: involvement of the basolateral amygdala

These experiments examined the involvement of glucocorticoid receptors (GRs or type II) located in the A2-noradrenergic cell group of the rat nucleus of the solitary tract (NTS) in modulating memory storage. Bilateral intra-NTS infusions (0.5 microL) of the specific GR agonist RU 28362 (11beta, 17beta-dihydroxy-6, 21-dimethyl-17alpha-pregna-4,6-trien-20yn-3-one), in doses ranging from 0.01 to 10.0 ng, immediately after inhibitory avoidance training produced a dose-dependent enhancement of 48 h retention performance. Infusions of 0.1 or 1.0 ng of the agonist enhanced retention, whereas lower or higher doses were ineffective. Post-training infusions of the GR antagonist RU 38486 [17beta-hydroxy-11beta-(4-dimethylaminophenyl)-17alpha-(1-pr opynyl)-o estra-4,9-dien-3-one, 0.01-10.0 ng] into the NTS did not significantly affect retention performance, but shifted the dose-response effects of post-training systemic injections of the synthetic glucocorticoid dexamethasone to the right. These results indicate that activation of GRs in the NTS can influence memory formation for inhibitory avoidance training, and suggest that the effects of circulating glucocorticoids on memory are mediated, in part, by an activation of GRs in the NTS. Additionally, pretraining infusions of the beta1-adrenergic antagonist atenolol (0.5 microg in 0.2 microL) into the basolateral nucleus of the amygdala (BLA), a brain structure which receives noradrenergic projections from the NTS and is implicated in memory storage modulation, blocked the memory-enhancing effects of the GR agonist (1.0 ng) infused into the NTS. These findings provide evidence that memory storage is modulated by glucocorticoid binding to GRs in noradrenergic cell bodies in the NTS and suggest that these modulatory effects are conveyed by ascending projections to the BLA.