The neurobiology of stress: from serendipity to clinical relevance

Impact of life-long macronutrient choice on neuroendocrine and cognitive functioning in aged mice: differential effects in stressor-reactive and stressor-resilient mouse strains

Nutrient selection emerges as a result of both genetic and environmental factors and may be further modified by stressors. The impact of this complex interrelationship on pathological outcomes is poorly understood. In the present investigation the stressor-reactive BALB/cByJ and the relatively stressor resilient C57BL/6ByJ mice were maintained on a macronutrient selection protocol or given free access to chow for 20 months. The C57BL/6ByJ mice exhibited a marked preference for fat over carbohydrates, whereas BALB/cByJ mice preferred carbohydrates over fat. Cognitive testing in a Morris water maze indicated that while BALB/cByJ mice were clearly more impaired in this task relative to their C57BL/6ByJ counterparts, there was no substantial effect of the diet at either 13 or 19 months of age. Furthermore, despite their stressor resiliency, at 19 months of age, C57BL/6ByJ mice who invariably consumed fat, exhibited greater plasma corticosterone responses to a 20-min period of restraint than chow fed animals. Indeed, the corticosterone rise was as pronounced as in the more reactive BALB/cByJ strain. Furthermore, the C57BL/6ByJ diet-fed mice showed features of insulin insensitivity and increased adiposity. These data suggest that the adverse effects of fat consumption need to be considered in the context of genetically determined vulnerability/resilience factors.

Affective style and in vivo immune response: neurobehavioral mechanisms

Considerable evidence exists to support an association between psychological states and immune function. However, the mechanisms by which such states are instantiated in the brain and influence the immune system are poorly understood. The present study investigated relations among physiological measures of affective style, psychological well being, and immune function. Negative and positive affect were elicited by using an autobiographical writing task. Electroencephalography and affect-modulated eye-blink startle were used to measure trait and state negative affect. Participants were vaccinated for influenza, and antibody titers after the vaccine were assayed to provide an in vivo measure of immune function. Higher levels of right-prefrontal electroencephalographic activation and greater magnitude of the startle reflex reliably predicted poorer immune response. These data support the hypothesis that individuals characterized by a more negative affective style mount a weaker immune response and therefore may be at greater risk for illness than those with a more positive affective style.

A multimethodological analysis of cumulative risk and allostatic load among rural children

This study merged two theoretical constructs: cumulative risk and allostatic load. Physical (crowding, noise, housing quality) and psychosocial (child separation, turmoil, violence) aspects of the home environment and personal characteristics (poverty, single parenthood, maternal highschool dropout status) were modeled in a cumulative risk heuristic. Elevated cumulative risk was associated with heightened cardiovascular and neuroendocrine parameters, increased deposition of body fat, and a higher summary index of total allostatic load. Previous findings that children who face more cumulative risk have greater psychological distress were replicated among a sample of rural children and shown to generalize to lower perceptions of self-worth. Prior cumulative risk research was further extended through demonstration of self-regulatory behavior problems and elevated learned helplessness.

Interaction effects of corticosterone and experience on aggressive behavior in the green anole lizard

Aggressive encounters are accompanied by a release of stress hormone, and this corticosterone (CORT) secretion could influence aggressive behavior in subsequent encounters. We investigated the modulating effects of CORT on aggressive behavior in the context of a 5-day social experience in male green anole lizards. In Experiment 1, we measured plasma CORT levels in animals that were exposed for different times to aggressive males. In Experiment 2, using metyrapone, a CORT synthesis blocker, we tested whether CORT secretion in response to the aggressive stimulus plays a role in experience-dependent facilitation of aggressive behavior. We hypothesized that aggressive encounters would increase plasma CORT levels, and that blocking CORT synthesis with metyrapone treatment during the aggressive encounter would cause an animal to become more aggressive. We also tested whether blocking CORT would interfere with the influence of 5-day social experience on animals' behavior in a subsequent aggressive encounter. Animals that were exposed to another male showed higher plasma CORT levels immediately after the 10 min encounter than animals exposed to the non-social video, and this high level was maintained through day 5. Within the aggressive video groups, in Experiment 2, there was a distinctly different pattern in displays depending on drug condition: vehicle-injected animals showed gradual increases followed by decreases in aggressive behavioral responses to the video as the five days proceeded (habituation), while animals injected with metyrapone started out with high aggressive behavior and did not decrease behavioral responses at later trials (no habituation). Finally, when tested with a novel conspecific on day 6, animals previously injected with metyrapone showed no higher aggression than did animals previously injected with vehicle and exposed to the aggressive video. These results suggest that blocking CORT synthesis during the exposure to the aggressive video induced animals to remain aggressive toward the repetitive stimulus without habituating, while not becoming more aggressive than controls toward a novel challenger.

Higher cortisol levels following exposure to traumatic reminders in abuse-related PTSD

Animal studies have found that prior stressful events can result in increased reactivity in the HPA-axis. However, baseline function of the HPA-axis has typically been normal or decreased in post-traumatic stress disorder (PTSD). The first purpose of this study was to assess cortisol responsivity to traumatic reminders in women with PTSD related to childhood abuse. The second aim was to assess the relationship between stress-induced cortisol levels and neutral and emotional memory. Salivary cortisol levels were measured before, during and after exposure to personalized trauma scripts in abused women with (N=12) and without current PTSD (N=12). Memory for neutral and emotional material was assessed immediately after trauma scripts exposure and 3 days later. PTSD patients had 122% higher cortisol levels during script exposure, 69% higher cortisol levels during recovery, and 60% higher levels in the period leading up to the script exposure compared to controls. PTSD symptoms were highly predictive of cortisol levels during trauma script exposure (r=0.70), but not during periods of rest. Both in PTSD patients and controls, memory consolidation after the trauma scripts was impaired relative to baseline (P<0.001), with no differences between the two groups on memory performance. There was no association between memory performance and cortisol levels. These results are consistent with higher cortisol levels following exposure to traumatic stressors in PTSD.

Depression and cardiovascular disease: mechanisms of interaction

This article explores the relationship between depression and cardiovascular disease from a mechanistic standpoint. Depression and cardiovascular disease are two of the most prevalent health problems in the United States and are the two leading causes of disability both in the United States and worldwide. Although depression is a known risk factor for the development of cardiovascular disease, as well as an independent predictor of poor prognosis following a cardiac event, the mechanistic relationship between the two remains unclear. Depression is associated with changes in an individual's health status that may influence the development and course of cardiovascular disease, including noncompliance with medical recommendations, as well as the presence of cardiovascular risk factors such as smoking and hypertension. In addition, depression is associated with physiologic changes, including nervous system activation, cardiac rhythm disturbances, systemic and localized inflammation, and hypercoagulability, that negatively influence the cardiovascular system. Further, stress may be an underlying trigger that leads to the development of both depression and cardiovascular disease. This article reviews seven potential mechanisms for the relationship between depression and cardiovascular disease and presents the available evidence surrounding each mechanism. Finally, future directions for research are discussed.

Social modulation of stress responses

Social interactions can profoundly affect the hypothalamic-pituitary-adrenal (HPA) axis. Although most research on social modulation of glucocorticoid concentrations has focused on the consequences of exposure to stressful social stimuli, there is a growing body of literature which suggests that social support in humans and affiliative behaviors in some animals can provide a buffer against stress and have a positive impact on measures of health and well-being. This review will compare HPA axis activity among individuals for whom social relationships are maintained through aggressive displays, such as dominance hierarchies, vs. individuals engaging in high levels of prosocial behavior. We also will examine oxytocin, a neuropeptide that is well known for promoting social behavior, as the physiological link between positive social interactions and suppression of the HPA axis. Despite many examples of social interaction modulating the HPA axis and improving health outcomes, there is relatively little known regarding the underlying mechanisms through which social behavior can provide a buffer against stress-related disease.

Adaptogenic effect of Bacopa monniera (Brahmi)

As stress is linked to many diseases, research on an effective antistress agent (adaptogen) from plants has gained importance. We report the investigations on the adaptogenic property of a standardized extract of Bacopa monniera against acute (AS) and chronic stress (CS) models in rats. Panax root powder (Panax quinquefolium) was taken as a standard. Male SD rats, weighing 180-200 g, exposed to immobilization stress for 150 min once only for AS and for seven consecutive days in CS, were fed with B. monniera or Panax root powder daily for 3 days in AS and for 7 days in CS, 45 min prior to each exposure of stress. Rats were sacrificed immediately after stress, the blood was collected, and the plasma was separated out for biochemical estimation. Adrenals, spleen, and thymus were dissected for organ weight and stomach for ulcer score. AS exposure significantly increased the ulcer index, adrenal gland weight, plasma glucose, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and creatine kinase (CK) but significantly decreased the spleen weight. Pretreatment with B. monniera at 40 mg/kg po significantly reduced the AS-induced increase in the ulcer index, adrenal gland weight, plasma glucose, AST, and CK. A dose of 80 mg/kg po significantly reversed the AS-induced changes in adrenal gland weight, spleen weight, plasma glucose, ALT, and AST. Panax root powder, 100 mg/kg po, significantly reversed the AS-induced changes in spleen weight, plasma ALT, AST, and CK. CS exposure resulted in a significant increase in the ulcer index, adrenal gland weight, plasma AST, and CK with a significant decrease in the thymus and spleen weight, plasma triglyceride, and cholesterol. Pretreatment with low dose of B. monniera extract at 40 mg/kg significantly reversed changes in ulcer index and plasma AST only, whereas the pretreatment with higher dose significantly reversed CS-induced changes in ulcer index, adrenal gland weight, CK, and AST. Panax root powder significantly reversed CS-induced increase in ulcer index, adrenal gland weight, CK, and AST. On the basis of our result, it is concluded that the standardized extract of B. monniera possesses a potent adaptogenic activity.

Voluntary wheel running modulates glutamate receptor subunit gene expression and stress hormone release in Lewis rats

Lewis rats that are known to be addiction-prone, develop compulsive running if they have access to running wheels. The present experiments were aimed 1) to evaluate the activation of stress systems following chronic and acute voluntary wheel running in Lewis rats by measurement of hormone release and gene expression of neuropeptides related to hypothalamic-pituitary-adrenocortical (HPA) axis activity and 2) to test the hypothesis that wheel running as a combined model of addictive behavior and stress exposure is associated with modulation of ionotropic glutamate receptor subunits in the ventral tegmental area. Voluntary running for three weeks but not for one night resulted in a rise in plasma corticosterone and adrenocorticotropic hormone (ACTH) levels (p<0.05) compared to those in control rats. Principal component analysis revealed the relation between POMC gene expression in the intermediate pituitary and running rate. Acute exposure of animals to voluntary wheel running induced a significant decrease in alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor GluR1 subunit mRNA levels (p<0.01), while repeated voluntary physical activity increased levels of GluR1 mRNA in the ventral tegmentum (p<0.05). Neither acute nor chronic wheel running influenced N-methyl-D-aspartate (NMDA) receptor subunit NR1 mRNA levels in the ventral tegmental area. Thus, the present study revealed changes in AMPA receptor subunit gene expression in a reward-related brain structure as well as an activation of HPA axis in response to compulsive wheel running in Lewis rats. It may be suggested that hormones of HPA axis and glutamate receptors belong to the factors that substantiate higher vulnerability to addictive behavior.

Antidepressant fluoxetine enhances glucocorticoid receptor function in vitro by modulating membrane steroid transporters

1. Incubation of LMCAT fibroblast cells with antidepressants potentiates glucocorticoid receptor (GR)-mediated gene transcription in the presence of dexamethasone and cortisol, but not of corticosterone. We have shown that antidepressants do so by inhibiting the LMCAT cell membrane steroid transporter (which is virtually identical to the multidrug resistance P-glycoprotein) and thus by increasing dexamethasone or cortisol intracellular concentrations. However, previous experiments with the antidepressant fluoxetine in the presence of dexamethasone have produced negative results (Pariante et al. (2001). Br. J. Pharmacol., 134, 1335-1343). 2. We have since re-examined the effects of fluoxetine on GR-mediated gene transcription in the presence of dexamethasone. Moreover, we have examined the effects of fluoxetine on GR-mediated gene transcription in the presence of cortisol and corticosterone, and on the intracellular accumulation of radioactive cortisol and corticosterone. Finally, we have examined the effects of fluoxetine on inhibition of P-glycoprotein activity in Caco-2 cells. 3. We now find that fluoxetine (1-10 micro M) enhances GR-mediated gene transcription in the presence of dexamethasone and cortisol (+140-170%), but not of corticosterone, and increases the intracellular accumulation of (3)H-cortisol (+5-15%), but not of (3)H-corticosterone. Moreover, fluoxetine (10 micro M) induces approximately 30% inhibition of PGP activity in Caco-2 cells. 4. Our results show that fluoxetine, like other antidepressants, inhibits membrane steroid transporters.

Juvenile hormone and division of labor in honey bee colonies: effects of allatectomy on flight behavior and metabolism

Three experiments were performed to determine why removal of the corpora allata (the glands that produce juvenile hormone) causes honey bees to fail to return to their hive upon initiating flight. In Experiment 1, the naturally occurring flights of allatectomized bees were tracked with radar to determine whether the deficit is physical or cognitive. The results indicated a physical impairment: allatectomized bees had a significantly slower ground speed than sham and untreated bees during orientation flights, but otherwise attributes such as flight range and area were normal. Flight impairment was confirmed in Experiment 2, based on observations of takeoff made in the field at the hive entrance. The allatectomized group had a significantly smaller percentage of flightworthy bees than did the sham and untreated groups. Experiment 3 confirmed the flight impairment in laboratory tests and showed that allatectomy causes a decrease in metabolic rate. Allatectomized bees had significantly lower metabolic rates than untreated and sham bees, while allatectomized bees receiving hormone replacement had intermediate values. These results indicate that allatectomy causes flight impairment, probably partly due to effects on metabolic rate. They also suggest that juvenile hormone plays an additional, previously unknown, role in coordinating the physiological underpinning of division of labor in honey bee colonies.

Need for recovery from work related fatigue and its role in the development and prediction of subjective health complaints

AIMS

To present the available empirical evidence for the assumed position of the concept of work related fatigue as: (1) short term effect of the working day; and (2) an intermediate variable between work demands and the development of subjective health complaints and sickness absence.

METHODS

Results from six single occupation studies, conducted between 1996 and 2002, are presented. Work demands (working hours, decision latitude, break control/autonomy, and mental, emotional, and physical demands) were assessed through validated scales. Work related fatigue was represented and assessed by means of the need for recovery after working time scale in all studies. Subjective health complaints and duration of sickness absence were quantified with the same instruments in most studies as well. Both cross sectional studies (four) as well as prospective studies (two; up to two years follow up) were performed. Cross sectional data of 3820 workers, in total, were available. Prospective data were accessible for 1200 workers in industry and health care. Models were tested with stepwise multiple regression analyses.

RESULTS

Strong associations between work demands and need for recovery were found in different occupations. The variance explained in need for recovery by work demands, age, and (baseline) need for recovery ranged between 14% and 48% in both types of studies. The amount of explained variance by work demands, age, and (baseline) need for recovery in subjective health complaints ranged between 24% and 58% in the different occupations. The prospective data showed the prognostic value of need for recovery in relation to subjective health complaints (in terms of psychosomatic complaints, emotional exhaustion, or sleep problems) and duration of future sickness absence.

CONCLUSIONS

The hypothesised role for work related fatigue as a link in the causal string of events, that is assumed to exist between repeated adverse work demands and the development of work related stress reactions, (psychological) overload and, eventually, health problems, was confirmed.

Stress and the brain

Stress is a risk factor for a variety of illnesses, involving the same hormones that ensure survival during a period of stress. Although there is a considerable ambiguity in the definition of stress, a useful operational definition is: "anything that induces increased secretion of glucocorticoids". The brain is a major target for glucocorticoids. Whereas the precise mechanism of glucocorticoid-induced brain damage is not yet understood, treatment strategies aimed at regulating abnormal levels of glucocorticoids, are worth examining.

Chronic unpredictable stress impairs long-term potentiation in rat hippocampal CA1 area and dentate gyrus in vitro

Rises in corticosteroid levels, e.g. after acute stress, impair synaptic plasticity in the rat hippocampus when compared with the situation where levels are basal, i.e. under rest. We here addressed the question whether basal and raised levels of corticosterone affect synaptic plasticity similarly in animals that experienced chronic stress prior to corticosterone application. To this end, rats were exposed to a 21-day variable stress paradigm. Synaptic plasticity was examined in vitro in the dentate gyrus and CA1 hippocampal region, 24 h after exposure to the last stressor, i.e. when corticosterone levels are basal (low). First we observed that long-term potentiation was greatly impaired in both CA1 and dentate gyrus after 3 weeks of exposure to variable stress, when recorded under conditions where plasma corticosterone levels are low. Second, administration of 100 nm corticosterone in vitro reduced synaptic plasticity in CA1 of control rats, but induced no further impairment of synaptic plasticity in chronically stressed rats. Third, in the dentate gyrus, corticosterone incubation did not affect synaptic plasticity in slices from both control and stressed animals. We conclude that: (i) exposure to chronic variable stress per se reduces synaptic plasticity both in CA1 and dentate gyrus; and (ii) acute rises in corticosterone level induce no additional impairment of synaptic plasticity in the CA1 region of chronically stressed rats. It is tempting to speculate that the stress-induced reduction of hippocampal efficacy provides a cellular substrate for cognitive deficits in hippocampus-dependent learning tasks seen after prolonged exposure to stressful events.

Antidepressive treatment with amitriptyline and paroxetine: effects on saliva cortisol concentrations

With regard to the course of basal human hypothalamus-pituitary-adrenal (HPA) system activity, there is a lack of data for comparing different classes of antidepressants. Ninety-four patients were included in a study comparing standardized treatment with paroxetine (PAROX) and amitriptyline (AMI) after a drug-free period of at least 6 days. Saliva for measurement of cortisol concentrations was obtained daily at 0800, 1600, and 2200 during the 6 days of drug-free washout and 35 days of active treatment. The course of HPA system activity and psychopathology, as assessed by the Hamilton Depression Scale, was compared by means of repeated-measurement analyses of variance (ANOVA-rm). Only AMI responders-not PAROX responders or nonresponders to either antidepressant-had a significant decline in saliva cortisol concentrations. In hypercortisolemically depressed patients, treatment with AMI may be preferable to PAROX in order to lower HPA system activity.

Agonistic encounters in aged male mouse potentiate the expression of endogenous brain NGF and BDNF: possible implication for brain progenitor cells' activation

The condition of dominance or submission following agonistic encounters in the adult male mouse is known to differentially affect brain nerve growth factor, a neurotrophin playing a role in brain remodeling, in the fine tuning of behaviour and in the regulation of the basal forebrain cholinergic neurons. During development and adult life nerve growth factor regulates brain expression of neurotransmitters and the stimulation of progenitor cells (stem cells) which, under different external stimuli, may differentiate into neuronal and/or glial cells promoting the recovery of the injured brain. However, little information is available for the aged brain. Thus in the present study we investigated the effect of the social status ('dominance' vs. 'submission') in the aged mouse on the presence of nerve growth factor, brain-derived neurotrophic factor, choline acetyltransferase, neuropeptide Y and progenitor cells of selected brain regions. We found that aged dominant mice showed increased brain-derived neurotrophic factor in the subventricular zone and hippocampus and increased choline acetyltransferase in the septum and basal nuclei, which were associated with increased presence of progenitor cells in the subventricular zone. Conversely, in aged subordinate mice the data showed a marked brain increase in nerve growth factor in the subventricular zone and hippocampus, choline acetyltransferase in the septum and basal nuclei and neuropeptide Y in the hippocampus and parietal cortex. The possible functional implications of these findings are discussed.

Sex-related influences on the neurobiology of emotionally influenced memory

In a recent report, the National Academy of Sciences concluded that "Sex matters. Sex, that is, being male or female, is an important basic human variable that should be considered when designing and analyzing studies in all areas and at all levels of biomedical and health-related research."(1) Recent findings from my laboratory concerning neural mechanisms of emotionally influenced memory further support this conclusion. This article first provides a brief, general overview of sex-related influences on brain and cognition. Upon this background, recent findings from my laboratory and others are described, demonstrating sex-related influences on neural mechanisms underlying emotionally influenced, explicit recall of emotionally arousing events. Both the hemispheric involvement of the human amygdala in memory for emotionally arousing events and the impairing effect of beta-adrenergic blockade on memory for emotional events exhibit pronounced sex-related differences. We interpret both of these effects in the context of evidence indicating hemispheric specialization in the processing of global/wholistic versus local/fine detail aspects of a situation. The more general conclusion that we draw from these investigations is that theories of the neurobiology of emotion and memory must begin to account for the seemingly substantial influences of sex.

Pravastatin protection from cold stress in myocardium of rats

The aim of this research was to evaluate the possible protective effect of pravastatin on ultrastructural alterations induced by cold stress in the myocardium of rats. Sixteen EPM-Wistar rats (Rattus norvegicus albinus) were used and distributed into four groups: 1) control; 2) pravastatin; 3) cold stress, and 4) pravastatin + cold stress. A daily oral dose of 10 mg/kg of weight of pravastatin was administered to each rat in groups 2 and 4 for 15 days. The stress induced by cold was obtained by keeping the group 3 and 4 rats in a freezer at -8 degrees C for 4 hours. The animals were killed and the heart and fragments of the left ventricles (LV) were removed and processed prior to conducting electron microscopic analysis. The ultrastructural alterations in cardiomyocytes were quantified through the number of mitochondrial cristae pattern (cristalysis). The group subjected only to cold stress showed a significant increase in cristalysis (391.9) when compared with control group (42.0). In the cold stress and pravastatin pretreatment group, a statistically significant (96.9)*, P<0.05 cristalysis reduction was observed when compared with cold stress group. The mitochondrial cristalysis profiles of the control and pravastatin groups were 42.0 and 65.7, respectively. Cold stress induced a significant increase in the rate of mitochondrial cristalysis. In the group that received pravastatin and was exposed to cold stress, the drug protected the LV cardiomyocytes. This fact was confirmed by a reduction mitochondrial cristalysis pattern.

Impact of chronic intermittent challenges in stressor-susceptible and resilient strains of mice

BACKGROUND

Stressors promote altered neurochemical functioning that may be of adaptive value. The sustained elevations of neurochemical activity elicited by chronic stressors may exact excessive demands on biological systems (allostatic load), thereby rendering the organism more vulnerable to pathology, but such effects may be dependent on individual characteristics.

METHODS

Stressor reactive BALB/cByJ mice and the relatively resilient C57BL/6ByJ mice were exposed to a variety of psychogenic and neurogenic stressors, twice a day over 60 days. The resultant neurochemical and behavioral changes in these strains was assessed relative to the effects of acute stressors.

RESULTS

Acute restraint elicited more pronounced and more widespread variations of norepinephrine and serotonin utilization in BALB/cByJ than in C57BL/6ByJ mice. Following the chronic stressor, BALB/cByJ mice showed marked behavioral alterations thought to be indicative of depression- and anxiety-like states. The chronic stressor was also associated with moderation of amine utilization in the C57BL/6ByJ mice, whereas such an outcome was less prominent or entirely absent in BALB/cByJ mice.

CONCLUSIONS

The sustained increase of amine activity in the BALB/cByJ, coupled with the marked depressionogenic-anxiogenic characteristics of this strain, may provide a useful preparation to assess the impact of chronic stressors on the development of behavioral and physical pathology.

Early maternal deprivation reduces the expression of BDNF and NMDA receptor subunits in rat hippocampus

It is well accepted that events that interfere with the normal program of neuronal differentiation and brain maturation may be relevant for the etiology of psychiatric disorders, setting the stage for synaptic disorganization that becomes functional later in life. In order to investigate molecular determinants for these events, we examined the modulation of the neurotrophin brain-derived neurotrophic factor (BDNF) and the glutamate NMDA receptor following 24 h maternal separation (MD) on postnatal day 9. We found that in adulthood the expression of BDNF as well as of NR-2A and NR-2B, two NMDA receptor forming subunits, were significantly reduced in the hippocampus of MD rats whereas, among other structures, a slight reduction of NR-2A and 2B was detected only in prefrontal cortex. These changes were not observed acutely, nor in pre-weaning animals. Furthermore we found that in MD rats the modulation of hippocampal BDNF in response to an acute stress was altered, indicating a persistent functional impairment in its regulation, which may subserve a specific role for coping with challenging situations. We propose that adverse events taking place during brain maturation can modulate the expression of molecular players of cellular plasticity within selected brain regions, thus contributing to permanent alterations in brain function, which might ultimately lead to an increased vulnerability for psychiatric diseases.

Psychoneuroimmunology in critically ill patients

Psychoneuroimmunology is the study of the interactions among behavior, neural, and endocrine functions and the immune system. The purpose of this review is to briefly summarize the evidence concerning interactions among behavior, the neuroendocrine system, and the immune system, and to show how this evidence relates to critical care patients. It has been shown that the immune function of many patients in the intensive care unit is suppressed as a result of trauma, sepsis, or profound physiologic and psychological stress. Three of the most common stressors among patients in the intensive care unit are pain, sleep deprivation, and fear or anxiety. Findings have shown each of these stressors to be associated with decreased immune functioning. Nurses have an important responsibility to protect their patients from infection and promote their ability to heal. Several actions are suggested that can help the nurse achieve these goals. It is hoped that nurses would keep these interactions in mind while caring for their patients in the intensive care unit.

The false organic-psychogenic distinction and related problems in the classification of erectile dysfunction

The traditional distinction between organic and psychogenic erectile dysfunction (ED) was maintained in the recent report of the Nomenclature Committee of the International Society for Sexual and Impotence Research. Among the major problems with this distinction are that it is based on an obsolete view of mind-body distinctions, does not take into account knowledge of the neurobiology of 'psychological' disorders, disregards the fundamental meaning of 'psychosomatic,' is too often diagnosed by exclusion, and may imply to the patient that his ED is 'all in the mind.' As a result, the distinction has become counterproductive in the diagnosis, classification, and treatment of ED, and in research into the causes of ED. An alternative taxonomy, based on that proposed by the Nomenclature Committee, reclassifies as organic several of the causes of ED now considered to be psychogenic, and considers others as situational ED, a class reserved for episodic occurrences of ED clearly due to particular attributes of sexual encounters.

Rapid habituation of hippocampal serotonin and norepinephrine release and anxiety-related behaviors, but not plasma corticosterone levels, to repeated footshock stress in rats

Prior stress exposure is known to alter the activation response to a subsequent stressor. In the present study, we examined neurochemical, neuroendocrinological, and behavioral correlates of short-term adaptation to homotypic stressors administered 60 min apart. An initial electric footshock significantly induced extracellular levels of both serotonin (5-HT) and norepinephrine (NE) in the rat hippocampus (650% and 200% above baseline, respectively), as measured by in vivo microdialysis. A rapid habituation in this response was evident in the inability of a second footshock to evoke similar increases. In contrast, the hypothalamic-pituitary-adrenal (HPA) response was augmented further after the second shock session: plasma corticosterone (CORT) levels were 18.1, 316.5, and 441.6 mg/ml in nonstressed, one-footshock-, or two-footshock-treated rats, respectively. In a social interaction paradigm, rats subjected to a single footshock showed several fear- and anxiety-related behaviors such as increases in freezing and decreases in rearing and active approach for social interaction. Exposure to a second footshock completely blocked the freezing response and restored rearing behavior without affecting the disruption in social interactions. Taken together, these data raise the possibility that neurochemical and neuroendocrine adaptations to short-term homotypic stressors differentially contribute to expression of different fear and anxiety-like responses in the rat.

Photoperiod and stress affect wound healing in Siberian hamsters

Changes in day length alter several indices of immune function in Siberian hamsters. These experiments tested the hypothesis that photoperiodic changes in immune function are integrated at an organismal level as reflected by the ability to heal a cutaneous wound. Given the well-documented effects of psychological stressors on immune function, we also tested the hypothesis that photoperiod modulates the effects of acute stress on wound healing. Male hamsters were housed in long (16L:8D; LD) or short (8L:16D; SD) day lengths for 8+/-2 weeks. SD-treatment was sufficient to induce winter reproductive status. Hamsters then received a dermal punch wound. Hamsters were subjected to either 2 h of daily restraint stress or a control treatment for 3 days prior to and 5 days after wounding. Wounds were digitally photographed daily, and wound size was measured to quantify healing. Wounds of LD hamsters healed significantly faster than did those of SD hamsters. Restraint stress significantly accelerated healing in SD hamsters. The results suggest that the enhancing effects of short-term psychological stressors on immune function are apparent only when reproductive function is suppressed. In nature, enhanced wound healing coincident with the breeding season and territorial defense may be adaptive.

Improvement of sleep and pituitary-adrenal inhibition after subchronic intranasal vasopressin treatment in elderly humans

Subchronic intranasal treatment with argininevasopressin (AVP) has been shown to exert a strong ameliorating effect on sleep and slow wave sleep (SWS) deficits in elderly. However, AVP is also a potent stimulus of the pituitary-adrenal stress system, which is usually inhibited during early, SWS-rich sleep. A disinhibition of pituitary-adrenal activity during sleep is correlated with aging and is considered a pathologic factor contributing to various age-related diseases. Here, we examined whether the beneficial effect of prolonged intranasal AVP administration on sleep in aged would be associated with a concomitant decrease in pituitary-adrenal inhibition and effects on other neuroendocrine features of sleep. Twenty-six healthy elderly (mean 72.9 yr) with mild sleep complaints were investigated in a placebo controlled double-blind study. One group was treated daily each morning and evening with intranasal AVP (2 x 20 IU) for 10 weeks, the other received placebo. During polysomnographical recordings taken at the beginning and end of the treatment period, blood was sampled every 15 min. Intranasal AVP increased SWS on average by +21.5 min (p<0.02). The effect persisted on the night after acute withdrawal of the peptide treatment with no rebound occurring. Notably, rather than increasing pituitary-adrenal activity, AVP decreased the early sleep cortisol nadir on average by 0.5 microg/dl (p<0.05). AVP did not induce any measurable changes in fluid balance or cardiovascular activity. Overall, results indicate a promoting effect of AVP on SWS in aged accompanied by a beneficial rather than impairing influence on the neuroendocrine pattern of sleep.

Chronic stress effects on memory: sex differences in performance and monoaminergic activity

Increasing evidence suggests that the time course of advantageous versus deleterious effects of stress on physiologic function is also apparent in some brain functions, including learning and memory. This article reviews the effects of chronic stress on behavioral performance and, more importantly, shows that sex of the subject, as well as duration and intensity of stress, is an important determinant of the functional/behavioral, neurochemical, and anatomical consequences of the stress. Following chronic stress (7-28 days of restraint, 6 h/day), male and female rats were tested on a visual memory task (object recognition) and two spatial memory tasks (object placement and radial arm maze). At 21 days, stress impaired males on all tasks while females were either enhanced (spatial memory tasks) or not impaired (nonspatial memory tasks). Additionally, the influence of the hypothalamic-pituitary-adrenocortical axis in mediating the sex-specific responses to stress is considered. Behavioral and neurochemical assessments following chronic stress in ovariectomized females, with and without estradiol, suggest that estrogen exerts both organizational and activational influences on the observed sex differences in response to stress. Furthermore, stress differentially affected central transmitter levels in the frontal cortex, hippocampus, and amygdala depending on sex. The possible role of these sex-specific changes in neurotransmitter levels in mediating behavioral differences in response to stress is discussed. While these results are thus far limited to a few studies and require both further investigation and verification, chronic stress appears to be associated with distinct, sex-differentiated behavioral/cognitive and neurochemical responses. We conclude that sex differences must be taken into account when investigating or describing stress and associated sequalae.

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.

Contemporary work characteristics, stress, and ill health

This study investigates the relationship between work and ill health resulting from stressors originating in the work environment. The association between work and health has been well-documented. Factors in the work environment leading to ill health have included generalized psychological stress and/or specific physical environmental characteristics. Data for this study come from a 1998 telephone survey, the Indiana Survey of Work in a Polarized Economy, under the auspices of the Center for Survey Research at Indiana University. The dependent variable is an index that measures ill health among workers; control variables include sociodemographic and lifestyle characteristics of these workers as well as their job characteristics; and the four key independent variables are occupational status, organizational disruption, layoff experience, and educational discordance of the workers. Multiple regression analysis on the entire sample (n = 919) demonstrates that occupational status is negatively associated with ill health, while organizational disruption, layoff experience, and educational discordance are positively associated with it. Separate analyses for male (n = 474) and female (n = 445) respondents find significant sex differences in the effects of the key variables: for males, organizational disruption is positively related to ill health while for women occupational status is negatively related and layoff experience and educational discordance are positively related to ill health. The findings from the present research provide insight into the interrelationship of occupational environment and health within the framework of evolutionary medicine.

Sleep-wake mechanisms and drug discovery: sleep EEG as a tool for the development of CNS-acting drugs

Sleep laboratory investigations constitute a unique noninvasive tool to analyze brain functioning, Polysomnographic recordings, even in the very early phase of development in humans, are mandatory in a developmental plan of a new sleep-acting compound. Sleep is also an interesting tool for the development of other drugs acting on the central nervous system (CNS), Indeed, changes in sleep electroencephalographic (EEG) characteristics are a very sensitive indication of the objective central effects of psychoactive drugs, and these changes are specific to the way the drug acts on the brain neurotransmitter systems. Moreover, new compounds can be compared with reference drugs in terms of the sleep EEG profile they induce. For instance, cognitive enhancers involving cholinergic mechanism have been consistently demonstrated to increase rapid eye movement (REM) sleep pressure, and studying drug-induced slow wave sleep (SWS) alteration is a particularly useful tool for the development of CNS compounds acting at the 5-HT(2A/C) receptor, such as most atypical antipsychotics and some antidepressant drugs. The sleep EEG profile of antidepressants, and particularly their effects on REM sleep, are specific to their ability to enhance noradrenergic or serotonergic transmission, it is suggested that the effects of noradrenergic versus serotonergic reuptake inhibition could be disentangled using specific monoamine depletion tests and by studying drug effects on sleep microsiructure.

Growth hormone-releasing hormone facilitates hypoglycemia-induced release of cortisol

Early sleep in humans is characterized by a distinct suppression of pituitary-adrenal activity coinciding with enhanced activity of the somatotropic axis. Here, we tested in awake humans the hypothesis of an inhibiting influence of hypothalamic growth hormone-releasing hormone (GHRH) on pituitary-adrenal activity. For this purpose, pituitary-adrenal activity was stimulated in 10 men through a standard insulin-hypoglycemia-test (IHT) and in another 10 men through combined administration of CRH/vasopressin. Stimulation was performed in each man on three conditions following pretreatment with Placebo and GHRH administered intravenously (50 microg) or intranasally (300 microg) 1 h before. GH, ACTH and cortisol as well as blood pressure and heart rate were measured repeatedly. Contrary to expectations, pretreatment with GHRH did not suppress but enhanced secretion of cortisol upon insulin-induced hypoglycemia regardless of the route of GHRH pretreatment (p<0.05). In contrast, GHRH did not facilitate cortisol release after stimulation with CRH/vasopressin. Changes in ACTH remained inconsistent. Plasma levels of GH increased significantly after i.v. GHRH application, but remained unchanged after the intranasal administration. Blood pressure and heart rate were not influenced by the treatments. Results indicate facilitating effects of GHRH mediated at a suprapituitary (i.e. hypothalamic) level as suggested by restriction of the effect to the hypoglycemia-induced cortisol release with no effects after pituitary stimulation with CRH/vasopressin.

Stress, immunity, cytokines and depression

The current issue of Acta Neuropsychiatrica presents a series of papers which together provide a broad overview relating stress, immunity, cytokine activity and depressive illness, as well as the influence of cytokines on other neurological disorders. This introduction to the issue presents a broad perspective of the impact of stressors on immune functioning in animal studies and in humans, considering the potential effects of acute, subchronic and chronic stressors, as well as the contribution of previous stressor experience in promoting neurochemical and immunological alterations. Given the supposition that cytokines may act as immunotransmitters, and immune challenge may be viewed as a stressor, a brief review is provided concerning the impact of stressors and cytokine challenges on central neurochemical functioning, with particular emphasis on the commonalties between the effects of these treatments. It is suggested that by virtue of the neurochemical changes imparted by cytokines, a depressive affect may be instigated, just as it is in response to psychogenic stressors. To this end, an overview is presented concerning the relationship between cytokines and depression, as well as the influence of cytokine treatments on behavioral changes in animal studies and among patients receiving immunotherapy. Provisionally, the data support the view that activation of the inflammatory response system may contribute to affective illness, and that cytokines may act as signaling molecules to activate central nervous system processes regulating mood states.

Nerve growth factor-induced neurite sprouting in PC12 cells involves sigma-1 receptors: implications for antidepressants

One theory concerning the action of antidepressants relates to the drugs' ability to induce an adaptive plasticity in neurons such as neurite sprouting. Certain antidepressants are known to bind to sigma-1 receptors (Sig-1R) with high affinity. Sig-1R are dynamic endoplasmic reticulum proteins that are highly concentrated at the tip of growth cones in cultured cells. We therefore tested the hypotheses that Sig-1R might participate in the neurite sprouting and that antidepressants with Sig-1R affinity may promote the neuronal sprouting via Sig-1R. The prototypic Sig-1R agonist (+)-pentazocine [(+)PTZ], as well as the Sig-1R-active antidepressants imipramine and fluvoxamine, although ineffective by themselves, were found to enhance the nerve growth factor (NGF)-induced neurite sprouting in PC12 cells in a dose-dependent manner. A Sig-1R antagonist N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]-ethylamine monohydrochloride (NE100) blocked the enhancements caused by these Sig-1R agonists. In separate experiments, we found that NGF dose and time dependently increased Sig-1R in PC12 cells. Chronic treatment of cells with (+)PTZ, imipramine, or fluvoxamine also increased Sig-1R. These latter results suggested that NGF induces the neurite sprouting by increasing Sig-1R. Indeed, the overexpression of Sig-1R per se in PC12 cells enhanced the NGF-induced neurite sprouting. Furthermore, antisense deoxyoligonucleotides directed against Sig-1R attenuated the NGF-induced neurite sprouting. Thus, when taken together, our results indicate that Sig-1R play an important role in the NGF-induced neurite sprouting and that certain antidepressants may facilitate neuronal sprouting in the brain via Sig-1R.

Circuits and systems in stress. II. Applications to neurobiology and treatment in posttraumatic stress disorder

This paper follows the preclinical work on the effects of stress on neurobiological and neuroendocrine systems and provides a comprehensive working model for understanding the pathophysiology of posttraumatic stress disorder (PTSD). Studies of the neurobiology of PTSD in clinical populations are reviewed. Specific brain areas that play an important role in a variety of types of memory are also preferentially affected by stress, including hippocampus, amygdala, medial prefrontal cortex, and cingulate. This review indicates the involvement of these brain systems in the stress response, and in learning and memory. Affected systems in the neural circuitry of PTSD are reviewed (hypothalamic-pituitary-adrenal axis (HPA-axis), catecholaminergic and serotonergic systems, endogenous benzodiazepines, neuropeptides, hypothalamic-pituitary-thyroid axis (HPT-axis), and neuro-immunological alterations) as well as changes found with structural and functional neuroimaging methods. Converging evidence has emphasized the role of early-life trauma in the development of PTSD and other trauma-related disorders. Current and new targets for systems that play a role in the neural circuitry of PTSD are discussed. This material provides a basis for understanding the psychopathology of stress-related disorders, in particular PTSD.

Psychopharmacological treatment in PTSD: a critical review

INTRODUCTION

Posttraumatic stress disorder (PTSD) is a prevalent psychiatric disorder that is heterogeneous in its nature, and often presents with other psychiatric comorbidities. As a result, empirical research on effective pharmacotherapy for PTSD has produced complex findings. This article reviews the existing research literature on pharmacological treatments for PTSD, identifies the most effective treatments, and where possible examines their mechanism of action with respect to the neurobiology of PTSD.

METHODS

We examined reports of clinical trials of psychotropic agents carried out with PTSD patients and published in peer-reviewed journals, as well as reports from presentations at scientific meetings between 1966 and 2001.

RESULTS

Numerous medications are effective in treating PTSD. These include tricyclic antidepressants, monoamine oxidase inhibitors, and serotonin reuptake inhibitors. Considering reported overall efficacy and side effects profiles, selective serotonin reuptake inhibitors emerge as the preferred first line treatment for PTSD. Mood stabilizers, atypical neuroleptics, adrenergic agents, and newer antidepressants also show promise, but require further controlled trials to clarify their place in the pharmacopoeia for PTSD.

DISCUSSION

There is clear evidence for effective pharmacotherapy of PTSD. Future improvements in the treatment of this disorder await further clinical trials and neurobiological research.

Neurochemical and behavioral alterations elicited by a chronic intermittent stressor regimen: implications for allostatic load

Although stressors induce a series of adaptive neurochemical changes, sustained physiological activation associated with protracted stressor exposure may engender adverse effects (allostatic load). In the present investigation CD-1 mice exposed to a series of different stressors, twice a day over 54 days, exhibited increased signs of depression and anxiety, including increased passivity in a forced swim test, reduced aggression in a social interaction test, and delayed approach to food in a novel environment. Consistent with the view that a chronic stressor regimen affects immune-related processes, sickness behavior elicited by the proinflammatory cytokine, interleukin-1beta, was augmented in response to a chronic but not an acute stressor. Relative to nonstressed mice, median eminence serotonin was augmented by the cytokine treatment administered 24 h after chronic stressor exposure. Treatment with IL-1beta diminished plasma growth hormone levels and increased circulating corticosterone levels irrespective of the animals stressor history. It is suggested that chronic stressor exposure may instigate relatively protracted neurochemical effects, thereby influencing the behavioral responses to later psychological and systemic challenges.

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.

Preclinical models: status of basic research in depression

Approximately one half-century ago several classes of medications, discovered by serendipity, were introduced for the treatment of depression and bipolar disorder. These highly effective medications revolutionized our approach to mood disorders and helped launch the modern era of psychiatry. Yet our progress since those serendipitous discoveries has been disappointing. We still do not understand with certainty how those medications produce their desired clinical effects. We have not introduced newer medications with fundamentally different mechanisms of action than the older agents. We have not identified the genetic and neurobiological mechanisms underlying depression and mania, nor do we understand the mechanisms by which nongenetic factors influence these disorders. We have only a rudimentary understanding of the circuits in the brain responsible for the normal regulation of mood and affect, and of those circuits that function abnormally in mood disorders. In approaching these gaps in our knowledge, this workgroup highlighted four major areas for future investment. These include developing better animal models of mood disorders; identifying genetic determinants of normal and abnormal mood in humans and animals; discovering novel targets and biomarkers of mood disorders and treatments; and increasing the recruitment of investigators from diverse backgrounds to mood disorders research.

Enhancement of stress-induced pituitary hormone release and cardiovascular activation by antidepressant treatment in healthy men

A randomized, double-blind, placebo-controlled trial was performed to verify the suggestion that (i) in accordance with the results of animal studies, treatment with antidepressants inhibits hormone release in response to stressful stimulation in humans and (ii) drugs with opposing effects on brain serotonine (citalopram and tianeptine) exert similar modulatory effects on neuroendocrine activation during stress. Healthy male volunteers were treated with citalopram (20 mg), tianeptine (37.5 mg) or placebo for 7 days. As a stress stimulus, insulin-induced hypoglycaemia was used. Measurement of hormone concentrations revealed an enhanced release of adrenocorticotropic hormone and growth hormone in response to stress of hypoglycaemia in subjects treated with both antidepressants used. A similar augmentation was observed in systolic blood pressure. Stress-induced prolactin release was potenciated by citalopram only. Plasma renin activity, epinephrine, norepinephrine and cortisol levels failed to be modified by antidepressants. The present study demonstrates that (i) repeated antidepressant treatment in healthy men does not inhibit, but enhances, neuroendocrine activation during stress and (ii) such effects were observed after treatment with antidepressants having opposing actions on brain serotonin, indicating involvement of nonserotoninergic mechanisms.

The antidepressant tianeptine persistently modulates glutamate receptor currents of the hippocampal CA3 commissural associational synapse in chronically stressed rats

Recent hypotheses on the action of antidepressants imply a modulation of excitatory amino acid transmission. Here, the effects of long-term antidepressant application in rats with the drug tianeptine were examined at hippocampal CA3 commissural associational (c/a) glutamate receptor ion channels, employing the whole-cell patch-clamp technique. The drug's impact was tested by subjecting rats to daily restraint stress for three weeks in combination with tianeptine treatment (10 mg/kg/day). Whereas stress increased the deactivation time-constant and amplitude of the N-methyl-d-aspartate (NMDA) receptor-mediated excitatory postsynaptic currents (EPSCs), it did not affect the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)/kainate receptor-mediated EPSCs. Concomitant pharmacological treatment of stressed animals with tianeptine resulted in a normalized scaling of the amplitude ratio of NMDA receptor to AMPA/kainate receptor-mediated currents and prevented the stress-induced attenuation of NMDA-EPSCs deactivation. Both paired-pulse-facilitation and frequency-dependent plasticity remained unchanged. Both in control and stressed animals, however, tianeptine treatment strengthened the slope of the input-output relation of EPSCs. The latter was mimicked by exposing hippocampal slices in vitro with 10 micro m tianeptine, which rapidly increased the amplitudes of NMDA- and AMPA/kainate EPSCs. The enhancement of EPSCs could be blocked by the intracellular presence of the kinase inhibitor staurosporine (1 micro m), suggesting the involvement of a postsynaptic phosphorylation cascade rather then presynaptic release mechanisms at CA3 c/a synapses. These results indicate that tianeptine targets the phosphorylation-state of glutamate receptors at the CA3 c/a synapse. This novel signal transduction mechanism for tianeptine may provide a mechanistic resolution for its neuroprotective properties and, moreover, a pharmacological trajectory for its memory enhancing and/or antidepressant activity.

Sleep deprivation impairs long-term potentiation in rat hippocampal slices

To determine if 12-h sleep deprivation disrupts neural plasticity, we compared long-term potentiation (LTP) in five sleep-deprived and five control rats. Thirty minutes after tetanus population spike amplitude increased 101 +/- 15% in 16 slices from sleep deprived rats and 139 +/- 14% in 14 slices from control rats. This significant (P < 0.05) reduction of LTP, the first demonstration that the sleep deprivation protocol impairs plasticity in adult rats, may be due to several factors. Reduced LTP may indicate that sleep provides a period of recuperation for cellular processes underlying neural plasticity. Alternatively, the stress of sleep deprivation, as indicated by elevated blood corticosterone levels, or other non-sleep-specific factors of deprivation may contribute to the LTP reduction.

PTSD symptoms and cognitive performance in recent trauma survivors

Chronic post-traumatic stress disorder (PTSD) has been associated with cognitive impairments involving memory and attention. The association between cognitive impairment and early PTSD symptoms is unknown, yet such association may lead to poorer processing of traumatic memories and thereby contribute to subsequent PTSD. This study evaluated the relationship between PTSD symptoms and cognitive functioning within 10 days of traumatic events. Forty-eight survivors were assessed for symptoms of PTSD, anxiety, depression and dissociation and for immediate and delayed verbal and figural memory, attention, learning and IQ. Survivors with high levels of PTSD symptoms showed impaired attention and immediate recall for figural information and lower IQ. They did not show, however, an impairment of verbal recall and learning. The observed difference was not explained by anxiety or dissociation. It disappeared, however, when the effect of depressive symptoms was controlled for. Lower IQ and impaired attention are associated with early PTSD and depressive symptoms. Poorer attention may have a role in shaping traumatic memories.

Effects of genetic background on neonatal Borna disease virus infection-induced neurodevelopmental damage. I. Brain pathology and behavioral deficits

The pathogenic mechanisms of gene-environment interactions determining variability of human neurodevelopmental disorders remain unclear. In the two consecutive papers, we used the neonatal Borna disease virus (BDV) infection rat model of neurodevelopmental damage to evaluate brain pathology, monoamine alterations, behavioral deficits, and responses to pharmacological treatments in two inbred rat strains, Lewis and Fisher344. The first paper reports that despite comparable virus replication and distribution in the brain of both rat strains, neonatal BDV infection produced significantly greater thinning of the neocortex in BDV-infected Fisher344 rats compared to BDV-infected Lewis rats, while no strain-related differences were found in BDV-induced granule cell loss in the dentate gyrus of the hippocampus and cerebellar hypoplasia. Unlike BDV-infected Lewis rats, more severe BDV-induced brain pathology in Fisher344 rats was associated with (1) greater locomotor activity to novelty and (2) impairment of habituation and prepulse inhibition of the acoustic startle response. The present data demonstrate that the same environmental insult can produce differential neuroanatomical and behavioral abnormalities in genetically different inbred rat strains.

Postnatally induced differences in adult pain sensitivity depend on genetics, gender and specific experiences: reversal of maternal deprivation effects by additional postnatal tactile stimulation or chronic imipramine treatment

Postnatal endotoxin exposure, handling or maternal deprivation produce long-lasting individual differences in various neuroendocrine and behavioural responses. However, the impact of postnatal experiences on adult pain sensitivity and its reversibility by postnatal additional tactile stimulation or antidepressants in adulthood is not well understood. Therefore, postnatal endotoxin application as a model for infection, maternal deprivation as a model for depression, and postnatal handling as a model for stimulation were compared with respect to the effects on pain sensitivity in adult Fischer 344 (F344) and Lewis (LEW) rats. Handling increased hot plate latencies in adult F344 and LEW rats, while maternal deprivation shortened hot plate latencies only in LEW rats. Prophylactic treatment strategies, such as tactile stimulation of the dorsal neck region of pups directly after maternal deprivation, or chronic treatment of adult maternally deprived rats using imipramine, successfully provide protection against the maternal deprivation-induced shortening of hot plate latencies. Thus, there is considerable specificity of certain postnatal experiences in modulating adult pain sensitivity and the maternal deprivation-induced hyperalgesia is reversible by different interventional regimes. These findings may explain some of the individual differences in pain sensitivity of humans and the differential efficacy of antidepressants in pain syndromes.

Circuits and systems in stress. I. Preclinical studies

This paper reviews the preclinical literature related to the effects of stress on neurobiological and neuroendocrine systems. Preclinical studies of stress provide a comprehensive model for understanding neurobiological alterations in post-traumatic stress disorder (PTSD). The pathophysiology of stress reflects long-standing changes in biological stress response systems and in systems involved in stress responsivity, learning, and memory. The neural circuitry involved includes systems mediating hypothalamic-pituitary-adrenal (HPA) axis, norepinephrine (locus coeruleus), and benzodiazepine, serotonergic, dopaminergic, neuropeptide, and central amino acid systems. These systems interact with brain structures involved in memory, including hippocampus, amygdala, and prefrontal cortex. Stress responses are of vital importance in living organisms; however excessive and/or repeated stress can lead to long-lasting alterations in these circuits and systems involved in stress responsiveness. Intensity and duration of the stressor, and timing of the stressor in life, have strong impact in this respect.

Allostatic load as a predictor of functional decline. MacArthur studies of successful aging

Allostatic load has been proposed as a cumulative measure of dysregulation across multiple physiological systems, and has been postulated to impact health risks. In the allostatic load model, increased risk is hypothesized to result not only from large and clinically significant dysregulation in individual systems, but also from more modest dysregulation, if present in multiple systems. Our objective was to construct an allostatic load score by optimally combining several physiologic measurements, and to examine its association with future functional decline. We analyzed data from a 7-year longitudinal study of a community-based cohort, whose age at baseline was between 70 and 79 years. Canonical correlation analysis was used to study the association of 10 biological measurements representing allostatic load with declines in scores on five tests each of physical and cognitive function over two follow-up periods: 1998-1991 and 1991-1995. We used bootstrapping to evaluate the stability of the canonical correlation and canonical weights. The canonical correlation between allostatic load and the 20 decline scores was 0.43 (P =.03) and the [25th, 75th] percentile interval of its distribution over 200 bootstrapped subsamples of the cohort was [0.48, 0.53]. These findings were not substantially affected by adjusting for covariates and cardiovascular disease. We conclude that a summary measure of physiologic dysregulation, such as allostatic load, is an independent predictor of functional decline in elderly men and women.

Hormonal interactions within the hypothalamus and pituitary with respect to stress and reproduction in sheep

Endocrine systems may be used as indicators of stress in two ways. The primary role of a hormone may be as part of the homeostatic response to a stimulus (e.g., adrenaline, corticosteroids). The amplitude of hormone response may correlate with the severity of the stimulus and any change indicate that the body is responding. Alternatively, a hormone may have a key role in normal body function (e.g., reproduction) and stress may deleteriously alter the hormone signal prevent normal function. This demonstrates that the stimulus was sufficiently severe that homeostatic mechanisms were unable to maintain normal function. Stress may effect reproduction by reducing both LH pulse amplitude and frequency. The LH surge may also be delayed. Several mechanisms may account for these effects both at the hypothalamus and pituitary. Corticosteroids have a broad, yet fundamental, role in homeostasis and have been used as primary indicators of stress for many years. Excess corticosteroid can be detrimental so the concentration is controlled via the hypothalamus-pituitary-adrenal (HPA) axis by multi-level feedback mechanisms. Under field and experimental conditions, after an initial large response prolonged stimulation leads to a gradually reducing plasma corticosteroid concentrations. This has been interpreted as a reduction in perceived stimulus severity or habituation to the stimulus and the animal deemed "less stressed" and its welfare "better." However, this reduction may be due to the intrinsic control mechanisms designed to prevent prolonged increases in corticosteroid concentrations. The stress signal at higher brain levels may still be present and the animal may still be experiencing the stimulus as aversive. Thus, the welfare interpretation of a corticosteroid concentration may differ during the time course of a stress response. A greater understanding of the mechanisms controlling corticosteroid secretion at each level of the HPA is required to determine what is the correct interpretation at any time point. To address these issues, we have used mathematical modelling to produce representations of possible control mechanisms at each level of the HPA. The starting point was to measure AVP and CRH concentrations in hypophysial portal blood and ACTH and cortisol concentrations in jugular blood in conscious sheep during 2h road transport (a cognitive stimulus). Modelling identified the signal inputs that were most likely to explain the secretion rate of each hormone. Modelling suggested that the reduction in AVP and CRH secretion observed during transport was most likely due to a reduction in stimulus input, with a significant contribution from cortisol negative feedback only on AVP secretion. At the pituitary level, ACTH secretion was stimulated more by AVP than by CRH (ratio 2.3:1) and there was also a stimulatory effect related to cortisol concentration at the time of sampling. However, the responses to both stimuli were curtailed by cortisol negative feedback and an inhibitory effect of prior CRH concentration. These are complex effects, but the modelling does suggest that while "stress" inputs may reduce over time hormone negative feedback is a major factor reducing hormone responses. When interpreting hormone data for animal welfare purposes, it is important not to interpret a reduction in hormone concentration due to intrinsic hormone control mechanisms as a reduction due to a decrease in the stress stimulus.

Antidepressants and neuroplasticity

OBJECTIVE

We review the literature on the cellular changes that underlie the structural impairments observed in brains of animals exposed to stress and in subjects with depressive disorders. We discuss the molecular, cellular and structural adaptations that underlie the therapeutic responses of different classes of antidepressants and contribute to the adaptive plasticity induced in the brain by these drugs.

METHODS

We review results from various clinical and basic research studies.

RESULTS

Studies demonstrate that chronic antidepressant treatment increases the rate of neurogenesis in the adult hippocampus. Studies also show that antidepressants up-regulate the cyclic adenosine monophosphate (cAMP) and the neurotrophin signaling pathways involved in plasticity and survival. In vitro and in vivo data provide direct evidence that the transcription factor, cAMP response element-binding protein (CREB) and the neurotrophin, brain derived-neurotrophic factor (BDNF) are key mediators of the therapeutic response to antidepressants.

CONCLUSIONS

These results suggest that depression maybe associated with a disruption of mechanisms that govern cell survival and neural plasticity in the brain. Antidepressants could mediate their effects by increasing neurogenesis and modulating the signaling pathways involved in plasticity and survival.