Central mechanisms of stress integration: hierarchical circuitry controlling hypothalamo-pituitary-adrenocortical responsiveness

Life history and the early origins of health differentials

Current epidemiologic models concerning the fetal origins of later health risk are evaluated from the perspectives of evolutionary and developmental biology. Claims of adaptive value for and biological status of fetal programming are critically examined. Life history theory is applied to identify key trade-offs in adaptive strategies that constrain developmental design to use information from the environment to guide ontogeny and establish cost-benefit trade-offs that weigh early survival advantage against remote or unlikely future costs. Expectable environments of evolutionary adaptedness, particularly of gestation, are characterized and their impact on human adaptive design discussed. The roles of neuroendocrine mechanisms in scaffolding life course development, negotiating ongoing cost-benefit trade-offs, and mediating their long-term impacts on function and health are reviewed in detail. Overviews of gestational biology and the postnatal physiologic, cognitive-affective, and behavioral effects of gestational stress identify a shared central role for the hypothalamic-pituitary-adrenal (HPA) axis. Rather than merely mediating stress responses, the axis emerges an agent of resource allocation that draws a common thread among conditions of gestation, postnatal environments, and functional and health-related outcomes. The preponderance of evolutionary and developmental analysis identifies environments as agents on both sides of the health risk equation, by influencing vulnerabilities and capacities established in early and later life course development, and determining exposures and demands encountered over the life course.

Corticotropin-releasing factor-binding protein, stress and major depression

Major depressive disorder (MDD) is characterized by a dysregulation of the stress response system. A corticotropin-releasing factor (CRF) hyperdrive is a consistent and well-documented finding. CRF-binding protein (CRF-BP) may play a role in the pathogenesis of MDD. CRF-BP reduces the availability of CRF by binding free CRF and inhibits CRF function at the pituitary level. Moreover, CRF-BP expression increases in the pituitary and amygdala in response to acute stress, providing an additional feedback mechanism to maintain the homeostasis of the stress response. There are different regulatory elements of the expression of CRF-BP gene that are implicated in the pathophysiology of MDD, including CRF, glucocorticoids, cytokines and estrogens. A specific haplotype within the CRF-BP gene has been associated with MDD, but confirmation of this finding is necessary. Currently, the possible role of CRF-BP in the pathophysiology of conditions that have been associated with a hypofunction of the CRF system and immune dysfunctions is unclear. Implications of the function of CRF-BP for therapeutic strategies in MDD are being discussed. An important advantage of ligands that target CRF-BP is that concentrations of free CRF can be altered without acting directly on the transmission of CRF through its receptor.

Expression of the glucocorticoid-induced receptor mRNA in rat brain

The glucocorticoid-induced receptor (GIR) is an orphan G-protein-coupled receptor awaiting pharmacological characterization. GIR was originally identified in murine thymoma cells, and shows a widespread, yet not completely complementary distribution in mouse and human brain. Expression of the mouse GIR gene is modulated by dexamethasone in the brain and periphery, suggesting that GIR function is directly responsive to glucocorticoid signals. The rat GIR was cloned from rat prefrontal cortex by our group and was shown to be up-regulated following chronic amphetamine. The physiological role of GIR in the rat is not known at present. In order to gain a clearer understanding of the potential functions of GIR in the rat, we performed a detailed mapping of GIR mRNA expression in the rat brain. GIR mRNA showed widespread distribution in forebrain limbic and thalamic structures, and a more restricted distribution in hindbrain areas such as the spinal trigeminal nucleus and the median raphe nucleus. Areas with moderate to high levels of GIR include olfactory regions such as the nucleus of olfactory tract, hippocampus, various thalamic nuclei, cortical layers, and some hypothalamic nuclei. In comparison with previous studies, significant regional differences exist in GIR distribution in mouse and rat brain, particularly in the thalamus, striatum and in hippocampus at a cellular level. Overall, the expression of GIR in rat brain more closely approaches that seen previously in human than mouse, suggesting that rat models may be more informative for understanding the role of GIR in glucocorticoid physiology and glucocorticoid-related disease states. GIR mRNA distribution in the rat indicates a potential role of this receptor in the control of feeding and ingestive behavior, regulation of stress and emotional behavior, learning and memory, and, drug reinforcement and reward.

Signaling pathways in brain involved in predisposition and pathogenesis of stress-related disease: genetic and kinetic factors affecting the MR/GR balance

Optimal regulation of the stress response is a prerequisite for adaptation, homeostasis, and health. There are two modes of operation in the stress response. First, an immediate response mode mediated by corticotrophin-releasing hormone-1 (CRH-1) receptors that organizes the behavioral, sympathetic, and hypothalamic-pituitary-adrenal (HPA) response to a stressor. Second, a slower mode, which facilitates behavioral adaptation, promotes recovery, and reestablishes homeostasis. Corticosteroid hormones are implicated in both stress system modes. On the one hand, cortisol and corticosterone determine the threshold or sensitivity of the fast responding mode, whereas the very same hormones in high concentrations facilitate termination of the stress response. In the brain, these actions exerted by the corticosteroid hormones are mediated by two distinct nuclear receptor types, that is, mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs). Whereas MRs maintain neuronal homeostasis and limit the disturbance by stress, GRs help to recover after the challenge and to store the experience for coping with future encounters. Imbalance in MR/GR-mediated actions compromises homeostatic processes in these neurons, which is thought to underlie maladaptive behavior and HPA dysregulation that may lead to aberrant metabolism, impaired immune function, and altered cardiovascular control. The balance in MR/GR-mediated actions depends on bioavailability of corticosteroids, access to the receptors, the stoichiometry of co-regulators, and other proteins as well as genetic factors, among which single nucleotide polymorphisms (SNPs) of the GRs are extensively documented. Stress can bias the receptor signaling pathways, changing "good" corticosteroid actions into "bad" ones.

Corticotropin-releasing hormone activates ERK1/2 MAPK in specific brain areas

Corticotropin-releasing hormone (CRH) coordinates hormonal and behavioral responses to stress. The mitogen-activated protein kinase extracellular signal-related kinase 1/2 (ERK1/2) mediates several functions in different forebrain structures and recently has been implicated in CRH signaling in cultured cells. To study in vivo CRH-mediated activation of central ERK1/2, we investigated the expression pattern of the phosphorylated ERK1/2(p-ERK1/2) in the mouse brain after intracerebroventricular CRH injections. As shown by immunohistochemistry and confocal microscopy analysis, CRH administration increased p-ERK1/2 levels specifically in the CA3 and CA1 hippocampal subfields and basolateral complex of the amygdala, both structures related to external environmental information processing and behavioral aspects of stress. Other regions such as hypothalamic nuclei and the central nucleus of the amygdala, also related to central CRH system but involved in the processing of the ascending visceral information and neuroendocrine-autonomic response to stress, did not show CRH-mediated ERK1/2 activation. To dissect the involvement of CRH receptor 1 (CRHR1) and CRHR2, we used conditional knockout mice in which Crhr1 is inactivated in the anterior forebrain and limbic structures. The conditional genetic ablation of Crhr1 inhibited the p-ERK1/2 increase, underlining the involvement of CRHR1 in the CRH-mediated activation. These findings underscore the fact that CRH activates p-ERK1/2 through CRHR1 only in selected brain regions, pointing to a specific role of this pathway in mediating behavioral adaptation to stress.

Neuro-evolutionary patterning of sociality

Evolutionary shifts in species-typical group size ('sociality') probably reflect natural selection on motivational processes such as social arousal, approach-avoidance, reward, stress/anxiety and dominance. Using four songbird species that differ selectively in sociality (one territorial, one modestly gregarious, and two highly gregarious species), we here examined immediate early gene (IEG) responses of relevant brain regions following exposure to a same-sex conspecific. The paradigm limited behavioural performance, thus species differences should reflect divergence in motivational and/or perceptual processes. Within the extended medial amygdala (which is involved in appetitive approach, social arousal and avoidance), we observed species differences in IEG response that are negatively graded in relation to sociality. In addition, brain areas that are involved in social stress and dominance-related behaviour (ventrolateral septum, anterior hypothalamus and lateral subdivision of the ventromedial hypothalamus) exhibited IEG responses that dichotomously distinguish the territorial species from the three gregarious species. The IEG responses of areas involved in reward (nucleus accumbens and ventral pallidum) and general stress processes (e.g. paraventricular hypothalamus, lateral bed nucleus of the stria terminalis and most areas of the lateral septum) do not correlate with sociality, indicating that social evolution has been accompanied by selection on a relatively discrete suite of motivational systems.

Dissecting the genetic effect of the CRH system on anxiety and stress-related behaviour

Corticotropin-releasing hormone (CRH) plays a central role in the adaptation of the body to stress. CRH integrates the endocrine, autonomic and behavioural responses to stress acting as a secretagogue within the line of the hypothalamic pituitary adrenocortical (HPA) system and as a neurotransmitter modulating synaptic transmission in the central nervous system. Accumulating evidence suggests that the neuroendocrine and behavioural symptoms observed in patients suffering from major depression are at least in part linked to a hyperactivity of the CRH system. Genetic modifications of the CRH system by conventional and conditional gene targeting strategies in the mouse allowed us to study the endogenous mechanisms underlying HPA system regulation and CRH-related neuronal circuitries involved in pathways mediating anxiety and stress-related behaviour.

RETRACTED: Maternal adversity, glucocorticoids and programming of neuroendocrine function and behaviour

The fetus may be exposed to increased endogenous glucocorticoid or synthetic glucocorticoid in late gestation. Approximately 7% of pregnant women in Europe and North America are treated with synthetic glucocorticoid to promote lung maturation in fetuses at risk of preterm delivery. Very little is known about the mechanisms by which synthetic glucocorticoid or prenatal stress influence neurodevelopment in the human, or whether specific time windows of increased sensitivity exist. Glucocorticoids are essential for many aspects of normal brain development, but exposure of the fetal brain to excess glucocorticoid can have life-long effects on neuroendocrine function and behaviour. Both endogenous glucocorticoid and synthetic glucocorticoid exposure have a number of rapid effects in the fetal brain, including modification of neurotransmitter systems and transcriptional machinery. Such fetal exposure permanently alters hypothalamo-pituitary-adrenal (HPA) function in prepubertal, postpubertal and aging offspring, in a sex-dependent manner. Prenatal glucocorticoid manipulation also leads to modification of behaviour, brain and organ morphology, as well as altered regulation of other endocrine systems. Permanent changes in endocrine function will impact on health, since elevated cumulative exposure to endogenous glucocorticoid is linked to the premature onset of pathologies associated with aging.

Stress, genes and the mechanism of programming the brain for later life

Adverse conditions during early life are a risk factor for stress-related diseases such as depression and post-traumatic stress disorder (PTSD). How this long-term effect of early adversity occurs is not known, although evidence accumulates that the action of stress hormones is an important determinant. In rodents after a variety of experiences, even minor ones, during postnatal life permanent changes in emotional and neuroendocrine reactivity have been observed. Also stressful events occurring prenatally and even the pre-implantation hormonal conditions can have permanent consequences. Here we will focus on evidence obtained from (i) the blastocyst implantation during conditions of ovarian hyperstimulation, which is commonly used in the generation of transgenic mice; (ii) the stress system activity in the newborn under various conditions of maternal care; (iii) the long-term consequences of maternal separation procedures. The results clearly demonstrate that early experiences trigger immediate changes in the stress system that may permanently alter brain and behaviour.

Measuring stress responses in postpartum mothers: perspectives from studies in human and animal populations

Reduced hypothalamic-pituitary-adrenal (HPA) responses to stress during the last week of pregnancy and lactation have been consistently observed in rat studies. Several contributing factors have been proposed for this phenomenon in lactation, including the suckling stimulus from the pups, hormones (oxytocin and prolactin) and opioids, a decrease in the ability of noradrenaline to potentiate hypothalamic responses and changes in pituitary responsiveness to ACTH secretagogues (AVP and CRF). In contrast to this vast literature using the rat model, only few studies have addressed this issue in the human population. The consensus is that women engaging in breastfeeding activities exhibit reduced anxiety, although the reductions in neuroendocrine and autonomic responses to stressors are variable, in part because of the different nature of the stressors used. Further work is required to investigate how additional factors, such as maternal parity or emotional salience of the stressor can affect stress responsiveness in postpartum women. Here, we review first the findings regarding stress responsiveness during lactation in both rat and human studies, and then discuss potential research avenues and methodological issues that could be the lead to future research protocols in human subjects. Knowing the reciprocal relationship in the mother-infant dyad, it is clear that investigation of the mechanisms regulating stress responses and mental health in postpartum mothers can only be beneficial to the development of the infant.

Postnatal ontogeny of hippocampal expression of the mineralocorticoid and glucocorticoid receptors in the common marmoset monkey

The mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) are nuclear transcription factors that mediate many of the basal and stress functions and effects of the corticosteroid hormones, including those related to brain development. Despite this, relatively little is known about the postnatal ontogeny of MR and GR gene and protein expression in the central nervous system, and this is particularly true of the primates, including humans. Here we describe the postnatal ontogeny of central MR and GR gene and protein expression in the common marmoset monkey. By developing marmoset-specific riboprobes and using in situ hybridization, it was demonstrated that MR mRNA expression in the dentate gyrus and Ammon's horn was significantly greater in marmoset infants (aged 4-6 weeks) than in neonates (1-2 days), juveniles (4-5 months) and adults (3-6 years), with expression in the latter three ontogenetic stages being broadly similar. In the same subjects and ontogenetic stages, GR mRNA expression was developmentally consistent in the marmoset dentate gyrus and Ammon's horn, as well as in the paraventricular nucleus of the hypothalamus. Qualitative immunohistochemical comparison of infants and adults demonstrated that MR protein expression in the hippocampus was, as for mRNA, also greater in infants than adults, and that hippocampal GR protein was, as for mRNA, also similar in infants and adults. The increase in MR mRNA expression between the stages of neonate and infant co-occurred with a reduction in basal plasma ACTH and cortisol titres. The ontogenetic profiles of MR and GR gene expression in the marmoset monkey are therefore fundamentally different from those described for the rat and the mouse. This evidence for the postnatal ontogeny of central corticosteroid nuclear receptor expression in a primate is important for understanding both the developmental stage-specific significance of stress exposure and its potential long-term effects on health and disease.

Chronic treatment with the monoamine oxidase inhibitor phenelzine increases hypothalamic-pituitary-adrenocortical activity in male C57BL/6 mice: relevance to atypical depression

Atypical depression has been linked to low hypothalamic-pituitary-adrenocortical axis activity and exhibits physical and affective symptoms resembling those of glucocorticoid deficiency. Because atypical depression has also been defined by preferential responsiveness to monoamine oxidase inhibitors (MAO-I), we hypothesized that MAO-I reverse these abnormalities by interfering with glucocorticoid feedback and increasing hypothalamic-pituitary-adrenocortical activity. To test this hypothesis, we measured plasma hormones and ACTH secretagogue gene expression in male C57BL/6 mice treated chronically with saline vehicle or phenelzine, a representative MAO-I. Changes in glucocorticoid feedback were evaluated using adrenalectomized (ADX) mice with and without corticosterone replacement. Antidepressant efficacy was confirmed by decreased immobility during forced swim testing. Phenelzine significantly increased circadian nadir and postrestraint plasma corticosterone levels in sham-operated mice, an effect that correlated with increased adrenocortical sensitivity to ACTH. Phenelzine increased circadian nadir, but not poststress ACTH in ADX mice, suggesting that phenelzine augmented corticosterone secretion in sham-operated mice by increasing stimulation and decreasing feedback inhibition of hypothalamic-pituitary activity. Consistent with the latter possibility, phenelzine significantly increased plasma ACTH and paraventricular hypothalamus CRH mRNA in ADX, corticosterone-replaced mice. Phenelzine did not increase paraventricular hypothalamus CRH or vasopressin mRNA in ADX mice lacking corticosterone replacement. We conclude that chronic phenelzine treatment induces sustained increases in glucocorticoids by impairing glucocorticoid feedback, increasing adrenocortical responsiveness to ACTH, and increasing glucocorticoid-independent stimulation of hypothalamic-pituitary activity. The resulting drive for adrenocortical activity could account for the ability of MAO-I to reverse endocrine and psychiatric symptoms of glucocorticoid deficiency in atypical depression.

Provocation of kainic acid receptor mRNA changes in the rat paraventricular nucleus by insulin-induced hypoglycaemia

Hypoglycaemia induced by insulin injection is a powerful stimulus to the hypothalamic-pituitary-adrenal (HPA) axis and drives the secretion of corticotropin-releasing hormone and vasopressin from the neurones in the paraventricular nucleus (PVN), as well as the downstream hormones, adrenocorticotropic hormone and corticosterone. In some brain regions, hypoglycaemia also provokes increases in extracellular fluid concentrations of glutamate. Regulation of glutamatergic mechanisms could be involved in the control of the HPA axis during hypoglycaemic stress and one potential site of regulation might be at the receptors for glutamate, which are expressed in the PVN. Insulin (2.0 IU/kg, i.p.) or saline was administered to adult male Sprague-Dawley rats and the animals were sacrificed 30 min, 180 min and 24 h after injection. The amount of several kainic acid-preferring glutamate receptor mRNAs (i.e. KA2, GluR5 and GluR6) were assessed in the PVN by in situ hybridisation histochemistry. Injection of insulin induced a rapid fall in plasma glucose concentrations, which was mirrored by an increase in plasma corticosterone concentrations. KA2 and GluR5 mRNAs are highly expressed within the rat PVN, and responded to hypoglycaemia with robust increases in expression that endured beyond the period of hypoglycaemia itself. However, GluR6 mRNA is expressed in the areas adjacent to the PVN and hypoglycaemic stress failed to alter expression of this mRNA. These experiments suggest that kainic acid-preferring glutamate receptors are responsive to changes in plasma glucose concentrations and may participate in the activation of the PVN neurones during hypoglycaemic stress.

Endurance treadmill training in rats alters CRH activity in the hypothalamic paraventricular nucleus at rest and during acute running according to its period

Running training on the treadmill increases the resting hypothalamic corticotropin-releasing hormone (CRH) content in rats, though is still unknown whether and how it occurs in the parvocellular region of the hypothalamic paraventricular nucleus (PVN) where is a predominant region of pituitary-adrenal activity and where CRH and arginine vasopressin (AVP) are colocalized. We thus aimed at examining whether treadmill training would alter the CRH and AVP mRNA levels in the PVN at rest and during acute running with different lengths of a training regime. Male Wistar rats were subjected to treadmill running (approximately 25 m/min, 60 minutes/day, 5 times/week) for training regimes of 0, 1, 2 or 4 weeks. All training regimes induced an adrenal hypertrophy. Plasma corticosterone levels before acute running increased with lengthening the training period. Four weeks of training produced a significant increase in the resting CRH, but not AVP, mRNA levels in the PVN though relatively shorter training regimes did not. Acute responses of lactate and ACTH release were reduced after 2 and 4 weeks of training, respectively. The responsive PVN CRH mRNA level to acute running decreased with 4 weeks of training but increased with relatively shorter training regimes. These results indicate that running training changes the PVN CRH biosynthetic activity with the regime lasting for 4 weeks, which follows adaptive changes in adrenal functions. Thus, running training-induced changes in hypothalamic CRH activity would originate from the PVN and be induced according to the training period.

Stress, cognitive impairment and cell adhesion molecules

Stress has profound effects on brain structure and function, but the underlying mechanisms are still poorly understood. Recent studies imply that neuronal cell adhesion molecules of the immunoglobulin superfamily--NCAM and L1--are important mediators of the effects of stress on the brain. Chronic stress regimes that lead to hippocampal atrophy and spatial-learning impairment in rodents simultaneously induce a pattern of changes in cell adhesion molecule expression that fits with a role for these molecules in stress-induced neuronal damage and neuroprotective mechanisms. These findings highlight cell adhesion molecules as potential therapeutic targets to treat stress-related cognitive disturbances.

Role of the central amygdala in modulating the pituitary-adrenocortical and clinical responses in experimental herpes simplex virus-1 encephalitis

The amygdala is known to regulate neuroendocrine and behavioral responses to a variety of stimuli. Herpes simplex virus-1 (HSV-1) is the common cause of viral encephalitis, manifested by hypothalamic-pituitary-adrenal (HPA) axis activation, fever, hypermotor activity and aggression. We examined here the role of the central amygdala (cAMG) in regulating the HPA axis function, febrile and behavioral responses to HSV-1 infection in rats. Bilateral electrolytic lesions were performed in the cAMG. HSV-1 encephalitis was induced by intracerebroventricular (ICV) inoculation of purified virions. Motor activity and body temperature were examined by a biotelemetric system. ICV inoculation of HSV-1 caused a marked time-dependent increase in serum corticotropin (ACTH) and corticosterone at 4 and 24 h post-infection. These responses were attenuated in rats with bilateral lesions of the cAMG. HSV-1 infection induced fever, motor hyperactivity and aggressive behavior. These responses were also attenuated in rats with cAMG lesions. The cAMG plays an important role in mediating the neuroendocrine, febrile and behavioral responses to HSV-1 infection.

A single dose of metyrapone caused long-term dysregulation of the hypothalamic–pituitary–adrenal axis in the rat

There is evidence that metyrapone (MET), apart from its inhibition of 11-beta steroid hydroxylation, may exert some stress-like effects in the brain, including the activation of the hypothalamic-pituitary-adrenal (HPA) axis and the induction of c-fos. Since a single exposure to some stressors has been found to exert long-term effects on the HPA axis, we hypothesized that a single dose of MET (200 mg/kg, s.c.) could exert even stronger effects, due to the combination of its stressful properties with the lack of constrain of the HPA axis by glucocorticoids. Whereas the inhibitory effect of the drug on corticosterone secretion lasted less than 24 h, its stimulatory effect on the HPA axis could be seen for at least 2 days after the injection. Surprisingly, on day 8, an exacerbated HPA response to immobilization stress was observed in MET rats, despite complete normalization of resting levels of HPA hormones. At this time it was also observed, under basal conditions, increased levels of mRNA for CRH and arginin-vasopressin in the parvocellular region of the paraventricular nucleus of the hypothalamus (pPVN), along with reduced mRNA for glucocorticoid receptors in dentate gyrus and hippocampus CA1, but not in pPVN or medial prefrontal cortex. These data suggest that a single MET administration can exert a marked and long-lasting dysregulation of both resting and stress-induced activity of the HPA axis. Thus, attention should be paid to these properties when using the drug to study the functional role of glucocorticoids.

Organization and regulation of paraventricular nucleus glutamate signaling systems: N-methyl-D-aspartate receptors

Stress activation of the hypothalamo-pituitary-adrenocortical (HPA) axis is mediated in part by glutamatergic neurotransmission. The precise nature of glutamate effects on stress-integrative hypothalamic paraventricular nucleus (PVN) neurons remains to be determined. Therefore, the current study was designed to delineate the organization of glutamate/NMDA receptor systems in the PVN and to assess regulation of PVN glutamate receptor subunit expression by chronic intermittent stress and glucocorticoids. Immunohistochemical studies verified that N-methyl-D-aspartate (NMDA) receptor subunit proteins NR1 and NR2A/2B are expressed in the medial parvocellular PVN, indicating the potential for NMDA receptor regulation of corticotropin-releasing hormone (CRH) release. Dual-label confocal analysis revealed that CRH neurons are apposed by vesicular glutamate transporter 2 (VGLUT2)-containing terminals, consistent with glutamatergic innervation from hypothalamus and/or brainstem. In situ hybridization analysis revealed a significant and selective stress-induced decrease (37%) in NR2B subunit mRNA expression in the CRH-containing region of the PVN. No changes were observed for NR1 or NR2A mRNAs. In contrast, none of the subunits investigated showed altered expression following adrenalectomy with or without low/high-dose corticosterone replacement. Thus, the observed stress regulation is likely mediated by neurogenic mechanisms in the PVN and upstream stress-transducing neurocircuitry. Because a loss of NR2B subunit inclusion in NR receptors would likely confer increased Ca(++) conductance and faster deactivation kinetics, the stress-induced decrease in NR2B mRNA is consistent with enhanced glutamate signaling in the PVN following chronic stress and, perhaps, increased basal HPA activity and more rapid and/or more robust HPA responses to stress.

A meta-analysis of cortisol response to challenge in human aging: importance of gender

An increased cortisol response to challenge is associated with a variety of age-related disorders such as Alzheimer's disease, depression, diabetes, metabolic syndrome, and hypertension. Among the healthy elderly, an increased cortisol response to challenge may be a risk factor for developing these age-related disorders. We searched Pubmed, Embase, PsychInfo, Biosis, and Digital Dissertations (January 1966-June 2003) and included 45 parallel-group (young vs. old subjects) studies that used either a pharmacological or psychological challenge in healthy volunteers and measured cortisol response to challenge. We calculated effect sizes (Cohen's d) for the standardized mean differences between groups. Compared to younger controls (n=670, mean age 28 years +/-5), older subjects (n=625, 69+/-6) showed a larger cortisol response to challenge defined as stronger response to stimulation or less inhibition after a suppression test (d=0.42, 95% confidence interval (CI), 0.26-0.57). The effect of age on cortisol release was significantly stronger in women (d=0.65, 95% CI 0.34-0.97) than men (d=0.24, 95% CI 0.02-0.47). Our results demonstrate that aging increases the cortisol response to challenge. This effect of age on cortisol response is almost three-fold stronger in women than men. Prospective studies should explore whether the higher cortisol response in the elderly is a risk factor for developing neuropsychiatric and medical disorders.

Gender and puberty interact on the stress-induced activation of parvocellular neurosecretory neurons and corticotropin-releasing hormone messenger ribonucleic acid expression in the rat

Individual variations in hypothalamic-pituitary-adrenal (HPA) function are most evident at or beyond the time of puberty, when marked changes in sex steroid release occur. To explore the nature by which gender differences in HPA function emerge we examined in prepubertal (approximately 30-d-old) and postpubertal (approximately 60-d-old) male and female rats HPA activity under basal conditions and in response to 30 min of restraint. Within the ACTH-regulating, medial parvocellular portion of the paraventricular nucleus, restraint-induced Fos protein and arginine vasopressin heteronuclear RNA were lower in 60- than in 30-d-old males. No such age-related shift in the response of these synaptic and transcriptional markers of cellular activation occurred in female rats. Basal CRH mRNA expression levels in the paraventricular nucleus increased with age in female but not male rats. Conversely, only male rats showed an age-related increase in basal CRH mRNA in the central amygdala, suggesting that neuronal and neurosecretory CRH-expressing cell types are subject to different pubertal and gender influences. We conclude that gonadal regulation of the HPA axis develops via distinct mechanisms in males and females. Puberty-related shifts in parvocellular neurosecretory function in males are emphasized by stress-induced shifts in neuronal activation, whereas biosynthetic alterations dominate in female rats.

Acquired deficit of forebrain glucocorticoid receptor produces depression-like changes in adrenal axis regulation and behavior

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis is a hallmark of major depressive disorder. A number of studies have shown that this dysregulation is correlated with impaired forebrain glucocorticoid receptor (GR) function. To determine whether a primary, acquired deficit in forebrain GR signaling is an etiologic factor in the pathogenesis of depression, we generated a line of mice with time-dependent, forebrain-specific disruption of GR (FBGRKO). These mice develop a number of both physiological and behavioral abnormalities that mimic major depressive disorder in humans, including hyperactivity of the HPA axis, impaired negative feedback regulation of the HPA axis and, increased depression-like behavior. Importantly, a number of these abnormalities are normalized by chronic treatment with the tricyclic antidepressant, imipramine. Our findings suggest that imipramine's proposed activities on forebrain GR function are not essential for its antidepressant effects, and that alteration in GR expression may play a causative role in disease onset of major depressive disorder.

Hypothalamic paraventricular nucleus differentially supports lumbar and renal sympathetic outflow in water-deprived rats

The present study sought to determine whether the hypothalamic paraventricular nucleus (PVN) contributes in a time-dependent manner to the differential patterning of lumbar and renal sympathetic nerve activity (SNA) in water-deprived rats. Mean arterial blood pressure (MAP) and both lumbar SNA (LSNA) and renal SNA (RSNA) were recorded simultaneously in control, 24 and 48 h water-deprived rats, and the PVN was inhibited bilaterally with microinjection of the GABA(A) agonist muscimol (100 pmol in 100 nl per side). Inhibition of the PVN significantly decreased RSNA in 48 h water-deprived rats but not in 24 h water-deprived or control rats (48 h, -17 +/- 4%; 24 h, -2 +/- 5%; control, 4 +/- 6%; P < 0.05). In addition, injection of muscimol significantly decreased LSNA in 48 and 24 h water-deprived rats but not in control rats (48 h, -41 +/- 4%; 24 h, -14 +/- 6%; control, -3 +/- 2%; P < 0.05). Interestingly, the decrease in LSNA was significantly greater than the decrease in RSNA of 24 and 48 h water-deprived rats (P < 0.05). Inhibition of the PVN also significantly decreased MAP to a greater extent in 48 and 24 h water-deprived rats compared to control rats (48 h, -34 +/- 5 mmHg; 24 h, -26 +/- 4 mmHg; control, -15 +/- 3 mmHg; P < 0.05). When 48 h water-deprived rats were acutely rehydrated by giving access to tap water 2 h before experiments, inhibition of the PVN with muscimol did not alter LSNA (-12 +/- 8%) or RSNA (7 +/- 4%) but did produce a small decrease in MAP (-15 +/- 4 mmHg) that was not different from control rats. In a parallel set of experiments, acute rehydration of 48 h water-deprived rats significantly attenuated the increased Fos immunoreactivity in PVN neurones that project to the spinal cord or rostral ventrolateral medulla. Collectively, the present findings suggest that PVN autonomic neurones are synaptically influenced during water deprivation, and that these neurones differentially contribute to LSNA and RSNA in water-deprived rats.

High antenatal maternal anxiety is related to impulsivity during performance on cognitive tasks in 14- and 15-year-olds

This study prospectively investigated the influence of antenatal maternal anxiety, measured with the State Trait Anxiety Inventory at 12-22, 23-31 and 32-40 postmenstrual weeks of pregnancy, on cognitive functioning in 57 adolescents (mean age 15 years). ANCOVAs showed effects of State anxiety at 12-22 weeks, after controlling for influences of State anxiety in later pregnancy and postnatal maternal Trait anxiety. Adolescents of high anxious pregnant women reacted impulsively in the Encoding task; they responded faster but made more errors than adolescents of low anxious women. They also scored lower on two administered WISC-R subtests. In the Stop task no differences in inhibiting ongoing responses were found between adolescents of high and low anxious pregnant women. We suspect that high maternal anxiety in the first half of pregnancy may negatively affect brain development of the fetus, reflected by impulsivity and lower WISC-R scores at 14-15 years.

Brain differences in newborn rats predisposed to helpless and depressive behavior

Inborn brain differences in metabolic capacity were mapped in congenitally helpless rats, a genetically selected strain predisposed to show helpless and depressive behavior. There are a number of brain regions showing abnormal metabolism in adult congenitally helpless rats. Some of these alterations may be innate while others may be due to environmental factors, such as maternal care and postnatal stress. To identify which brain structures show innate differences, brains of newborn rats from congenitally helpless and non-helpless strains were compared using cytochrome oxidase histochemistry, an endogenous marker of regional metabolic capacity. A smaller subset of regions affected in adults showed significantly less metabolic activity in the newborn brains, including paraventricular hypothalamus, habenula, hippocampus, subiculum, lateral septal nucleus, anterior cingulate cortex, infralimbic cortex, and medial orbitofrontal cortex. A covariance analysis further revealed a striking reduction of functional connectivity in the congenitally helpless brain, including a complete decoupling of limbic forebrain regions from midbrain/diencephalic regions. This pattern of brain metabolism suggests that helplessness vulnerability is linked to altered functioning of limbic networks that are key to controlling the hypothalamic-pituitary-adrenal axis. This implies that vulnerable animals have innate deficits in brain systems that would normally allow them to cope with stress, predisposing them in this manner to more readily develop helpless and depressive behaviors.

Localisation of NMU1R and NMU2R in human and rat central nervous system and effects of neuromedin-U following central administration in rats

RATIONALE

Neuromedin-U (NmU) is an agonist at NMU1R and NMU2R. The brain distribution of NmU and its receptors, in particular NMU2R, suggests widespread central roles for NmU. In agreement, centrally administered NmU affects feeding behaviour, energy expenditure and pituitary output. Further central nervous system (CNS) roles for NmU warrant investigation.

OBJECTIVES

To investigate the CNS role of NmU by mapping NMU1R and NMU2R mRNA and measuring the behavioural, endocrine, neurochemical and c-fos response to intracerebroventricular (i.c.v.) NmU.

METHODS

Binding affinity and functional potency of rat NmU was determined at human NMU1R and NMU2R. Expression of NMU1R and NMU2R mRNA in rat and human tissue was determined using semi-quantitative reverse-transcription polymerase chain reaction. In in-vivo studies, NmU was administered i.c.v. to male Sprague-Dawley rats, and changes in grooming, motor activity and pre-pulse inhibition (PPI) were assessed. In further studies, plasma endocrine hormones, [DOPAC + HVA]/[dopamine] and [5-HIAA]/[5-HT] ratios and levels of Fos-like immunoreactivity (FLI) were measured 20 min post-NmU (i.c.v.).

RESULTS

NmU bound to NMU1R ( K(I), 0.11+/-0.02 nM) and NMU2R ( K(I), 0.21+/-0.05 nM) with equal affinity and was equally active at NMU1R (EC(50), 1.25+/-0.05 nM) and NMU2R (EC(50), 1.10+/-0.20 nM) in a functional assay. NMU2R mRNA expression was found at the highest levels in the CNS regions of both rat and human tissues. NMU1R mRNA expression was restricted to the periphery of both species with the exception of the rat amygdala. NmU caused a marked increase in grooming and motor activity but did not affect PPI. Further, NmU decreased plasma prolactin but did not affect levels of corticosterone, luteinising hormone or thyroid stimulating hormone. NmU elevated levels of 5-HT in the frontal cortex and hypothalamus, with decreased levels of its metabolites in the hippocampus and hypothalamus, but did not affect dopamine function. NmU markedly increased FLI in the nucleus accumbens, frontal cortex and central amygdala.

CONCLUSIONS

These data provide further evidence for widespread roles for NmU and its receptors in the brain.

Endocannabinoid signaling negatively modulates stress-induced activation of the hypothalamic-pituitary-adrenal axis

Activation of the hypothalamic-pituitary-adrenal (HPA) axis is critical for the adaptation and survival of animals upon exposure to stressful stimuli, and data suggest that endocannabinoid (eCB) signaling modulates neuroendocrine function. We have explored the role of eCB signaling in the modulation of stress-induced HPA axis activation. Administration of the CB1 receptor antagonist/inverse agonist SR141716 (0.01, 0.1, 1, and 5 mg/kg, i.p.) to male mice produced a small, dose-dependent increase in the serum corticosterone (CORT) concentration. Despite this effect, the highest dose of SR141716 did not significantly increase neuronal activity within the paraventricular nucleus of the hypothalamus, as measured by the induction of Fos protein. Similarly, exposure of mice to 30 min of restraint increased serum CORT concentrations, but did not produce a consistent, statistically significant increase in Fos expression within the PVN. However, pretreatment of mice with SR141716 before restraint stress robustly potentiated restraint-induced CORT release and Fos expression within the PVN. Pretreatment of mice with either the CB1 receptor agonist CP55940, the eCB transport inhibitor AM404, or the fatty acid amide hydrolase inhibitor URB597 significantly decreased or eliminated restraint-induced CORT release. Upon exposure to acute restraint, hypothalamic 2-arachidonylglycerol content was reduced compared with the control value; however, after 5 d of restraint exposure (which resulted in an attenuated CORT response), the hypothalamic 2-arachidonylglycerol content was increased compared with the control value. These data indicate that eCB signaling negatively modulates HPA axis function in a context-dependent manner and suggest that pharmacological augmentation of eCB signaling could serve as a novel approach to the treatment of anxiety-related disorders.

Decreased plasma membrane targeting of NMDA-NR1 receptor subunit in dendrites of medial nucleus tractus solitarius neurons in rats self-administering morphine

Opioid abuse is associated with repeated administration and escalation of dose that can result in profound adaptations in homeostatic processes. Potential cellular mechanisms and neural sites mediating opiate-dependent adaptations may involve NMDA-dependent synaptic plasticity within brain areas participating in behaviors related to consumption of natural reinforcers, as well as affective-autonomic integration, notably the medial nucleus tractus solitarius (mNTS). NMDA-dependent synaptic plasticity may be mediated by changes in the intracellular and surface targeting of NMDA receptors, particularly in postsynaptic sites including spines or small distal dendrites. High-resolution immunogold electron microscopic immunocytochemistry combined with morphometry were used to measure changes in targeting of the NMDA-NR1 (NR1) receptor subunit between intracellular and plasmalemmal sites in dendrites of neurons of the intermediate mNTS of rats self-administering escalating doses of morphine (EMSA). In control and EMSA rats, the density of plasmalemmal and cytosolic gold particles was inversely related to profile size. Collapsed across all NR1-labeled dendrites, rats self-administering morphine had a lower number of plasmalemmal gold particles per unit surface area (7.1 +/- 0.8 vs. 14.4 +/- 1 per 100 microm), but had a higher number of intracellular gold particles per unit cross-sectional area (169 +/- 6.1 vs. 148 +/- 5.1 per 100 microm2) compared to saline self-administering rats. Morphometric analysis showed that the decrease in plasma membrane labeling of NR1 was most robust in small dendritic profiles (<1 microm), where there was a reciprocal increase in the density of intracellular particles. These results indicate that the plasmalemmal distribution of the essential NR1 subunits in distal sites may prominently contribute to NMDA receptor-dependent modulation of neural circuitry regulating homeostatic processes, and targeting of these proteins can be prominently affected by morphine self-administration.

Neural responses to territorial challenge and nonsocial stress in male song sparrows: segregation, integration, and modulation by a vasopressin V1 antagonist

The present experiments were conducted to determine (1) which basal forebrain regions and/or their peptidergic components are responsive to social challenge and nonsocial stress, and (2) the influence of an arginine vasopressin V(1) antagonist (AVPa) on these responses. Experiments were conducted in wild-caught male song sparrows (Melospiza melodia) that were housed on seminatural territories (field-based flight cages). Subjects were each fitted with a chronic guide cannula directed at the lateral ventricle and exposed to one of five conditions before sacrifice and histochemistry: saline + simulated territorial intrusion (STI; consisting of song playback and presentation of a caged conspecific male), AVPa + STI, saline + empty cage, AVPa + empty cage, unhandled. Two tissue series were prepared and immunofluorescently double-labeled for ZENK (egr-1) protein and either arginine vasotocin (AVT; avian homologue of AVP) or corticotropin releasing factor (CRF). The results indicate that the neuronal populations that are sensitive to nonsocial stress (capture, handling and infusion) and STI are at least partially segregated. Increases in ZENK-immunoreactive (-ir) nuclei following handling and infusion were observed in a large number of areas, whereas neural responses that were specific to STI were more limited. However, multiple areas showed responses to both handling and STI. AVPa infusions significantly reduced or eliminated most experimental increases in ZENK-ir, suggesting a broad role for endogenous AVT in the modulation of baseline activity and/or stress responsivity, and a much more limited role in the specific response to social challenge. Particular attention is given to the numerous zones of the lateral septum (LS), which are differentially responsive to handling, STI, and V(1)-like receptor blockade. These data suggest that septal AVT modulates neural responses to general stressors, not social stimuli specifically. Thus, species differences in septal AVT function (as previously described in songbirds) likely reflect differences in the relationship of stress or anxiety to species-specific behaviors, or to behavior in species-typical contexts.

Medial prefrontal cortex modulation of the baroreflex parasympathetic component in the rat

The ventral portion of the medial prefrontal cortex (vMPFC) that comprises the prelimbic and infralimbic cortex is involved in arterial blood pressure and heart rate control. In the present study, we attempted to verify the effect of an acute and reversible blockade of vMPFC activity by local bilateral microinjections of either lidocaine (a local anesthetic) or CoCl2 (a nonselective synapse blocker) on the baroreflex response of unanesthetized rats. Bilateral microinjection of lidocaine into the vMPFC did not affect the tachycardiac response to mean arterial pressure (MAP) decreases caused by i.v. infusion of sodium nitroprusside or the baroreflex gain in unanesthetized rats. However, lidocaine caused a reversible shift of the reflex threshold pressure toward higher (MAP) increases in response to i.v. infusion of phenylephrine, thus indicating an action on the parasympathetic component of the baroreflex. The effects of the blockade of local synapses in the vMPFC by CoCl2 were similar to those observed after the acute ablation of that area caused by lidocaine. Bilateral microinjection of CoCl2 into the vMPFC also caused a shift of the reflex threshold pressure bradycardiac responses to MAP increases toward higher MAP values, without affecting the baroreflex gain. In conclusion, our data indicate that the vMPFC is involved in baroreflex control, and more specifically in the modulation of the parasympathetic baroreflex component. The temporary ablation of this area by local microinjections of lidocaine caused a shift of the reflex threshold pressure toward higher MAP values, which is compatible with the idea that the vMPFC has a modulatory action on the baroreflex. The observation that CoCl2 and lidocaine microinjections had similar effects on the baroreflex also suggests that this modulation involves local synaptic neurotransmission within the vMPFC.

Medial prefrontal cortical integration of psychological stress in rats

The present study aimed to determine whether the medial prefrontal cortex (mPFC) (prelimbic and infralimbic regions) is implicated in the integration of a stress response. Sprague-Dawely rats were implanted with telemetry probes and guide cannulae so that either muscimol or vehicle could be administered locally within the mPFC or dorsomedial hypothalamus (DMH). The heart rate and blood pressure of rats was continuously recorded as either muscimol or vehicle was administered centrally and rats were either exposed to restraint stress or left alone in their home cages. After the stress challenge, or equivalent period, rats that had received intra-mPFC injections were processed for immunohistochemical detection of Fos throughout the neuraxis. Bilateral microinjection of muscimol into the mPFC had no effect upon either baseline cardiovascular parameters or restraint stress-induced tachycardia or pressor responses whereas, in the DMH, pretreatment with muscimol attenuated the cardiovascular stress response. Analysis of Fos expression throughout the CNS of nonstressed rats showed no effect of muscimol injections into the mPFC on baseline expression in the nuclei examined. In contrast, rats that had received muscimol injections into their mPFC and were subsequently restrained exhibited an increase in the number of Fos-positive cells in the DMH, medial amygdala, and medial nucleus tractus solitarius as compared to vehicle-injected rats that experienced restraint stress. These results indicate that, during acute psychological stress, the mPFC does not modulate the cardiovascular system in rats but does inhibit specific subcortical nuclei to exert control over aspects of an integrated response to a stressor.

The pattern of brain c-fos mRNA induced by a component of fox odor, 2,5-dihydro-2,4,5-Trimethylthiazoline (TMT), in rats, suggests both systemic and processive stress characteristics

Predators to rodents and their associated odors are increasingly chosen to study the neural mechanisms of stress and anxiety. Specifically, predatory odors are believed to elicit responses based on the perceived threat (psychological or processive), rather than to any direct systemic effects (pain, blood loss, infection, etc.) of the stimulus, which are mediated by distinct neural pathways. The hypothesis that a chemical component from fox feces, 2,5-dihydro-2,4,5-trimethylthiazoline (TMT), elicits stress responses by specific activation of processive neural pathways was tested. Different amounts of TMT (range: 0-600 micromol) or the control odor butyric acid (0-1200 micromol) were presented to male Sprague-Dawley rats for 30 min. Immediately after odor presentation, rats were sacrificed, blood levels of adrenocorticotropic hormone (ACTH) and corticosterone were measured, and brains were rapidly harvested to measure regional brain c-fos mRNA induction by in situ hybridization. Presentation of TMT (> or =75 micromol), but not butyric acid (up to 1200 micromol), significantly increased ACTH and corticosterone release. TMT presentation, especially with amounts (> or =75 micromol) producing endocrine activation, induced c-fos mRNA in several brain areas, including the olfactory bulb, lateral septal nucleus, septohypothalamic nucleus, anteromedial and oval nuclei of the bed nucleus of the stria terminalis, the central nucleus of the amygdala, the anteroventral, anterodorsal, and medial preoptic nuclei, the anterior, dorsomedial, lateral, supramammillary, dorsal premammillary and paraventricular hypothalamic nuclei, the external lateral parabrachial nucleus, the locus coeruleus, and the nucleus of the solitary tract. Interestingly, these brain regions represent a mix of regional c-fos mRNA induction pattern not reported previously with any other single stressor. These results suggest that TMT elicits stress responses through a relatively unique and complex mix of brain regions associated with both processive and systemic neural pathways, unlike those seen in response to cat odors.

A single exposure to severe stressors causes long-term desensitisation of the physiological response to the homotypic stressor

Although some laboratories have reported that a single session of stress is able to induce a long-lasting sensitisation of the hypothalamic-pituitary-adrenal (HPA) response to further exposures to stress, we have found that a single exposure to severe emotional (immobilisation, restraint or shock) or systemic (endotoxin) stressors reduces the responsiveness of the HPA to the same, but not to a novel (heterotypic), stressor, in which case a slight sensitisation was observed. Long-term desensitisation has been found to reduce not only secretion of peripheral HPA hormones (ACTH and corticosterone), but also to reduce responses of central components of the HPA axis (c-fos and CRF gene expression at the level of the paraventricular nucleus of the hypothalamus, PVN). In addition, desensitisation also applies to the impact of the stressor on food intake and, probably, to stress-induced hyperglycaemia. The development of long-term desensitisation of the HPA axis does not appear to be a universal consequence of exposure to severe stressors as it was not observed in response to insulin-induced hypoglycaemia. Whether or not the development of long-term effects of stress depend on the specific pathways activated by particular stressors remains to be tested. The observed desensitisation of the HPA axis in response to the homotypic stressor shows two special features which makes it difficult to be interpreted in terms of an habituation-like process: (a) the effect increased with time (days to weeks) elapsed between the first and second exposure to the stressor, suggesting a progressive maturational process; and (b) the stronger the stressor the greater the long-term desensitisation. Therefore, it is possible that desensitisation of the HPA axis is the sum of two different phenomena: long-term effects and habituation-like processes. The contribution of the former may be more relevant with severe stressors and longer inter-stress intervals, and that of the latter with mild stressors and repeated exposures. Long-term stress-induced changes may not take place at the level of the PVN itself, but in brain nuclei showing synaptic plasticity and putatively involved in the control of the HPA axis and other physiological responses. As for the precise areas involved, these remain to be characterized.

Maternal separation suppresses TGF alpha mRNA expression in the prefrontal cortex of male and female neonatal C57BL/6 mice

Male C57BL/6 mice that undergo maternal separation (MS) early in life demonstrate higher levels of anxiety upon reaching adulthood compared to normally reared offspring. This study reports that neonatal males and females that undergo MS have reduced mRNA levels of transforming growth factor-alpha (TGF alpha) in the prefrontal cortex, an area of the brain implicated in emotionality, compared to normally reared animals. TGF alpha expression was unaffected by MS in the hippocampus. These data indicate that MS leads to a brain region-specific suppression of TGF alpha expression early in development.

The selfish brain: competition for energy resources

The brain occupies a special hierarchical position in the organism. It is separated from the general circulation by the blood-brain barrier, has high energy consumption and a low energy storage capacity, uses only specific substrates, and it can record information from the peripheral organs and control them. Here we present a new paradigm for the regulation of energy supply within the organism. The brain gives priority to regulating its own adenosine triphosphate (ATP) concentration. In that postulate, the peripheral energy supply is only of secondary importance. The brain has two possibilities to ensure its energy supply: allocation or intake of nutrients. The term 'allocation' refers to the allocation of energy resources between the brain and the periphery. Neocortex and the limbic-hypothalamus-pituitary-adrenal (LHPA) system control the allocation and intake. In order to keep the energy concentrations constant, the following mechanisms are available to the brain: (1) high and low-affinity ATP-sensitive potassium channels measure the ATP concentration in neurons of the neocortex and generate a 'glutamate command' signal. This signal affects the brain ATP concentration by locally (via astrocytes) stimulating glucose uptake across the blood-brain barrier and by systemically (via the LHPA system) inhibiting glucose uptake into the muscular and adipose tissue. (2) High-affinity mineralocorticoid and low-affinity glucocorticoid receptors determine the state of balance, i.e. the setpoint, of the LHPA system. This setpoint can permanently and pathologically be displaced by extreme stress situations (chronic metabolic and psychological stress, traumatization, etc.), by starvation, exercise, infectious diseases, hormones, drugs, substances of abuse, or chemicals disrupting the endocrine system. Disorders in the 'energy on demand' process or the LHPA-system can influence the allocation of energy and in so doing alter the body mass of the organism. In summary, the presented model includes a newly discovered 'principle of balance' of how pairs of high and low-affinity receptors can originate setpoints in biological systems. In this 'Selfish Brain Theory', the neocortex and limbic system play a central role in the pathogenesis of diseases such as anorexia nervosa and obesity.

Cognitive correlates of white matter growth and stress hormones in female squirrel monkey adults

Neurobiological studies of stress and cognitive aging seldom consider white matter despite indications that complex brain processes depend on networks and white matter interconnections. Frontal and temporal lobe white matter volumes increase throughout midlife adulthood in humans, and this aspect of aging is thought to enhance distributed brain functions. Here, we examine spatial learning and memory, neuroendocrine responses to psychological stress, and regional volumes of gray and white matter determined by magnetic resonance imaging in 31 female squirrel monkeys between the ages of 5 and 17 years. This period of lifespan development corresponds to the years 18-60 in humans. Older adults responded to stress with greater increases in plasma levels of adrenocorticotropic hormone and modest reductions in glucocorticoid feedback sensitivity relative to young adults. Learning and memory did not differ with age during the initial cognitive test sessions, but older adults more often failed to inhibit the initial learned response after subsequent spatial reversals. Impaired cognitive response inhibition correlated with the expansion of white matter volume statistically controlling for age, stress hormones, gray matter, and CSF volumes. These results indicate that instead of enhancing cognitive control during midlife adulthood, white matter volume expansion contributes to aspects of cognitive decline. Cellular and molecular research combined with brain imaging is needed to determine the basis of white matter growth in adults, elucidate its functions during lifespan development, and provide potential new targets for therapies aimed at maintaining in humans cognitive vitality with aging.

High Antenatal Maternal Anxiety Is Related to ADHD Symptoms, Externalizing Problems, and Anxiety in 8- and 9-Year-Olds

Associations between antenatal maternal anxiety, measured with the State Trait Anxiety Inventory, and disorders in 8- and 9-year-olds were studied prospectively in 71 normal mothers and their 72 firstborns. Clinical scales were completed by the mother, the child, the teacher, and an external observer. Hierarchical multiple regression analyses showed that maternal state anxiety during pregnancy explained 22%, 15%, and 9% of the variance in cross-situational attention deficit hyperactivity disorder symptoms, externalizing problems, and self-report anxiety, respectively, even after controlling for child's gender, parents' educational level, smoking during pregnancy, birth weight, and postnatal maternal anxiety. Anxiety at 12 to 22 weeks postmenstrual age turned out to be a significant independent predictor whereas anxiety at 32 to 40 weeks was not. Results are consistent with a fetal programming hypothesis.

Neonatal stress alters adult breathing

The epigenetic effect of deprivation and stress on brain development is one of the most enduring topics in neurobiology and one that arguably has had the most far reaching influences on modern societies. Persistent deficits in perception, cognition, and social development are attributed to maternal separation and/or environmental deprivation of human infants. Given the retrospective nature of these human studies, the animal experiments they have inspired are particularly significant insofar as objective changes in physiology, neuronal structure and brain size follow manipulations of the perinatal sensory environment.

Behavioural endocrine immune-conditioned response is induced by taste and superantigen pairing

Administration of bacterial superantigen, such as staphylococcal enterotoxin B (SEB), induces in vivo stimulation of T cell proliferation and cytokine production such as interleukin-2 (IL-2). It has been previously reported that SEB administration induces fever, c-Fos expression in the brain, and hypothalamus-pituitary-adrenal axis activation, demonstrating that the brain is able to sense and respond to SEB. Previously it had been shown that immune functions can be behaviourally conditioned pairing a novel gustatory stimulus together with an immunomodulatory drug or an antigen. We designed an experimental protocol using Dark Agouti rats in which saccharin taste, as conditioned stimulus, was paired with an i.p. injection of SEB (2 mg/kg), as unconditioned stimulus. Six days later, when conditioned animals were re-exposed to the conditioned stimulus they displayed strong conditioned taste avoidance to the saccharin. More importantly, re-exposure to the conditioned stimulus significantly increased IL-2, interferon-gamma and corticosterone plasma levels, in comparison with conditioned animals which had not been re-exposed to saccharin taste. These results demonstrate a behavioural-immune-endocrine conditioned response using a superantigen as unconditioned stimulus. In addition, they illustrate the brain abilities to mimic the unconditioned effects of a superantigen by yet unknown mechanisms.

Decreased hypothalamic and adrenal angiotensin II receptor expression and adrenomedullary catecholamines in transgenic mice with impaired glucocorticoid receptor function

In transgenic mice expressing an antisense mRNA against the glucocorticoid receptor (GR), which partially blocks GR expression, impaired glucocorticoid feedback efficacy is accompanied by reduced hypothalamic corticotropin-releasing hormone (CRH) and vasopressin (AVP) activity and reduced peripheral sympathetic tone, indications of a shift in the balance of hypothalamic CRH and sympathetic regulation. As angiotensin II (Ang II) regulates CRH, AVP and sympathetic activity, we studied the expression of Ang II receptors in the hypothalamus and adrenal gland of GR transgenic and wild-type mice, adrenal catecholamines and mRNA for their rate-limiting enzyme, tyrosine hydroxylase (TH). We found that transgenic mice expressed significantly less numbers of Ang II AT(1) receptors in the hypothalamic paraventricular nucleus and median eminence, lower numbers of AT(2) receptors in supraoptic and paraventricular nuclei and lower numbers of AT(2) receptors in the adrenal medulla when compared with wild-type controls. The expression of TH mRNA and the concentration of adrenomedullary epinephrine and norepinephrine were also lower in transgenic mice when compared with wild-type controls. Decreased hypothalamic and adrenal Ang II receptor stimulation as a result of decreased GR expression may explain the decreased hypothalamic CRH and AVP and decreased adrenomedullary and sympathetic activities in this model.