Corticosteroid receptors in brain: relationship of receptors to effects in stress and aging

Good overall behavioural adjustment in children and adolescents with classic congenital adrenal hyperplasia

PURPOSE

Patients with classic congenital adrenal hyperplasia (CAH) are treated postnatally with life-long glucocorticoid (GC) replacement therapy. Although prolonged exposure to GCs may have a negative impact on behaviour, few studies have studied this issue. We therefore investigated behavioural outcomes in male and female children and adolescents with CAH.

METHODS

An observational study in which Swedish and Italian children and adolescents with CAH identified through neonatal screening for CAH (n = 57, age range 7-17 years) were compared with healthy population controls matched for age and sex (n = 72, age range 7-17 years). Thirteen (eight females) of the fifty-seven children and adolescents with CAH had been treated prenatally with dexamethasone (DEX). Standardised questionnaires for parents and self-report scales for children/adolescents were used to assess behavioural and emotional problems, social anxiety, temperament and scholastic competence.

RESULTS

There were no statistically significant differences between CAH patients (not prenatally treated with DEX) and controls on most of the scales measuring adaptive functioning or behavioural problems. However, children with CAH were rated by their parents to have more social problems than controls (Child Behaviour Checklist, CBCL social problems, p = 0.032). In the small group (n = 13) of prenatally DEX-treated cases parents rated their children/adolescents to have more mood problems compared with non-DEX-treated children/adolescents with CAH (CBCL-withdrawn/depressed, p = 0.019).

CONCLUSION

Children/adolescents with CAH showed good overall adjustment. The clinical significance of the parentally perceived increase in social problems in children/adolescents with CAH requires further investigation. The findings underline the importance of psychological support for children/adolescents with a chronic condition.

Cardiovascular effects of prenatal stress-Are there implications for cerebrovascular, cognitive and mental health outcome?

Prenatal stress programs offspring cognitive and mental health outcome. We reviewed whether prenatal stress also programs cardiovascular dysfunction which potentially modulates cerebrovascular, cognitive and mental health disorders. We focused on maternal stress and prenatal glucocorticoid (GC) exposure which have different programming effects. While maternal stress induced cortisol is mostly inactivated by the placenta, synthetic GCs freely cross the placenta and have different receptor-binding characteristics. Maternal stress, particularly anxiety, but not GC exposure, has adverse effects on maternal-fetal circulation throughout pregnancy, probably by co-activation of the maternal sympathetic nervous system, and by raising fetal catecholamines. Both effects may impair neurodevelopment. Experimental data also suggest that severe maternal stress and GC exposure during early and mid-gestation may increase the risk for cardiovascular disorders. Human data are scarce and especially lacking for older age. Programming mechanisms include aberrations in cardiac and kidney development, and functional changes in the renin-angiotensin-aldosterone-system, stress axis and peripheral and coronary vasculature. Adequate experimental or human studies examining the consequences for cerebrovascular, cognitive and mental disorders are unavailable.

5-HT(1A) [corrected] receptors in mood and anxiety: recent insights into autoreceptor versus heteroreceptor function

RATIONALE

Serotonin (5-HT) neurotransmission is intimately linked to anxiety and depression and a diverse body of evidence supports the involvement of the main inhibitory serotonergic receptor, the serotonin-1A (5-HT(1A)) subtype, in both disorders.

OBJECTIVES

In this review, we examine the function of 5-HT(1A) receptor subpopulations and re-interpret our understanding of their role in mental illness in light of new data, separating both spatial (autoreceptor versus heteroreceptor) and the temporal (developmental versus adult) roles of the endogenous 5-HT(1A) receptors, emphasizing their distinct actions in mediating anxiety and depression-like behaviors.

RESULTS

It is difficult to unambiguously distinguish the effects of different populations of the 5-HT(1A) receptors with traditional genetic animal models and pharmacological approaches. However, with the advent of novel genetic systems and subpopulation-selective pharmacological agents, direct evidence for the distinct roles of these populations in governing emotion-related behavior is emerging.

CONCLUSIONS

There is strong and growing evidence for a functional dissociation between auto- and heteroreceptor populations in mediating anxiety and depressive-like behaviors, respectively. Furthermore, while it is well established that 5-HT(1A) receptors act developmentally to establish normal anxiety-like behaviors, the developmental role of 5-HT(1A) heteroreceptors is less clear, and the specific mechanisms underlying the developmental role of each subpopulation are likely to be key elements determining mood control in adult subjects.

Glucocorticoid and polyamine interactions in the plasticity of glutamatergic synapses that contribute to ethanol-associated dependence and neuronal injury

Stress contributes to the development of ethanol dependence and is also a consequence of dependence. However, the complexity of physiological interactions between activation of the hypothalamic-pituitary-adrenal (HPA) axis and ethanol itself is not well delineated. Emerging evidence derived from examination of corticotropin-releasing factor systems and glucocorticoid receptor systems in ethanol dependence suggests a role for pharmacological manipulation of the HPA axis in attenuating ethanol intake, though it is not clear how activation of the HPA axis may promote ethanol dependence or contribute to the neuroadaptative changes that accompany the development of dependence and the severity of ethanol withdrawal. This review examines the role that glucocorticoids, in particular, have in promoting ethanol-associated plasticity of glutamatergic synapses by influencing expression of endogenous linear polyamines and polyamine-sensitive polypeptide subunits of N-methyl-D-aspartate (NMDA)-type glutamate receptors. We provide evidence that interactions among glucocorticoid systems, polyamines and NMDA receptors are highly relevant to both the development of ethanol dependence and to behavioral and neuropathological sequelae associated with ethanol withdrawal. Examination of these issues is likely to be of critical importance not only in further elucidating the neurobiology of HPA axis dysregulation in ethanol dependence, but also with regard to identification of novel therapeutic targets that may be exploited in the treatment of ethanol dependence.

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

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

Effects of maternal separation on hypothalamic-pituitary-adrenal responses, cognition and vulnerability to stress in adult female rats

We studied the long term effects of neonatal stress in female rats and subsequent responses to stress when adults. Female rats that experienced maternal separation (MS) showed in adulthood depressive-like behavior in the forced swimming test and cognitive impairments in the novel object recognition test, which were reverted by the glucocorticoid receptor antagonist mifepristone or the beta-adrenoceptor antagonist propranolol. Markers of HPA axis (corticosterone levels, CRF mRNA levels in the paraventricular nucleus and glucocorticoid receptor density in the hippocampus) were altered by MS, suggesting that an altered HPA axis function may be associated to behavioral and cognitive deficits in MS female rats. In addition, MS rats were found to be more vulnerable to chronic stress than controls as shown by decreases in open field activity, increases in immobility time in the forced swim test, and changes in markers of HPA axis (decreases in the density of glucocorticoid receptors). These present findings are discussed in terms of gender differences in adulthood.

Cognitive impairment associated to HPA axis hyperactivity after maternal separation in rats

Exposure to early stressful adverse life events may increase vulnerability to psychopathology in adult life. There are important memory disturbances in stress-related psychiatric disorders. Therefore, there is much interest in understanding the mechanisms responsible for interactions between stress and cognition. Male Wistar rats that experienced 3-h daily separations from the dam during the first 3 weeks of life (maternal separation, MS) showed in adulthood a depressive-like behaviour in the forced swimming test, increased hypothalamic-pituitary-adrenal (HPA) axis responsiveness to stressors and elevated CRF mRNA in the paraventricular nucleus of the hypothalamus (PVN). In the hippocampus of MS rats, there was a lower glucocorticoid receptor density. MS produced significant learning impairments both in the Morris water maze and in the novel object recognition test (NORT). The glucocorticoid receptor antagonist mifepristone and the beta-adrenoceptor antagonist propranolol were able to completely reverse the increased immobility time in the forced swimming test and the memory deficits in the NORT observed in MS rats. Our data support the hypothesis that elevated secretion of glucocorticoids may be associated to behavioural and cognitive deficits in MS rats. The stress hyperresponsiveness observed in MS rats could be attributed, at least in part, to an impaired feedback sensitivity mediated by hippocampal glucocorticoid receptors. It can also be suggested the possible involvement of the noradrenergic system in cognitive impairments mediated by glucocorticoids in the MS model.

Glucocorticoid receptors in lateral septum are involved in the modulation of the emotional sequelae induced by social defeat

The current research studied the behavior adopted in the elevated plus maze (EPM) of rats previously subjected to a social defeat using the resident-intruder paradigm. One day after defeat, intruder animals exhibited an anxiogenic-like behavior in the EPM. In addition, we also evaluated the role of the corticosteroid receptor system (minerlocorticoid - MR - and glucocorticoid - GR - receptors) from the lateral septum (LS) on the anxiety generated by social defeat. The LS is an area of the aversive circuitry that is preferentially activated in passive defensive postures, and participates - together with other brain areas - in the modulation of aversive states. Intruder animals were infused into the LS with the MR or GR antagonist (ZK 91587 and RU 38486, respectively) and then submitted to social stress. All rats were tested in the EPM 1 day later. Only the administration of the GR antagonist, but not the MR antagonist, into the LS normalized the anxiogenic response induced by defeat. Furthermore, we examined whether a single injection of corticosterone (CS) could induce the same influence on the behavior in the EPM as that observed after social defeat. Moreover, we explored the effect of local infusions of MR or GR antagonists into the LS on the behavior exhibited by CS-treated rats in a subsequent EPM exposure. CS administration also exerted an increased anxiogenic-like behavior, which was normalized only by the local infusion of the GR antagonist. Based on these findings, we suggest that CS secreted by emotionally relevant stimuli acting via GR in LS plays an important role in the modulation of the emotional sequelae induced by social defeat.

Low and high circulating cortisol levels predict mortality and cognitive dysfunction early after stroke

OBJECTIVE

Elevated cortisol levels are associated with confusion and poor outcome after stroke. Dehydroepiandrosterone sulphate (DS), the most abundant adrenal androgen may act as an anti-glucocorticoid. An altered regulation of these steroids may affect numerous brain functions, including neuronal survival. The purpose of this study was to investigate serum cortisol and DS levels and the cortisol/DS ratio early after stroke and relate our findings to the presence of disorientation and mortality.

DESIGN

Patients with acute ischaemic stroke (n = 88, 56 men and 32 women) admitted to a stroke unit were investigated with repeated clinical assessments and scores for degree of confusion, extent of paresis and level of functioning. Serum cortisol (C) and DS were measured on day 1 and/or day 4. Data for 28-day and 1-year mortality are presented. A control group of 65 age-matched healthy individuals was used. Multivariate analyses of mortality rates in the different tertiles or sixtiles of serum cortisol were performed with logistic regression, adjusting for age, sex, diabetes and level of consciousness.

RESULTS

There was no difference in serum cortisol levels on day 1 for stroke patients when compared with control group values. Initial cortisol levels were significantly higher in the patients with acute disorientation versus orientated patients (P < 0.05). Cortisol levels on day 1 were an independent predictor of 28-day mortality, and patients with low cortisol levels (<270 nmol L(-1)) and increased levels (>550 nmol L(-1)) both had an increased 1-year mortality. DS levels on day 1 were significantly elevated in stroke patients.

CONCLUSION

Hypercortisolism is associated with cognitive dysfunction early after ischaemic stroke. High and low circulating cortisol levels are associated with increased mortality after stroke. DS levels were not associated with clinical outcome.

Effect of antenatal betamethasone treatment on microtubule-associated proteins MAP1B and MAP2 in fetal sheep

Betamethasone has been used extensively to accelerate fetal lung maturation, yet little is known of its effects on neuronal morphogenesis in the developing fetus. Microtubule-associated proteins (MAPs) are a diverse family of cytoskeletal proteins that are important for brain development and the maintenance of neuroarchitecture. Vehicle (n = 7) or betamethasone (10 ug h-1, n = 7) was infused I.V. to fetal sheep over 48 h beginning at 0.87 of gestation (128 days of gestation), producing fetal plasma betamethasone concentrations resembling those to which the human fetus is exposed during antenatal glucocorticoid therapy. Paraffin sections of the left hemisphere were stained with monoclonal antibodies against MAP1B and the MAP2 isoforms MAP2a,b,c and MAP2a,b. The level of the juvenile isoform MAP2c was determined by comparison of the two MAP2 immunostainings. We were able to detect MAP1B and MAP2 immunoreactivity (IR) in the fetal sheep brain. MAP2c was the major MAP2, constituting 90.2 % of the total MAPBetamethasone exposure diminished MAP1B IR in the frontal cortex and caudate putamen (P < 0.05) but not in the hippocampus. A decrease of MAP2 IR was found in the frontal cortex, hippocampus and caudate putamen (P < 0.05). Loss of MAP2 IR was mainly due to the loss of MAP2c IR. Haematoxylin-eosin staining did not demonstrate irreversible neuronal damage. Regional cerebral blood flow determined using coloured microspheres was significantly decreased by 28 % in the frontal cortex and by 36 % in the caudate putamen but not in the hippocampus 24 h after the onset of betamethasone exposure (P < 0.05). The loss of MAP1B and MAP2a,b,c IR showed a significant correlation to the cerebral blood flow decrease only in the frontal cortex (P < 0.05). These data suggest that mechanisms other than metabolic insufficiency caused by the decreased cerebral blood flow may contribute to the loss of MAPs. The results suggest that clinical doses of betamethasone may have acute effects on cytoskeletal proteins in the fetal brain.

Effects of betamethasone administration to the fetal sheep in late gestation on fetal cerebral blood flow

Glucocorticoid administration to women at risk of preterm delivery to accelerate fetal lung maturation has become standard practice. Antenatal glucocorticoids decrease the incidence of intraventricular haemorrhage as well as accelerating fetal lung maturation. Little is known regarding side effects on fetal cerebral function. Cortisol and synthetic glucocorticoids such as betamethasone increase fetal blood pressure and femoral vascular resistance in sheep. We determined the effects of antenatal glucocorticoid administration on cerebral blood flow (CBF) in fetal sheep. Vehicle (n = 8) or betamethasone (n = 8) was infused over 48 h via the jugular vein of chronically instrumented fetal sheep at 128 days gestation (term 146 days). The betamethasone infusion rate was that previously shown to produce fetal plasma betamethasone concentrations similar to human umbilical vein concentrations during antenatal glucocorticoid therapy. Regional CBF was measured in 10 brain regions, using coloured microspheres, before and 24 and 48 h after onset of treatment, and during hypercapnic challenges performed before and 48 h after onset of betamethasone exposure. Betamethasone exposure decreased CBF in all brain regions measured except the hippocampus after 24 h of infusion (P < 0.05). The CBF decrease was most pronounced in the thalamus and hindbrain (45-50% decrease) and least pronounced in the cortical regions (35-40% decrease). It was mediated by an increase in cerebral vascular resistance (CVR, P < 0.05) and led to a decrease in oxygen delivery to subcortical and hindbrain structures of 30-40%, to 8.6 +/- 1.1 ml x (100 g)(-1) x min(-1), and 40-45 %, to 11.0 +/- 1.6 ml x 100 g(-1) x min(-1), respectively (P < 0.05). After 48 h of betamethasone treatment, the reduction in CBF was diminished to about 25-30 %, but was still significant in comparison to vehicle-treated fetuses in all brain regions except three of the five measured cortical regions (P < 0.05). CVR and oxygen delivery were unchanged in comparison to values at 24 h of treatment. The CBF increase in response to hypercapnia was diminished (P < 0.05). These observations demonstrate for the first time that glucocorticoids exert major vasoconstrictor effects on fetal CBF. This mechanism may protect the fetus against intraventricular haemorrhage both at rest and when the fetus is challenged. Betamethasone exposure decreased the hypercapnia-induced increase in CBF (P < 0.05) due to decreased cerebral vasodilatation (P < 0.05).

Endogenous glucocorticoids down regulate central effects of interleukin-1 beta on body temperature and behaviour in mice

Adrenalectomy sensitizes laboratory animals to the pyrogenic and behavioural effects of proinflammatory cytokines. To determine whether these effects are mediated by central sites of action of glucocorticoids, interleukin-1 beta was injected intracerebroventricularly (i.c.v.) in adrenalectomized mice with or without corticosterone supplementation and in mice pretreated i.c.v. with the glucocorticoid type II receptor antagonist RU38486. Adrenalectomized mice were more sensitive to the depressing effects of i.c.v. IL-1 beta on body temperature and social exploration than sham-operated mice. Corticosterone supplementation reversed the increased sensitivity to the low (300 pg/mouse) but not to the high dose (900 pg/mouse) of IL-1 beta. Central administration of RU38486 (0.5-1 microgram/mouse) mimicked the effects of adrenalectomy on behaviour but not on body temperature. These results suggest that endogenous glucocorticoids released in response to IL-1 beta act in the brain to modulate the sensitivity of the cellular targets of this cytokine.

Effects of age on messenger RNA expression of glucocorticoid, thyroid hormone, androgen, and estrogen receptors in postmortem human hippocampus

We studied messenger RNA (mRNA) expressions of receptors for glucocorticoid (GR), thyroid hormone (TR), androgen (AR), and estrogen (ER) and their changes with age in the hippocampal subregions in postmortem human brain. In situ hybridization was done with biotin-labeled antisense synthetic oligonucleotide probes. About 80% or more of the pyramidal neurons in the hippocampal subregions expressed mRNAs for individual receptors in the brains of subjects younger than 65. The ratio of mRNA-containing neuron density to total neuron density significantly decreased with age for GR in CA1 and CA3, and for AR in CA1. Non-significant trends in the reduction with age in the ratio of ER mRNA-containing neurons in CA1 and the ratio of GR mRNA-containing neurons in the hilus also were found. Age-related reductions in nuclear receptor protein mRNA expression in neurons in the hippocampal subfields may be important in the impairments of cognition, emotion, and responses to acute stress in the aged.

Effect of adrenal steroids on preproneurokinin-A gene expression in discrete regions of the rat brain

An in situ hybridization histochemical procedure was developed to monitor the cellular distributions of the three major alternatively spliced alpha, beta and gamma species of mRNA encoding neurokinin molecules of the CNS. Two oligodeoxyribonucleotide probes were synthesized corresponding to common sequences of the alpha, beta, and gamma NK-A mRNA. The first experiment used rats that were sham-operated (Sham), adrenalectomized (ADX), and ADX rats treated with corticosterone (ADX+CORT). Intense labelling was observed within the habenula (Hb), while strong labelling was detected within the olfactory tubercle (OT), the lateral olfactory tubercle (LOT), the horizontal diagonal band of Broca (HDB), the bed nucleus of the stria terminalis (BNST), and the dorsal and ventral part of the caudate putamen (d-CP, v-CP). Moderate labelling of a number of cells was observed within the medial preoptic area (mPOA), the postero-dorsal part of the medial amygdala (MePD), and the dorsal and ventral part of the premamillary nucleus of the hypothalamus (PM-D; PM-V). ADX decreased NK-A mRNA in OT, LOT, HDB, BNST, CP compared to sham-operated rats, whereas CORT replacement elevated NK-A mRNA to above sham levels in OT, LOT, HDB, BNST and CP. There was no effect of ADX or CORT in Hb, while smaller, and often non-significant, effects of ADX and CORT replacement were found in other areas. Since there are two types of adrenal steroid receptors in brain, we next investigated the effects of agonists for type I and type II adrenal steroid receptors. ADX rats were given either aldosterone (ALDO, 10 micrograms/ml/h, Alzet minipumps) or RU 28362 (10 micrograms/ml/h, Alzet minipumps) for 8 days. Type I receptor activation by ALDO partially reversed the ADX-induced decrease in NK-A mRNA, whereas type II steroid receptor activation by RU 28362 restored the decrease caused by ADX and caused an elevation of NK-A mRNA above sham levels in OT. These findings show that adrenal steroids regulate NK-A gene expression through both type I and type II receptors in a number of brain areas. The results are consistent with a role for adrenal steroids and neurokinins in the regulation of body fluid homeostasis.

Chronic corticosterone treatment maintains synaptic activity of CA1 hippocampal pyramidal cells: acute high corticosterone administration increases action potential number

The hypothalamic-pituitary-adrenocortical (HPA) axis controls the levels of plasma corticosterone (CT) in the rat and the levels of cortisol in man. CT is important in maintaining homeostasis and regulating energy production. Homeostasis is maintained by basal activation of the hippocampal-HPA axis. In response to stress CT secretion is increased. CT activation of receptors in the hippocampus provides feedback inhibition of the HPA axis to return the system to basal activity. There are two types of CT receptors: the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). CT has a 10-fold higher affinity for MR than GR. Normal basal levels of CT occupy the majority of the MR. During the diurnal surge of CT and following the presentation of a stressful stimulus, the MR and GR are both maximally occupied. To begin to understand how CT influences the hippocampal-HPA axis, intracellular recording techniques in the hippocampal brain slice preparation were used to determine how high concentrations of CT may alter cell characteristics and/or evoked synaptic activity. Two treatment groups were used, i.e., adrenalectomized (ADX) and ADX with CT pellet replacement (ADX+CT) that produced plasma blood levels equal to that seen in a normal rat in the morning. Acute administration of 100 nM CT decreased action potential threshold and the number of action potentials elicited by a depolarizing current pulse in cells from both the ADX and ADX+CT treated rats. The amplitude of the evoked excitatory postsynaptic potentials (EPSP) or inhibitory postsynaptic potentials (IPSP) declined in cells recorded from ADX animals and ADX rats acutely treated with high concentrations of CT (ADX/CT).(ABSTRACT TRUNCATED AT 250 WORDS)

Hypothalamic neuropeptide Y, its gene expression and receptor activity: relation to circulating corticosterone in adrenalectomized rats

Previous evidence has suggested a possible relationship between the adrenal steroid, corticosterone (CORT) and neuropeptide Y (NPY) in the brain. To provide a more systematic analysis of this interaction, the present study employed a variety of techniques, including in situ hybridization to measure NPY gene expression, radioimmunoassay to examine peptide levels and radioligand [125I]peptide YY (PYY) binding for analysis of peptide receptors. The results show that adrenalectomy (ADX), which caused a decline in CORT to levels < 0.3 micrograms %, has generally little impact on the hypothalamic NPY projection system under normal, basal conditions. This includes peptide gene expression or content in the area of its cell bodies (arcuate nucleus, ARC), in addition to peptide binding at its receptor sites. While it also includes peptide content at most hypothalamic terminal sites, there are three notable exceptions, namely, the medial paraventricular (PVN) and dorsomedial nuclei and medial preoptic area, where NPY nerve terminals and glucocorticoid receptors are particularly dense and the decline in CORT through ADX markedly reduces NPY content. In contrast, evidence obtained from CORT replacement in ADX rats shows that this steroid has profound impact on all components of the hypothalamic NPY system. This peptide-steroid interaction is apparent at the level of the cell body (ARC), as well as at the nerve terminal or receptor site (PVN and ARC), where CORT levels > 10 micrograms % strongly potentiate NPY gene expression, peptide content and radioligand binding. These and other findings suggest that this CORT-NPY interaction in the hypothalamus occurs physiologically under conditions, e.g., at the onset of the active feeding cycle, when circulating CORT normally rises.

Adrenal steroid receptors: interactions with brain neuropeptide systems in relation to nutrient intake and metabolism

The glucocorticoid, corticosterone (CORT), is believed to have an important function in modulating nutrient ingestion and metabolism. Recent evidence described in this review suggests that the effects of this adrenal hormone are mediated through two steroid receptor subtypes, the type I mineralocorticoid receptor and the type II glucocorticoid receptor. These receptors, which have different affinities for CORT, respond to different levels of circulating hormone. They mediate distinct effects of the steroid, which can be distinguished by the specific nutrient ingested and by the particular period of the circadian cycle. Under normal physiological conditions, the type I receptor is tonically activated, either by low basal levels of circulating CORT (0.5-2 microgram %) normally available across the circadian cycle or possibly by the mineralocorticoid aldosterone. This type I activation is required for the maintenance of fat ingestion and fat deposition that occurs during most meals of the feeding cycle. In contrast, the type II receptor is phasically activated by moderate levels of CORT (2-10 micrograms %) normally reached during the circadian peak. Activation of this receptor is required for the natural surge in carbohydrate ingestion and metabolism that is essential at the onset of the active feeding cycle when the body's glycogen stores are at their nadir, and gluconeogenesis is needed to maintain blood glucose levels. This receptor is also activated during periods of increased energy requirements, such as, after exercise and food restriction, when CORT levels rise further (> 10 micrograms %) and when its catabolic effects on fat and protein stores predominate to provide additional substrates for glucose homeostasis. These functions of CORT on fat and carbohydrate balance are mediated, in part, by type I and type II receptors located within the hypothalamic paraventricular nucleus, which is known to have key functions in controlling nutrient intake and metabolism, as well as circulating CORT levels. Moreover, the type II receptors within this nucleus, in addition to the arcuate nucleus, may interact positively with the peptide, neuropeptide Y, and the catecholamine, norepinephrine, both of which act to enhance natural carbohydrate feeding and CORT release at the onset of the natural feeding cycle. Thus, under normal conditions, endogenous CORT has a primary function in controlling nutrient ingestion and metabolism over the natural circadian cycle, through the coordinated action of the type I and type II steroid receptor systems. Through this action, CORT has impact on total caloric intake and body weight gain over the long term.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of adrenal steroid agonists on food intake and macronutrient selection

These experiments tested the effects of subcutaneous (SC) and paraventricular nucleus (PVN) administration of the steroid receptor agonists, corticosterone (CORT), aldosterone (ALDO), RU28362, and dexamethasone (DEX), on food intake and macronutrient selection during the first h of the dark feeding period in the rat. Results indicate that CORT and the selective type II receptor agonist RU28362 specifically stimulate carbohydrate ingestion after SC or PVN administration, while DEX has no effect on feeding. This selective effect of SC CORT on carbohydrate ingestion is dose dependent, seen at doses ranging from 0.125 to 2.0 mg/kg. Moreover, the stimulatory effects of CORT and RU28362 on carbohydrate intake are observed in ADX rats but not in sham rats. This is in contrast to SC and PVN administration of the type I receptor agonist ALDO, which specifically enhances fat ingestion in both sham and ADX rats. These results, with both peripheral and central steroid administration, reveal selective effects of type I and type II receptor stimulation on fat and carbohydrate intake, respectively.

Regulation of glucocorticoid receptor immunoreactivity in the rat hippocampus by androgenic-anabolic steroids

To determine whether androgenic-anabolic steroids (AAS) regulate glucocorticoid receptors (GR), the effects of a mixture of three commonly abused AAS (testosterone cypionate, nandrolone decanoate and boldenone undecylenate) on GR immunoreactivity (ir), were examined in hippocampi of adrenalectomized male rats. Treatment with AAS for 1 week increased nuclear GRir in pyramidal cells of CA1, and granule cells of the dentate gyrus. These findings suggest a role for GR in the mediation of some of the CNS effects of androgenic-anabolic steroids.

Androgen metabolism in the brain

The paper summarizes the most recent views on androgen metabolism in the brain. In particular it will be shown that: (1) the enzyme 5 alpha-reductase is particularly concentrated in the white matter; (2) 5 alpha-reductase is also present in the myelin; 5 alpha-reductase is present in higher concentrations in neurons (isolated or cultured) that in glial cells (astrocytes and oligodendrocytes); (4) only neurons possess the capability of aromatizing androgens to estrogens; and (5) a possible role of steroid metabolism in the control of the process of myelinogenesis is suggested.

Disturbed glucocorticoid receptor autoregulation and corticotropin response to dexamethasone in depressives pretreated with metyrapone

We studied glucocorticoid receptor autoregulation and corticotropin response to dexamethasone in depressed patients and controls, attempting to control for the confounding effect of endogenous glucocorticoids. After depletion of endogenous cortisol, depressed patients showed an attenuated suppressibility of corticotropin by dexamethasone in the face of unchanged dexamethasone plasma levels. Beta-endorphin levels were strongly correlated with adrenocorticotropic hormone (ACTH) concentrations. Although metyrapone administration resulted in a marked rise of glucocorticoid receptor sites per cell in controls, this effect was not present in depressives. These data support the hypothesis of a decreased glucocorticoid receptor plasticity and a partial steroid resistance in depression.

Lymphocyte glucocorticoid receptor binding during depression and after clinical recovery

Lymphocyte glucocorticoid receptor binding parameters were studied in 15 severely depressed patients during depression and after clinical recovery, and in 15 healthy controls. There was no difference in glucocorticoid receptor number or affinity between depressed patients and recovered or control subjects. Afternoon ACTH and cortisol concentrations did not differ significantly between the three groups. No relationship could be established between glucocorticoid receptor binding and antidepressant medication. These data support the view of an impaired ligand-induced plasticity of glucocorticoid receptor regulation rather than the hypothesis of decreased glucocorticoid receptor numbers during depression.

Characterization of Glucocorticoid Binding Capacity in Human Mononuclear Lymphocytes: Increase by Metyrapone is Prevented by Dexamethasone Pretreatment

Abstract Autoregulation of receptor systems by their own ligands is a well established biological phenomenon. While down-regulation of the glucocorticoid binding capacity by glucocorticoids has been shown in animals and humans, data on up-regulation processes in humans are lacking. To further explore glucocorticoid receptor plasticity in relation to endogenous ligands, glucocorticoid binding parameters were assessed in 15 healthy controls before and after oral administration of 1.5 g metyrapone with and without dexamethasone pretreatment. Administration of metyrapone resulted in blockade of the feedback of the hypothalamic-pituitary-adrenal system as shown by the rise in adrenocorticotropin levels, while pretreatment with 1 mg dexamethasone completely suppressed adrenocorticotropin concentrations. Glucocorticoid binding sites per lymphocyte exhibited an increase of 63% following metyrapone administration, which was prevented by dexamethasone pretreatment. Comparison of morning and afternoon glucocorticoid binding sites per cell in 11 healthy volunteers further revealed a diurnal rhythm of glucocorticoid receptor sites. These data suggest that human lymphocyte glucocorticoid receptors are under autoregulatory control.

Glucocorticoid receptors on mononuclear leukocytes in Alzheimer's disease

Several lines of evidence suggest disturbances of the hypothalamic-pituitary-adrenal (HPA) system in Alzheimer's disease (AD). In an exploration of the potential role of the glucocorticoid receptor (GR) in AD, GR density and affinity were assessed on mononuclear leukocytes of 12 AD patients and 12 healthy controls. GR binding characteristics did not differ between patients and controls or between patients subdivided according to diagnosis or associated clinical features. These data suggest that the abnormalities of the HPA system in AD are not related to a GR deficiency.

Granule cell potentials in the dentate gyrus of the hippocampus: coping behavior and stress ulcers in rats

Evoked population potentials of the granule cells in the dentate gyrus of the hippocampus were increased in stress-resistant rats and decreased in stress-susceptible rats, as indexed by restraint-induced gastric ulcers. Inescapable, uncontrollable shock stimulation also suppressed granule cell population spikes and interfered with subsequent coping responses when escape was possible, i.e. the so-called helplessness effect. The data were interpreted to indicate that the hippocampus is part of a coping system in stressful situations.

PVN steroid implants: effect on feeding patterns and macronutrient selection

The glucocorticoid corticosterone (CORT) plays a major role in feeding behavior, body weight regulation and metabolism. Recent work has demonstrated an interaction between circulating CORT and the alpha 2-noradrenergic feeding system of the hypothalamic paraventricular nucleus (PVN) and the existence of two different subtypes of glucocorticoid receptors in this nucleus. To examine the function of these specific PVN receptors, crystalline CORT and other steroid hormones were implanted directly into the PVN, and feeding patterns and macronutrient selection, of freely feeding adrenalectomized (ADX) and sham rats, were monitored at the beginning and end of the nocturnal feeding cycle. Results indicate that PVN CORT implants stimulate carbohydrate intake in ADX rats, at the onset of the dark cycle when the feeding-suppressive effects of ADX are strongest. Corticosterone was ineffective in sham rats and was also ineffective in potentiating food intake in ADX rats at the end of the dark phase. In contrast, implants of the mineralocorticoid aldosterone (ALDO) stimulated the ingestion of the fat diet, in both sham and ADX rats and during both the early and the late dark periods. Implants of ALDO also enhanced carbohydrate intake, but only in ADX rats and at dark onset. While the synthetic glucocorticoid, dexamethasone, had a small carbohydrate stimulatory effect similar to CORT, other steroids (deoxycorticosterone, progesterone and estrogen) were without effect. These results indicate a central site of action for the adrenal hormones in modulating nutrient intake. Based on a variety of evidence, it is suggested that the stimulatory effects of ALDO and CORT on macronutrient intake may be differentially mediated by Type 1 and Type 2 steroid receptor subtypes within the brain.

Selective loss of hippocampal granule cells in the mature rat brain after adrenalectomy

Adrenalectomy of adult male rats resulted in a nearly complete loss of hippocampal granule cells 3 to 4 months after surgery. Nissl and immunocytochemical staining of hippocampal neurons revealed that the granule cell loss was selective; there was no apparent loss of hippocampal pyramidal cells or of gamma-amino butyric acid (GABA)-, somatostatin-, neuropeptide Y-, calcium binding protein-, or parvalbumin-containing hippocampal interneurons. The hippocampal CA1 pyramidal cells of adrenalectomized animals exhibited normal electrophysiological responses to afferent stimulation, whereas responses evoked in the dentate gyrus were severely attenuated. Corticosterone replacement prevented both the adrenalectomy-induced granule cell loss and the attenuated physiological response. Thus, the adrenal glands play a role in maintaining the structural integrity of the normal adult brain.