Effect of neonatal handling on age-related impairments associated with the hippocampus

In rats, an environmental manipulation occurring early in life resulted in changes in the adrenocortical axis that persisted throughout the entire life of the animals and attenuated certain deficits associated with aging. Rats handled during infancy had a permanent increase in concentrations of receptors for glucocorticoids in the hippocampus, a critical region in the negative-feedback inhibition of adrenocortical activity. Increased receptor concentrations led to greater hippocampal sensitivity to glucocorticoids and enhanced negative-feedback efficacy in the handled rats. Thus, at all ages tested, rats that were not handled secreted more glucocorticoids in response to stress than did handled rats. At later ages, nonhandled rats also showed elevated basal glucocorticoid levels, with the result that there was a greater cumulative exposure to glucocorticoids in nonhandled rats. Increased exposure to adrenal glucocorticoids can accelerate hippocampal neuron loss and cognitive impairments in aging. Hippocampal cell loss and pronounced spatial memory deficits emerged with age in the nonhandled rats, but were almost absent in the handled rats. Previous work showed that glucocorticoid hypersecretion, hippocampal neuron death, and cognitive impairments form a complex degenerative cascade of aging in the rat. The present study shows that a subtle manipulation early in life can retard the emergence of this cascade.

Neuroanatomical basis for facilitation of hypothalamic-pituitary-adrenal responses to a novel stressor after chronic stress

Animals exposed to chronic stress exhibit normal or enhanced hypothalamic-pituitary adrenal responses to novel, acute stimuli despite the inhibitory endogenous corticosteroid response to the chronic stressor. Prior stress is thought to induce a central facilitatory trace that, upon exposure to a novel stimulus, balances or overcomes the inhibitory effects of corticosterone. The neuroanatomical basis for this facilitation of hypothalamic pituitary adrenal responses is unknown. In this study, we first show increased adrenocorticotropin and corticosterone responses to the novel stressor of restraint in rats exposed to intermittent cold for seven days. We then compared numbers of Fos-immunoreactive cells in 26 sites in control and chronically stressed rats at various times after onset of a 30 min restraint. At 60 min, density of Fos-stained cells was significantly higher in chronically stressed than in control rats in the parabrachial/Kölliker-Fuse area, posterior paraventricular thalamus, central, basolateral and basomedial nuclei of the amygdala and parvocellular paraventricular hypothalamus. The posterior paraventricular nucleus of the thalamus receives projections from the parabrachial nucleus and projects heavily to the differentially stained subnuclei of the amygdala, which in turn project to the parvocellular paraventricular nucleus of the hypothalamus. We propose that increased activity in the parabrachial-posterior paraventricular thalamus-amygdala-parvocellular paraventricular hypothalamus underlies facilitation of the hypothalamic pituitary-adrenal axis to novel stress in chronically stressed rats. We confirmed part of this proposal by showing that lesions of the posterior paraventricular nucleus of the thalamus increase adrenocorticotropin responses to restraint only in previously chronically stressed animals. This potential circuit provides a basis for further examination of the functional roles of these regions in stress-induced facilitation of hypothalamic pituitary-adrenal activity.

The effects of neonatal handling on the development of the adrenocortical response to stress: implications for neuropathology and cognitive deficits in later life

Several years ago Levine, Denenberg, Weininger, Ader, and others described the effects of postnatal "handling" on the development of behavioral and endocrine responses to stress. The handling procedure usually involved removing rat pups from their cages, placing the animals together in small containers, and 15-20 min later, returning the animals to their cages and their mothers. The manipulation was performed daily for the first 21 days of life. As adults, handled (H) rats exhibited attenuated fearfulness (e.g., decreased freezing, increased exploration) in novel environments and a less pronounced increase in the secretion of adrenal glucocorticoids in response to a variety of stressors. These findings clearly demonstrated that the development of rudimentary, adaptive responses to stress could be modified by environmental events. We have followed on these earlier handling studies, convinced that this paradigm provides a marvelous opportunity to examine how subtle variations in the early environment alter the development of specific biochemical systems in the brain, leading to stable individual differences in biological responses to stimuli that threaten homeostasis. In this work we have shown how early handling influences the neurochemical development of certain brain regions that regulate the adrenocortical response to stress. Neonatal handling increases the efficiency of this endocrine response to stress, preventing excessive exposure to the highly catabolic adrenal steroids. In later life, this effect appears to protect the animal from potentially damaging effects of these steroids, ensuring the anatomical integrity of brain structures involved in cognitive functioning.

Postnatal handling attenuates certain neuroendocrine, anatomical, and cognitive dysfunctions associated with aging in female rats

Hippocampal degeneration with aging is associated with increased hypothalamic-pituitary-adrenal (HPA) activity and, in male rats, both are attenuated by postnatal handling. Considering the important sex differences in the effects of handling and in HPA responses to stress in older rats, we have examined the effects of postnatal handling on aging in females. Female, Long-Evans rats were handled (H) during the first 3 weeks of life and later compared with nonhandled (NH) controls at various ages. Handling resulted in permanently increased hippocampal type II, glucocorticoid receptor binding. Relative to H females, NH females showed increased basal corticosterone levels in later life and hypersecreted corticosterone following stress at all ages examined. Both effects are similar to those reported in males. However, unlike males, H and NH females did not differ in corticosterone levels achieved during stress, a finding that may be related to sex-dependent effects of handling on pituitary transcortin receptors. There were no differences in hippocampal neuron density in 6-month-old animals. However, the older NH animals showed considerable neuron loss in the CA1 and CA3 hippocampal cellfields. There was little or no neuron loss in the H animals. Finally, the NH animals exhibited age-related spatial memory impairments, such that by 24 months of age the performance of the NH females was profoundly worse than that of the younger NHs and same-aged H animals. These data suggest that early handling permanently alters CNS systems that regulate hypothalamic-pituitary-adrenal (HPA) function, although the effect may depend on the gender of the animal. In both males and females, however, handling appears to prevent (or minimize) increased adrenal secretion in later life and to attenuate hippocampal cell loss and spatial memory impairments.

Lesions of the posterior paraventricular thalamus block habituation of hypothalamic-pituitary-adrenal responses to repeated restraint

We examined the role of the posterior division of the paraventricular nucleus of the thalamus (pPVTh) in habituation of hypothalamic-pituitary-adrenal (HPA) responses to repeated restraint. Habituation refers to the decrement in HPA activity that occurs with repeated exposure to the same or homotypic stressor. To date, the pPVTh has been shown to inhibit the enhanced or facilitated HPA responses to novel, heterotypic restraint in previously chronically cold stressed rats. We hypothesized that the pPVTh also inhibits HPA activity under conditions of habituation. In the first experiment, we lesioned the pPVTh and examined adrenocorticotropic hormone (ACTH) and corticosterone responses to the first or eighth restraint exposure. In sham-lesioned rats, we found lower ACTH and corticosterone responses to the eighth period of 30 min restraint compared to the first exposure, evidence for habituation. In pPVTh-lesioned rats, there was no difference in ACTH and corticosterone responses to the eighth compared to the first restraint exposure. Therefore, pPVTh lesions prevented the habituation of HPA responses to repeated restraint. In the second experiment, we examined whether habituation to restraint is observable in response to an acute, single restraint on day 28 in sham and pPVTh lesioned rats that were exposed to restraint only on days 1 through 8. In this experiment, we replicated the results from the first experiment, and found evidence that habituation to restraint can be observed weeks after chronic stress has been terminated. Furthermore, pPVTh lesions had no additional effects on HPA responses to acute stress on day 28. In summary, pPVTh lesions inhibit habituation of HPA activity to a homotypic stressor, without altering HPA responses to the first restraint. Thus, the intact pPVTh inhibits HPA activity under conditions of habituation, as well as facilitation, and represents an important regulator of HPA activity under conditions of chronic stress.

Changes in hypothalamic-pituitary-adrenal function, body temperature, body weight and food intake with repeated social stress exposure in rats

These present studies aimed to compare changes in hypothalamic-pituitary-adrenal (HPA) activity and body temperature in response to acute social defeat, to repeated social stress and to novel restraint after repeated stress, as well as to assess effects on metabolic parameters by measuring body weight gain and food and water intake. We found that social defeat produced a marked increase in both adrenocorticotrophic hormone and corticosterone compared to placement in a novel cage. Similarly, body temperature was also increased during social defeat and during 30 min of recovery from defeat. We then examined the effects of 6 days of repeated social stress and observed minimal HPA responses to repeated social stress compared to control rats. These neuroendocrine responses were contrasted by robust increases in body temperature during stress and during recovery from stress during 6 days of repeated stress. However, in response to novel restraint, repeatedly stressed rats displayed facilitated body temperature responses compared to controls, similar to our previous findings with HPA activity. Food intake was increased during the light period during which defeat took place, but later intake during the dark period was not affected. Repeated stress decreased body weight gain in the dark period but food intake was increased overall during the 6 days of repeated stress in the light period. As a result, repeated stress increased cumulative food intake during the light period in the stressed rats but these relatively small increases in food intake were unable to prevent the diminished total weight gain in repeatedly stressed rats. Overall, the results demonstrate that, although acute social defeat has similar effects on temperature and HPA activity, repeated exposure to social stress has divergent effects on HPA activity compared to body temperature and that dampened weight gain produced by repeated social stress cannot be fully explained by changes in food intake.

Zinc and cognitive development

Cognition is a field of thought processes by which an individual processes information through skills of perception, thinking, memory, learning and attention. Zinc deficiency may affect cognitive development by alterations in attention, activity, neuropsychological behavior and motor development. The exact mechanisms are not clear but it appears that zinc is essential for neurogenesis, neuronal migration, synaptogenesis and its deficiency could interfere with neurotransmission and subsequent neuropsychological behavior. Studies in animals show that zinc deficiency during the time of rapid brain growth, or during the juvenile and adolescent period affects cognitive development by decreasing activity, increasing emotional behavior, impairing memory and the capacity to learn. Evidence from human studies is limited. Low maternal intakes of zinc during pregnancy and lactation were found to be associated with less focused attention in neonates and decreased motor functions at 6 months of age. Zinc supplementation resulted in better motor development and more playfulness in low birth weight infants and increased vigorous and functional activity in infants and toddlers. In older school going children the data is controversial but there is some evidence of improved neuropsychological functions with zinc supplementation. Additional research is required to determine the exact biological mechanisms, the critical periods, the threshold of severity and the long-term effects of zinc deprivation on cognitive development.

Starvation: early signals, sensors, and sequelae

To identify the sequences of changes in putative signals, reception of these and responses to starvation, we sampled fed and starved rats at 2- to 6-h intervals after removal of food 2 h before dark. Metabolites, hormones, hypothalamic neuropeptide expression, fat depots, and leptin expression were measured. At 2 h, insulin decreased, and FFA and corticosterone (B) increased; by 4 h, leptin and glucose levels decreased. Neuropeptide Y messenger RNA (mRNA) increased 6 h after food removal and thereafter. Adrenal and plasma B did not follow ACTH and were elevated throughout, with a nadir at the dark-light transition. Leptin correlated inversely with adrenal B. Fat stores decreased during the last 12 h. Leptin mRNA in perirenal and sc fat peaked during the dark period, resembling plasma leptin in fed rats. We conclude that 1) within the first 4 h, hormonal and metabolic signals relay starvation-induced information to the hypothalamus; 2) hypothalamic neuropeptide synthesis responds rapidly to the altered metabolic signals; 3) catabolic activity quickly predominates, reinforced by elevated B, not driven by ACTH, but possibly to a minor extent by leptin, and more by adrenal neural activity; and 4) leptin secretion decreases before leptin mRNA or fat depot weight, showing synthesis-independent regulation.

The paraventricular nucleus of the thalamus alters rhythms in core temperature and energy balance in a state-dependent manner

Exposure to chronic stress facilitates activity within the hypothalamic-pituitary-adrenal (HPA) axis and is associated with enhanced neuronal activity in a discreet set of brain regions, including the posterior division of the paraventricular nucleus of the thalamus (pPVTh). Because HPA function is intimately associated with systems that regulate metabolism, including core temperature and energy balance, we examined the effects of chronic stress on circadian rhythms in temperature, locomotor activity, body weight gain and food intake and adipose depot weights in rats. We also examined the potential role of the pPVTh in mediating these functions using ibotenate lesions of this nucleus. Chronic stress lowered the amplitude of core temperature rhythms, and lesions of the pPVTh blocked this effect in chronically stressed animals, but did not affect the amplitude of temperature rhythms in unstressed controls. In addition, lesions of the pPVTh increased cumulative food intake and overall body weight gain in controls but they increased subcutaneous white adipose depot weight in chronically stressed animals. Thus, the functional paraventricular nucleus of the thalamus appears to inhibit both temperature rhythms and specific white adipose depots only in chronically stressed animals. Together with our previous results, we show that the PVTh affects rhythms in food intake and body weight and is a nexus that differentially regulates core temperature rhythms/HPA activity/specific white adipose depots depending on the stress state of the animal.

Hypothalamic-pituitary-adrenal function in chronic intermittently cold-stressed neonatally handled and non handled rats

Neonatally handled (H) animals, as adults, exhibit lower ACTH and corticosterone (B) responses to a number of acute stressors compared to their non-handled (NH) counterparts. However, little is known about activity within the hypothalamic-pituitary-adrenal (HPA) axis of H and NH animals under conditions of chronic stress. We, therefore, examined HPA function in adult H and NH rats exposed to chronic intermittent cold stress (4 h of 4 degrees C cold a day for 21 days; H CHR and NH CHR) and in control H and NH (H CTL and NH CTL) rats. H CTL and NH CTL animals displayed comparable ACTH and B responses to a single, acute exposure to cold. We found that H CHR animals exhibited lower levels of ACTH, but not B, during the 21st exposure to cold (the homotypic stressor) compared to the first exposure to cold in H CTL; however, ACTH and B levels in NH CHR were not different from those in NH CTL. In contrast, NH CHR animals hypersecreted ACTH and B in response to restraint (the novel, heterotypic stressor) compared to NH CTL and both H groups, whereas H CHR and H CTL animals did not differ in their responses to restraint. These endocrine responses were associated with increased basal median eminence levels of both CRH and AVP in H CHR and NH CHR relative to their control groups (with NH CHR exhibiting the highest absolute levels of each secretagogue), and with decreased glucocorticoid receptor densities in septum of both H CHR and NH CHR. In addition, the expected lower glucocorticoid receptor density in hippocampus and frontal cortex of NH rats compared to H rats was observed. We believe that the difference in glucocorticoid receptor density between H and NH animals in the hippocampus and frontal cortex and the associated differences in secretagogue content in the median eminence are related to the hypersecretion of ACTH and B in the NH CHR relative to the other groups. Furthermore, we hypothesize that an active inhibitory process is involved in the adaptation of HPA responses of H CHR animals to the homotypic stressor, and present a working model of regulation of activity within the CRH/AVP neurons in the PVN.

Molecular basis for the development of individual differences in the hypothalamic-pituitary-adrenal stress response

1. Several years ago, investigators described the effects of infantile handling on the development of hypothalamic-pituitary-adrenal (HPA) responses to stress in the rat. Rat pups exposed to brief periods of innocuous handling early in life showed reduced HPA responses to a wide variety of stressors, and the effect persists throughout the life of the animal. These effects are robust and provide an excellent model for understanding how early environmental stimuli, which are external to the organism, alter neural differentiation and, thus, neuroendocrine responsivity to stress. 2. This paper reviews the endocrine mechanisms affected by early handling and our current understanding of the neural transduction of environmental events and their effects at the level of the target neurons (in the hippocampus and frontal cortex). 3. In brief, handling serves to increase glucocorticoid receptor gene transcription, increasing sensitivity to glucocorticoid negative feedback regulation and, thus, altering the activity within hypothalamic corticotropin-releasing factor/vasopressin neurons. Together these changes serve to determine neuroendocrine responsivity to stress.

Voluntary sucrose ingestion, like corticosterone replacement, prevents the metabolic deficits of adrenalectomy

We tested whether corticosterone replacement causes increased sucrose drinking in adrenalectomized (ADX) rats compared to sham-ADX (sham) rats. ADX rats given high doses of corticosterone drank as much sucrose as sham rats, whereas at three lower doses of corticosterone, drinking was similar between groups and was only approximately 40% of that ingested by shams. Compared to sham rats, ADX rats drinking saline, or saline and saccharin, gain weight more slowly, contain less white adipose tissue, and have higher sympathetic outflow as assessed by uncoupling protein content in brown adipose tissue. Allowing sucrose as well as saline to drink restored all of these variables to normal in ADX rats with no- or low-corticosterone. All endpoints from sucrose-drinking ADX rats with no-or low-corticosterone were indistinguishable from those in water-drinking shams. By contrast, sucrose-drinking ADX rats that were given high doses of corticosterone exhibited the usual catabolic effects of corticosterone on body weight gain and, unlike sucrose-drinking shams, were obese. We conclude that (i) high corticosterone stimulates the potability of sucrose and inhibits sympathetic stimulation of uncoupling protein; (ii) sucrose, without corticosterone, normalizes metabolic deficits in ADX rats probably through actions mediated both peripherally and by the central nervous system; and (iii) ADX rats have a distinct sucrose appetite.

Sucrose ingestion normalizes central expression of corticotropin-releasing-factor messenger ribonucleic acid and energy balance in adrenalectomized rats: a glucocorticoid-metabolic-brain axis?

Both CRF and norepinephrine (NE) inhibit food intake and stimulate ACTH secretion and sympathetic outflow. CRF also increases anxiety; NE increases attention and cortical arousal. Adrenalectomy (ADX) changes CRF and NE activity in brain, increases ACTH secretion and sympathetic outflow and reduces food intake and weight gain; all of these effects are corrected by administration of adrenal steroids. Unexpectedly, we recently found that ADX rats drinking sucrose, but not saccharin, also have normal caloric intake, metabolism, and ACTH. Here, we show that ADX (but not sham-ADX) rats prefer to consume significantly more sucrose than saccharin. Voluntary ingestion of sucrose restores CRF and dopamine-beta-hydroxylase messenger RNA expression in brain, food intake, and caloric efficiency and fat deposition, circulating triglyceride, leptin, and insulin to normal. Our results suggest that the brains of ADX rats, cued by sucrose energy (but not by nonnutritive saccharin) maintain normal activity in systems that regulate neuroendocrine (hypothalamic-pituitary-adrenal), behavioral (feeding), and metabolic functions (fat deposition). We conclude that because sucrose ingestion, like glucocorticoid replacement, normalizes energetic and neuromodulatory effects of ADX, many of the actions of the steroids on the central nervous system under basal conditions may be indirect and mediated by signals that result from the metabolic effects of adrenal steroids.

Bottomed out: metabolic significance of the circadian trough in glucocorticoid concentrations

Mild chronic stressors characteristically increase circadian trough corticosteroid concentrations in rats and man. The elevation in trough concentrations is often accompanied by a reduction in peak concentrations and no change in the daily mean values. Here we point out that elevation of trough glucocorticoids, probably through daily increases of glucocorticoid receptor occupancy, has major metabolic effects that bias organisms toward storage of calories as fat. Thus, chronic mild stress, by overriding the normal mineralocorticoid receptor-mediated corticosteroid feedback regulation of trough CRF and ACTH secretion, facilitates development of the metabolic syndrome.

Corticosterone facilitates saccharin intake in adrenalectomized rats: does corticosterone increase stimulus salience?

Unlike normal rats, adrenalectomized rats do not voluntarily drink sweet saccharin solutions. To test whether this is a function of corticosterone in the circulation, and if corticosterone also increases the impetus for drinking saccharin after a period of withdrawal, we performed the following experiments. Young male rats were sham adrenalectomized (sham) or adrenalectomized (ADX); the ADX rats were provided with subcutaneous pellets containing (percent replacement of corticosterone, %B) 0%B, 15%B, 30%B or 100%B. Sham and ADX rats were immediately provided with saline (0.5%) and saccharin (2 mM) bottles in their home cages. Saccharin was allowed for 4 days on, 3 days off, 4 days on, 3 days off and a final day on, over the 15 days experiment. The dose of corticosterone determined both how much saccharin was voluntarily drunk by the ADX rats and the degree of overshoot after days off. Corticosterone also determined energy balance of the groups of ADX rats. The 30%B pellets restored food intake, body weight gain, insulin and caloric efficiency to the normal levels observed in sham rats. White fat depot weights and uncoupling protein concentration in brown adipose tissue were restored to sham levels by 100%B, suggesting that these variables which depend on activity in the sympathetic nervous system require considerable glucocorticoid receptor occupancy. We conclude that corticosterone increases the willingness to ingest sweetened water in a unimodal, dose-related manner, while moderate doses of corticosterone restore energy balance.

Stress-induced occupancy and translocation of hippocampal glucocorticoid receptors

Using an exchange assay for glucocorticoid receptors, we found that immobilization stress resulted in a approximately 50% translocation of receptors (i.e. receptors assumed to be chromatin bound) from soluble fractions prepared from hippocampal tissue. The increased hormone-receptor signal persisted for about 2-4 h following the termination of the stressor. This time course is consistent with the known temporal pattern for the negative feedback of glucocorticoids on adrenocortical activity.

Cellular mechanisms underlying the development and expression of individual differences in the hypothalamic-pituitary-adrenal stress response

Several years ago Levine, Denenberg, Ader, and others described the effects of postnatal "handling" on the development of behavioral and endocrine responses to stress. As adults, handled rats exhibited attenuated fearfulness in novel environments and a less pronounced increase in the secretion of the adrenal glucocorticoids in response to a variety of stressors. These findings clearly demonstrated that the development of rudimentary, adaptive responses to stress could be modified by environmental events. We have followed these earlier studies, convinced that this paradigm provides a marvellous opportunity to examine how subtle variations in the early environment alter the development of specific neurochemical systems, leading to stable individual differences in biological responses to stimuli that threaten homeostasis. In this work we have shown how early handling influences the development of certain brain regions that regulate glucocorticoid negative-feedback inhibition over hypothalamic-pituitary-adrenal (HPA) activity. Specifically, handling increases glucocorticoid (type II corticosteroid) receptor density in the hippocampus and frontal cortex, enhancing the sensitivity of these structures to the negative-feedback effects of elevated circulating glucocorticoids, and increasing the efficacy of neural inhibition over ACTH secretion. These effects are reflected in the differential secretory pattern of ACTH and corticosterone in handled and nonhandled animals under conditions of stress. In more recent years, using a hippocampal cell culture system, we have provided evidence for the importance of serotonin-induced changes in cAMP levels in mediating the effect of postnatal handling on hippocampal glucocorticoid receptor density. The results of these studies are consistent with the idea that environmental events in early life can permanently alter glucocorticoid receptor gene expression in the hippocampus, providing evidence for a neural mechanism for the development of individual differences in HPA function.

MicroRNAs as biomarkers of resilience or vulnerability to stress

Identifying novel biomarkers of resilience or vulnerability to stress could provide valuable information for the prevention and treatment of stress-related psychiatric disorders. To investigate the utility of blood microRNAs as biomarkers of resilience or vulnerability to stress, microRNAs were assessed before and after 7days of chronic social defeat in rats. Additionally, microRNA profiles of two important stress-regulatory brain regions, the medial prefrontal cortex (mPFC) and basolateral amygdala (BLA), were assessed. Rats that displayed vulnerability to subsequent chronic stress exhibited reductions in circulating miR-24-2-5p, miR-27a-3p, miR-30e-5p, miR-3590-3p, miR-362-3p, and miR-532-5p levels. In contrast, rats that became resilient to stress displayed reduced levels of miR-139-5p, miR-28-3p, miR-326-3p, and miR-99b-5p compared to controls. In the mPFC, miR-126a-3p and miR-708-5p levels were higher in vulnerability compared to resilient rats. In the BLA, 77 microRNAs were significantly altered by stress but none were significantly different between resilient and vulnerable animals. These results provide proof-of-principle that assessment of circulating microRNAs is useful in identifying individuals who are vulnerable to the effects of future stress or individuals who have become resilient to the effects of stress. Furthermore, these data suggest that microRNAs in the mPFC but not in the BLA are regulators of resilience/vulnerability to stress.

Optogenetic examination identifies a context-specific role for orexins/hypocretins in anxiety-related behavior

Maladaptation to stress is associated with psychopathology. However, our understanding of the underlying neural circuitry involved in adaptations to stress is limited. Previous work from our lab indicated the paraventricular hypothalamic neuropeptides orexins/hypocretins regulate behavioral and neuroendocrine responses to stress. To further elucidate the role of orexins in adaptation to stress, we employed optogenetic techniques to specifically examine the effects of orexin cell activation on behavior in the social interaction test and in the home cage as well as orexin receptor 1 internalization and ERK phosphorylation in brain regions receiving orexin inputs. In the social interaction test, optogenetic stimulation of orexin neurons decreased time spent in the interaction zone while increasing the frequency of entries into the interaction zone. In addition, optogenetic stimulation of orexin neurons increased the total distance traveled in the social interaction arena but had no effect on their home cage behavior. Together, these results suggest that orexin release increases anxiety in the social interaction test while increasing the salience of novel but not familiar environmental stimuli. Consistent with activation of orexin neurons, optogenetic stimulation increased orexin receptor1 internalization and ERK phosphorylation in the paraventricular thalamus (PVT) and locus coeruleus (LC), two regions heavily innervated by orexin neurons. Together these results show for the first time that elevation of orexin activity, possibly in the PVT and LC, is associated with increased anxiety, activity, and arousal in a context-specific manner.

Pediatric celiac disease in India is associated with multiple DR3-DQ2 haplotypes

The role of human leukocyte antigen (HLA) DQ2 heterodimer (DQA1*0501-DQB1*0201) in presenting gluten peptides to effector T cells in celiac disease (CD) has been well documented. Because HLA-DQ2 is carried on DR3 haplotypes due to linkage disequilibrium, such haplotypes are encountered more frequently in patients with autoimmune disease. This study analyzed 35 North Indian children below 15 years of age and diagnosed to have CD as per the ESPGAN criteria, which included histopathologic alterations in duodenal biopsies, clinical response to gluten withdrawal, and presence of antiendomysial antibodies. The HLA class I and class II alleles were determined by polymerase chain reaction-sequence-specific primers, sequence-specific oligonucleotide probe, and reverse line strip molecular techniques. A statistically significant positive association of the disease with HLA-DRB1*03 (94.2% versus 22.1% in controls, chi(2) = 73.4, p = 7.54E-11), and a negative association with DRB1*15 (chi(2) = 7.4, p = 6.5E-03) and DRB1*13 alleles was observed. The HLA-DQB1*0201 was observed in all the 35 patients (100%), whereas the DQ2 heterodimer alpha(0)beta(0) occurred in 97.1% of CD patients (31.4% in double dose, 65.7% in single dose) and revealed significant deviation from healthy controls (chi(2) = 102.08, p = 7.56E-11). Further analysis revealed involvement of multiple DR3+ve haplotypes with CD in Indians, of which A26-B8-DR3 was the most common DR3 haplotype among patients (34.28%, chi(2) = 40.57, p = 2.65E-10) followed by Ax-B21-DR3 (11.4%) (chi(2) = 13.8, p = 2E-04) and the classical Caucasian haplotype A1-B8-DR3 (5.7%). The former two haplotypes are characteristic of Asian Indians and are involved in the development of CD. We conclude that the high risk DR3 haplotypes that play a crucial role in the development of CD are unique in Asian Indians. Detailed analysis of these haplotypes in Indian patients with autoimmune diseases may help understand the influence of other intervening genes within the major histocompatibility complex.

Muscarinic antagonists are anxiogenic in rats tested in the black-white box

Central cholinergic (ACh) projections have been shown to modulate stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis and are integral to the expression of electrophysiological correlates of arousal, namely hippocampal theta rhythm. The degree to which these actions of ACh are behaviorally relevant has received comparatively less attention, and we sought to investigate if manipulations of ACh systems might also affect behaviors related to stress and arousal. We chose to examine indices of anxiety as revealed by changes in behavior elicited by the black-white box test, a relatively novel and recently validated model of rodent anxiety. Groups of rats were injected with either scopolamine hydrobromide (SCOP; 0, 0.05, and 0.10 mg/kg i.p.) or the peripherally acting scopolamine methyl bromide (methyl-SCOP; 0, 0.05, and 0.10 mg/kg i.p.) to compare and contrast the effects of central and peripheral ACh blockade on measures of anxiety. SCOP pretreatment significantly lowered latencies for rats to escape from the white to black compartment, while methyl-SCOP elevated latencies to reenter the white chamber from the black. Both drugs increased the amount of time rats spent in the black compartment and also suppressed exploration as revealed by decreased episodes of intercompartmental locomotion. Neither drug deleteriously affected locomotor activity, however; in fact, SCOP significantly increased locomotion in the white chamber. In the absence of motor disturbances to account for any group differences, we contend that both central and peripheral ACh blockade may affect measures of anxiety, perhaps by directly or indirectly affecting HPA activity. Central ACh systems may underlie sensory filtering whereby irrelevant stimuli are excluded from sensory processing. Antagonism of ACh transmission may render an animal incapable of correctly processing sensory information leading to hyperresponsiveness, which can manifest itself as enhanced anxiety and fear.

The effects of intrahippocampal scopolamine infusions on anxiety in rats as measured by the black-white box test

Hippocampal cholinergic projections mediate attention to arousing stimuli as demonstrated by behavioral, electrophysiological, and endocrine studies. We recently reported that peripheral injections of the cholinergic antagonist scopolamine (SCOP) increased anxiety-like behaviour (ALB) in rats and we sought to investigate if this response might be hippocampally mediated. Adult male, Lister Hooded rats were implanted bilaterally with hippocampal cannulae 3 weeks prior to testing. On the test day, rats were injected with vehicle (VEH; artificial CSF at 3 microl), 15 or 30 microg SCOP, 20 min prior to being placed into the white chamber of the black-white box (n = 10/group). Rats were scored for latencies to exit and reenter the white chamber, total time spent in the white chamber, intercompartmental crossings, and activity. SCOP at 30 microg significantly reduced time to exit the white arena, while both doses of SCOP elevated latencies to reenter the white chamber. There were no effects of SCOP on intercompartmental crossing, time spent in the white chamber, or on activity levels. Loss of hippocampal cholinergic function impairs processing of threatening stimuli that manifests itself as increased ALB.

Effects of chronic intermittent cold stress on pituitary adrenocortical and sympathetic adrenomedullary functioning

Basal and stress-induced pituitary-adrenocortical (PA) and sympathetic adrenomedullary (SAM) function was investigated in rats exposed to chronic intermittent cold stress (4 degrees C for 4 h a day for 21 days; CHR). We found that basal plasma levels of corticosterone (B), corticosteroid-binding-globulin, ACTH, epinephrine (E) and norepinephrine (NE) were similar in CHR and control (CTL) animals. In contrast, activity of the adrenal catecholamine-synthesizing enzyme tyrosine hydroxylase, but not phenylethanolamine-N-methyl transferase, was significantly elevated in CHR compared to CTL. Following exposure to a heterotypic stressor (20 min restraint), plasma levels of B were significantly higher in CHR than CTL, but the stress-induced levels of E and NE were not different between groups. These data suggest that, although basal PA function is not altered by exposure to chronic intermittent cold stress, components of the SAM system are affected by this paradigm, and that co-ordinate facilitation of both PA and SAM responses to a novel stressor is not a necessary consequence of exposure to chronic intermittent stress.

The effects of prior chronic stress on cardiovascular responses to acute restraint and formalin injection

Exposure to acute stressors activates both the hypothalamic-pituitary-adrenal (HPA) and cardiovascular systems. Prior chronic stress enhances HPA responses to novel, acute stressors, but whether it alters cardiovascular responsivity to novel, acute stress is unknown. In the present study, we examined mean arterial blood pressure (MAP) and heart rate (HR) to two distinct stimuli, restraint and formalin, following prior exposure to 7 days of intermittent cold. In two sets of control and chronically stressed animals, we measured MAP and HR for 60 min following onset of 30 min restraint and MAP, HR and behavioral responses to intraplantar injection of formalin. Chronic stress raised MAP and HR under resting conditions and elevated HR during, but not following termination of, restraint. These increases in HR during restraint were due to the differences in resting levels of HR, since both control and chronically stressed animals exhibited similar increases from resting levels in HR during restraint. Conversely, chronically stressed animals exhibited lower changes in MAP and HR from resting levels following termination of restraint. Formalin produced the characteristic biphasic pattern of cardiovascular and behavioral responses. Prior chronic stress did not alter behavior, but increased MAP and HR in Interphase and only MAP in Phase 2. The increases in MAP during Interphase and Phase 2 were a result of the elevations in resting levels of MAP, but even when differences in resting levels were taken into account, HR remained elevated in the Interphase in chronically stressed animals. Together, these data demonstrate that prior chronic intermittent cold stress modifies cardiovascular function both under resting conditions and, in very specific ways, under stimulated conditions produced by restraint and formalin. We propose that these modifications are produced by brain regions that are known to regulate cardiovascular function and which are activated by chronic stress.