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

Dorsal Bed Nucleus of the Stria Terminalis-Subcortical Output Circuits Encode Positive Bias in Pavlovian Fear and Reward

Opposite emotions like fear and reward states often utilize the same brain regions. The bed nucleus of the stria terminalis (BNST) comprises one hub for processing fear and reward processes. However, it remains unknown how dorsal BNST (dBNST) circuits process these antagonistic behaviors. Here, we exploited a combined Pavlovian fear and reward conditioning task that exposed mice to conditioned tone stimuli (CS)s, either paired with sucrose delivery or footshock unconditioned stimuli (US). Pharmacological inactivation identified the dorsal BNST as a crucial element for both fear and reward behavior. Deep brain calcium imaging revealed opposite roles of two distinct dBNST neuronal output pathways to the periaqueductal gray (PAG) or paraventricular hypothalamus (PVH). dBNST neural activity profiles differentially process valence and Pavlovian behavior components: dBNST-PAG neurons encode fear CS, whereas dBNST-PVH neurons encode reward responding. Optogenetic activation of BNST-PVH neurons increased reward seeking, whereas dBNST-PAG neurons attenuated freezing. Thus, dBNST-PVH or dBNST-PAG circuitry encodes oppositely valenced fear and reward states, while simultaneously triggering an overall positive affective response bias (increased reward seeking while reducing fear responses). We speculate that this mechanism amplifies reward responding and suppresses fear responses linked to BNST dysfunction in stress and addictive behaviors.

Socio-demographic and psychosocial predictors of salivary cortisol from older male participants in the Speedwell prospective cohort study

INTRODUCTION

Associations between measures of socio-economic position and cortisol remain controversial. We examined the association between social class and cortisol reactivity in an aging male population.

METHODS

The Speedwell cohort study recruited 2348 men aged 45-59 years from primary care between 1979 and 1982 (phase I) where occupational social class was used to classify socioeconomic position. Men were seen on four more occasions, the last being between 1997 and 1999 (phase 5) when salivary samples were obtained capturing cortisol reactivity to stressors (cognitive test and venepuncture) and circadian variations (awakening and night-time cortisol levels, circadian slope and area under curve) at morning and afternoon clinic sessions. Longitudinal association between social class at phase 3 and log-transformed salivary cortisol measures at phase 5 was assessed using multivariable linear regression adjusted for variables associated with sampling time and age as a potential confounder, stratified by time of clinic session. We also explored possible mediation by psychosocial factors (e.g. work dislike) and health-related factors (e.g. waist-to-hip ratio and high-density lipoprotein cholesterol).

RESULTS

From 1768 living men, 1003 men (57%) attended a clinic at phase five, 854 participants (85% of attendees) returned home cortisol samples (mean age 71.7 years). We found little evidence of association between social class and baseline cortisol (i.e. prior to stress), cortisol response to stressors, and cortisol diurnal variation. However, we found lower social class was associated with higher and delayed post-stress recovery cortisol for participants that visited the clinic in the morning (adjusted β coefficient for manual versus non-manual 0.25 ng/ml; 95% CI: 0.06-0.48; P = 0.008). This association did not appear to be mediated by any of the measured psychosocial or health-related factors.

CONCLUSION

Our data did not show an overall association between social class and cortisol variability either diurnal or in response to a stressor. Lower social class was associated with a slower time to recover from exposure to stress in the morning, thereby increasing overall cortisol exposure. These findings provide some evidence for a mechanism that may contribute to the association between lower social class and a higher risk of adverse health outcomes.

Corticosterone and Glucocorticoid Receptor in the Cortex of Rats during Aging-The Effects of Long-Term Food Restriction

Numerous beneficial effects of food restriction on aging and age-related pathologies are well documented. It is also well-established that both short- and long-term food restriction regimens induce elevated circulating levels of glucocorticoids, stress-induced hormones produced by adrenal glands that can also exert deleterious effects on the brain. In the present study, we examined the effect of long-term food restriction on the glucocorticoid hormone/glucocorticoid receptor (GR) system in the cortex during aging, in 18- and 24-month-old rats. Corticosterone level was increased in the cortex of aged ad libitum-fed rats. Food restriction induced its further increase, accompanied with an increase in the level of 11β-hydroxysteroid dehydrogenase type 1. However, alterations in the level of GR phosphorylated at Ser²³² were not detected in animals on food restriction, in line with unaltered CDK5 level, the decrease of Hsp90, and an increase in a negative regulator of GR function, FKBP51. Moreover, our data revealed that reduced food intake prevented age-related increase in the levels of NFκB, gfap, and bax, confirming its anti-inflammatory and anti-apoptotic effects. Along with an increase in the levels of c-fos, our study provides additional evidences that food restriction affects cortical responsiveness to glucocorticoids during aging.

The role of the corticotropin-releasing hormone and its receptors in the regulation of stress response

Stress is an essential part of everyday life. The neuropeptide corticotropin-releasing hormone (CRH, also called CRF and corticoliberin) plays a key role in the integration of neuroendocrine, autonomic and behavioral responses to stress. The activation of the hypothalamic-pituitary-adrenal axis (HPA axis) by neurons of the paraventricular hypothalamic nucleus (PVN), the primary site of synthesis CRH, triggers stress reactions. In addition to the hypothalamus, CRH is widespread in extrahypothalamic brain structures, where it functions as a neuromodulator for coordination and interaction between the humoral and behavioral aspects of a stress response. The axons of neurons expressing CRH are directed to various structures of the brain, where the neuropeptide interacts with specific receptors (CRHR1, CRHR2) and can affect various mediator systems that work together to transmit signals to different brain regions to cause many reactions to stress. Moreover, the effect of stress on brain functions varies from behavioral adaptation to increased survival and increased risk of developing mental disorders. Disturbances of the CRH system regulation are directly related to such disorders: mental pathologies (depression, anxiety, addictions), deviations of neuroendocrinological functions, inflammation, as well as the onset and development of neurodegenerative diseases such as Alzheimer’s disease. In addition, the role of CRH as a regulator of the neurons structure in the areas of the developing and mature brain has been established. To date, studies have been conducted in which CRHR1 is a target for antidepressants, which are, in fact, antagonists of this receptor. In this regard, the study of the participation of the CRH system and its receptors in negative effects on hormone-dependent systems, as well as the possibility of preventing them, is a promising task of modern physiological genetics. In this review, attention will be paid to the role of CRH in the regulation of response to stress, as well as to the involvement of extrahypothalamic CRH in pathophysiology and the correction of mental disorders.

Psychological intervention to treat distress: An emerging frontier in cancer prevention and therapy

Psychological distress, such as chronic depression and anxiety, is a topical problem. In the context of cancer patients, prevalence rates of psychological distress are four-times higher than in the general population and often confer worse outcomes. In addition to evidence from epidemiological studies confirming the links between psychological distress and cancer progression, a growing body of cellular and molecular studies have also revealed the complex signaling networks which are modulated by psychological distress-derived chronic stress during cancer progression. In this review, aiming to uncover the intertwined networks of chronic stress-driven oncogenesis and progression, we summarize physiological stress response pathways, like the HPA, SNS, and MGB axes, that modulate the release of stress hormones with potential carcinogenic properties. Furthermore, we discuss in detail the mechanisms behind these chronic stimulations contributing to the initiation and progression of cancer through direct regulation of cancer hallmarks-related signaling or indirect promotion of cancer risk factors (including obesity, disordered circadian rhythms, and premature senescence), suggesting a novel research direction into cancer prevention and therapy on the basis of psychological interventions.

Does older adults' cognition particularly suffer from stress? A systematic review of acute stress effects on cognition in older age

This literature review provides the first comprehensive qualitative and quantitative systematic synthesis of acute laboratory stress effects on older adults' cognition by specifying the direction and magnitude of those effects both overall and for different cognitive processes separately. A systematic literature search was performed, and effect sizes estimated whenever possible. We found meta-analytical evidence that stress has negative effects on older adults' verbal fluency (g_adj = -0.53, 95 % CI [-2.70, 1.63]), null-to-negative effects on episodic memory (g_adj = -0.26, 95 % CI [-0.44, -0.08]), null effects on executive functions (g_adj = 0.07, 95 % CI [-0.31, 0.46]), and enhancing effects on working memory (g_adj = 0.16, 95 % CI [-0.01, 0.33]). Relating these findings to those in young adults, notable differences emerged for some cognitive functions, such as opposing effects on working memory between age groups. Our review further reveals that stress effects on older adults' memory retention, associative memory, prospective memory, interference control or cognitive flexibility are heavily understudied. We provide a conceptual and methodological framework for future studies in older adults.

Advances in Research on Adolescent Suicide and a High Priority Agenda for Future Research

Suicide is the second leading cause of death for adolescents in the United States, yet remarkably little is known regarding risk factors for suicidal thoughts and behaviors (STBs), relatively few federal grants and scientific publications focus on STBs, and few evidence-based approaches to prevent or treat STBs are available. This "decade in review" article discusses five domains of recent empirical findings that span biological, environmental, and contextual systems and can guide future research in this high priority area: (1) the role of the central nervous system; (2) physiological risk factors, including the peripheral nervous system; (3) proximal acute stress responses; (4) novel behavioral and psychological risk factors; and (5) broader societal factors impacting diverse populations and several additional nascent areas worthy of further investigation.

The impact of adolescent nicotine exposure on alcohol use during adulthood: The role of neuropeptides

Nicotine and alcohol abuse and co-dependence represent major public health crises. Indeed, previous research has shown that the prevalence of alcoholism is higher in smokers than in non-smokers. Adolescence is a susceptible period of life for the initiation of nicotine and alcohol use and the development of nicotine-alcohol codependence. However, there is a limited number of pharmacotherapeutic agents to treat addiction to nicotine or alcohol alone. Notably, there is no effective medication to treat this comorbid disorder. This chapter aims to review the early nicotine use and its impact on subsequent alcohol abuse during adolescence and adulthood as well as the role of neuropeptides in this comorbid disorder. The preclinical and clinical findings discussed in this chapter will advance our understanding of this comorbid disorder's neurobiology and lay a foundation for developing novel pharmacotherapies to treat nicotine and alcohol codependence.

Physiological and electroencephalogram responses in goats subjected to pre-and during slaughter stress

A comprehensive stress assessment is vital in understanding the impact of the pre-slaughter procedure on animal welfare. The transportation and handling process was commonly reported to cause stress in animals. This research utilises electroencephalography (EEG) as an alternative stress indicator to non-painful acute stress measurement. EEG has been proved to be instantaneous and sensitive with specific results. Therefore, this study was aimed to determine the stress level of goats subjected to two different transportation duration and the effect of lairage based on their EEG activities and blood parameters changes. Eighteen adult male goats were divided into two transportation stress groups based on the transport duration: the two-hour (TS2) and six-hour (TS6) groups. Then, each group was then again divided into three smaller groups according to the lairage duration, which was three-hour (L3), six-hour (L6), and overnight (L12) groups. Blood was sampled before transport, after transport, and during slaughter while EEG was recorded before transport, after transport, after lairage, and during slaughter. Results revealed that there was a significant decrease in beta wave activity compared to baseline in TS2 goats (P < 0.05) after transportation, whereas no significant difference was detected in the TS6 goats. At the same time, goats from the TS2 group showed increase in creatine kinase (CK) and lactate dehydrogenase (LDH) compared to that in TS6 goats. Together with the observed cortisol concentration, these findings showed that the TS6 goats were fully adapted to the transportation stress while the TS2 goats were still under stress. As for the lairage duration, it was observed that the TS2L3 goats showed lower EEG activities than the values obtained after two-hour transportation, while lower EEG activities were found from the TS6L6 goats after six-hour transportation. Therefore, it can be concluded that three-hour lairage was adequate to lower the impact of two hours transportation stress, whereas six-hour lairage was required to reduce the impact of six hours transportation stress. Finally, it was also found that the TS6L3, TS6L6, and TS6L12 groups took a long time to die after slaughter than the TS2L3, TS2L6, and TS2L12 goats based on the time their EEG activity reached isoelectric.

Effects of Acute Stress on the Oscillatory Activity of the Hippocampus-Amygdala-Prefrontal Cortex Network

Displaying a stress response to threatening stimuli is essential for survival. These reactions must be adjusted to be adaptive. Otherwise, even mental illnesses may develop. Describing the physiological stress response may contribute to distinguishing the abnormal responses that accompany the pathology, which may help to improve the development of both diagnoses and treatments. Recent advances have elucidated many of the processes and structures involved in stress response management; however, there is still much to unravel regarding this phenomenon. The main aim of the present research is to characterize the response of three brain areas deeply involved in the stress response (i.e., to an acute stressful experience). Specifically, the electrophysiological activity of the infralimbic division of the medial prefrontal cortex (IL), the basolateral nucleus of the amygdala (BLA), and the dorsal hippocampus (dHPC) was recorded after the infusion of 0.5 µl of corticosterone-releasing factor into the dorsal raphe nucleus (DRN), a procedure which has been validated as a paradigm to cause acute stress. This procedure induced a delayed reduction in slow waves in the three structures, and an increase in faster oscillations, such as those in theta, beta, and gamma bands. The mutual information at low theta frequencies between the BLA and the IL increased, and the delta and slow wave mutual information decreased. The low theta-mid gamma phase-amplitude coupling increased within BLA, as well as between BLA and IL. This electrical pattern may facilitate the activation of these structures, in response to the stressor, and memory consolidation.

Understanding how stress responses and stress-related behaviors have evolved in zebrafish and mammals

Stress response is essential for the organism to quickly restore physiological homeostasis disturbed by various environmental insults. In addition to well-established physiological cascades, stress also evokes various brain and behavioral responses. Aquatic animal models, including the zebrafish (Danio rerio), have been extensively used to probe pathobiological mechanisms of stress and stress-related brain disorders. Here, we critically discuss the use of zebrafish models for studying mechanisms of stress and modeling its disorders experimentally, with a particular cross-taxon focus on the potential evolution of stress responses from zebrafish to rodents and humans, as well as its translational implications.

The stress response in Atlantic salmon (Salmo salar L.): identification and functional characterization of the corticotropin-releasing factor (crf) paralogs

Corticotropin-Releasing Factor (CRF) is one of the main mediators of the Hypothalamic-Pituitary-Interrenal (HPI) axis to stress response. In Atlantic salmon, a comparative understanding of the crf1 paralogs role in the stress response is still incomplete. Our database searches have identified four crf1 genes in Atlantic salmon, named crf1a1, crf1a2, crf1b1 and crf1b2. Brain distribution analysis revealed that the four crf1 paralogs were widely distributed, and particularly abundant in the telencephalon, midbrain, and hypothalamus of Atlantic salmon post-smolts. To increase the knowledge on crf1-mediated response to stress, Atlantic salmon post-smolts were exposed to either repeated chasing, hypoxia or a combination of chasing and hypoxia for eight days, followed by a novel-acute stressor, confinement. Cortisol, glucose, lactate, and creatinine levels were used as markers for the stress response. The crf1 paralogs mRNA abundance showed to be dependent on the stress exposure regime. Both crf1 mRNA levels in the telencephalon and crf1a1 mRNA levels in the hypothalamus showed similar response profiles to the serum cortisol levels, i.e., increasing levels during the first 24 h after stress exposure followed by a decline during the eight-day exposure. The similar trend between crf1 and cortisol disappeared once exposed to the novel-acute stressor. There was a minor response to stress for both crf1b1 and crf1b2 in the hypothalamus, while no changes at mRNA level were observed in the hypothalamic crf1a2 under the different stress conditions. No or weak relationship was found between the crf1 paralogs mRNA expression and the other serum stress-indicators analysed. In summary, our data provide novel insights on the dynamic of the HPI axis activation in Atlantic salmon, and thus underline the involvement of the crf1 paralogs as additional factors in the regulation of the stress response in this species. Likewise, the data highlight the importance of analysing all crf1 paralogues response to a stress-condition, in particular in this premature knowledge stage of their functionality. Further analysis and a more detailed time-point series will help to elucidate the response of the HPI axis and the link of crf1 paralogs in the stress response mechanism.

HPA Axis in the Pathomechanism of Depression and Schizophrenia: New Therapeutic Strategies Based on Its Participation

The hypothalamic-pituitary-adrenal (HPA) axis is involved in the pathophysiology of many neuropsychiatric disorders. Increased HPA axis activity can be observed during chronic stress, which plays a key role in the pathophysiology of depression. Overactivity of the HPA axis occurs in major depressive disorder (MDD), leading to cognitive dysfunction and reduced mood. There is also a correlation between the HPA axis activation and gut microbiota, which has a significant impact on the development of MDD. It is believed that the gut microbiota can influence the HPA axis function through the activity of cytokines, prostaglandins, or bacterial antigens of various microbial species. The activity of the HPA axis in schizophrenia varies and depends mainly on the severity of the disease. This review summarizes the involvement of the HPA axis in the pathogenesis of neuropsychiatric disorders, focusing on major depression and schizophrenia, and highlights a possible correlation between these conditions. Although many effective antidepressants are available, a large proportion of patients do not respond to initial treatment. This review also discusses new therapeutic strategies that affect the HPA axis, such as glucocorticoid receptor (GR) antagonists, vasopressin V1B receptor antagonists and non-psychoactive CB1 receptor agonists in depression and/or schizophrenia.

Pubertal probiotics mitigate lipopolysaccharide-induced programming of the hypothalamic-pituitary-adrenal axis in male mice only

Puberty is a period of rapid cortical and neuronal development. Stress exposure during puberty programs the hypothalamic-pituitary-adrenal (HPA) axis responsiveness to future stressors. However, programming can result in an enduring maladaptation of the HPA axis activity and can be associated with long-term anxiety- and depression-like behaviours. Probiotic treatment mitigates the effect of stress on mental health, suggesting that the gut microbiome may mediate the programming of the HPA axis. However, the mechanism underlying this effect remains elusive. Thus, we investigated the effect of probiotic exposure on lipopolysaccharide (LPS)-induced programming of the HPA axis and glucocorticoid receptor (GR) expression in the paraventricular (PVN), basolateral amygdala (BLA), piriform cortex (PIR), and medial prefrontal cortex (mPFC). Male and female mice were exposed to either probiotics or control skim milk and were treated with either saline or LPS during puberty. Prior to euthanasia in adulthood, mice were restrained for 30 min. The results showed that pubertal LPS treatment permanently decreased GR expression in the PVN in milk fed control males. However, pubertal probiotic treatment blocked the LPS-induced decrease in GR expression in males. Given that this effect is limited to males, further research is required to better understand sex differences in the interactions between the gut microbiome and the programming of the HPA axis during puberty. Nevertheless, our findings suggest that the gut microbiome influences the neurophysiology of the HPA axis and mediates its programming in pubertal males. The prevention of GR reduction in the male PVN and PIR using probiotics illustrates the complexity of the gut-brain communication and compels continued investigation.

Arginine vasopressin in the medial amygdala causes greater post-stress recruitment of hypothalamic vasopressin neurons

Arginine vasopressin (AVP) is expressed in both hypothalamic and extra-hypothalamic neurons. The expression and role of AVP exhibit remarkable divergence between these two neuronal populations. Polysynaptic pathways enable these neuronal groups to regulate each other. AVP neurons in the paraventricular nucleus of the hypothalamus increase the production of adrenal stress hormones by stimulating the hypothalamic–pituitary–adrenal axis. Outside the hypothalamus, the medial amygdala also contains robust amounts of AVP. Contrary to the hypothalamic counterpart, the expression of extra-hypothalamic medial amygdala AVP is sexually dimorphic, in that it is preferentially transcribed in males in response to the continual presence of testosterone. Male gonadal hormones typically generate a negative feedback on the neuroendocrine stress axis. Here, we investigated whether testosterone-responsive medial amygdala AVP neurons provide negative feedback to hypothalamic AVP, thereby providing a feedback loop to suppress stress endocrine response during periods of high testosterone secretion. Contrary to our expectation, we found that AVP overexpression within the posterodorsal medial amygdala increased the recruitment of hypothalamic AVP neurons during stress, without affecting the total number of AVP neurons or the number of recently activated neurons following stress. These observations suggest that the effects of testosterone on extra-hypothalamic AVP facilitate stress responsiveness through permissive influence on the recruitment of hypothalamic AVP neurons.

Distinctive Regulation of Emotional Behaviors and Fear-Related Gene Expression Responses in Two Extended Amygdala Subnuclei With Similar Molecular Profiles

The central nucleus of the amygdala (CeA) and the lateral division of the bed nucleus of the stria terminalis (BNST) are the two major nuclei of the central extended amygdala that plays essential roles in threat processing, responsible for emotional states such as fear and anxiety. While some studies suggested functional differences between these nuclei, others showed anatomical and neurochemical similarities. Despite their complex subnuclear organization, subnuclei-specific functional impact on behavior and their underlying molecular profiles remain obscure. We here constitutively inhibited neurotransmission of protein kinase C-δ-positive (PKCδ+) neurons-a major cell type of the lateral subdivision of the CeA (CeL) and the oval nucleus of the BNST (BNSTov)-and found striking subnuclei-specific effects on fear- and anxiety-related behaviors, respectively. To obtain molecular clues for this dissociation, we conducted RNA sequencing in subnuclei-targeted micropunch samples. The CeL and the BNSTov displayed similar gene expression profiles at the basal level; however, both displayed differential gene expression when animals were exposed to fear-related stimuli, with a more robust expression change in the CeL. These findings provide novel insights into the molecular makeup and differential engagement of distinct subnuclei of the extended amygdala, critical for regulation of threat processing.

Delirium in Intensive Care

Purpose of Review

Delirium in the intensive care unit (ICU) has become increasingly acknowledged as a significant problem for critically ill patients affecting both the actual course of illness as well as outcomes. In this review, we focus on the current evidence and the gaps in knowledge.

Recent Findings

This review highlights several areas in which the evidence is weak and further research is needed in both pharmacological and non-pharmacological treatment. A better understanding of subtypes and their different response to therapy is needed and further studies in aetiology are warranted. Larger studies are needed to explore risk factors for developing delirium and for examining long-term consequences. Finally, a stronger focus on experienced delirium and considering the perspectives of both patients and their families is encouraged.

Summary

With the growing number of studies and a better framework for research leading to stronger evidence, the outcomes for patients suffering from delirium will most definitely improve in the years to come.

Effect of air cleaner on stress hormones of pig and pork quality

The objective of this study is to investigate effect of air cleaner operated during pig breeding period on stress hormones of pigs and their pork quality. The stress hormones (cortisol, epinephrine and norepinephrine) in blood sample of pigs reared in the housing rooms with or without air cleaner have been measured according to a pig’s rearing stage: 0 day (farrowing), 21st day (farrowing–weaning), 70th day (weaning–nursery), 140th day (nursery–growing), and 180th day (growing–fattening). The comparison of pork quality according to the application of an air cleaner was performed through the carcass analysis of the pigs shipped from swine house. The levels of cortisol, epinephrine, and norepinephrine in pigs reared in housing rooms with and without air cleaners were found to be within the range of normal reference values. Among pork quality evaluation items, the thickness of intermuscular fat and final carcass grade of pigs raised in housing room with air cleaner was generally superior to those of pigs raised in housing room without air cleaner (p < 0.05). Based on the results obtained from this study, it is concluded that air cleaner does not have a significant effect on reducing pig stress but contributes to improving pork quality in pig breeding.

The association of the 5-HTTLPR polymorphism and the response to different stressors in healthy males

The experience of stress is related to individual wellbeing and vulnerability to psychopathology. Therefore, understanding the determinants of individual differences in stress reactivity is of great concern from a clinical perspective. The functional promotor polymorphism of the serotonin transporter gene (5-HTTLPR/rs25531) is such a factor, which has been linked to the acute stress response as well as the adverse effect of life stressors. In the present study, we compared the impact of two different stress induction protocols (Maastricht Acute Stress Test and ScanSTRESS) and the respective control conditions on affective ratings, salivary cortisol levels and cognitive performance. To this end, 156 healthy young males were tested and genotyped for the 5-HTTLPR/rs25531 polymorphism. While combined physiological and psychological stress in the MAST led to a greater cortisol increase compared to control conditions as well as the psychosocial ScanSTRESS, subjective stress ratings were highest in the ScanSTRESS condition. Stress induction in general affected working memory capacity but not response inhibition. Subjective stress was also influenced by 5-HTTLPR/rs25531 genotype with the high expression group showing lower stress ratings than lower expression groups. In line with previous research, we identified the low expression variant of the serotonin transporter gene as a risk factor for increased stress reactivity. While some dimensions of the human stress response may be stressor specific, cognitive outcomes such as working memory performance are influenced by stress in general. Different pathways of stress processing and possible underlying mechanisms are discussed.

Cannabinoid receptor type 1 modulates the effects of polyunsaturated fatty acids on memory of stressed rats

Memory and GABAergic activity in the hippocampus of stressed rats improve after n-3 polyunsaturated fatty acid (PUFA) supplementation. On the other hand, cannabinoid receptor type 1 (CB1) strongly regulates inhibitory neurotransmission in the hippocampus. Speculation about a possible relation between stress, endocannabinoids, and PUFAs. Here, we examined whether the effects of PUFAs on memory of chronically stressed rats depends on pharmacological manipulation of CB1 receptors. Male Sprague-Dawley rats were orally supplemented with n-3 (fish oil) or n-6 (primrose oil) PUFAs during chronic restraint stress (CRS) protocol (6 h/day; 21 days). First, we studied if the expression of CB1 receptors in the hippocampus may be affected by CRS and PUFAs supplementation by real-time PCR and immunofluorescence. CRS up-regulated the CB1 expression compared with the non-stressed rats, while only n-3 PUFAs countered this effect. Memory was evaluated in the Morris water maze. Stressed rats were co-treated with PUFAs and/or modulators of CB1 receptor (AM251, antagonist, 0.3 mg/kg/day; WIN55,212-2, agonist, 0.5 mg/kg/day) by intraperitoneal injections. Memory improved in the stressed rats that were treated with AM251 and/or n-3 PUFAs. Supplementation with n-6 PUFAs did not affect memory of stressed rats, but co-treatment with AM251 improved it, while co-treatment with WIN55,212-2 did not affect memory. Our results demonstrate that activity of the CB1 receptors may modulate the effects of PUFAs on memory of stressed rats. This study suggests that endocannabinoids and PUFAs can both become a singular system by being self-regulated in limbic areas, so they control the effects of stress on the brain.

Association between hippocampal structure and serum Brain-Derived Neurotrophic Factor (BDNF) in healthy adults: A registered report

The hippocampus is a highly plastic brain structure supporting functions central to human cognition. Morphological changes in the hippocampus have been implicated in development, aging, as well as in a broad range of neurological and psychiatric disorders. A growing body of research suggests that hippocampal plasticity is closely linked to the actions of brain-derived neurotrophic factor (BDNF). However, evidence on the relationship between hippocampal volume (HCV) and peripheral BDNF levels is scarce and limited to elderly and patient populations. Further, despite evidence that BDNF expression differs throughout the hippocampus and is implicated in adult neurogenesis specifically in the dentate gyrus, no study has so far related peripheral BDNF levels to the volumes of individual hippocampal subfields. Besides its clinical implications, BDNF-facilitated hippocampal plasticity plays an important role in regulating cognitive and affective processes. In the current registered report, we investigated how serum BDNF (sBDNF) levels relate to volumes of the hippocampal formation and its subfields in a large sample of healthy adults (N = 279, 160 f) with a broad age range (20-55 years, mean 40.5) recruited in the context of the ReSource Project. We related HCV to basal sBDNF and, in a subsample (n = 103, 57 f), to acute stress-reactive change in sBDNF. We further tested the role of age as a moderator of both associations. Contrary to our hypotheses, neither basal sBDNF levels nor stress-reactive sBDNF change were associated with total HCV or volume of the dentate gyrus/cornu ammonis 4 (DG/CA4) subfield. We also found no evidence for a moderating effect of age on any of these associations. Our null results provide a first point of reference on the relationship between sBDNF and HCV in healthy mid-age, in contrast to patient or aging populations. We suggest that sBDNF levels have limited predictive value for morphological differences of the hippocampal structure when notable challenge to its neuronal integrity or to neurotrophic capacity is absent.

Brain preparedness: The proactive role of the cortisol awakening response in hippocampal-prefrontal functional interactions

Upon awakening from nighttime sleep, the stress hormone cortisol in humans exhibits a robust rise within thirty to forty-five minutes. This cortisol awakening response (CAR), a crucial point of reference within the healthy cortisol circadian rhythm, has been linked to various psychological, psychiatric and health-related conditions. The CAR is thought to prepare the brain for anticipated challenges of the upcoming day to maintain one's homeostasis and promote adaptive responses. Using brain imaging with a prospective design and pharmacological manipulation, we investigate the neurobiological mechanisms underlying this preparation function of the CAR across two studies. In Study 1, a robust CAR is predictive of less hippocampal and prefrontal activity, though enhanced functional coupling between those regions during a demanding task hours later in the afternoon. Reduced prefrontal activity is in turn linked to better working memory performance, implicating that the CAR proactively promotes brain preparedness based on improved neurocognitive efficiency. In Study 2, pharmacologically suppressed CAR using Dexamethasone mirrors this proactive effect, which further causes a selective reduction of prefrontal top-down functional modulation over hippocampal activity. These findings establish a causal link between the CAR and its proactive role in optimizing functional brain networks involved in neuroendocrine control, executive function and memory.

The Long-Term Effects of Neonatal Inflammatory Pain on Cognitive Function and Stress Hormones Depend on the Heterogeneity of the Adolescent Period of Development in Male and Female Rats

Exposure to stress at an early age programs the HPA axis which can lead to cognitive deficits in adults. However, it is not known whether these deficits emerge in adulthood or are expressed earlier in life. The aims of the study were to investigate (1) the immediate effects of early injury-induced stress in one-day-old (P1) and repeated stress on at P1 and P2 rat pups on plasma corticosterone levels; and (2) examine the subsequent long-term effects of this early stress on spatial learning and memory, and stress reactivity in early P26-34 and late P45-53 adolescent male and female rats. Intra-plantar injection of formalin induced prolonged and elevated levels of corticosterone in pups and impaired spatial learning and short- and long-term memory in late adolescent males and long-term memory in early adolescent females. There were sex differences in late adolescence in both learning and short-term memory. Performance on the long-term memory task was better than that on the short-term memory task for all early adolescent male and female control and stressed animals. Short-term memory was better in the late age control rats of both sexes and for formalin treated females as compared with the early age rats. These results are consistent with an impaired function of structures involved in memory (the hippocampus, amygdala, prefrontal cortex) after newborn pain. However, activation of the HPA axis by neonatal pain did not directly correlate with spatial learning and memory outcomes and the consequences of neonatal pain remain are likely multi-determined.

Effects of Lysine Cell Mass Supplementation as a Substitute for L-Lysine·HCl on Growth Performance, Diarrhea Incidence, and Blood Profiles in Weaning Pigs

This study was conducted to evaluate the effects of lysine cell mass (LCM) as an alternative lysine source in diets for weaning pigs on growth performance, diarrhea incidence, and blood profiles. In experiment 1, a total of 200 weaning pigs, with an average body weight (BW) of 6.89 ± 1.04 kg, were allotted into one of five treatments with four replicates of 10 pigs per pen in a randomized complete block design (RCBD). The dietary treatments were composed of LCM supplementation (0, 0.25, 0.5, 0.75, or 1.0%) with partial replacement of L-lysine·HCl (0 to 0.8% for phase 1 diets and 0 to 0.07% for phase 2 diets). The BW and feed intake were recorded at the end of each phase (d 0 to 14 for phase 1, d 14 to 35 for phase 2), and diarrhea incidence was checked daily throughout the experimental period. Blood samples were taken from the jugular vein of pigs at 2 weeks and 5 weeks to determine the blood profiles of weaning pigs. In experiment 2, a total of 144 weaning pigs with an average BW of 6.44 ± 1.19 kg were allotted into one of six treatments with six replicates of four pigs per pen in RCBD. The dietary treatments were composed of LCM supplementation (0 to 3.5% for phase 1 diets and 0 to 2.2% for phase 2 diets) with replacement of L-lysine·HCl from 0 to 100%. In experiment 1, partial replacement of L-lysine·HCl with 0 to 1% LCM did not affect growth performance and diarrhea incidence of pigs. An increase in the LCM supplementation from 0 to 1% with partial replacement of L-lysine·HCl had no influence on the blood urea nitrogen concentrations, whereas it resulted in a linear decrease (p < 0.05) in the serum IgG concentrations for 5 weeks. In experiment 2, increasing the dietary level of LCM with replacement of L-lysine·HCl quadratically decreased (p < 0.05) ADG and G-F ratio for phase 2 and G-F ratio for the overall period such that 100% replacement of L-lysine·HCl with LCM decreased ADG and G-F ratio of weaning pigs. An increase in the LCM supplementation with replacement of L-lysine·HCl tended to decrease linearly (p < 0.10) the diarrhea incidence of weaning pigs for the overall period and linearly decrease (p < 0.05) the serum IgG concentrations for 2 weeks. In conclusion, partial replacement of L-lysine·HCl with LCM from 0 to 1% had no negative impacts on the growth performance, but 100% replacement of L-lysine·HCl with LCM decreased the growth performance of weaning pigs. Therefore, LCM could be included in the diets for weaning pigs up to 2.8% and 1.76% for phase 1 and phase 2, respectively, as a substitute for L-lysine·HCl without detrimental effects on the performance of weaning pigs.

Norepinephrine and Glucocorticoids Modulate Chronic Unpredictable Stress-Induced Increase in the Type 2 CRF and Glucocorticoid Receptors in Brain Structures Related to the HPA Axis Activation

The stress response is multifactorial and enrolls circuitries to build a coordinated reaction, leading to behavioral, endocrine, and autonomic changes. These changes are mainly related to the hypothalamus-pituitary-adrenal (HPA) axis activation and the organism's integrity. However, when self-regulation is ineffective, stress becomes harmful and predisposes the organism to pathologies. The chronic unpredictable stress (CUS) is a widely used experimental model since it induces physiological and behavioral changes and better mimics the stressors variability encountered in daily life. Corticotropin-releasing factor (CRF) and glucocorticoids (GCs) are deeply implicated in the CUS-induced physiological and behavioral changes. Nonetheless, the CUS modulation of CRF receptors and GR and the norepinephrine role in extra-hypothalamic brain areas were not well explored. Here, we show that 14 days of CUS induced a long-lasting HPA axis hyperactivity evidenced by plasmatic corticosterone increase and adrenal gland hypertrophy, which was dependent on both GCs and NE release induced by each stress session. CUS also increased CRF₂ mRNA expression and GR protein levels in fundamental brain structures related to HPA regulation and behavior, such as the lateral septal nucleus intermedia part (LSI), ventromedial hypothalamic nucleus (VMH), and central nucleus of the amygdala (CeA). We also showed that NE participates in the CUS-induced increase in CRF₂ and GR levels in the LSI, reinforcing the locus coeruleus (LC) involvement in the HPA axis modulation. Despite the CUS-induced molecular changes in essential areas related to anxiety-like behavior, this phenotype was not observed in CUS animals 24 h after the last stress session.

Interaction of FKBP5 variant rs3800373 and city living alters the neural stress response in the anterior cingulate cortex

Psychosocial stress effects of urban living are associated with substantially increased risk for schizophrenia, mood and anxiety disorders, by altering stress-induced activity in the amygdala and pregenual anterior cingulate cortex (ACC). Genetic factors are likely to modulate the impact of city living on stress processing. Growing evidence suggests a key role of FKBP5, a co-chaperone regulating the glucocorticoid receptor sensitivity, in the etiology of stress-related disorders. Here we investigated the interaction of city living and genetic variation in FKBP5 (rs3800373) on neural activity in stress-sensitive brain systems. Functional magnetic resonance imaging was performed in 31 healthy young adults using the Montreal Imaging Stress Task. Subjects were divided into groups depending on the number of inhabitants of their current residency. There was a significant main effect of city living on neural activity in the amygdala-hippocampus complex, replicating prior findings. Moreover, we found an interaction between rs3800373 and city living modulating responses in the bilateral subgenual ACC and right pregenual ACC. Specifically, only city dwellers carrying the FKBP5 minor risk allele showed increased stress responses in the subgenual and pregenual ACC when compared to those living in small towns. A significant gene-environment interaction on neural stress responses in the amygdala or hippocampus was only found in FKBP5 major allele carriers. These results point to a potential role of the FKBP5 rs3800373 minor risk allele in predisposing those who live in bigger cities to changes of functional responsivity in the pre- and subgenual ACC, thereby increasing the risk for developing stress-related mental disorders.

Molecular Targets of Cannabinoids Associated with Depression

Novel therapeutic strategies are needed to address depression, a major neurological disorder affecting hundreds of millions of people worldwide. Cannabinoids and their synthetic derivatives have demonstrated numerous neurological activities and may potentially be developed into new treatments for depression. This review highlights cannabinoid (CB) receptors, monoamine oxidase (MAO), N-methyl-D-aspartate (NMDA) receptor, gamma-aminobutyric acid (GABA) receptor, and cholecystokinin (CCK) receptor as key molecular targets of cannabinoids that are associated with depression. The anti-depressant activity of cannabinoids and their binding modes with cannabinoid receptors are discussed, providing insights into rational design and discovery of new cannabinoids or cannabimimetic agents with improved druggable properties.

Sex-Specific Effects of Stress on Respiratory Control: Plasticity, Adaptation, and Dysfunction

As our understanding of respiratory control evolves, we appreciate how the basic neurobiological principles of plasticity discovered in other systems shape the development and function of the respiratory control system. While breathing is a robust homeostatic function, there is growing evidence that stress disrupts respiratory control in ways that predispose to disease. Neonatal stress (in the form of maternal separation) affects "classical" respiratory control structures such as the peripheral O₂ sensors (carotid bodies) and the medulla (e.g., nucleus of the solitary tract). Furthermore, early life stress disrupts the paraventricular nucleus of the hypothalamus (PVH), a structure that has emerged as a primary determinant of the intensity of the ventilatory response to hypoxia. Although underestimated, the PVH's influence on respiratory function is a logical extension of the hypothalamic control of metabolic demand and supply. In this article, we review the functional and anatomical links between the stress neuroendocrine axis and the medullary network regulating breathing. We then present the persistent and sex-specific effects of neonatal stress on respiratory control in adult rats. The similarities between the respiratory phenotype of stressed rats and clinical manifestations of respiratory control disorders such as sleep-disordered breathing and panic attacks are remarkable. These observations are in line with the scientific consensus that the origins of adult disease are often found among developmental and biological disruptions occurring during early life. These observations bring a different perspective on the structural hierarchy of respiratory homeostasis and point to new directions in our understanding of the etiology of respiratory control disorders. © 2021 American Physiological Society. Compr Physiol 11:1-38, 2021.

Endocannabinoids, cannabinoids and the regulation of anxiety

Cannabis has been used for hundreds of years, with its ability to dampen feelings of anxiety often reported as a primary reason for use. Only recently has the specific role cannabinoids play in anxiety been thoroughly investigated. Here we discuss the body of evidence describing how endocannabinoids and exogenous cannabinoids are capable of regulating the generation and termination of anxiety states. Disruption of the endogenous cannabinoid (eCB) system following genetic manipulation, pharmacological intervention or stress exposure reliably leads to the generation of an anxiety state. On the other hand, upregulation of eCB signaling is capable of alleviating anxiety-like behaviors in multiple paradigms. When considering exogenous cannabinoid administration, cannabinoid receptor 1 (CB1) agonists have a biphasic, dose-dependent effect on anxiety such that low doses are anxiolytic while high doses are anxiogenic, a phenomenon that is evident in both rodent models and humans. Translational studies investigating a loss of function mutation in the gene for fatty acid amide hydrolase, the enzyme responsible for metabolizing AEA, have also shown that AEA signaling regulates anxiety in humans. Taken together, evidence reviewed here has outlined a convincing argument for cannabinoids being powerful regulators of both the manifestation and amelioration of anxiety symptoms, and highlights the therapeutic potential of targeting the eCB system for the development of novel classes of anxiolytics. This article is part of the special issue on 'Cannabinoids'.

Effects of stress associated with academic examination on the kynurenine pathway profile in healthy students

The effects of stress on the neuroendocrine, central nervous and immune systems are extremely complex. The kynurenine pathway (KP) of the tryptophan metabolism is recognised as a cross-link between the neuroendocrine- and immune systems. However, the effects of acute stress from everyday life on KP activation have not yet been studied. This study aims to investigate changes in the levels of the KP neuroactive metabolites and cytokines in response to stress triggered by academic examinations. Ninety-two healthy first year medical students benevolently participated in the study. Parameters were measured pre- examination, which is considered to be a high-stress period, and post-examination, as a low-stress period. Stress induced by academic examinations significantly increases the perceived stress scores (p<0.001), serum cortisol levels (p<0.001) and brain-derived neurotrophic factor (BDNF) levels (p<0.01). It decreased IL-10 levels (p<0.05) but had no effect on IL-6 and TNF-alpha levels. Only the KP neuroactive metabolite, 3-hydroxykynurenine (3-HK) significantly increased (p<0.01) in the post-examination period. In addition, the stress scores positively correlated with the levels of cortisol (r² = 0.297, p<0.01) at post examination. Acute stress triggered by academic examinations increases cortisol and BDNF production and suppresses the anti-inflammatory cytokine, IL-10, but did not increase significantly the levels of other pro-inflammatory cytokines, tryptophan, kynurenine and downstream KP metabolites. The concomitant increased levels of BDNF under the duress of acute examination stress appear to limit the levels pro-inflammatory markers, which may attenuate the action of cortisol and the neuroinflammatory branch of the KP.

Should I Stay or Should I Go? CRHPVN Neurons Gate State Transitions in Stress-Related Behaviors

Corticotropin-releasing hormone (CRH) neurons in the paraventricular nucleus of the hypothalamus are the canonical controllers of the endocrine response to stress. Here we propose a new role for these cells as a gate for state transitions that allow the organism to engage in stress-related behaviors. Specifically, we review evidence indicating that activation of these cells at critical times allows organisms to move to a state that is permissive for motor action. This is evident when the organism is under duress (defensive behavior), when the organism has successfully vanquished a threat (coping behavior), and when an organism initiates approach to a conspecific (social behavior). The motor behavior that follows from the activation of CRH neurons is not necessarily under the control of these cells but is determined by higher order circuits that discriminate more refined features of environmental context to execute the appropriate behavior.

Amygdala microglia modify neuronal plasticity via complement C1q/C3-CR3 signaling and contribute to visceral pain in a rat model

Stress can trigger symptoms in patients with irritable bowel syndrome (IBS). Previously we demonstrated that chronic psychological stress induced microglial remodeling in the central nucleus of amygdala (CeA) and contributed to the development of visceral hypersensitivity via synaptic engulfment. However, the specific signaling mechanisms that microglia depend upon to recognize target neurons to facilitate visceral pain remain unknown. Here, we test the hypothesis that the microglia in the CeA contribute to chronic stress-induced visceral hypersensitivity via complement C1q/C3-CR3 signaling-mediated synaptic remodeling. In male and female Fischer-344 rats, micropellets of corticosterone (CORT) or cholesterol (control) were stereotaxically implanted bilaterally onto the CeA. After 7 days, microglial C1q, complement receptor 3 (CR3) expression, and microglia-mediated synaptic engulfment were assessed via RNAscope, quantitative PCR, and immunofluorescence. The microglial inhibitor minocycline, CR3 antagonist neutrophil inhibitory factor (NIF), or vehicle were daily infused into the CeA following CORT implantations. Visceral sensitivity was assessed via a visceromotor response (VMR) to graded pressures of isobaric colorectal distension (CRD). Our results suggest that chronic exposure to elevated CORT in the CeA induced visceral hypersensitivity and amygdala microglial morphological remodeling. CORT increased microglial C1q and CR3 expression and increased microglia-mediated synaptic engulfment. Both groups of animals with minocycline or NIF infusions reversed microglia-mediated synaptic remodeling and attenuated CORT-induced visceral hypersensitivity. Our findings demonstrate that C1q/C3-CR3 signaling is critical for microglia-mediated synaptic remodeling in the CeA and contributes to CORT-induced visceral hypersensitivity.NEW & NOTEWORTHY Patients with irritable bowel syndrome (IBS) show altered amygdala activity. We showed previously that stress induces visceral hypersensitivity partially through microglia-modulated synaptic plasticity in the central nucleus of the amygdala (CeA). Our current data suggest that the C1q/C3-CR3 cascade initiates microglia-mediated synaptic remodeling in the CeA. Blocking C3-CR3 interaction attenuates stress-induced visceral hypersensitivity. These findings uncover a role of microglia-synapse signaling in the brain-gut regulation and support a future therapeutic target to treat visceral pain.

Cardiovascular correlates of human emotional vasovagal syncope differ from those of animal freezing and tonic immobility

It has been suggested that vertebrate freezing and tonic immobility (TI) represent the antecedents of human emotional vasovagal syncope. When a prey detects an approaching predator, it suddenly interrupts its ongoing activity and behaves according to the predator's distance. A prey enters TI when the fight or flight reaction is not feasible and the animal is captured. TI is defined as a post-contact, all or none, innate immobility reflex response that persists after the end of the prey-predator contact. In humans, vasovagal syncope, a reversible adaptive response frequently associated with fainting, occurs in response to emergency conditions such as strong emotions, orthostatic stress, anoxia, visceral pain and decrease in blood volume. The aim of the present review is to dispute the hypothesis that human vasovagal syncope represents the evolution of the bradycardia observed during freezing in a prey-predator condition in other vertebrates. The hypothesis does not take into account three crucial issues: 1) freezing and TI are defence responses which differ from each other in behavioural, cardiovascular and neurophysiological correlates; 2) the initial phase of vasovagal syncope is associated with tachycardia, whereas freezing is associated with a sudden fast-developing bradycardia; 3) the second phase of vasovagal syncope terminates with a blood pressure collapse, whereas blood pressure levels remain at basal levels during both freezing and TI.

Male Goal-Tracker and Sign-Tracker Rats Do Not Differ in Neuroendocrine or Behavioral Measures of Stress Reactivity

Environmental cues attain the ability to guide behavior via learned associations. As predictors, cues can elicit adaptive behavior and lead to valuable resources (e.g., food). For some individuals, however, cues are transformed into incentive stimuli and elicit motivational states that can be maladaptive. The goal-tracker (GT)/sign-tracker (ST) animal model captures individual differences in cue-motivated behaviors, with reward-associated cues serving as predictors of reward for both phenotypes but becoming incentive stimuli to a greater degree for STs. While these distinct phenotypes are characterized based on Pavlovian conditioned approach (PavCA) behavior, they exhibit differences on a number of behaviors relevant to psychopathology. To further characterize the neurobehavioral endophenotype associated with individual differences in cue-reward learning, neuroendocrine and behavioral profiles associated with stress and anxiety were investigated in male GT, ST, and intermediate responder (IR) rats. It was revealed that baseline corticosterone (CORT) increases with Pavlovian learning, but to the same degree, regardless of phenotype. No significant differences in behavior were observed between GTs and STs during an elevated plus maze (EPM) or open field test (OFT), nor were there differences in CORT response to the OFT or physiological restraint. Upon examination of central markers associated with stress reactivity, we found that STs have greater glucocorticoid receptor (GR) mRNA expression in the ventral hippocampus, with no phenotypic differences in the dorsal hippocampus or prelimbic cortex (PrL). These findings demonstrate that GTs and STs do not differ on stress-related and anxiety-related behaviors, and suggest that differences in neuroendocrine measures between these phenotypes can be attributed to distinct cue-reward learning styles.

Adult Women First Exposed to Early Adversity After 8 Years Old Show Attentional Bias to Threat

Exposure to early adversity (EA) is associated with long-lasting dysregulations in cognitive processes sustained by brain regions that are sensitive to stress hormones: the hippocampus, the amygdala, and the prefrontal cortex. The Life Cycle Model of Stress highlights the importance of considering the timing at which EA began, as these brain regions follow distinct developmental trajectories. We aimed to test this hypothesis by assessing whether adults exposed to EA exhibit different cognitive patterns as a function of the age at which they were first exposed to EA. Eighty-five healthy men and women aged 21-40 years old (y/o) exposed to EA, as assessed by the Adverse Childhood Experience Questionnaire, were grouped based on the age of first exposure to EA: 0-2 y/o ("Infancy": hippocampal development), 3-7 y/o ("Early childhood": amygdala development) and after the age of 8 ("Childhood/Adolescence": frontoamygdala connectivity development). Declarative memory, attentional bias to threat and emotion regulation were measured. Results revealed increased attentional bias to threat in women first exposed to EA after 8 years. This result is in line with the Life Cycle Model of Stress and highlights the importance of considering the age at exposure to EA when investigating the effects of EA on cognitive processes.

Cardinal role of the environment in stress induced changes across life stages and generations

The stress response in rodents and humans is exquisitely dependent on the environmental context. The interactive element of the environment is typically studied by creating laboratory models of stress-induced plasticity manifested in behavior or the underlying neuroendocrine mediators of the behavior. Here, we discuss three representative sets of studies where the role of the environment in mediating stress sensitivity or stress resilience is considered across varying windows of time. Collectively, these studies testify that environmental variation at an earlier time point modifies the relationship between stressor and stress response at a later stage. The metaplastic effects of the environment on the stress response remain possible across various endpoints, including behavior, neuroendocrine regulation, region-specific neural plasticity, and regulation of receptors. The timescale of such variation spans adulthood, across stages of life history and generational boundaries. Thus, environmental variables are powerful determinants of the observed diversity in stress response. The predominant role of the environment suggests that it is possible to promote stress resilience through purposeful modification of the environment.

Prelimbic cortex glucocorticoid receptors regulate the stress-mediated inhibition of pain contagion in male mice

Experiencing pain with a familiar individual can enhance one's own pain sensitivity, a process known as pain contagion. When experiencing pain with an unfamiliar individual, pain contagion is suppressed in males by activating the endocrine stress response. Here, we coupled a histological investigation with pharmacological and behavioral experiments to identify enhanced glucocorticoid receptor activity in the prelimbic subdivision of the medial prefrontal cortex as a candidate mechanism for suppressing pain contagion in stranger mice. Acute inhibition of glucocorticoid receptors in the prelimbic cortex was sufficient to elicit pain contagion in strangers, while their activation prevented pain contagion in cagemate dyads. Slice physiology recordings revealed enhanced excitatory transmission in stranger mice, an effect that was reversed by pre-treating mice with the corticosterone synthesis inhibitor metyrapone. Following removal from dyadic testing, stranger mice displayed enhanced affective-motivational pain behaviors when placed on an inescapable thermal stimulus, which were reversed by metyrapone. Together, our data suggest that the prelimbic cortex may play an integral role in modulating pain behavior within a social context and provide novel evidence towards the neural mechanism underlying the prevention of pain contagion.

Impaired hypothalamic feedback dysregulates brain glucocorticoid signaling in genetically-selected Marchigian Sardinian alcohol-preferring rats

Genetically-selected Marchigian Sardinian alcohol-preferring (msP) rats display comorbid symptoms of increased alcohol preference and elevated anxiety-like behavior. Heightened stress sensitivity in msPs is influenced by genetic polymorphisms of the corticotropin-releasing factor receptor in the central nucleus of the amygdala (CeA), as well as reduced influence of anti-stress mechanisms that normally constrain the stress response. Given this propensity for stress dysregulation, in this study, we expand on the possibility that msPs may display differences in neuroendocrine processes that normally terminate the stress response. We utilized behavioral, biochemical, and molecular assays to compare basal and restraint stress-induced changes in the hypothalamic-pituitary-adrenal (HPA) axis of male and female msPs relative to their nonselected Wistar counterparts. The results showed that msPs display deficits in marble-burying behavior influenced by environmental factors and procedures that modulate arousal states in a sex-dependent manner. Whereas male msPs display evidence of dysregulated neuroendocrine function (higher adrenocorticotropic hormone levels and subthreshold reductions in corticosterone), females display restraint-induced elevations in corticosterone levels that were persistently higher in msPs. A dexamethasone challenge reduced the circulation of these stress hormones, although the reduction in corticosterone was generally attenuated in msP versus Wistar rats. Finally, we found evidence of diminished stress-induced glucocorticoid receptor (GR) phosphorylation in the hypothalamic paraventricular nucleus of msPs, as well as innate increases in phosphorylated GR levels in the CeA of male msPs. Collectively, these findings suggest that negative feedback processes regulating HPA responsiveness are diminished in msP rats, possibly underlying differences in the expression of anxiety-like behaviors.

Amygdala Circuit Substrates for Stress Adaptation and Adversity

Brain systems that promote maintenance of homeostasis in the face of stress have significant adaptive value. A growing body of work across species demonstrates a critical role for the amygdala in promoting homeostasis by regulating physiological and behavioral responses to stress. This review focuses on an emerging body of evidence that has begun to delineate the contribution of specific long-range amygdala circuits in mediating the effects of stress. After summarizing the major anatomical features of the amygdala and its connectivity to other limbic structures, we discuss recent findings from rodents showing how stress causes structural and functional remodeling of amygdala neuronal outputs to defined cortical and subcortical target regions. We also consider some of the environmental and genetic factors that have been found to moderate how the amygdala responds to stress and relate the emerging preclinical literature to the current understanding of the pathophysiology and treatment of stress-related neuropsychiatric disorders. Future effort to translate these findings to clinics may help to develop valuable tools for prevention, diagnosis, and treatment of these diseases.

A proposed role for glucocorticoids in mediating dopamine-dependent cue-reward learning

Learning to respond appropriately to one's surrounding environment is fundamental to survival. Importantly, however, individuals vary in how they respond to cues in the environment and this variation may be a key determinant of psychopathology. The ability of seemingly neutral cues to promote maladaptive behavior is a hallmark of several psychiatric disorders including, substance use disorder, post-traumatic stress disorder, eating disorders and obsessive-compulsive disorder. Thus, it is important to uncover the neural mechanisms by which such cues are able to attain inordinate control and promote psychopathological behavior. Here, we suggest that glucocorticoids play a critical role in this process. Glucocorticoids are primarily recognized as the main hormone secreted in response to stress but are known to exert their effects across the body and the brain, and to affect learning and memory, cognition and reward-related behaviors, among other things. Here we speculate that glucocorticoids act to facilitate a dopamine-dependent form of cue-reward learning that appears to be relevant to a number of psychiatric conditions. Specifically, we propose to utilize the sign-tracker/goal-tracker animal model as a means to capture individual variation in stimulus-reward learning and to isolate the role of glucocorticoid-dopamine interactions in mediating these individual differences. It is hoped that this framework will lead to the discovery of novel mechanisms that contribute to complex neuropsychiatric disorders and their comorbidity.

Experience and activity-dependent control of glucocorticoid receptors during the stress response in large-scale brain networks

The diversity of actions of the glucocorticoid stress hormones among individuals and within organs, tissues and cells is shaped by age, gender, genetics, metabolism, and the quantity of exposure. However, such factors cannot explain the heterogeneity of responses in the brain within cells of the same lineage, or similar tissue environment, or in the same individual. Here, we argue that the stress response is continuously updated by synchronized neural activity on large-scale brain networks. This occurs at the molecular, cellular and behavioral levels by crosstalk communication between activity-dependent and glucocorticoid signaling pathways, which updates the diversity of responses based on prior experience. Such a Bayesian process determines adaptation to the demands of the body and external world. We propose a framework for understanding how the diversity of glucocorticoid actions throughout brain networks is essential for supporting optimal health, while its disruption may contribute to the pathophysiology of stress-related disorders, such as major depression, and resistance to therapeutic treatments.

Prepubertal and adult male rats differ in the degree and pattern of stress reactive neurons in brain regions that project to the paraventricular nucleus of the hypothalamus

The hormonal stress response, mediated by the hypothalamic-pituitary-adrenal (HPA) axis, shows greater responsiveness to various stressors in prepubertal compared to adult animals. Though the implications of this age-related change are unclear, this heightened reactivity might contribute to the increase in stress-related dysfunctions observed during adolescence. Interestingly, prepubertal animals show greater stress-induced neural activation compared to adults in the paraventricular nucleus of the hypothalamus (PVN), the area responsible for initiating the hormonal stress response. Thus, it is possible that direct afferents to the PVN, such as the anterior bed nucleus of the stria terminalis (aBST), nucleus of the solitary tract (NTS), posterior BST (pBST), medial preoptic area (MPOA), and dorsomedial nucleus (DMN), contribute to this age-dependent change in reactivity. To investigate these possibilities, two separate experiments were conducted in prepubertal (30 days old) and adult (70 days old) male rats using the retrograde tracer, Fluoro-Gold (FG), and FOS immunohistochemistry to study neural connectivity and activation, respectively. Though there was no difference in the number or size of FG-positive cells in the PVN afferents we examined, we found a significantly greater number of stress-induced FOS-like-positive cells in the aBST and significantly fewer in the DMN in prepubertal compared to adult animals. Together these data suggest that functional, instead of structural, changes in nuclei that project to the PVN may lead to the greater PVN stress responsiveness observed prior to adolescence. Furthermore, these data indicate that nuclei known to directly modulate HPA stress responsiveness show differential activation patterns before and after adolescent development.

Long term effects of early life stress on HPA circuit in rodent models

Adaptation to environmental challenges represents a critical process for survival, requiring the complex integration of information derived from both external cues and internal signals regarding current conditions and previous experiences. The Hypothalamic-pituitary-adrenal axis plays a central role in this process inducing the activation of a neuroendocrine signaling cascade that affects the delicate balance of activity and cross-talk between areas that are involved in sensorial, emotional, and cognitive processing such as the hippocampus, amygdala, Prefrontal Cortex, Ventral Tegmental Area, and dorsal raphe. Early life stress, especially early critical experiences with caregivers, influences the functional and structural organization of these areas, affects these processes in a long-lasting manner and may result in long-term maladaptive and psychopathological outcomes, depending on the complex interaction between genetic and environmental factors. This review summarizes the results of studies that have modeled this early postnatal stress in rodents during the first 2 postnatal weeks, focusing on the long-term effects on molecular and structural alteration in brain areas involved in Hypothalamic-pituitary-adrenal axis function. Moreover, a brief investigation of epigenetic mechanisms and specific genetic targets mediating the long-term effects of these early environmental manipulations and at the basis of differential neurobiological and behavioral effects during adulthood is provided.

Molecular links between endocrine, nervous and immune system during chronic stress

INTRODUCTION

The stress response is different in various individuals, however, the mechanisms that could explain these distinct effects are not well known and the molecular correlates have been considered one at the time. Particular harmful conditions occur if the subject, instead to cope the stressful events, succumb to them, in this case, a cascade reaction happens that through different signaling causes a specific reaction named "sickness behaviour." The aim of this article is to review the complex relations among important molecules belonging to Central nervous system (CNS), immune system (IS), and endocrine system (ES) during the chronic stress response.

METHODS

After having verified the state of art concerning the function of cortisol, norepinephrine (NE), interleukin (IL)-1β and melatonin, we describe as they work together.

RESULTS

We propose a speculative hypothesis concerning the complex interplay of these signaling molecules during chronic stress, highlighting the role of IL-1β as main biomarker of this effects, indeed, during chronic stress its increment transforms this inflammatory signal into a nervous signal (NE), in turn, this uses the ES (melatonin and cortisol) to counterbalance again IL-1β. During cortisol resistance, a vicious loop occurs that increments all mediators, unbalancing IS, ES, and CNS networks. This IL-1β increase would occur above all when the individual succumbs to stressful events, showing the Sickness Behaviour Symptoms. IL-1β might, through melatonin and vice versa, determine sleep disorders too.

CONCLUSION

The molecular links here outlined could explain how stress plays a role in etiopathogenesis of several diseases through this complex interplay.

Bed nucleus of the stria terminalis modulates baroreflex cardiac activity: an interaction between alpha-1 receptors and NMDA/nitric oxide pathway

The bed nucleus of the stria terminalis (BNST) is a forebrain structure, involved in the modulation of neuroendocrine, cardiovascular and autonomic responses. One of the responses is baroreflex activity, which consists in a neural mechanism responsible for keeping the blood pressure within a narrow range of variation. It has been reported that blockade of BNST α1-adrenoceptors increased the bradycardic component of baroreflex. In addition, such receptors are able to modulate glutamate release in this structure. Interestingly, BNST NMDA receptor antagonism and neuronal nitric oxide synthase (nNOS) inhibition led to the same effect of the α1-adrenoceptors blockade on baroreflex bradycardic response. Therefore, the hypothesis of the present study is that BNST noradrenergic transmission interacts with NMDA/NO pathway through α1 adrenoceptors to modulate the baroreflex activity. Male Wistar rats had stainless steel guide cannulas bilaterally implanted in the BNST. Subsequently, a catheter was inserted into the femoral artery for cardiovascular recordings, and into the femoral vein for assessing baroreflex activation. Injection of the noradrenaline reuptake inhibitor reboxetine in the BNST did not modify the tachycardic, but significantly decreased the bradycardic component of baroreflex. Administration of an α1, but not an α2 antagonist into the BNST prior to reboxetine prevented this effect. Likewise, previous injection of NMDA/NO pathway blockers inhibited the effect of reboxetine on bradycardic response. In conclusion, it was demonstrated for the first time the existence of an interaction between BNST noradrenergic, glutamatergic and nitrergic neurotransmissions in the modulation of bradycardic baroreflex response.

Early childhood adversity and HPA axis activity in adulthood:The importance of considering minimal age at exposure

Early adversity (EA) modulates stress hormone secretion in mixed directions. The Accumulation Model suggests that the number of EA predicts patterns of cortisol dysregulations, while the Life Cycle Model of Stress highlights the importance of considering the timing at which EA began, given that brain regions sensitive to stress hormones follow distinct developmental trajectories. We aimed to test these two models in 85 healthy men and women, aged 21-40 years old who reported having been exposed to EA during childhood. Participants were grouped based on the number of EA events to which they were exposed during their lifespan (Accumulation Model) and the age of first exposure to EA (Life Cycle Model). Diurnal and stress-induced reactive cortisol secretion were measured in all participants. Results showed that although the number of EA was not associated with patterns of basal or reactive cortisol secretion, adults first exposed to EA between the ages of 3 and 7 - an important time window for amygdala development - showed greater cortisol awakening response and lower cortisol reactivity relative to those first exposed to EA before 3 or after 7. These results provide support for the Life Cycle Model of Stress and highlight the importance of considering minimal age at exposure to EA when assessing the effects of early adversity on patterns of cortisol secretion.

Maladaptive emotion regulation traits predict altered corticolimbic recovery from psychosocial stress

BACKGROUND

Adaptive recovery from stress promotes healthy cognitive affective functioning, whereas maladaptive recovery is linked to poor psychological outcomes. Neural regions, like the anterior cingulate and hippocampus, play critical roles in psychosocial stress responding and serve as hubs in the corticolimbic neural system. To date, however, it is unknown how cognitive emotion regulation traits (cER), adaptive and maladaptive, influence corticolimbic stress recovery. Here, we examined acute psychosocial stress neural recovery, accounting for cER.

METHODS

Functional neuroimaging data were collected while forty-seven healthy participants performed blocks of challenging, time-sensitive, mental calculations. Participants immediately received performance feedback (positive/negative/neutral) and their ranking, relative to fictitious peers. Participants rested for 90 seconds after each feedback, allowing for a neural stress recovery period. Collected before scanning, cER scores were correlated with neural activity during each recovery condition.

RESULTS

Negative feedback recovery yielded increased activity within the dorsomedial prefrontal cortex and amygdala, but this effect was ultimately explained by maladaptive cER (M-cER), like rumination. Isolating positive after-effects (i.e. positive > negative recovery) yielded a significant positive correlation between M-cER and the anterior cingulate, anterior insula, hippocampus, and striatum.

CONCLUSIONS

We provide first evidence of M-cER to predict altered neural recovery from positive stress within corticolimbic regions. Positive feedback may be potentially threatening to individuals with poor stress regulation. Identifying positive stress-induced activation patterns in corticolimbic neural networks linked to M-cER creates the possibility to identify these neural responses as risk factors for social-emotional dysregulation subsequent to rewarding social information, often witnessed in affective disorders, like depression.