Effects of crowding stress on the hypothalamo-pituitary-interrenal axis of the self-fertilizing fish, Kryptolebias marmoratus.

We tested whether crowding stress affects the hypothalamo-pituitary-interrenal (HPI) axis of the self-fertilizing fish, Kryptolebias marmoratus, which is known to be aggressive in the laboratory conditions but sometimes found as a group from a single land crab burrow in the wild. The projection of corticotropin-releasing hormone (CRH) neurons to the adrenocorticotropic hormone (ACTH) cells in the pituitary was confirmed by dual-label immunohistochemistry; CRH-immunoreactive (ir) fibers originating from cell bodies located in the lateral tuberal nucleus (NLT) of the hypothalamus were observed to project to ACTH-ir cells in the rostral pars distalis of the pituitary. Then, fish were reared solitary or in pairs for 14 days, and the number of CRH-ir cell bodies in the NLT of the hypothalamus and cortisol levels in the body without head region were compared. The number of CRH-ir cell bodies and cortisol levels were significantly higher in paired fish. These results indicate that crowding stress affects the HPI axis in K. marmoratus which thrive in small burrows with limited water volume.

The development of stress reactivity and regulation during human development.

Adverse experiences during childhood can have long-lasting impacts on physical and mental health. At the heart of most theories of how these effects are transduced into health impacts is the activity of stress-mediating systems, most notably the hypothalamic-pituitary-adrenocortical (HPA) axis. Here we review the anatomy and physiology of the axis, models of stress and development, the development of the axis prenatally through adolescence, the role of experience and sensitive periods in shaping its regulation, the social regulation of the axis at different points in development, and finally conclude with suggestions for future research. We conclude that it is clear that early adversity sculpts the stress system, but we do not understand which dimensions have the most impact and at what points in early development. It is equally clear that secure attachment relationships buffer the developing stress system; however, the mechanisms of social buffering and how these may change with development are not yet clear. Another critical issue that is not understood is when and for whom adversity will result in hypo- vs hyperactivity of stress-mediating systems. These and other issues are important for advancing our understanding of how early adversity "gets under the skin" and shapes human physical and mental health.

Salivary Biomarkers of Parenting Stress in Mothers Under Community Criminal Justice Supervision.

BACKGROUND: Community criminal justice supervised mothers are an underserved population who experience high rates of psychological distress and unique parenting challenges, but little is known about physiological stress system function in this population. OBJECTIVE: We tested the salivary biomarkers of the sympathetic nervous system (SNS) and hypothalamic-pituitary-adrenal (HPA) axis function as predictors of subjective maternal stress. METHOD: We recruited 23 mothers (age: M = 35.6 years, SD = 9.3 years; 35% Hispanic, 22% Black, 22% White, 22% multiracial) who were court mandated to a residential treatment center. We measured salivary alpha-amylase (AA) and cortisol, which index SNS and HPA activity, respectively, before and after a naturalistic reminder of a stressful parenting experience. We assessed self-reported parenting stress using the Parenting Stress Index-Short Form (PSI-SF) subscales Parental Distress, Parent-Child Dysfunctional Interactions, and Difficult Child. We used regression to test AA and cortisol mean levels and reactivity as predictors of subscale scores. RESULTS: Mean, but not reactive, salivary stress biomarker levels were associated with parenting stress domains. Mean cortisol levels predicted scores on the Parent-Child Dysfunctional Interaction subscale (adj. R = .48), whereas mean AA predicted Difficult Child subscale scores (adj. R = .28). DISCUSSION: Our results demonstrate the potential predictive utility of AA and cortisol as salivary biomarkers of maternal stress in community-supervised mothers. Given that maternal stress is associated with criminal recidivism and child behavioral health in this population, these biomarkers could potentially inform interventions to improve dyadic health and social outcomes.

Neuroimaging of central diabetes insipidus-when, how and findings.

Central or neurogenic diabetes insipidus (CDI) is due to deficient synthesis or secretion of antidiuretic hormone (ADH), also known as arginine vasopressin peptide (AVP). It is clinically characterised by polydipsia and polyuria (urine output > 30 mL/kg/day) of dilute urine (< 250 mOsm/L). It is the result of a defect in one of more sites involving the hypothalamic osmoreceptors, supraoptic or paraventricular nuclei of the hypothalamus, median eminence of the hypothalamus, infundibulum or the posterior pituitary gland. A focused MRI pituitary gland or sella protocol is essential. There are several neuroimaging correlates and causes of CDI, illustrated in this review. The most common causes are benign or malignant neoplasms of the hypothalamic-pituitary axis (25%), surgery (20%), head trauma (16%) or familial causes (10%). No cause is identified in up to 30% of cases. Knowledge of the anatomy and physiology of the hypothalamo-neurohypophyseal axis is crucial when evaluating a patient with CDI. Establishing the aetiology of CDI with MRI in combination with clinical and biochemical assessment facilitates appropriate targeted treatment. The aim of the pictorial review is to illustrate the wide variety of causes of CDI on neuroimaging, highlight the optimal MRI protocol and to revise the detailed neuroanatomy and neurophysiology required to interpret these studies.

Local Corticotropin-Releasing Factor Signaling in the Hypothalamic Paraventricular Nucleus.

Corticotropin-releasing factor (CRF) neurons in the hypothalamic paraventricular nucleus (PVN) initiate hypothalamic-pituitary-adrenal axis activity through the release of CRF into the portal system as part of a coordinated neuroendocrine, autonomic, and behavioral response to stress. The recent discovery of neurons expressing CRF receptor type 1 (CRFR1), the primary receptor for CRF, adjacent to CRF neurons within the PVN, suggests that CRF also signals within the hypothalamus to coordinate aspects of the stress response. Here, we characterize the electrophysiological and molecular properties of PVN-CRFR1 neurons and interrogate their monosynaptic connectivity using rabies virus-based tracing and optogenetic circuit mapping in male and female mice. We provide evidence that CRF neurons in the PVN form synapses on neighboring CRFR1 neurons and activate them by releasing CRF. CRFR1 neurons receive the majority of monosynaptic input from within the hypothalamus, mainly from the PVN itself. Locally, CRFR1 neurons make GABAergic synapses on parvocellular and magnocellular cells within the PVN. CRFR1 neurons resident in the PVN also make long-range glutamatergic synapses in autonomic nuclei such as the nucleus of the solitary tract. Selective ablation of PVN-CRFR1 neurons in male mice elevates corticosterone release during a stress response and slows the decrease in circulating corticosterone levels after the cessation of stress. Our experiments provide evidence for a novel intra-PVN neural circuit that is activated by local CRF release and coordinates autonomic and endocrine function during stress responses.SIGNIFICANCE STATEMENT The hypothalamic paraventricular nucleus (PVN) coordinates concomitant changes in autonomic and neuroendocrine function to organize the response to stress. This manuscript maps intra-PVN circuitry that signals via CRF, delineates CRF receptor type 1 neuron synaptic targets both within the PVN and at distal targets, and establishes the role of this microcircuit in regulating hypothalamic-pituitary-adrenal axis activity.

Landmark discoveries in elucidating the origins of the hypothalamic-pituitary system from the perspective of a basal vertebrate, sea lamprey.

The hypothalamic-pituitary (HP) system, which is specific to vertebrates, is considered to be an evolutionary innovation that emerged prior to or during the differentiation of the ancestral jawless vertebrates (agnathans) leading to the neuroendocrine control of many complex functions. Along with hagfish, lampreys represent the oldest lineage of vertebrates, agnathans (jawless fish). This review will highlight our discoveries of the major components of the lamprey HP axis. Generally, gnathostomes (jawed vertebrates) have one or two hypothalamic gonadotropin-releasing hormones (GnRH) while lampreys have three hypothalamic GnRHs. GnRH(s) regulate reproduction in all vertebrates via the pituitary. In gnathostomes, there are three classical pituitary glycoprotein hormones (luteinizing hormone, LH; follicle stimulating hormone, FSH; and thyrotropin, TSH) interacting specifically with three receptors, LH-R, FSH-R, and TSH-R, respectively. In general, FSH and LH regulate gonadal activity and TSH regulates thyroidal activity. In contrast to gnathostomes, we propose that lampreys only have two heterodimeric pituitary glycoprotein hormones, lamprey glycoprotein hormone (lGpH) and thyrostimulin, and two lamprey glycoprotein hormone receptors (lGpH-R I and -R II). Our existing data also suggest the existence of a primitive, overlapping yet functional hypothalamic-pituitary-gonadal (HPG) and HP-thyroidal (HPT) endocrine systems in lampreys. The study of basal vertebrates provides promising models for understanding the evolution of the hypothalamic-pituitary-thyroidal and gonadal axes in vertebrates. We hypothesize that the glycoprotein hormone/glycoprotein hormone receptor systems emerged as a link between the neuroendocrine and peripheral control levels during the early stages of gnathostome divergence. Our discovery of a functional HPG axis in lamprey has provided important clues for understanding the forces that ensured a common organization of the hypothalamus and pituitary as essential regulatory systems in all vertebrates. This paper will provide a brief snapshot of my discoveries, collaborations and latest findings including phylogenomic analyses on the origins, co-evolution and divergence of ligand and receptor protein families from the perspective of the lamprey hypothalamic-pituitary system.

Income inequality, gene expression, and brain maturation during adolescence.

Income inequality is associated with poor health and social outcomes. Negative social comparisons and competition may involve the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes in underlying some of these complex inter-relationships. Here we investigate brain maturation, indexed by age-related decreases in cortical thickness, in adolescents living in neighborhoods with differing levels of income inequality and household income. We examine whether inter-regional variations relate to those in glucocorticoid receptor (HPA) and androgen receptor (HPG) gene expression. For each sex, we used a median split of income inequality and household income (income-to-needs ratio) to create four subgroups. In female adolescents, the high-inequality low-income group displayed the greatest age-related decreases in cortical thickness. In this group, expression of glucocorticoid and androgen receptor genes explained the most variance in these age-related decreases in thickness across the cortex. We speculate that female adolescents living in high-inequality neighborhoods and low-income households may experience greater HPA and HPG activity, leading to steeper decreases in cortical thickness with age.

Neuroanatomical pathways underlying the effects of hypothalamo-hypophysial-adrenal hormones on exploratory activity.

When injected via the intracerebroventricular route, corticosterone-releasing hormone (CRH) reduced exploration in the elevated plus-maze, the center region of the open-field, and the large chamber in the defensive withdrawal test. The anxiogenic action of CRH in the elevated plus-maze also occurred when infused in the basolateral amygdala, ventral hippocampus, lateral septum, bed nucleus of the stria terminalis, nucleus accumbens, periaqueductal grey, and medial frontal cortex. The anxiogenic action of CRH in the defensive withdrawal test was reproduced when injected in the locus coeruleus, while the amygdala, hippocampus, lateral septum, nucleus accumbens, and lateral globus pallidus contribute to center zone exploration in the open-field. In addition to elevated plus-maze and open-field tests, the amygdala appears as a target region for CRH-mediated anxiety in the elevated T-maze. Thus, the amygdala is the principal brain region identified with these three tests, and further research must identify the neural circuits underlying this form of anxiety.

60 YEARS OF NEUROENDOCRINOLOGY: The structure of the neuroendocrine hypothalamus: the neuroanatomical legacy of Geoffrey Harris.

In November 1955, Geoffrey Harris published a paper based on the Christian A Herter Lecture he had given earlier that year at Johns Hopkins University in Baltimore, MD, USA. The paper reviewed the contemporary research that was starting to explain how the hypothalamus controlled the pituitary gland. In the process of doing so, Harris introduced a set of properties that helped define the neuroendocrine hypothalamus. They included: i) three criteria that putative releasing factors for adenohypophysial hormones would have to fulfill; ii) an analogy between the representation of body parts in the sensory and motor cortices and the spatial localization of neuroendocrine function in the hypothalamus; and iii) the idea that neuroendocrine neurons are motor neurons and the pituitary stalk functions as a Sherringtonian final common pathway through which the impact of sensory and emotional events on neuroendocrine neurons must pass in order to control pituitary hormone release. Were these properties a sign that the major neuroscientific discoveries that were being made in the early 1950s were beginning to influence neuroendocrinology? This Thematic Review discusses two main points: the context and significance of Harris's Herter Lecture for how our understanding of neuroendocrine anatomy (particularly as it relates to the control of the adenohypophysis) has developed since 1955; and, within this framework, how novel and powerful techniques are currently taking our understanding of the structure of the neuroendocrine hypothalamus to new levels.

Neuroanatomy and physiology of the avian hypothalamic/pituitary axis: clinical aspects.

This article describes the anatomy of the avian hypothalamic/pituitary axis, the hypothalamic-pituitary-thyroid axis, the hypothalamic-pituitary-adrenal axis, the hypothalamic-pituitary-gonadal axis, the somatotrophic axis, and neurohypophysis.

Hypothalamic-pituitary-adrenal axis hyperactivity and brain differences in healthy women.

BACKGROUND: Previous studies have suggested that dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis leads to brain changes. However, few studies have examined the whole brain configuration for an association with HPA axis activity. We examined the relationship between HPA axis activity and the whole brain configuration. METHODS: The subjects in this study were 34 healthy female volunteers. HPA axis activity was assessed by the dexamethasone/corticotropin-releasing hormone test. Structural volumes of the brain and diffusion tensor images were obtained, and correlations were evaluated voxel-wise. RESULTS: There was a significantly negative correlation between fractional anisotropy value and cortisol levels at 16:00 h (CL-2) in the anterior cingulum, left parahippocampus and right occipital region. There were significantly positive correlations between mean diffusivity value and CL-2 in the left hippocampus and bilateral parahippocampal regions. CONCLUSIONS: Our data suggest that reduced feedback of the HPA axis is associated with reduced neural connectivity throughout the brain, and such an association may be strong in the anterior cingulate, the hippocampus and the parahippocampal regions.

Stress abnormalities in individuals at risk for psychosis: a review of studies in subjects with familial risk or with "at risk" mental state.

Increased sensitivity to stress is known to play an important role in the transition to first episode psychosis (FEP). Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, and, in general, an increased sensitivity to stress, have been hypothesised to be components of the vulnerability to psychosis, but whether these abnormalities are already present before the onset of psychosis has not yet been systematically reviewed. Here we have reviewed all studies examining psychological and biological markers of the stress response in the relatives of psychotic patients and in individuals at Ultra High Risk (UHR) for psychosis. In relatives, there is evidence of increased sensitivity to stress, as shown by increased emotional reactivity to daily life stress, increased adrenocorticotropic hormone (ACTH) in response to stress, increased pituitary volume and reduced hippocampal volume. However, evidence of increased cortisol levels is less consistent. On the other hand, subjects who experience attenuated psychotic symptoms show increased cortisol levels as well as increased pituitary and reduced hippocampal volumes. Moreover, this HPA axis hyperactivity seems to be even greater among those individuals who subsequently develop frank psychosis. In summary, an enhanced HPA axis response to stress appears to be part of the biological vulnerability to psychosis which is present prior to the onset of psychosis. A further increase in cortisol levels during the transition to FEP suggests the presence of an additive factor, possibly environmental, at this stage of the illness. Possible causes and consequences of HPA axis impairment in risk for psychosis are discussed.

Genistein stimulates the hypothalamo-pituitary-adrenal axis in adult rats: morphological and hormonal study.

Genistein, the soy isoflavone structurally similar to estradiol, is widely consumed for putative beneficial health effects. However, there is a lack of data about the genisteins' effects in adult males, especially its effects on the hipothalamo-pituitary-adrenal (HPA) axis. Therefore, the present study was carried out to investigate the effects of genistein on the HPA axis in orchidectomized adult rats, and to create a parallel with those of estradiol. Changes in the hypothalamic corticotrophin-releasing hormone (CRH) neurons and pituitary corticotrophs (ACTH cells) were evaluated stereologically, while corticosterone and ACTH levels were determined biochemically. Orchidectomy (Orx) provoked the enlargement (p<0.05) of: hypothalamic paraventricular nucleus volume (60%), percentage of CRH neurons (23%), percentage of activated CRH neurons (45%); pituitary weight (15%) and ACTH level (57%). In comparison with Orx, estradiol treatment provoked the enlargement (p<0.05) of: percentage of CRH neurons (28%), percentage of activated CRH neurons (2.7-fold), pituitary weight (131%) and volume (82%), ACTH level (69%), the serum (103%) and adrenal tissue (4.8 fold) level of corticosterone. Clearly, Orx has induced the increase in HPA axis activity, which even augments after estradiol treatment. Also, compared to Orx, genistein treatment provoked the enhancement (p<0.05) of: percentage of activated CRH neurons (2.3-fold), pituitary weight (28%) and volume (21%), total number of ACTH cells (22%) ACTH level (45%), the serum (2.6-fold) and adrenal tissue (2.8 fold) level of corticosterone. It can be concluded that an identical tendency, concerning the HPA axis parameters, follows estradiol and genistein administration to the orchidectomized adult rats.

Zebrafish in endocrine systems: recent advances and implications for human disease.

Since its introduction as a genetic vertebrate model system approximately 30 years ago, the focus of zebrafish research has increasingly shifted to questions that are also relevant for human development and disease. Here, we review the potential of the zebrafish as a model for human endocrine systems. A recent review compared the functions of the different endocrine systems and glands in zebrafish with those in other vertebrates, including humans, coming to the conclusion that major aspects are conserved. Here, we present an updated overview of this rapidly growing field of zebrafish research, focusing on the hypothalamo-pituitary axis, which links the central nervous system with the endocrine systems, and on major processes that are under (neuro)endocrine control and are the subject of intensive current research in other endocrine model organisms, such as feeding circuits and energy homeostasis, sleep, stress, reproduction, osmoregulation, and calcium homeostasis. Finally, we summarize the strengths and weaknesses of zebrafish as a model for studying endocrine systems.

Adrenomedullin 2/intermedin in the hypothalamo-pituitary-adrenal axis.

Adrenomedullin 2/intermedin (AM2/IMD) is a new member of the calcitonin/calcitonin gene-related peptide (CGRP) family. CGRP, adrenomedullin (AM), and AM2/IMD share the receptor system consisting of calcitonin receptor-like receptor (CRLR) and receptor activity-modifying proteins (RAMP). The CRLR/RAMP2 or CRLR/RAMP3 complex forms the AM receptor, whereas the CRLR/RAMP1 forms the CGRP receptor. AM2/IMD binds non-selectively to all three CRLR/RAMP complexes. AM2/IMD has various actions, such as a potent vasodilator action and a protective action against oxidative stress, like AM and CGRP. When administered intracerebroventricularly, AM2/IMD stimulates the sympathetic nervous system and increases blood pressure. In human hypothalamus, AM2/IMD is expressed in the paraventricular and supraoptic nuclei and colocalized with arginine vasopressin. Anterior pituitary cells were diffusely immunostained for AM2/IMD. AM2/IMD stimulates the release of ACTH, prolactin, and oxytocin, but suppresses GH release. Some of these pituitary actions of AM2/IMD have been supposed to be mediated by an unidentified unique receptor for AM2/IMD. In the adrenal gland, immunoreactive (IR)-AM2/IMD and IR-AM were detected in the medulla, while the degree of IR-AM2/IMD and IR-AM in the cortex was relatively weak or undetectable. Furthermore, AM2/IMD and AM were expressed in adrenocortical tumors, such as aldosterone-secreting adenomas, and pheochromocytomas. CRLR and RAMPs are expressed in the hypothalamus, pituitaries, adrenal glands, and adrenal tumors. Thus, AM2/IMD is expressed in every endocrine organ of the hypothalamo-pituitary-adrenal axis together with its receptor. AM2/IMD may act as a neurotransmitter or modulator in the brain and as a paracrine/autocrine regulator in the hypothalamo-pituitary-adrenal axis.

Natriuretic peptides in the regulation of the hypothalamic-pituitary-adrenal axis.

Atrial (ANP), brain (BNP), and C-type (CNP) natriuretic peptides act by binding to three main subtypes of receptors, named NPR-A, -B, and -C. NPR-A and NPR-B are coupled with guanylate cyclase. Not only NPR-C is involved in removing natriuretic peptides from the circulation but it also acts through inhibition of adenylyl cyclase. NPR-A binds ANP and BNP; NPR-B preferentially binds CNP; and NPR-C binds all natriuretic peptides with similar affinities. All natriuretic peptides and their receptors are widely present in the hypothalamus, pituitary, adrenal cortex, and medulla. In the hypothalamus, they reduce norepinephrine release, inhibit oxytocin, vasopressin, corticotropin-releasing factor, and luteinizing hormone-releasing hormone release. In the hypophysis, natriuretic peptides inhibit basal and induced ACTH release. Conversely, the effects of natriuretic peptides on secretion of growth, luteinizing, and follicle-stimulating hormones are not clear. Natriuretic peptides are known to inhibit basal and stimulated aldosterone secretion, through an increase of intracellular cGMP, and to inhibit the growth of zona glomerulosa. Inhibition or stimulation of glucocorticoid secretion by adrenocortical cells has been reported on the basis of the species involved, and an indirect effect mediated by adrenalmedullary cells has been hypothesized. In the adrenal medulla, natriuretic peptides inhibit catecholamine release and increase catecholamine uptake. It appears that natriuretic peptides may play a role in the pathophysiology of adrenocortical neoplasias and pheochromocytomas.

Interactions between the immune and neuroendocrine systems.

The growing spark of interest in research concerning the molecular links between the nervous, endocrine and immune systems has caused an explosion of new knowledge concerning the fine mechanisms that orchestrate the integrated response to an immune challenge. For instance, elevation in plasma glucocorticoid (GC) levels is one of the most powerful and well-controlled feedback mechanisms on the proinflammatory signal transduction machinery taking place across the organism. Circulating inflammatory molecules have the ability to target their cognate receptors at the levels of blood-brain barrier, the latter in return produces specific prostaglandins (PGs). This chapter presents the brain circuits involved in the activation of the hypothalamic-pituitary-adrenal (HPA) axis by endogenously produced prostaglandin E(2) (PGE(2)) during systemic innate immune insults.

Hypocretin/orexin in arousal and stress.

Multiple lines of evidence indicate that hypocretin/orexin (HCRT) participates in the regulation of arousal and arousal-related process. For example, HCRT axons and receptors are found within a variety of arousal-related systems. Moreover, when administered centrally, HCRT exerts robust wake-promoting actions. Finally, a dysregulation of HCRT neurotransmission is associated with the sleep/arousal disorder, narcolepsy. Combined, these observations suggested that HCRT might be a key transmitter system in the regulation of waking. Nonetheless, subsequent evidence indicates that HCRT may not play a prominent role in the initiation of normal waking. Instead HCRT may participate in a variety of processes such as consolidation of waking and/or coupling metabolic state with behavioral state. Additionally, substantial evidence suggests a potential involvement of HCRT in high-arousal conditions, including stress. Thus, HCRT neurotransmission is closely linked to high-arousal conditions, including stress, and HCRT administration exerts a variety of stress-like physiological and behavioral effects that are superimposed on HCRT-induced increases in arousal. Combined, this evidence suggests the hypothesis that HCRT may participate in behavioral responding under high-arousal aversive conditions. Importantly, these actions of HCRT may not be limited to stress. Like stress, appetitive conditions are associated with elevated arousal levels and a stress-like activation of various physiological systems. These and other observations suggest that HCRT may, at least in part, exert affectively neutral actions that are important under high-arousal conditions associated with elevated motivation and/or need for action.

Stress regulation in the central nervous system: evidence from structural and functional neuroimaging studies in human populations - 2008 Curt Richter Award Winner.

The metabolic effects of stress are known to have significant health effects in both humans and animals. Most of these effects are mediated by the major stress hormonal axis in the body, the hypothalamic-pituitary-adrenal (HPA) axis. Within the central nervous system (CNS), the hippocampus, the amygdala and the prefrontal cortex as part of the limbic system are believed to play important roles in the regulation of the HPA axis. With the advent of structural and functional neuroimaging techniques, the role of different CNS structures in the regulation of the HPA axis can be investigated more directly. In the current paper, we summarize the findings obtained in our laboratory in the context of stress and HPA axis regulation. Our laboratory has developed and contributed to the development of manual and automated segmentation protocols from structural magnetic resonance imaging (MRI) scans for assessment of hippocampus, amygdala, medial temporal lobe and frontal lobe structures. Employing these protocols, we could show significant age-related changes in HC volumes, which were different between men and women, with pre-menopausal women showing smaller age-related volume decline compared to men. We could recently extent these findings by showing how estrogen therapy after menopause leads to higher volumes in the HC. Investigating possible neurotoxicity effects of steroids, we showed effects of long-term steroid exposure on HC volumes, and investigated variability of HC volumes in relation to HPA axis regulation in young and elderly populations. Here, we were able to follow-up from non-imaging studies showing that subjects low in self-esteem have higher cortisol stress responses, and the HC emerged as the critical link between these variables. Recently, we have made two more important discoveries with regard to HC volume: we could show that HC volume is as variable in young as it is in older adults, in subjects ranging in age from 18 to 80 years. Also, we have linked birth weight and maternal care to HC volumes in young adults, demonstrating the effects of variations in maternal care on the integrity of the CNS. Besides structural assessments, there is increasing interest in functional techniques to investigate possible links between CNS activity and HPA axis regulation. These two approaches complement each other; some aspects of HPA axis regulation might be linked to the integrity of a specific CNS structure, while other aspects might be linked to the function of a specific structure with no involvement of CNS morphology. Thus, we have developed a mental arithmetic stress task that can be employed in functional neuroimaging studies, and have used it in a number of functional neuroimaging studies. Employing positron emission tomography (PET), we were able to demonstrate that stress causes dopamine release if subjects reported low maternal care early in life. Finally, employing the task in functional magnetic resonance imaging (fMRI), we could show how exposure to stress and activation of the HPA axis are associated with decreased activity in major portions of the limbic system, a result that allows to speculate on the effects of stress on cognitive and emotional regulation in the brain. Taken together, the use of neuroimaging techniques in Psychoneuroendocrinology opens exciting new possibilities for the investigation of stress effects in the central nervous system.