Psychoneuroendocrinology of depression. Hypothalamic-pituitary-adrenal axis

A prospective evaluation of the directionality of the depression-inflammation relationship

Cross-sectional studies have found that individuals with depressive disorders or symptoms have elevated levels of inflammatory markers predictive of coronary artery disease, including interleukin-6 (IL-6) and C-reactive protein (CRP). Due to the paucity of prospective studies, however, the directionality of the depression-inflammation relationship is unclear. We evaluated the longitudinal associations between depressive symptoms and both IL-6 and CRP among 263 healthy, older men and women enrolled in the Pittsburgh Healthy Heart Project, a 6-year prospective cohort study. During the baseline and follow-up visits, participants completed the Beck Depression Inventory-II (BDI-II) to assess depressive symptoms and underwent blood draws to quantify serum IL-6 and CRP. Path analyses revealed that baseline BDI-II (beta=0.18, p=0.01, DeltaR(2)=0.02) was a predictor of 6-year change in IL-6, even after adjustment for demographic, biomedical, and behavioral factors as well as other negative emotions. Of all the factors examined, only body-mass index was a stronger predictor of IL-6 change than depressive symptoms. In contrast to these results, baseline IL-6 did not predict 6-year change in BDI-II. Evidence of a weak bidirectional relationship between BDI-II and CRP was also observed; however, neither of these longitudinal associations was significant. The present findings indicate that depressive symptoms may precede and augment some inflammatory processes relevant to coronary artery disease among healthy, older adults. Therefore, our results imply that depression may lead to inflammation and that inflammation may be one of the mechanisms through which depression contributes to cardiovascular risk.

Disruptions of the mother-infant relationship and stress-related behaviours: altered corticosterone secretion does not explain everything

The hypothalamic-pituitary-adrenal (HPA) axis is the main neuroendocrine system of response to stress, and an imbalance of this system's activity is believed to be at the core of numerous psychiatric pathologies. During the neonatal period, the glucocorticoid response to stress is maintained at low levels by specific maternal behaviours, which is essential for proper brain development. Effective evaluation of the impact of increased secretion of corticosterone during an essentially anabolic developmental period on adulthood behaviour involved separation of the neonate from its mother for periods ranging from 3 to 24h. It has been shown that disinhibition of the stress response is achieved by such procedures. The pioneering studies by Seymour Levine set the stage for a prolific and promising field of study that may help neuroscientists unveil the neurobiological underpinnings of stress-related disorders. Based on a series of studies, we propose that maternal separation and maternal deprivation change stress-related behaviours, but that corticosterone seem to be only partially involved in these changes in adulthood. It appears that extra-hypothalamic corticotrophin-releasing factor and neurotransmitter systems may be the primary mediators of these behavioural outcomes.

Internalizing disorders in early childhood: a review of depressive and anxiety disorders

This article reviews the use of the broad category of internalizing disorders and data on young children using this definition. It also reviews the emerging support for more specific internalizing diagnoses in very young children. The current empiric database on nosology and treatment of mood and anxiety disorders in young children is examined, and a clinical case example is included. Identification of recent advances in the understanding and treatment of anxiety disorders in young children and areas in which future studies are needed also are explored.

No association of depression and anxiety with the metabolic syndrome: the Norwegian HUNT study

OBJECTIVE

To examine the associations of depression and anxiety with the metabolic syndrome.

METHOD

Cross-sectional study of 9571 participants aged 20-89 years in the Nord-Trøndelag Health Study (HUNT 2). We assessed anxiety and depression with the Hospital Anxiety and Depression Scale and the metabolic syndrome with the International Diabetes Federation criteria.

RESULTS

Despite generous statistical power and use of both continuous and categorical approaches, we found no association between anxiety or depression and the metabolic syndrome in models adjusted for age, gender, educational level, smoking, physical activity and pulse rate. When adjusted for age and gender only, we found a weak positive association for depression when a continuous measure was used, but not at the case level. The findings were similar across sexes, and robust for exclusion of cardiovascular disease and antidepressants.

CONCLUSION

In this largest study to date we found no association of anxiety and depression with the metabolic syndrome.

A discrete GABAergic relay mediates medial prefrontal cortical inhibition of the neuroendocrine stress response

Complementing its roles in cognitive and affective information processing, the medial prefrontal cortex (mPFC) is a nodal point of a limbic forebrain circuit that modulates stress-related homeostatic mechanisms, including the hypothalamic-pituitary-adrenal (HPA) axis. mPFC influences on HPA output are predominantly inhibitory and emanate from the prelimbic and/or dorsal anterior cingulate cortical fields (PL and ACd, respectively). mPFC projections do not target HPA effector neurons in the paraventricular hypothalamic nucleus (PVH) directly, distributing instead to nearby forebrain regions, including some that house GABAergic neurons implicated in inhibitory PVH control. To identify pathway(s) subserving HPA-inhibitory mPFC influences, an initial screen for sources of GABAergic input to PVH whose sensitivity to an acute emotional (restraint) stress was diminished by PL/ACd lesions identified a discrete region of the anterior bed nucleus of the stria terminalis (aBST) as a candidate for fulfilling this role. Anatomical tracing experiments confirmed projections from PL (but not ACd) to implicated aBST cell groups, and from these to PVH. Finally, selective immunotoxin-mediated ablation of GABAergic aBST neurons recapitulated the effects of PL/ACd lesions on acute stress-induced activation of HPA output. The identification of a proximate mediator of HPA-inhibitory limbic influences provides a framework for clarifying how inhibitory neural and hormonal controls of HPA output are integrated, adaptations of the axis to chronic stress are effected, and how endocrine abnormalities may contribute to stress-related psychiatric illnesses in which mPFC dysfunction is implicated.

Genetic, epigenetic and environmental impact on sex differences in social behavior

The field of behavioral neuroendocrinology has generated thousands of studies that indicate differences in brain structure and reactivity to gonadal steroids that produce sex-specific patterns of social behavior. However, rapidly emerging evidence shows that genetic polymorphisms and resulting differences in the expression of neuroactive peptides and receptors as well as early-life experience and epigenetic changes are important modifiers of social behavior. Furthermore, due to its inherent complexity, the neurochemical mechanisms underlying sex differences in social behavior are usually studied in a tightly regulated laboratory setting rather than in complex environments. Importantly, specific hormones may elicit a range of different behaviors depending on the cues present in these environments. For example, individuals exposed to a psychosocial stressor may respond differently to the effects of a gonadal steroid than those not exposed to chronic stress. The objective of this review is not to re-examine the activational effects of hormones on sex differences in social behavior but rather to consider how genetic and environmental factors modify the effects of hormones on behavior. We will focus on estrogen and its receptors but consideration is also given to the role of androgens. Furthermore, we have limited our discussions to the importance of oxytocin and vasopressin as targets of gonadal steroids and how these effects are modified by genetic and experiential situations. Taken together, the data clearly underscore the need to expand research initiatives to consider gene-environment interactions for better understanding of the neurobiology of sex differences in social behavior.

Serotonin transporter gene variation, infant abuse, and responsiveness to stress in rhesus macaque mothers and infants

A functional polymorphism in the promoter region of the serotonin transporter (5-HTTLPR) gene has been associated with variation in anxiety and hypothalamus-pituitary-adrenal (HPA) axis function in humans and rhesus macaques. Individuals carrying the short allele are at a higher risk for developmental psychopathology, and this risk is magnified in short allele carriers who have experienced early life stress. This study investigated the relationship between 5-HTTLPR allelic variation, infant abuse, and behavioral and hormonal responses to stress in rhesus macaques. Subjects were 10 abusive mothers and their infants, and 10 nonabusive mother-infant pairs. Mothers and infants were genotyped for the rh5-HTTLPR, and studied in the first 6 months of infant life. For mothers and infants, we measured social group behavior, behavioral responses to handling procedures, and plasma concentrations of ACTH and cortisol under basal conditions and in response to stress tests. The proportion of individuals carrying the short rh5-HTTLPR allele was significantly higher among abusive mothers than controls. Among mothers and infants, the short allele was associated with higher basal cortisol levels and greater hormonal stress responses in the infants. In addition, infants who carried the short rh5-HTTLPR allele had higher anxiety scores than infants homozygous for the long allele. The rh5-HTTLPR genotype also interacted with early adverse experience to impact HPA axis function in the infants. These results are consistent with those of previous studies which demonstrate associations between serotonergic activity and anxiety and stress reactivity, and add additional evidence suggesting that genetic variation in serotonergic function may contribute to the occurrence of abusive parenting in rhesus macaques and modulate emotional behavior and HPA axis function.

Investigating the molecular basis of major depressive disorder etiology: a functional convergent genetic approach

Genes play a major role in behavioral adaptation to challenging environmental stimuli, but the complexity of their contribution remains unclear. There is growing evidence linking disease phenotypes with genes on the one hand, and the genesis of stress-related disorders like major depression, as a result of exposure to stressful environmental pathogens on the other. Here we illustrate the convergent role of monoaminergic genes in regulating the underlying biological mechanisms of stress and the emotions. By reviewing data that support a role of monoaminergic and other related genes in environmental adaptation, we conclude by advocating the use of convergent approaches in examining the genetic modulation of disease phenotypes.

Stress response and the adolescent transition: performance versus peer rejection stressors

Little is known about normative variation in stress response over the adolescent transition. This study examined neuroendocrine and cardiovascular responses to performance and peer rejection stressors over the adolescent transition in a normative sample. Participants were 82 healthy children (ages 7-12 years, n = 39, 22 females) and adolescents (ages 13-17, n = 43, 20 females) recruited through community postings. Following a habituation session, participants completed a performance (public speaking, mental arithmetic, mirror tracing) or peer rejection (exclusion challenges) stress session. Salivary cortisol, salivary alpha amylase (sAA), systolic and diastolic blood pressure (SBP, DBP), and heart rate were measured throughout. Adolescents showed significantly greater cortisol, sAA, SBP, and DBP stress response relative to children. Developmental differences were most pronounced in the performance stress session for cortisol and DBP and in the peer rejection session for sAA and SBP. Heightened physiological stress responses in typical adolescents may facilitate adaptation to new challenges of adolescence and adulthood. In high-risk adolescents, this normative shift may tip the balance toward stress response dysregulation associated with depression and other psychopathology. Specificity of physiological response by stressor type highlights the importance of a multisystem approach to the psychobiology of stress and may also have implications for understanding trajectories to psychopathology.

Morning cortisol Levels in preschool-aged foster children: differential effects of maltreatment type

Maltreated foster children are subjected to a range of early adverse experiences, including neglect, abuse, and multiple caregiver disruptions. Research suggests that such disturbances alter the development and subsequent functioning of the hypothalamic-pituitary-adrenocortical system. The current study was designed to investigate morning cortisol levels in 117 foster children and 60 low-income, nonmaltreated children. Maltreatment and foster care placement experiences were coded from official records. Analyses revealed that the foster children were significantly more likely than the nonmaltreated children to have low morning cortisol levels. Additionally, specific maltreatment experiences were significantly associated with the foster children's morning cortisol levels. Foster children with low morning cortisol levels experienced more severe physical neglect than the other foster children. In contrast, foster children with high morning cortisol levels experienced more severe emotional maltreatment. These results suggest that specific early adverse experiences have differential effects on the functioning of the hypothalamic-pituitary-adrenocortical system.

Elevated 5-HT 2A receptors in postmortem prefrontal cortex in major depression is associated with reduced activity of protein kinase A

Previous human postmortem brain tissue research has implicated abnormalities of 5-HT receptor availability in depression and suicide. Although altered abundance of 5-HT 1A, 5-HT 2A, and 5-HT 2C receptors (5-HT(1A), 5-HT(2A), and 5-HT(2C)) has been reported, the causes remain obscure. This study evaluated the availability of these three receptor subtypes in postmortem brain tissue specimens from persons with a history of major depression (MDD) and normal controls and tested the relationships to protein kinases A and C (PKA, PKC). Samples were obtained from postmortem brain tissue (Brodmann area 10) from 20 persons with a history of MDD and 20 matched controls as determined by a retrospective diagnostic evaluation obtained from family members. Levels of 5-HT(1A), 5-HT(2A), and 5-HT(2C) receptor were quantitated via Western blot analyses. Basal and stimulated PKA and PKC activity were also determined. The depressed samples showed significantly increased 5-HT(2A) receptor abundance relative to controls, but no differences in 5-HT(1A) or 5-HT(2C) receptors. Basal and cyclic AMP-stimulated PKA activity was also reduced in the depressed sample; PKC activity was not different between groups. 5-HT(2A) receptor availability was significantly inversely correlated with PKC activity in controls, but with PKA activity in the depressed sample. Increased 5-HT(2A) receptor abundance and decreased PKA activity in the depressed sample are consistent with prior reports. The correlation of 5-HT(2A) receptor levels with PKA activity in the depressed group suggests that abnormalities of 5-HT(2A) receptor abundance may depend on receptor uncoupling and heterologous regulation by PKA.

IL-10 modulates depressive-like behavior

The role of pro-inflammatory cytokines in psychiatric disorders has been the focus of great research attention in recent years. Paradoxically, the same is not true for anti-inflammatory cytokines. In the present study, we assessed the behavioral profile of animals with altered expression of the anti-inflammatory cytokine IL-10. We performed a battery of tests to assess anxiety, depressive-like and cognitive behaviors in mice overexpressing IL-10 (PMT10) and IL-10(-/-) animals; in the later mice we also tested the behavioral effect of IL-10 administration. In the forced-swimming test, IL-10(-/-) females displayed increased depressive-like behavior; importantly, this phenotype was reverted by the injection of IL-10. Moreover, mice overexpressing IL-10 presented a decreased depressive-like behavior. Despite the presence of a similar trend, male animals did not reach significant differences in depressive-like behavior. Assessment in the open-field showed that the absence of IL-10 decreased the percentage of time spent in the center of the arena in both male and female mice, while male animals overexpressing IL-10 revealed an opposite behavior. For both sexes, imbalance in IL-10 levels did not affect spatial reference memory. In conclusion, variations in IL-10 expression are associated with an altered depressive-like behavior, but do not influence cognitive performance. Interestingly, IL-10 imbalance produced more profound behavioral changes in females than in male animals. This is in accordance with clinical data demonstrating an increased susceptibility of women to mood disorders, suggesting an interplay between anti-inflammatory cytokines and sexual steroids.

Children's delayed development and behavior problems: impact on mothers' perceived physical health across early childhood

Mothers of children with developmental delays may experience poorer psychological well-being than other mothers; however, little research has examined how delayed development in children might predict mothers' perceived physical well-being. Children with delayed development manifest heightened behavior problems, which may negatively affect maternal well-being. We examined the associations between developmental delay and behavior problems at child age 3 and mothers' self-perceived physical health at child ages 3, 4, and 5, in families of 218 children with and without developmental delays. The study sample comprised 218 families from central Pennsylvania and Southern California, USA who were recruited through community agencies that provide diagnostic and intervention services for individuals with development difficulties. We found that mothers of children with delayed development at age 3 reported poorer concurrent and later physical health than mothers of children with typical development. Broadening the analyses to include not only child development status (delayed development versus typical development) but also child behavior problems at age 3, only child behavior problems and the interaction of development status and behavior problems, but not development status itself, predicted maternal health. Early child behavior problems contributed to later maternal health above and beyond early maternal health, suggesting a possible causal association between child behavior problems and mothers' physical health. The relation between child behavior problems and maternal health was moderated by mothers' parenting stress and mediated by depressive symptoms. Mothers of children with both delayed development and high behavior problems are a particular risk group that may be especially in need of early intervention. Further research should examine the behavioral and biological pathways by which these child-related stressors influence mothers' physical health.

The association of pain and depression in preadolescent girls: moderation by race and pubertal stage

OBJECTIVE

To test whether an association between pain response and depression in females is present during preadolescence using a controlled pain stimulus and a clinically relevant assessment of depressive symptoms.

METHOD

In a sample of 232 girls, pain threshold and tolerance were assessed at age 10 years using the cold pressor task, and a diagnostic interview was used to assess depression symptoms at 10 and 11 years of age.

RESULTS

Response to pain at age 10 was associated with depressive symptoms at ages 10 and 11; race and pubertal stage moderated the association. Pain response and depression were more strongly associated among girls who had reached advanced stages of pubertal development and among European American girls.

CONCLUSIONS

The results add to the existing literature on the co-occurrence of depression and pain by demonstrating modest but consistent concurrent and prospective associations between response to pain and depression among girls during preadolescence.

Maternal depression and infant cortisol: influences of timing, comorbidity and treatment

BACKGROUND

The current study examines the relationship between maternal depression and infant cortisol concentrations. The potential roles of comorbid maternal anxiety disorders, timing of maternal depression, and maternal treatment with psychotropic medications during pregnancy are addressed.

METHODS

Women with 6-month-old infants (105 boys and 84 girls) participated in a laboratory paradigm that included infant saliva collection at six points, noise burst and arm restraint stressor tasks, and a diagnostic interview of the mother.

RESULTS

Lifetime history of maternal depression was associated with increased baseline and mean (average) infant cortisol levels. Comorbidity with anxiety disorder was related to infant cortisol reactivity. Peripartum (prepartum and/or postpartum) maternal depression, rather than a pre-pregnancy history of disorder, was associated with higher infant cortisol reactivity. Prenatal and postnatal exposure to maternal disorder had similar effects, but prenatal maternal psychotropic medication treatment appeared to attenuate infant cortisol increases associated with prenatal maternal disorder exposure.

CONCLUSIONS

These data suggest that exposure to maternal depression and anxiety during pregnancy and the postpartum period may increase infant salivary cortisol. This maternal depression-infant cortisol association is independent of the effects of delivery complications, and appears to be modulated by prenatal maternal psychotropic treatment.

Salivary cortisol and suicidal behavior--a follow-up study

INTRODUCTION

Hyperactivity of the hypothalamic-pituitary-adrenal (HPA)-axis is a common finding in major depressive disorder. Similar studies on suicide attempters are less abundant, and the results are divergent. The main aim of the present study was to investigate HPA-axis parameters by the time of a suicide attempt and at follow-up in search for associations between HPA-axis function and suicidal behavior.

METHODS

Thirty-five suicide attempters and 16 non-suicidal controls were admitted to a psychiatric ward between the years of 1986 and 1992. Corticotrophin-releasing hormone (CRH) in cerebrospinal fluid and urinary cortisol were obtained for the suicide attempters. The patients were followed up approximately 12 years after the index admission. Cortisol was measured in saliva, and additional suicide attempts and current psychiatric symptoms were registered.

RESULTS

At follow-up, evening salivary cortisol was lower in suicide attempters compared to controls. Low cortisol levels at follow-up were associated with severe psychiatric symptoms. Among women, repeated suicide attempts were associated with low morning and lunch salivary cortisol, and in this subgroup we also found significant correlations between salivary cortisol at follow-up, and CRH as well as urinary cortisol at index.

CONCLUSION

We found evidence for an association between low HPA-axis activity and suicidal behavior. This could be due to long-lasting and severe psychiatric morbidity, which in turn has exhausted the HPA-axis of these patients. The potential role of hypocortisolism should be given more attention in studies on suicidal patients.

Diurnal cortisol patterns and stress reactivity in child Holocaust survivors reaching old age

OBJECTIVES

Late-life implications of early traumatic stress for the adreno-cortical system were examined in a sample of 133 child survivors of the Holocaust, who were subjected to Nazi persecution during infancy.

METHOD

In a non-convenience sample of child survivors, born between 1935 and 1944, basal circadian cortisol release and cortisol reactivity to a stressor were assessed.

RESULTS

Age, parental loss during the Holocaust, current depression, post-traumatic stress disorder (PTSD) and physical illness were not associated with differences in basal diurnal cortisol levels. Neuro-endocrine effects, however, were found in stress reactivity through elevated cortisol levels in male respondents in the youngest age group (born 1941-1945), and in male respondents suffering from PTSD-related functional impairment.

CONCLUSION

The youngest survivors of Nazi persecution show late-life effects of traumatic stress during early childhood, evidenced by the early onset of differential neuroendocrine pathways to stress-regulating strategies.

Depression is associated with flatter cortisol rhythms in patients with coronary artery disease

OBJECTIVE

Depression is associated with coronary heart disease, but the underlying mechanisms are not fully understood. Cortisol is involved in the development of coronary artery disease (CAD), but evidence directly linking depression with cortisol in patients with CAD is limited. This study evaluated cortisol output over the day in patients with suspected CAD in relation to depressive symptoms.

METHODS

Eighty-eight patients who were being investigated for suspected CAD (defined by clinical symptoms plus positive exercise tests or myocardial perfusion scans) took eight saliva samples over the day and evening. Depressed mood was assessed with the Beck Depression Inventory. Actigraphy was used to define time of waking objectively.

RESULTS

The cortisol awakening response and cortisol rhythm over the remainder of the day and evening were analyzed separately. Fifty-two (61.9%) patients were later found to have definite CAD on angiography, while the remainder did not. The cortisol slope over the day was flatter in more depressed patients with CAD (P<.001) but was not related to depression in patients without CAD (P=.68). This effect was due to the combination of lower cortisol early in the day and higher cortisol in the evening in more depressed CAD patients, independent of age, gender, medication, and times of waking and sleeping (P=.003). Additionally, cortisol measured on waking and 15 and 30 min after waking was greater in CAD than in non-CAD patients (P=.04), but was not related to depression.

CONCLUSIONS

The flatter cortisol rhythms of more depressed CAD patients may contribute to the progression of coronary atherosclerosis.

Combined dexamethasone/corticotropin-releasing factor test in chronic fatigue syndrome

BACKGROUND

Studies of hypothalamic-pituitary-adrenal (HPA) axis function in chronic fatigue syndrome (CFS) point to hypofunction, although there are negative reports. Suggested mechanisms include a reduced hypothalamic or supra-hypothalamic stimulus to the HPA axis and enhanced sensitivity to the negative feedback of glucocorticoids. The aim of the current study was to investigate HPA axis function in CFS with the dexamethasone/corticotropin-releasing factor (Dex/CRF) test, in analogy with research in affective disorders.

METHOD

Thirty-four well-characterized female CFS patients and 25 healthy control subjects participated in the low-dose Dex/CRF test. Current major depressive episode was an exclusion criterion. History of early-life stress (ELS) was assessed with the Structured Trauma Interview.

RESULTS

Salivary cortisol responses after 0.5 mg Dex were lower in CFS patients than in controls (before 100 microg CRF, p=0.038; after 100 microg CRF, p=0.015). A secondary analysis revealed an influence of early-life stress and of oestrogen intake. After removal of the 10 participants who were taking an oral oestrogen, patients without a history of ELS showed lower cortisol responses than patients with ELS and controls (before CRF, p=0.005; after CRF, p=0.008).

CONCLUSIONS

CFS is globally associated with reduced cortisol responses in the combined low-dose Dex/CRF test, but this effect is only clearly present in CFS patients without a history of ELS. This study provides further support for an enhanced glucocorticoid negative feedback and/or a reduced central HPA axis drive in CFS. Furthermore, it demonstrates that ELS is an important variable to consider in CFS research.

Chronic psychosocial stress affects corticotropin-releasing factor in the paraventricular nucleus and central extended amygdala as well as urocortin 1 in the non-preganglionic Edinger-Westphal nucleus of the tree shrew

Stressful stimuli evoke neuronal and neuroendocrine responses helping an organism to adapt to changed environmental conditions. Chronic stressors may induce maladaptive responses leading to psychiatric diseases, such as anxiety and major depression. A suitable animal model to unravel mechanisms involved in the control of adaptation to chronic stress is the psychological subordination stress in the male tree shrew. Subordinate male tree shrews exhibit chronic hypothalamo-pituitary-adrenal (HPA) activation as reflected in continuously elevated cortisol secretion, and structural changes in the hippocampal formation. Corticotropin-releasing factor (CRF) is the major peptide released upon activation of the HPA axis in response to stress. Recent evidence suggests that besides CRF, urocortin 1 (Ucn1) also plays a role in stress adaptation. We have tested the significance of CRF and Ucn1 in adaptation to chronic psychosocial stress in male tree shrews exposed for 35 days to daily psychosocial conflict, by performing semi-quantitative immunocytochemistry for CRF in the parvocellular hypothalamic paraventricular nucleus (pPVN), extended amygdala, viz. central extended amygdala (CeA) and dorsolateral nucleus of the bed nucleus of the stria terminalis (BNSTdl) as well as that for Ucn1 in the non-preganglionic Edinger-Westphal nucleus (npEW). Compared to unstressed animals, psychosocial stress resulted in an immediate and sustained activation of the HPA axis and sympathetic tone as well as reduced testosterone concentration and decreased body and testis weights vs. non-stressed tree shrews. In the pPVN, the number of CRF-immunoreactive neurons and the specific signal density of CRF-immunoreactive fiber terminals in the CeA were strongly reduced (-300 and -40%, respectively; P<0.05), whereas no significant difference in CRF fiber density was found in BNSTdl. The npEW revealed 4 times less Ucn1-immunoreactive neurons (P<0.05). These clear effects on both Ucn1- and CRF-neuropeptide contents may reflect a crucial mechanism enabling the animal to adapt successfully to the stressors, and point to the significance of the pPVN, CeA and npEW in stress-induced brain diseases.

Circadian affective, cardiopulmonary, and cortisol variability in depressed and nondepressed individuals at risk for cardiovascular disease

Depression is a risk factor for cardiovascular disease (CVD) perhaps mediated by hypothalamic-pituitary-adrenal (HPA) axis or vagal dysregulation. We investigated circadian mood variation and HPA-axis and autonomic function in older (55 years) depressed and nondepressed volunteers at risk for CVD by assessing diurnal positive and negative affect (PA, NA), cortisol, and cardiopulmonary variables in 46 moderately depressed and 19 nondepressed volunteers with elevated CVD risk. Participants sat quietly for 5-min periods (10:00, 12:00, 14:00, 17:00, 19:00, and 21:00), and then completed an electronic diary assessing PA and NA. Traditional and respiration-controlled heart rate variability (HRV) variables were computed for these periods as an index of vagal activity. Salivary cortisols were collected at waking, waking+30min, 12:00, 17:00, and 21:00h. Cortisol peaked in the early morning after waking, and gradually declined over the day, but did not differ between groups. PA was lower and NA was higher in the depressed group throughout the day. HRV did not differ between groups. Negative emotions were inversely related to respiratory sinus arrhythmia in nondepressed participants. We conclude that moderately depressed patients do not show abnormal HPA-axis function. Diurnal PA and NA distinguish depressed from nondepressed individuals at risk for CVD, while measures of vagal regulation, even when controlled for physical activity and respiratory confounds, do not. Diurnal mood variations of older individuals at risk for CVD differ from those reported for other groups and daily fluctuations in NA are not related to cardiac autonomic control in depressed individuals.

Role of metabotropic glutamate receptors in the control of neuroendocrine function

Glutamate exerts its effects through binding and activation of two classes of specific receptors: ionotropic (iGluRs) and metabotropic (mGluRs). Group I mGluR includes mGluR1 and mGluR5 subtypes, group II includes mGluR2 and mGluR3 subtypes and group III includes the subtypes mGluR 4, 6, 7 and 8. Glutamate and its receptors are found in all key hypothalamic areas critically involved in reproduction and neuroendocrine function. To date, considerable data support an important role for iGluRs in the control of neuroendocrine function; however, the role of mGluRs as regulators of hypothalamic-pituitary function has not been clearly elucidated. mGluRs could be exerting a fine tune on the release of hypothalamic factors that regulate hormone release such as Substance P, GABA, alpha-MSH and CRH. Group II mGluR exert a direct inhibitory effect on anterior pituitary prolactin and GH secretion. Moreover, some group II mGluR agonists, like LY 354,740 and LY 379,268, can modulate PRL secretion from the anterior pituitary through their actions as dopamine receptor agonists. Evidence suggests a role for group III mGluR subtypes in stress-related behavioral disorders. Several reports indicate that selective ligands for mGluR subtypes have potential for the treatment of a wide variety of neurological and psychiatric disorders, including depression, anxiety disorders, schizophrenia, epilepsy and Alzheimer's disease among others. Since converging lines of evidence suggest a role for mGluRs subtypes in neuroendocrine regulation of hormone secretion, mGluRs neuroendocrine actions must be taken in consideration to insure proper treatment of these diseases. Moreover, discovery of selective agonists provides an opportunity to investigate the physiological role of mGluR subtypes and to directly test the neuroendocrine actions of mGluRs. Finally, mGluRs selective agonists may have an impact in the treatment of conditions involving chronic stress, such as depression and anxiety disorders, since they regulate neuroendocrine stress circuits involving the HPA axis and stress-sensitive hormones such as oxytocin and prolactin. This review aims to provide a survey of our current understanding of the effects of mGluR activation on neuroendocrine function.

Peer rejection and physical health problems in early adolescence

OBJECTIVE

Rejection from the peer group may constitute an important source of stress that may weaken children's immune system and leave them vulnerable to infection and physical illness. Controlling for family adversity and depressed mood, this study examined the predictive link between peer rejection and physical health problems, as well as the putative moderating effect of adolescents' reactivity/emotional negativity in this context.

METHOD

A total of 122 high school students (50% girls) were assessed over two consecutive years in grades 7 (time [T] 1) and 8 (time [T] 2). More than 90% of the participants were white and French speaking and were from average socioeconomic backgrounds. Physical health problems at T1 and T2 as well as depression symptoms at T1 were assessed using adolescent self-reports. Peer rejection at T1 was assessed through peer nominations. Reactivity/negative emotionality at T1 was assessed via teacher ratings. Family adversity at T1 was assessed via mother reports.

RESULTS

Peer rejection at T1 predicted an increase in physical health problems from T1 to T2, even when controlling for physical health problems and depression symptoms at T1. This result, however, was only true for girls with moderate or high levels of reactivity/negative emotionality. For boys, peer rejection was unrelated to change in physical health problems.

CONCLUSIONS

The present findings are in line with the diathesis stress model of disease and emphasize the need for health education programs that specifically target girls and that foster problem-solving skills to help vulnerable adolescents cope more effectively with peer conflict.

Effect of selective serotonin reuptake inhibitors on cardiovascular morbidity and mortality

Depression in patients with coronary artery disease is associated with increased cardiovascular morbidity and mortality. It is not clear, however, if treatment with selective serotonin reuptake inhibitors (SSRIs) decreases the rate of future cardiovascular events. This paper reviews the available literature regarding the effect of SSRI use on cardiovascular outcomes. Thirteen studies addressing this issue were identified. Of these, 5 concluded that SSRI use is associated with decreased cardiovascular morbidity or mortality, 2 concluded that SSRI use was associated with worsened prognosis, and 6 studies found no statistically significant association. Almost all of the published literature examining the effect of SSRIs on cardiovascular outcomes is based on observational studies, thereby precluding definitive conclusions. Randomized controlled studies are clearly needed to definitively address this issue.

Glucocorticoids in the treatment of children with acute lymphoblastic leukemia and hodgkin's disease: a pilot study on the adverse psychological reactions and possible associations with neurobiological, endocrine, and genetic markers

PURPOSE

We did a controlled study to assess adverse psychological reactions (APR) associated with high-dose glucocorticoid therapy and tried to detect somatic correlates for the observed reactions.

PATIENTS AND METHODS

Our study included 37 patients with acute lymphoblastic leukemia (ALL) and 11 patients with Morbus Hodgkin (MH) disease, who were treated with high-dose glucocorticoid therapy, and 26 control patients with other types of malignancies. APRs were assessed with a standardized measure via parent-report. Patients with ALL and MH were further analyzed for signs of neuronal cell death in the cerebrospinal fluid, polymorphisms of the glucocorticoid receptor gene, as well as cortisol, adrenocorticorticotropic hormone, and dehydroepiandrosterone sulfate blood levels.

RESULTS

Fifty-four percent of ALL, 36% of MH, and 23% of control patients developed APR in the first few weeks of therapy. Approximately 3.5 months later, the majority of patients with ALL showed no APR, similar to control patients. Patients demonstrating a higher, nonsuppressible secretion of cortisol and/or adrenocorticorticotropic hormone during glucocorticoid therapy were found to be more likely to develop APR. No sign of neuronal cell destruction and no correlation of APR with specific glucocorticoid receptor polymorphisms were found.

CONCLUSION

Our results suggest that the development of APR due to glucocorticoid therapy is measurable and correlates with hormonal reaction patterns.

Relationship between nocturnal urinary cortisol excretion and symptom severity in subgroups of patients with depressive episodes

INTRODUCTION

The aim of this naturalistic study was to gain more information about the elevation of basal hypothalamic-pituitary-adrenal (HPA) activity in relationship to symptom severity in specific subtypes of depressive episodes.

METHOD

Hamilton Depression Rating Scale scores and aggregated nocturnal urinary cortisol excretion were measured in 4 groups of inpatients with depressive episodes (n = 48; monopolar nonpsychotic, monopolar psychotic, bipolar nonpsychotic and bipolar psychotic) at the beginning and at the end of inpatient treatment.

RESULTS

The initial elevation of nocturnal urinary cortisol excretion was most pronounced in psychotic patients. At the end of treatment, the Hamilton Depression Rating Scale scores had decreased significantly in all patients to comparable levels, whereas the nocturnal cortisol excretion values were still relatively elevated in mono- and bipolar psychotic patients compared to mono- and bipolar nonpsychotic ones.

CONCLUSION

The observation that the basal HPA activity remains elevated even after remission of symptoms in patients with psychotic depression supports the concept that a dysfunctional regulation of the HPA system is possibly a trait- rather than a state-related feature.

Relationships of DEX/CRH and GHRH test results to the outcome of depression--preliminary results suggest the GHRH test may predict relapse after discharge

To explore and compare hypothalamic-pituitary-somatotropic (HPS) axis function and hypothalamic-pituitary-adrenocortical (HPA) axis function in depression, the dexamethasone (DEX)/CRH test and growth hormone releasing hormone (GHRH) test were prospectively performed on patients with depression at the time of admission and discharge. The patients who relapsed within six months after discharge exhibited significantly lower growth hormone (GH) responses to GHRH at the time of discharge than those who did not relapse. There were no significant correlations between GH response to GHRH and the results of DEX/CRH tests after controlling for age, sex, and body mass index. The findings of this study suggest that results of the GHRH test may be a predictor of future relapse in patients with depression.

Emotional memory function, personality structure and psychopathology: a neural system approach to the identification of vulnerability markers

It is well established that emotional events are ingrained stronger into memory relative to neutral events. Facilitated emotional memory is highly variable between individuals within the normal population and is particularly exacerbated in those diagnosed with mood and anxiety disorders. In order to elucidate how variation of enhanced emotional memory within the normal population may manifest into psychopathological states, we explored the convergence between studies investigating the neural systems engaged in emotional memory facilitation and studies investigating how these systems differ from person to person. Converging evidence highlights the roles of three neural systems (1. Amygdala function and attention, 2. Neuroendocrine function, 3. Interactive effects with mood) that all govern emotional memory facilitation and are highly variable between individuals as a function of personality. We applied this neural system approach to models of vulnerability of three forms of psychopathology that are particularly characterized by atypical emotional memory function (depression, generalized anxiety disorder and post-traumatic stress disorder). This application suggests that the incorporation of known vulnerability markers across psychological, neuroimaging and neuroendocrinological domains is cardinal to how susceptibility is conceptualized and assessed in these disorders.

Longitudinal neuroendocrine changes assessed by dexamethasone/CRH and growth hormone releasing hormone tests in psychotic depression

Although psychotic depression has been reported to exhibit a greater degree of dysregulation of hypothalamic-pituitary-adrenocortical (HPA) function than non-psychotic depression, little is known concerning hypothalamic-pituitary-somatotropic (HPS) function in psychotic depression and how neuroendocrine function changes after treatment. To investigate the longitudinal changes in HPA and HPS system function in psychotic depression, we performed repeated dexamethasone/corticotropin releasing hormone (DEX/CRH) tests and growth hormone (GH) releasing hormone (GHRH) tests in inpatients with major depressive disorder. The psychotic depression group exhibited greater elevation of ACTH responses to the DEX/CRH test and stronger decreases in GH responses to the GHRH test than the non-psychotic depression group at admission. At discharge, the neuroendocrine responses to the DEX/CRH test of the psychotic depression group were still stronger than those of the non-psychotic depression group, though there were no significant differences in severity of depression between the groups. There were significant longitudinal changes in neuroendocrine responses to the DEX/CRH test between admission and discharge. The psychotic depression group exhibited increased GH responses to GHRH at discharge compared with those at admission, whereas no significant longitudinal change in GH response was found in the non-psychotic depression group. Consequently, there were no significant differences in GH responses to GHRH between the psychotic and non-psychotic depression groups at discharge. The results of GHRH test showed no significant relationships with severity of depression except psychotic features and the results of the DEX/CRH test. Our findings suggest that the HPS axis may be associated with psychotic features rather than general severity of depression. Further longitudinal studies are needed to clarify the role of HPS function in psychotic depression and whether sustained dysregulation of HPA function in psychotic depression is associated with a poor outcome after discharge.

Depressive symptoms moderate the influence of hostility on serum interleukin-6 and C-reactive protein

OBJECTIVE

Recent evidence suggests that depressive symptoms and hostility may act together, as interacting factors, to have an effect on the circulating levels of inflammatory markers relevant to coronary artery disease. Further research, however, is needed to clarify the nature of this interaction and to determine whether previous findings extend to older adults. In this report we examined the cross-sectional associations of depressive symptoms, hostility, and their interaction with circulating levels of two such inflammatory markers-interleukin-6 (IL-6) and C-reactive protein (CRP).

METHODS

A total of 316 healthy, older adults underwent a blood draw for the assessment of serum IL-6 and CRP and completed the Beck Depression Inventory-II and the Cook-Medley Hostility Scale. Regression analyses were performed to examine depressive symptoms, hostility, and their interaction as predictors of serum IL-6 and CRP.

RESULTS

After adjustment for demographic factors, cardiovascular risk factors, and health behaviors, we detected depressive symptoms x hostility interactions for serum IL-6 (DeltaR(2) = .027, p < .01) and CRP (DeltaR(2) = .015, p < .05). Simple slope analyses revealed that hostility was positively related to serum IL-6 only among individuals with higher depressive symptoms. The pattern of results was similar for serum CRP, although none of the simple slopes was significant.

CONCLUSIONS

Our findings suggest that depressive symptoms may moderate the hostility-inflammation relationship such that hostility may augment inflammatory processes relevant to coronary artery disease only in the presence of depressive symptoms. Our results also extend previous findings from younger adults to older adults from the general community.

Corticotropin-releasing factor 1 and 2 receptors in the dorsal raphé differentially affect serotonin release in the nucleus accumbens

Corticotropin-releasing factor (CRF) is a neurohormone that mediates stress, anxiety, and affects serotonergic activity. Studies have shown that CRF has dose-dependent opposing effects on serotonergic activity. This effect has been hypothesized to be differentially mediated by CRF(1) and CRF(2) receptors in the dorsal raphé nucleus. We directly tested this hypothesis by using in vivo microdialysis to determine the effects of CRF and CRF receptor antagonists in the dorsal raphé nucleus on serotonin (5-HT) release in the nucleus accumbens, a brain region implicated in the neuropathology of stress-related psychiatric disorders. Male urethane-anesthetized rats were implanted with a microdialysis probe into the nucleus accumbens, and CRF (0, 100 or 500 ng) was infused into the dorsal raphé. Infusion of CRF into the dorsal raphé nucleus had dose-dependent opposite effects, with 100 ng of CRF significantly decreasing 5-HT levels in the nucleus accumbens and 500 ng CRF significantly increasing accumbal 5-HT levels. In subsequent experiments, the raphé was pre-treated with the CRF(1) receptor antagonist antalarmin (0.25 microg) or the CRF(2) receptor antagonist antisauvagine-30 (ASV-30; 2 microg) prior to CRF infusion. Antagonism of CRF(1) receptors in the dorsal raphé nucleus abolished the decrease in accumbal 5-HT levels elicited by 100 ng CRF, and CRF(2) receptor antagonism in the raphé blocked the increase in accumbal 5-HT levels elicited by 500 ng CRF. These results suggest that the opposing effects of dorsal raphé CRF on 5-HT release in the nucleus accumbens are dependent on differential activation of CRF(1) and CRF(2) receptors in the dorsal raphé nucleus.

Suicidal intent and the HPA-axis characteristics of suicide attempters with major depressive disorder and adjustment disorders

The main purpose of the study was to investigate Hypothalamic-Pituitary-Adrenal (HPA) axis characteristics in relation to suicidal intent among suicide attempters with Major Depressive Disorder (MDD) and Adjustment Disorders (AD). The relationship between suicidal intent, assessed by means of the Suicidal Intent Scale (SIS), and serum cortisol after a Dexamethasone Suppression Test (DST) was investigated in 78 suicide attempters, divided into diagnostic subgroups. There was a significant negative correlation between suicidal intent and post DST cortisol in patients with MDD. Our findings may be attributed to pathophysiological processes, where a high suicidal intent is revealed during a potential chronic course of MDD, which in turn results in a seemingly normal stress system.

Dexamethasone suppression test in borderline personality disorder: impact of PTSD symptoms

The purpose of the present study was to investigate the impact of post-traumatic stress disorder (PTSD) symptoms on hypothalamic-pituitary-adrenal axis feedback regulation in 18 female patients with borderline personality disorder (BPD) and 21 healthy controls. Reduced feedback sensitivity was found in BPD patients with a low number of PTSD symptoms, while findings in the BPD group with a high number of PTSD symptoms did not differ from those in controls. The results suggest a hypo-suppression in the dexamethasone suppression test in BPD with few PTSD symptoms.

Stress-induced changes in primate prefrontal profiles of gene expression

Stressful experiences that consistently increase cortisol levels appear to alter the expression of hundreds of genes in prefrontal limbic brain regions. Here, we investigate this hypothesis in monkeys exposed to intermittent social stress-induced episodes of hypercortisolism or a no-stress control condition. Prefrontal profiles of gene expression compiled from Affymetrix microarray data for monkeys randomized to the no-stress condition were consistent with microarray results published for healthy humans. In monkeys exposed to intermittent social stress, more genes than expected by chance appeared to be differentially expressed in ventromedial prefrontal cortex compared to monkeys not exposed to adult social stress. Most of these stress responsive candidate genes were modestly downregulated, including ubiquitin conjugation enzymes and ligases involved in synaptic plasticity, cell cycle progression and nuclear receptor signaling. Social stress did not affect gene expression beyond that expected by chance in dorsolateral prefrontal cortex or prefrontal white matter. Thirty four of 48 comparisons chosen for verification by quantitative real-time polymerase chain reaction (qPCR) were consistent with the microarray-predicted result. Furthermore, qPCR and microarray data were highly correlated. These results provide new insights on the regulation of gene expression in a prefrontal corticolimbic region involved in the pathophysiology of stress and major depression. Comparisons between these data from monkeys and those for ventromedial prefrontal cortex in humans with a history of major depression may help to distinguish the molecular signature of stress from other confounding factors in human postmortem brain research.

The leptin hypothesis of depression: a potential link between mood disorders and obesity?

The adipose-derived hormone leptin is well known for its function in the control of energy homeostasis. Recent studies suggest a novel role for this adipokine in the regulation of mood and emotion. Low levels of leptin have been found to be associated with depressive behaviors in rodents and humans. Pharmacological studies indicate that leptin has antidepressant-like efficacy. Both leptin insufficiency and leptin resistance may contribute to alterations of affective status. Identifying the key brain regions that mediate leptin's antidepressant activity and dissecting its intracellular signal transduction pathways may provide new insights into the pathogenesis of depression and facilitate the development of novel therapeutic strategies for the treatment of this illness.

Differential effect of environment enrichment and social isolation on depressive-like behavior, spontaneous activity and serotonin and norepinephrine concentration in prefrontal cortex and ventral striatum

In order to determine the effect of postnatal environments on some behavioral and neurochemical depressive-like parameters, male Sprague-Dawley rats were reared from weaning in either social isolation, standard laboratory conditions, or environmental enrichment. Open-field activity was assessed at postnatal days 37, 65, 93 and 107 and 1 h before the last open-field test, a forced-swimming test was carried out. After behavioral tests, the monoamines concentrations were analyzed in prefrontal cortex and ventral striatum. Relative to control and isolation rearing, the environmental enrichment reduced open-field activity, led to antidepressive-like effects and increased serotonin concentrations in the prefrontal cortex. Social isolation, on the other hand, did not affect open-field activity, but increased depressive-like behavior and reduced the amount of norepinephrine in the ventral striatum. Those neurochemical changes induced by rearing conditions correlated with the behavioral performance in the forced-swimming test. Also, immobility behavior could be predicted by locomotor activity even from the first week of housing. Overall, specific variations in physical and social environment during early rearing lead to some behavioral and neurochemical alterations which might be relevant for understanding the role that neurodevelopmental and experiential factors could have in human depression.

Single nucleotide polymorphism analysis of corticotropin-releasing factor-binding protein gene in bipolar disorder

Corticotropin-releasing factor-binding protein regulates the availability of free corticotropin-releasing factor and is a functional candidate gene for affective disorders. The aim of this study was to examine the association between polymorphisms in CRF-BP gene and bipolar disorder in an isolated Swedish population. One hundred and eighty-two patients with bipolar I disorder and 333 controls from Northern Sweden were included in the study. Five single nucleotide polymorphisms and a deletion polymorphism in the CRF-BP gene were genotyped. The haplotype block structure of the gene was considered and the expectation maximization algorithm was adopted to estimate the haplotype frequencies. As a result, there were no significant associations of the different polymorphisms in the CRF-BP gene with bipolar disorder. In conclusion, this study in an isolated Swedish population does not support a role for the CRF-BP gene in the vulnerability for bipolar disorder.

Causality of stem cell based neurogenesis and depression--to be or not to be, is that the question?

Mood disorders compose a considerable portion of the worldwide prevailing diseases with high suicide rates and urgent demand for novel therapeutic interventions as efficacious treatment is still lacking. Depression is thought to feature distinct morphological correlatives in the brain and has recently been linked to adult neurogenesis (NG) in the hippocampal formation. Numerous findings give rise to the hypothesis that depression and declining NG in the hippocampus may be causally connected. This implies that depressive symptoms could originate from impairments in NG and, vice versa, that improved NG could mediate antidepressant action and alleviate symptoms. Thus, great hopes rest on the question whether the observed increase in NG following antidepression treatment may have the potential to become a novel drug target and specific mechanism in the development of the next generation of antidepressants that specifically involves targeting of neuropoetic factors in addition to their "traditional" effects as modulators of synaptic transmission. Along the still hypothetical association of depression and NG, however, several controversies and unresolved questions exist with respect to the presently available data and interpretation. This article highlights and summarizes some of the most pressing issues and identifies the crucial ones that await urgent clarification and resolving. Without their reliable answering, the fascinating notion of a neurogenic basis for depression will remain to be greatly speculative.

An anti-immobility effect of exogenous corticosterone in mice

Although traditionally considered to be etiological factors in depression, corticosteroids have been shown to exert an acute antidepressant action under some conditions. To investigate the mechanism of this effect, the present experiment sought to develop an animal model of it in mice using the repeated forced swim procedure. Corticosterone or desmethylimipramine was administered in the drinking water before, during or after repeated daily forced swims or a tail suspension test. Glucocorticoid and mineralocorticoid receptor involvement were assessed by coadministration of RU486 or spironolactone. Plasma corticosterone and fos expression in the paraventricular nucleus of the hypothalamus and piriform cortex were also measured in the treated animals. Corticosterone, given either before/during or after repeated swim, was found to produce a rapid reduction of immobility that was greater than that produced by desmethylimipramine given by the same route and dose and for the same duration. There was a nonsignificant tendency toward this effect in the tail suspension test. RU486 failed to block the effect but results with spironolactone were ambiguous. Plasma corticosterone was elevated in an inverted U-shaped fashion by the hormone treatment. Fos expression in response to the last swim was blunted in the paraventricular hypothalamus but enhanced in the piriform cortex. It is concluded that short-term treatment with corticosterone has a marked antidepressant effect in the mouse repeated forced swim test and merits further consideration as a short-term therapeutic agent in low doses. The hormone may act by suppression of neural activity in central stress circuits leading to a disinhibition of regions involved in active behavioral coping.

Effects of rapid eye movement sleep deprivation on hypocretin neurons in the hypothalamus of a rat model of depression

Hypocretin (Hcrt, also known as orexin) is a hypothalamic neuropeptide linked to narcolepsy, a disorder diagnosed by the appearance of rapid eye-movement sleep (REMS)-state characteristics during waking. Major targets of Hcrt-containing fibers include the locus coeruleus and the raphe nucleus, areas with important roles in regulation of mood and sleep. A relationship between REMS and mood is suggested by studies demonstrating that REMS-deprivation (REMSD) ameliorates depressive symptoms in humans. Additional support is found in animal studies where antidepressants and REMSD have similar effects on monoamiergic systems thought to be involved in major depression. Recently, we have reported that Wistar-Kyoto (WKY) rats, an animal model of depression, have reduced number and size of hypothalamic cells expressing Hcrt-immunoractivity compared to the parent, Wistar (WIS) strain, suggesting the possibility that the depressive-like attributes of the WKY rat may be determined by this relative reduction in Hcrt cells [Allard, J.S., Tizabi, Y., Shaffery, J.P., Trouth, C.O., Manaye, K., 2004. Stereological analysis of the hypothalamic hypocretin/orexin neurons in an animal model of depression. Neuropeptides 38, 311-315]. In this study, we sought to test the hypothesis that REMSD would result in a greater increase in the number and/or size of hypothalamic, Hcrt-immunoreactive (Hcrt-ir) neurons in WKY, compared to WIS rats. The effect of REMSD, using the multiple-small-platforms-over-water (SPRD) method, on size and number of Hcrt-ir cells were compared within and across strains of rats that experienced multiple-large-platforms-over-water (LPC) as well as to those in a normal, home-cage-control (CC) setting. In accord with previous findings, the number of Hcrt-ir cells was larger in all three WIS groups compared to the respective WKY groups. REMSD produced a 20% increase (p<0.02) in the number of hypothalamic Hcrt-ir neurons in WKY rats compared to cage control WKY (WKY-CC) animals. However, an unexpected higher increase in number of Hcrt-ir cells was also observed in the WKY-LPC group compared to both WKY-CC (31%, p<0.001) and WKY-SPRD (20%, p<0.002) rats. A similar, smaller, but non-significant, pattern of change was noted in WIS-LPC group. Overall the data indicate a differential response to environmental manipulations where WKY rats appear to be more reactive than WIS rats. Moreover, the findings do not support direct antidepressant-like activity for REMSD on hypothalamic Hcrt neurons in WKY rats.