Chronic treatment with imipramine reverses immobility behaviour, hippocampal corticosteroid receptors and cortical 5-HT1A receptor mRNA in prenatally stressed rats

CaMKIV-Mediated Phosphorylation Inactivates Freud-1/CC2D1A Repression for Calcium-Dependent 5-HT1A Receptor Gene Induction

Calcium calmodulin-dependent protein kinase (CaMK) mediates calcium-induced neural gene activation. CaMK also inhibits the non-syndromic intellectual disability gene, Freud-1/CC2D1A, a transcriptional repressor of human serotonin-1A (5-HT1A) and dopamine-D2 receptor genes. The altered expression of these Freud-1-regulated genes is implicated in mental illnesses such as major depression and schizophrenia. We hypothesized that Freud-1 is blocked by CaMK-induced phosphorylation. The incubation of purified Freud-1 with either CaMKIIα or CaMKIV increased Freud-1 phosphorylation that was partly prevented in Freud-1-Ser644Ala and Freud-1-Thr780Ala CaMK site mutants. In human SK-N-SH neuroblastoma cells, active CaMKIV induced the serine and threonine phosphorylation of Freud-1, and specifically increased Freud-1-Thr780 phosphorylation in transfected HEK-293 cells. The activation of purified CaMKIIα or CaMKIV reduced Freud-1 binding to its DNA element on the 5-HT1A and dopamine-D2 receptor genes. In SK-N-SH cells, active CaMKIV but not CaMKIIα blocked the Freud-1 repressor activity, while Freud-1 Ser644Ala, Thr780Ala or dual mutants were resistant to inhibition by activated CaMKIV or calcium mobilization. These results indicate that the Freud-1 repressor activity is blocked by CaMKIV-induced phosphorylation at Thr780, resulting in the up-regulation of the target genes, such as the 5-HT1A receptor gene. The CaMKIV-mediated inhibition of Freud-1 provides a novel de-repression mechanism to induce 5-HT1A receptor expression for the regulation of cognitive development, behavior and antidepressant response.

Chronic Piromelatine Treatment Alleviates Anxiety, Depressive Responses and Abnormal Hypothalamic-Pituitary-Adrenal Axis Activity in Prenatally Stressed Male and Female Rats

The prenatal stress (PNS) model in rodents can induce different abnormal responses that replicate the pathophysiology of depression. We applied this model to evaluate the efficacy of piromelatine (Pir), a novel melatonin analog developed for the treatment of insomnia, in male and female offspring. Adult PNS rats from both sexes showed comparable disturbance associated with high levels of anxiety and depressive responses. Both males and females with PNS demonstrated impaired feedback inhibition of the hypothalamic-pituitary-adrenal (HPA) axis compared to the intact offspring and increased glucocorticoid receptors in the hippocampus. However, opposite to female offspring, the male PNS rats showed an increased expression of mineralocorticoid receptors in the hippocampus. Piromelatine (20 mg/kg, i.p., for 21 days injected from postnatal day 60) attenuated the high anxiety level tested in the open field, elevated plus-maze and light-dark test, and depressive-like behavior in the sucrose preference and the forced swimming tests in a sex-specific manner. The drug reversed to control level stress-induced increase of plasma corticosterone 120 min later in both sexes. Piromelatine also corrected to control level the PNS-induced alterations of corticosteroid receptors only in male offspring. Our findings suggest that the piromelatine treatment exerts beneficial effects on impaired behavioral responses and dysregulated HPA axis in both sexes, while it corrects the PNS-induced changes in the hippocampal corticosteroid receptors only in male offspring.

Orexin A injection into the ventral medial prefrontal cortex induces antidepressant-like effects: Possible involvement of local Orexin-1 and Trk receptors

RATIONALE

Reduced levels of orexin-A (OXA) in the central nervous system (CNS) have been associated with the pathophysiology of depression and its exogenous administration promotes antidepressant-like effect. The mechanisms associated with these effects are, however, not yet known. Herein, we investigated the hypothesis that OXA effects could be associated with orexin 1 receptor (OX1R) and tyrosine receptor kinase B (TrkB) activation, in the ventromedial prefrontal cortex (vmPFC), a brain region that is central to depression neurobiology.

OBJECTIVES

1. To Investigate the effects induced by OXA administration into the vmPFC; 2. Evaluate the participation of OX1R and TrkB in behavioral responses induced by OXA.

METHODS

Male Wistar rats received intra-vmPFC injections of OXA (10, 50 and 100 pmol/0.2 μL) and were exposed to the forced swimming test (FST) or the open field test (OFT). Independent groups received an intra-vmPFC injection of SB334867 (OX1R antagonist, 10 nmol/0.2 μL) or K252a (non-selective Trk antagonist, 10 pmol/0.2 μL), before local injection of OXA, and were exposed to the same tests.

RESULTS

OXA injection (100 pmol/0.2 μL) into the vmPFC induced antidepressant-like effect, which was prevented by SB334867 and K252a pretreatments.

CONCLUSION

OXA signaling in the vmPFC induces antidepressant-like effect in the FST which is dependent on OX1R and Trk receptors.

Maternal stressors and the developmental origins of neuropsychiatric risk

The maternal environment during pregnancy is critical for fetal development and perinatal perturbations can prime offspring disease risk. Here, we briefly review evidence linking two well-characterized maternal stressors - psychosocial stress and infection - to increased neuropsychiatric risk in offspring. In the current climate of increasing obesity and globalization of the Western-style diet, maternal overnutrition emerges as a pressing public health concern. We focus our attention on recent epidemiological and animal model evidence showing that, like psychosocial stress and infection, maternal overnutrition can also increase offspring neuropsychiatric risk. Using lessons learned from the psychosocial stress and infection literature, we discuss how altered maternal and placental physiology in the setting of overnutrition may contribute to abnormal fetal development and resulting neuropsychiatric outcomes. A better understanding of converging pathophysiological pathways shared between stressors may enable development of interventions against neuropsychiatric illnesses that may be beneficial across stressors.

Prenatal stress promotes icv-STZ-induced sporadic Alzheimer's pathology through central insulin signaling change

AIM

Insulin resistance and neuroinflammation play roles in Alzheimer's (AD) etiology. Insulin receptors (IR) are developmentally expressed in neurons as well as astrocytes. Moreover, prolonged stress can induce brain insulin resistance and astrogliosis. Also, prenatal stress could advance AD-related abnormalities in a transgenic model of AD. Besides, postnatal maternal care (PMC) has antagonistic effects on prenatal stress (PS)-induced neuronal and immunological malfunctions. Using an icv-STZ subclinical model of sAD, we assessed PS and/or abnormal PMC impacts on advancing sAD-like pathology in adult male rats. We also sought astrocyte- and/or neuron-oriented change in central insulin programming.

MAIN METHODS

Pregnant rats were exposed to PS. Thereafter, a group of pups was fostered onto unstressed mothers and the others remained intact. Real-time RT-PCR- for hippocampal IR, Tau, and ChAT transcripts- and immunohistochemistry analysis- for GFAP⁺ astrocytes- were performed at the first- and forth-postnatal-week, respectively. The other animals received icv-STZ0.5 mg/kg in adulthood and subjected to cognitive tests, molecular, and histological experiments at appropriate time-point post-injection.

KEY FINDINGS

PS could advance sAD-related symptoms in icv-STZ-treated animals. PS changed expression levels of hippocampal IR in one-week-old and 5.5-month-old offspring. PS could worsen cognitive, molecular and histological impairments of icv-STZ. Adequate PMC prevented some destructive effects of PS.

SIGNIFICANCE

PS can potentially change central insulin programming and induce long-lasting astrogliosis in rat hippocampus. PS-related cognitive and histological pathologies can rescue by PMC probably via IR-dependent pathways. Astrocyte involvement in AD-like neuropathology observed in stressed-animals needs more detailed investigations.

Role of Chronic Administration of Antidepressant Drugs in the Prenatal Stress-Evoked Inflammatory Response in the Brain of Adult Offspring Rats: Involvement of the NLRP3 Inflammasome-Related Pathway

Evidence indicates that adverse experiences in early life may be a factor for immune disturbances leading to the depression in adulthood. Recently, a pivotal role in the pathogenesis of depression has been assigned to the activation of the brain Nod-like receptor pyrin-containing 3 (NLRP3) inflammasome. We investigated the impact of chronic treatment with antidepressant drugs on the behavioral disturbances and the levels of proinflammatory factors in the hippocampus and frontal cortex of adult male rats after prenatal stress exposure. Next, we explored the involvement of the NLRP3 inflammasome-related pathways in the mechanism of antidepressant action. Our study confirmed that chronic antidepressant treatment attenuated depression-like disturbances and exerted an anxiolytic action. All antidepressants diminished the prenatal stress-induced increase in IL-1β in both brain areas, while IL-18 only in the hippocampus. Moreover, tianeptine administration diminished the increase in CCR2 levels in both brain areas, while in the hippocampus, tianeptine, along with venlafaxine CCL2 and iNOS levels. Next, we observed that in the hippocampus, tianeptine and fluoxetine suppressed upregulation of TLR4. Furthermore, venlafaxine suppressed NFкB p65-subunit phosphorylation, while fluoxetine enhanced the IкB level. Importantly, in the hippocampus, all antidepressants normalized evoked by stress changes in caspase-1 level, while tianeptine and venlafaxine also affect the levels of ASC and NLRP3 subunits. Our results provide new evidence that chronic administration of antidepressants exerts anti-inflammatory effects more pronounced in the hippocampus, through suppression of the NLRP3 inflammasome activation. These effects are accompanied by an improvement in the behavioral dysfunctions evoked by prenatal stress.

Inhibition of acid-sensing ion channels reduces the hypothalamus-pituitary-adrenal axis activity and ameliorates depression-like behavior in rats

Depression is the leading cause of disability worldwide, and its treatment represents a major clinical challenge. The hypothalamus–pituitary–adrenal (HPA) axis has been known to play a crucial role in depression and serves as a target for antidepressants. Acid-sensing ion channels (ASICs) are widely expressed in the nervous system and may be implicated in depression. Whether ASICs could act on the HPA axis to affect depression-related behaviors is not fully understood. In this study, we investigated the effect of inhibition of ASICs on the HPA axis activity in chronic stress-subjected rats. We found that treatment with the ASIC selective antagonist amiloride reversed chronic stress-induced elevation of adrenocorticotropic hormone (ACTH) and corticosterone in serum, which is reflective of the HPA axis activity. In addition, amiloride also alleviated chronic stress-induced anhedonia-like behavior. These results suggest that inhibition of ASICs may act on the HPA axis to alleviate the symptoms of depression.

Depression is the leading cause of disability worldwide, and its treatment represents a major clinical challenge.

Potassium 2-(1-hydroxypentyl)-benzoate improves depressive-like behaviors in rat model

Potassium 2-(1-hydroxypentyl)-benzoate (PHPB) is a novel drug candidate for acute ischemic stroke. PHPB has been also shown to be beneficial for some neurodegenerative diseases. In this study, we demonstrated that PHPB improved depressive-like behaviors induced by chronic unpredictable mild stress (CUMS) in rats. Male SD rats were subjected to the stress for five weeks. PHPB (30 and 100 mg/kg) or fluoxetine (FLX 10 mg/kg, as positive control) was administered orally from the third week in CUMS procedure. The behavioral tests were applied and then the biochemical studies were carried out. PHPB or FLX treatment rescued the behavioral deficiency in CUMS-exposed rats. Meanwhile, PHPB normalized the enhanced level of serum corticosterone, improved hippocampal and serum BDNF levels, as well as p-CREB level in hippocampus. In addition, PHPB could reverse the reduced level of extracellular 5-HT and its metabolite 5-HIAA in prefrontal cortex (PFC) of depressed rats. In summary, our results showed that PHPB improved depression-like behaviors in CUMS-exposed rats. The mechanisms might relate to the reverse of neurotrophic disturbance in the brain, reducing excessive HPA axis response and facilitating the release of 5-HT.

The reduced level of growth factors in an animal model of depression is accompanied by regulated necrosis in the frontal cortex but not in the hippocampus

In the present study, we asked if the different types of stress alter neuronal plasticity markers distinctively in the frontal cortex (FCx) and in the hippocampus (Hp). To do so, we implemented various stress regimens to analyze changes evoked in these rat brain structures. We utilized several molecular techniques, including western blot, ELISA, quantitative RT-PCR, and various biochemical assays, to examine a range of proteins and subjected rats to behavioral tests to evaluate potential maladaptive alterations. A decrease in the level of growth factors in the FCx was accompanied by changes suggesting damage of this structure in the manner of regulated necrosis, while the Hp appeared to be protected. The observed changes in the brain region-specific alterations in neurotrophin processing may also depend on the period of life, in which an animal experiences stress and the duration of the stressful stimuli. We conclude that chronic stress during pregnancy can result in serious alterations in the functioning of the FCx of the progeny, facilitating the development of depressive behavior later in life. We also suggest that the altered energy metabolism may redirect pro-NGF/p75^NTR/ATF2 signaling in the cortical neurons towards cellular death resembling regulated necrosis, rather than apoptosis.

Reduced maternal behavior caused by gestational stress is predictive of life span changes in risk-taking behavior and gene expression due to altering of the stress/anti-stress balance

Exposure of the mother to adverse events during pregnancy is known to induce pathological programming of the HPA axis in the progeny, thereby increasing the vulnerability to neurobehavioral disorders. Maternal care plays a crucial role in the programming of the offspring, and oxytocin plays a key role in mother/pup interaction. Therefore, we investigated whether positive modulation of maternal behavior by activation of the oxytocinergic system could reverse the long-term alterations induced by perinatal stress (PRS; gestational restraint stress 3 times/day during the last ten days of gestation) on HPA axis activity, risk-taking behavior in the elevated-plus maze, hippocampal mGlu5 receptor and gene expression in Sprague-Dawley rats. Stressed and control unstressed dams were treated during the first postpartum week with an oxytocin receptor agonist, carbetocin (1 mg/kg, i.p.). Remarkably, reduction of maternal behavior was predictive of behavioral disturbances in PRS rats as well as of the impairment of the oxytocin and its receptor gene expression. Postpartum carbetocin corrected the reduction of maternal behavior induced by gestational stress as well as the impaired oxytocinergic system in the PRS progeny, which was associated with reduced risk-taking behavior. Moreover, postpartum carbetocin had an anti-stress effect on HPA axis activity in the adult PRS progeny and increased hippocampal mGlu5 receptor expression in aging. In conclusion, the activation of the oxytocinergic system in the early life plays a protective role against the programming effect by adverse experiences and could be considered as a novel and powerful potential therapeutic target for stress-related disorders.

Garcinia mangostana Linn displays antidepressant-like and pro-cognitive effects in a genetic animal model of depression: a bio-behavioral study in the Flinders Sensitive Line rat

There is abundant evidence for both disorganized redox balance and cognitive deficits in major depressive disorder (MDD). Garcinia mangostana Linn (GM) has anti-oxidant activity. We studied the antidepressant-like and pro-cognitive effects of raw GM rind in Flinders Sensitive Line (FSL) rats, a genetic model of depression, following acute and chronic treatment compared to a reference antidepressant, imipramine (IMI). The chemical composition of the GM extract was analysed for levels of α- and γ-mangostin. The acute dose-dependent effects of GM (50, 150 and 200 mg/kg po), IMI (20 mg/kg po) and vehicle were determined in the forced swim test (FST) in FSL rats, versus Flinders Resistant Line (FRL) control rats. Locomotor testing was conducted using the open field test (OFT). Using the most effective dose above coupled with behavioral testing in the FST and cognitive assessment in the novel object recognition test (nORT), a fixed dose 14-day treatment study of GM was performed and compared to IMI- (20 mg/kg/day) and vehicle-treated animals. Chronic treated animals were also assessed with respect to frontal cortex and hippocampal monoamine levels and accumulation of malondialdehyde. FSL rats showed significant cognitive deficits and depressive-like behavior, with disordered cortico-hippocampal 5-hydroxyindole acetic acid (5-HIAA) and noradrenaline (NA), as well as elevated hippocampal lipid peroxidation. Acute and chronic IMI treatment evoked pronounced antidepressant-like effects. Raw GM extract contained 117 mg/g and 11 mg/g α- and γ-mangostin, respectively, with acute GM demonstrating antidepressant-like effects at 50 mg/kg/day. Chronic GM (50 mg/kg/d) displayed significant antidepressant- and pro-cognitive effects, while demonstrating parity with IMI. Both behavioral and monoamine assessments suggest a more prominent serotonergic action for GM as opposed to a noradrenergic action for IMI, while both IMI and GM reversed hippocampal lipid peroxidation in FSL animals. Concluding, FSL rats present with cognitive deficits and depressive-like behaviors that are reversed by acute and chronic GM treatment, similar to that of IMI.

The α2C-adrenoceptor antagonist, ORM-10921, exerts antidepressant-like effects in the Flinders Sensitive Line rat

Depression involves deficits in monoaminergic neurotransmission. Differential roles for α2A, B and C subtypes of the α2-adrenoceptor (AR) are evident, with selective α2C-AR antagonists purported to have antidepressant and procognitive properties. However, this has not been demonstrated in a genetic animal model of depression. The role of the α2C-AR in modulating two key depression-related behaviours in the Flinders Sensitive Line (FSL) rat was studied using a dose-response analysis following subcutaneous administration with the selective α2C-AR antagonist ORM-10921 (0.03; 0.3 mg/kg), the nonselective α2-AR antagonist idazoxan (3 mg/kg), or vehicle once daily for 14 days. Behaviour in the novel object recognition test, forced swim test (FST) and locomotor activity test was assessed. To ratify the validity of the FSL model, the reference tricyclic antidepressant imipramine (15 mg/kg, intraperitoneally) was used as a comparator drug in the FST. FSL rats demonstrated significantly increased immobility and recognition memory deficits versus Flinders Resistant Line controls, with imipramine significantly reversing said immobility. Similarly, ORM-10921 at both doses but not idazoxan significantly reversed immobility in the FST as well as attenuated cognitive deficits in FSL animals. We conclude that selective α2C-AR antagonism has potential as a novel therapeutic strategy in the treatment of depression and cognitive dysfunction.

YL-0919, a dual 5-HT1A partial agonist and SSRI, produces antidepressant- and anxiolytic-like effects in rats subjected to chronic unpredictable stress

YL-0919 has been identified as a novel dual 5-HT_1A partial agonist and serotonin reuptake inhibitor. In the current study, we demonstrated that YL-0919 produced prominent antidepressant-like and anxiolytic-like effects in a chronic unpredictable stress (CUS) rat model. Male SD rats were exposed to CUS for 5 weeks; YL-0919 (1.25 and 2.5 mg/kg) or a positive control fluoxetine (Flx, 10 mg/kg) was orally administered daily. YL-0919 or Flx treatment significantly increased the sucrose preference rate, the locomotor activity in an open field test (OFT), the latency to feed in a novelty-suppressed feeding test (NSFT), and both the percentage of time spent in the open arms and the number of entries into the open arms in an elevated plus-maze test. YL-0919 or Flx treatment significantly suppressed the serum levels of ACTH and corticosterone in CUS-exposed rats. Additionally, YL-0919 or Flx treatment significantly enhanced the levels of cAMP, the expression of phosphorylated cAMP response element-binding protein (pCREB) and brain-derived neurotrophic factor (BDNF) in the hippocampus of CUS-exposed rats. Similar to Flx, YL-0919 treatment significantly enhanced the dendritic complexity, and increased the number of dendritic nodes as well as the spine length and number of branch nodes in the hippocampal pyramidal neurons of CUS-exposed rats. Overall, our results reveal that YL-0919 suppresses the HPA axis and exerts antidepressant-like and anxiolytic-like effects in CUS-exposed rats, which are associated with the enhanced cAMP signaling and hippocampal dendritic complexity.

Perinatal inflammation and adult psychopathology: From preclinical models to humans

Perinatal environment plays a crucial role in brain development and determines its function through life. Epidemiological studies and clinical reports link perinatal exposure to infection and/or immune activation to various psychiatric disorders. In addition, accumulating evidence from animal models shows that perinatal inflammation can affect various behaviors relevant to psychiatric disorders such as schizophrenia, autism, anxiety and depression. Remarkably, the effects on behavior and brain function do not always depend on the type of inflammatory stimulus or the perinatal age targeted, so diverse inflammatory events can have similar consequences on the brain. Moreover, other perinatal environmental factors that affect behavior (e.g. diet and stress) also elicit inflammatory responses. Understanding the interplay between perinatal environment and inflammation on brain development is required to identify the mechanisms through which perinatal inflammation affect brain function in the adult animal. Evidence for the role of the peripheral immune system and glia on perinatal programming of behavior is discussed in this review, along with recent evidence for the role of epigenetic mechanisms affecting gene expression in the brain.

Convergence of glycogen synthase kinase 3β and GR signaling in response to fluoxetine treatment in chronically stressed female and male rats

Accumulating evidence strongly suggest that impaired glucocorticoid receptor (GR) signaling is involved in stress-related mood disorders, and nominate GR as a potential target for antidepressants (ADs). It is known that different classes of ADs affects the GR action via modifying its phosphorylation, while the mechanism through which ADs alter GR phosphorylation targeted by GSK3β, a kinase modulated via serotonin neurotransmission, are unclear. On this basis, we investigated whether GSK3β-GR signaling could be a convergence point of fluoxetine action on brain function and behavior, by examining its effect on GSK3β targeted-GR phosphorylation on threonine 171 (pGR171), and expression of GR-regulated genes in the hippocampus of female and male rats exposed to chronic isolation stress. Stress induced sex-specific GSK3β-targeted phosphorylation of pGR171 in the nucleus of the hippocampus of stressed animals. Namely, while in females stress triggered coupled action of GSK3β-pGR171 signaling, in males changes in pGR171 levels did not correspond to GSK3β activity. On the other hand, fluoxetine managed to up-regulate this pathway in sex-unbiased manner. Furthermore, fluoxetine reverted stress-induced changes in most of the analyzed genes in males, CRH, 5-HT1a and p11, while in females its effect was limited to CRH. These data further suggest that pGR171 signaling affects cellular localization of GR in response to chronic stress and fluoxetine in both sexes. Collectively, our results describe a novel convergence point between GR signaling and GSK3β pathway in rat hippocampus in response to stress and fluoxetine in both sexes and its involvement in fluoxetine-regulated brain function in males.

HPA Axis Interactions with Behavioral Systems

Perhaps the most salient behaviors that individuals engage in involve the avoidance of aversive experiences and the pursuit of pleasurable experiences. Engagement in these behaviors is regulated to a significant extent by an individual's hormonal milieu. For example, glucocorticoid hormones are produced by the hypothalamic-pituitary-adrenocortical (HPA) axis, and influence most aspects of behavior. In turn, many behaviors can influence HPA axis activity. These bidirectional interactions not only coordinate an individual's physiological and behavioral states to each other, but can also tune them to environmental conditions thereby optimizing survival. The present review details the influence of the HPA axis on many types of behavior, including appetitively-motivated behaviors (e.g., food intake and drug use), aversively-motivated behaviors (e.g., anxiety-related and depressive-like) and cognitive behaviors (e.g., learning and memory). Conversely, the manuscript also describes how engaging in various behaviors influences HPA axis activity. Our current understanding of the neuronal and/or hormonal mechanisms that underlie these interactions is also summarized. © 2016 American Physiological Society. Compr Physiol 6:1897-1934, 2016.

Early-life experiences and the development of adult diseases with a focus on mental illness: The Human Birth Theory

In mammals, early adverse experiences, including mother-pup interactions, shape the response of an individual to chronic stress or to stress-related diseases during adult life. This has led to the elaboration of the theory of the developmental origins of health and disease, in particular adult diseases such as cardiovascular and metabolic disorders. In addition, in humans, as stated by Massimo Fagioli's Human Birth Theory, birth is healthy and equal for all individuals, so that mental illness develop exclusively in the postnatal period because of the quality of the relationship in the first year of life. Thus, this review focuses on the importance of programming during the early developmental period on the manifestation of adult diseases in both animal models and humans. Considering the obvious differences between animals and humans we cannot systematically move from animal models to humans. Consequently, in the first part of this review, we will discuss how animal models can be used to dissect the influence of adverse events occurring during the prenatal and postnatal periods on the developmental trajectories of the offspring, and in the second part, we will discuss the role of postnatal critical periods on the development of mental diseases in humans. Epigenetic mechanisms that cause reversible modifications in gene expression, driving the development of a pathological phenotype in response to a negative early postnatal environment, may lie at the core of this programming, thereby providing potential new therapeutic targets. The concept of the Human Birth Theory leads to a comprehension of the mental illness as a pathology of the human relationship immediately after birth and during the first year of life.

Pro-apoptotic Action of Corticosterone in Hippocampal Organotypic Cultures

Elevated levels of glucocorticoids exert neurotoxic effects, and the hippocampus is particularly sensitive to the effects of glucocorticoids. Because some data have indicated that an increased action of glucocorticoids in the perinatal period enhances the susceptibility of brain tissue to adverse substances later in life, the main purpose of the present study was to compare necrotic/apoptotic corticosterone action in hippocampal organotypic cultures obtained from control animals with the effect of this steroid in tissue from prenatally stressed rats. Because the adverse effects of glucocorticoid action on nerve cell viability appear to result mainly from an increase in the intensity of the effects of glutamate and changes in growth factor and pro-inflammatory cytokine synthesis, the involvement of these factors in corticosterone action were also determined. In stress-like concentration (1 μM), corticosterone, when added to hippocampal cultures for 1 and 3 days, alone or jointly with glutamate, did not induce necrosis. In contrast, in 3-day cultures, corticosterone (1 μM) increased caspase-3 activity and the mRNA expression of the pro-apoptotic Bax. Moreover, corticosterone’s effect on caspase-3 activity was stronger in hippocampal cultures from prenatally stressed compared to control rats. Additionally, 24 h of exposure to corticosterone and glutamate, when applied separately and together, increased Bdnf, Ngf, and Tnf-α expression. In contrast, after 72 h, a strong decrease in the expression of both growth factors was observed, while the expression of TNF-α remained high. The present study showed that in stress-like concentrations, corticosterone exerted pro-apoptotic but not necrotic effects in hippocampal organotypic cultures. Prenatal stress increased the pro-apoptotic effects of corticosterone. Increased synthesis of the pro-inflammatory cytokine TNF-α may be connected with the adverse effects of corticosterone on brain cell viability.

Altered monoamine system activities after prenatal and adult stress: A role for stress resilience?

INTRODUCTION

Prenatal stress (PNS) and stress in adulthood are risk factors for development of major depressive disorder. The present study aimed to 1) confirm previous neuroendocrine and behavioral changes induced by PNS, and 2) to characterize the effect of early- and late life stress on the in vivo activity of monoamine systems.

METHODS

Gestational dams were restrained thrice daily under bright illumination from gestational day (GD)11-20. Behavior and neuroendocrine responses to the forced swim test (FST) were determined in adult (50-80 days) offspring, and electrophysiological single unit recordings of dorsal raphe nucleus serotonin (5-HT), ventral tegmental area dopamine (DA) and locus coeruleus norepinephrine (NE) neurons were obtained at baseline and 24h after the FST.

RESULTS

Gestational dams did not habituate to chronic restraint stress, and PNS reduced the birth weight of offspring. In adulthood, swim stress elevated CORT levels longer in PNS animals, while it had no effect on swim behaviors. Baseline firing activity of 5-HT neurons was decreased in PNS animals, while the firing activity of NE and DA neurons was increased. Swim stress had no effect on the firing on 5-HT neurons, but normalized the firing activity of catecholamine neurons in PNS animals.

CONCLUSION

The present data confirm previously established effects on neuroendocrine and physiological measures, and demonstrate an altering effect of PNS and stress on monoamine system activities in adulthood. Since PNS did not result in a depressive-like phenotype, these central changes following PNS might play reflect adaptive changes contributing to stress resilience in adulthood.

[Early life stressful experiences and neuropsychiatric vulnerability: evidences from human and animal models]

The human newborn is highly dependent on parental care for its survival but also for the healthy development of its brain. A large body of literature demonstrates the impact of early life adversity, even during the prenatal period, on the adult's health. The susceptibility to neuropsychiatric diseases is often potentiated by early stress. If there is an agreement that a critical developmental period exists, the mechanisms underlying the long term effects of early life adversity are still poorly understood. Recent studies in animals highlight the involvement of epigenetic processes in the transmission of such vulnerabilities, notably via modifications in germ cells, which can be transmitted in the next generations.

The Beneficial Impact of Antidepressant Drugs on Prenatal Stress-Evoked Malfunction of the Insulin-Like Growth Factor-1 (IGF-1) Protein Family in the Olfactory Bulbs of Adult Rats

Insulin-like growth factor-1 (IGF-1) promotes the growth, differentiation, and survival of both neurons and glial cells, and it is believed to exert antidepressant-like activity. Thus, disturbances in the IGF-1 system could be responsible for the course of depression. To date, there have been no papers showing the impact of chronic antidepressant treatment on the IGF-1 network in the olfactory bulb (OB) in an animal model of depression. Prenatal stress was used as model of depression. Twenty-four 3-month-old male offspring of control and stressed mothers were subjected to behavioral testing (forced swim test). The mRNA expression of IGF-1 and IGF-1 receptor (IGF-1R) and the protein level of IGF-1 and its phosphorylation, as well as the concentrations of IGF-binding proteins (IGFBP-2, -4, -3, and -6), were measured in OBs before and after chronic imipramine, fluoxetine, or tianeptine administration. Adult rats exposed prenatally to stressful stimuli displayed not only depression-like behavior but also decreased IGF-1 expression, dysregulation in the IGFBP network, and diminished mRNA expression, as well as IGF-1R phosphorylation, in the OB. The administration of antidepressants normalized most of the changes in the IGF-1 system of the OB evoked by prenatal stress. These results suggested a beneficial effect of chronic antidepressant drug treatment in the alleviation of IGF-1 family malfunction in OBs in an animal model of depression.

Prenatal stress induces vulnerability to nicotine addiction and alters D2 receptors' expression in the nucleus accumbens in adult rats

Prenatal stress (PS) can induce several long-lasting behavioral and molecular abnormalities in rats. It can also be considered as a risk factor for many psychiatric diseases like schizophrenia, depression or PTSD and predispose to addiction. In this study, we investigated the effect of prenatal stress on the reinforcing properties of nicotine in the CPP paradigm. Then, we examined the mRNA expression of the D2 dopaminergic receptors using the quantitative real-time PCR technique in the nucleus accumbens (NAcc). We found that prenatally stressed rats exhibited a greater place preference for the nicotine-paired compartment than the control rats. Moreover, we observed an overexpression of the DRD2 gene in adult offspring stressed in utero and a downregulation in the PS NIC group (PS rats treated with nicotine) compared with their control counterparts (C NIC). These data suggest that maternal stress can permanently alter the offspring's addictive behavior and D2 receptors' expression.

Sex dependent reduction by prenatal stress of the expression of 5HT1A receptors in the prefrontal cortex and CRF type 2 receptors in the raphe nucleus in rats: reversal by citalopram

RATIONALE

Alterations in the serotonergic transmission and activity of corticotropin-releasing factor (CRF) family may underlie anxiety and depressive disorders. These could be corrected by treatment with SSRIs.

OBJECTIVES

The objective of the current study is to determine whether the increased anxiety of prenatally stressed (PS) rats of both sexes is associated with changes in 5HT1A and CRF type 2 receptors (5HT1AR and CRFR2) in the prefrontal cortex (PFC)-dorsal raphe nuclei (DRN) axis, and how these are affected by chronic treatment with citalopram (10 mg/kg/day). We focussed on GABAergic cells that co-express parvalbumin and/or neuropeptide Y, and 5HT1AR in the medial prefrontal cortex (mPFC) and on cells that express 5HT, parvalbumin, 5HT1AR or CRFR2 in the DRN.

RESULTS

Immunohistochemistry with fluorescent antibodies demonstrated sex differences in the expression of 5HT1AR and CRFR2 protein. Prenatal stress selectively reduced the expression of 5HT1AR on GABAergic cells in the mPFC in males and that of CRFR2 in the DRN of females. Citalopram treatment for 5 weeks abolished the increase in anxiety in both sexes, restored the intensity of expression of 5HT1AR in the mPFC in males and increased their expression in the mPFC and DRN in females. Citalopram reduced CRFR2 expression in control and PS males but increased it in PS females.

CONCLUSIONS

Male and female rats show differences in the expression of 5HT1AR and CRFR2 protein that are selectively reduced by prenatal stress. Reversal by citalopram of the changes in the expression of these receptors induced by prenatal stress support their role in the aetiology of anxiety.

Brain glucose metabolism in an animal model of depression

An increasing number of data support the involvement of disturbances in glucose metabolism in the pathogenesis of depression. We previously reported that glucose and glycogen concentrations in brain structures important for depression are higher in a prenatal stress model of depression when compared with control animals. A marked rise in the concentrations of these carbohydrates and glucose transporters were evident in prenatally stressed animals subjected to acute stress and glucose loading in adulthood. To determine whether elevated levels of brain glucose are associated with a change in its metabolism in this model, we assessed key glycolytic enzymes (hexokinase, phosphofructokinase and pyruvate kinase), products of glycolysis, i.e., pyruvate and lactate, and two selected enzymes of the tricarboxylic acid cycle (pyruvate dehydrogenase and α-ketoglutarate dehydrogenase) in the hippocampus and frontal cortex. Additionally, we assessed glucose-6-phosphate dehydrogenase activity, a key enzyme in the pentose phosphate pathway (PPP). Prenatal stress increased the levels of phosphofructokinase, an important glycolytic enzyme, in the hippocampus and frontal cortex. However, prenatal stress had no effect on hexokinase or pyruvate kinase levels. The lactate concentration was elevated in prenatally stressed rats in the frontal cortex, and pyruvate levels remained unchanged. Among the tricarboxylic acid cycle enzymes, prenatal stress decreased the level of pyruvate dehydrogenase in the hippocampus, but it had no effect on α-ketoglutarate dehydrogenase. Like in the case of glucose and its transporters, also in the present study, differences in markers of glucose metabolism between control animals and those subjected to prenatal stress were not observed under basal conditions but in rats subjected to acute stress and glucose load in adulthood. Glucose-6-phosphate dehydrogenase activity was not reduced by prenatal stress but was found to be even higher in animals exposed to all experimental conditions, i.e., prenatal stress, acute stress, and glucose administration. Our data indicate that glycolysis is increased and the Krebs cycle is decreased in the brain of a prenatal stress animal model of depression.

Maternal restraint stress during pregnancy in mice induces 11β-HSD1-associated metabolic changes in the livers of the offspring

In rats, maternal exposure to restraint stress during pregnancy can induce abnormalities in the cardiovascular and central nervous systems of the offspring. These effects are mediated by long-lasting hyperactivation of the hypothalamic–pituitary–adrenal axis. However, little is known about the potential effects of stress during pregnancy on metabolic systems. We examined the effect of restraint stress in pregnant mice on the liver function of their offspring. The offspring of stressed mothers showed significantly higher lipid accumulation in the liver after weaning than did the controls; this accumulation was associated with increased expression of lipid metabolism-related proteins such as alanine aminotransferase 2 diglyceride acyltransferase 1, peroxisome proliferator-activated receptor gamma and glucocorticoid receptor. Additionally, we observed increased levels of 11β-hydroxysteroid dehydrogenase type 1, an intercellular mediator that converts glucocorticoid from the inactive to the active form, in the foetal and postnatal periods. These results indicate that restraint stress in pregnancy in mice induces metabolic abnormalities via 11β-hydroxysteroid dehydrogenase type 1-related pathways in the foetal liver. It is therefore possible that exposure to stress in pregnant women may be a risk factor for metabolic syndromes (e.g. fatty liver) in children.

Individual differences in the effects of prenatal stress exposure in rodents

Exposure to prenatal stress alters the phenotype of the offspring in adulthood. When the prenatal and adult environments do not match, these alterations may induce pathology risk. There are, however, large individual differences in the effects of prenatal stress. While some individuals seem vulnerable, others appear to be relatively resistant to its effects. In this review we discuss potential mechanisms underlying these individual differences with a focus on animal models. Differences between rodent models selected for stress coping traits are discussed. In addition, the role of circulating factors, like glucocorticoids and cytokines, factors involved in brain development and influences of epigenetic and genetic factors in prenatal stress induced phenotype are covered.

Sleep in prenatally restraint stressed rats, a model of mixed anxiety-depressive disorder

Prenatal restraint stress (PRS) can induce persisting changes in individual's development. PRS increases anxiety and depression-like behaviors and induces changes in the hypothalamo-pituitary-adrenal (HPA) axis in adult PRS rats after exposure to stress. Since adaptive capabilities also depend on temporal organization and synchronization with the external environment, we studied the effects of PRS on circadian rhythms, including the sleep-wake cycle, that are parameters altered in depression. Using a restraint stress during gestation, we showed that PRS induced phase advances in hormonal/behavioral circadian rhythms in adult rats, and an increase in the amount of paradoxical sleep, positively correlated to plasma corticosterone levels. Plasma corticosterone levels were also correlated with immobility in the forced swimming test, indicating a depressive-like profile in the PRS rats. We observed comorbidity with anxiety-like profile on PRS rats that was correlated with a reduced release of glutamate in the ventral hippocampus. Pharmacological approaches aimed at modulating glutamate release may represent a novel therapeutic strategy to treat stress-related disorders. Finally, since depressed patients exhibit changes in HPA axis activity and in circadian rhythmicity as well as in the paradoxical sleep regulation, we suggest that PRS could represent an original animal model of depression.

Changes induced by prenatal stress in behavior and brain morphology: can they be prevented or reversed?

This chapter presents a critical analysis of the behavioral alterations reported in the offspring of women exposed to stress and/or depression during pregnancy and the neurochemical and structural changes underlying them. Among the alterations attributed to prenatal stress in humans and experimental rats of both sexes is impaired regulation of the hypothalamic-pituitary-adrenal (HPA) axis, anxiety and exaggerated fear of novelty, and decreased social interaction. Learning and attention deficits are more prevalent in boys and male rats. Fear of novelty and anxiety are associated with enlargement of the amygdala and its corticotropin-releasing factor content, and decreased socialization, with lower oxytocin activity in the amygdala. Learning deficits are associated with a decrease in neurogenesis, dendritic complexity, and spine number in the dorsal hippocampus. Fostering prenatally stressed (PS) pups onto control mothers prevents the dysregulation of the HPA axis and heightened anxiety, indicating a role for postnatal factors in their etiology. By contrast, learning impairment and decreased socialization are not affected by this fostering procedure and are therefore prenatally mediated.In spite of their widespread use in depressed pregnant women, selective serotonin reuptake inhibitor (SSRI) antidepressants do not normalize the behavior of their children. When administered during gestation to stressed rats, SSRIs do not reduce anxiety or learning deficits in their offspring. Moreover, when given to unstressed mothers, SSRIs induce anxiety in the offspring. The detrimental effect of SSRIs may result from inhibition of the serotonin transporter exposing the brain to excess amounts of 5-hydroxytryptamine (5-HT) at a critical time during fetal development.

The consequences of early-life adversity: neurobiological, behavioural and epigenetic adaptations

During the perinatal period, the brain is particularly sensitive to remodelling by environmental factors. Adverse early-life experiences, such as stress exposure or suboptimal maternal care, can have long-lasting detrimental consequences for an individual. This phenomenon is often referred to as 'early-life programming' and is associated with an increased risk of disease. Typically, rodents exposed to prenatal stress or postnatal maternal deprivation display enhanced neuroendocrine responses to stress, increased levels of anxiety and depressive-like behaviours, and cognitive impairments. Some of the phenotypes observed in these models of early-life adversity are likely to share common neurobiological mechanisms. For example, there is evidence for impaired glucocorticoid negative-feedback control of the hypothalamic-pituitary-adrenal axis, altered glutamate neurotransmission and reduced hippocampal neurogenesis in both prenatally stressed rats and rats that experienced deficient maternal care. The possible mechanisms through which maternal stress during pregnancy may be transmitted to the offspring are reviewed, with special consideration given to altered maternal behaviour postpartum. We also discuss what is known about the neurobiological and epigenetic mechanisms that underpin early-life programming of the neonatal brain in the first generation and subsequent generations, with a view to abrogating programming effects and potentially identifying new therapeutic targets for the treatment of stress-related disorders and cognitive impairment.

Prenatal stress affects insulin-like growth factor-1 (IGF-1) level and IGF-1 receptor phosphorylation in the brain of adult rats

It has been shown that stressful events occurring in early life have a powerful influence on the development of the central nervous system. Insulin-like growth factor-1 (IGF-1) promotes the growth, differentiation and survival of both neurons and glial cells and is thought to exert antidepressant-like activity. Thus, it is possible that disturbances in the function of the IGF-1 system may be responsible for disturbances observed over the course of depression. Prenatal stress was used as a valid model of depression. Adult male offspring of control and stressed rat dams were subjected to behavioural testing (forced swim test). The level of IGF-1 in the blood and the expression of IGF-1, IGF-1R, and IRS-1/2 in the hippocampus and frontal cortex using RT-PCR, ELISA and western blotting were measured. In addition the effect of intracerebroventricularly administered IGF-1 and/or the IGF-1R receptor antagonist JB1 in the forced swim test was studied. Prenatally stressed rats showed depressive like behaviour, including increased immobility time as well as decreased mobility and climbing. Intracerebroventricular administration of IGF-1 reversed these effects in stressed animals, whereas concomitant administration of the IGF-1R antagonist JB1 completely blocked the effects. Biochemical analysis of homogenates from the hippocampus and frontal cortex revealed decreases in IGF-1 level and IGF-1R phosphorylation along with disturbances in IRS-1 phosphorylation. These findings reveal that prenatal stress alters IGF-1 signalling, which may contribute to the behavioural changes observed in depression.

Delayed BDNF alterations in the prefrontal cortex of rats exposed to prenatal stress: preventive effect of lurasidone treatment during adolescence

Psychiatric diseases may often represent the consequence of exposure to adverse events early in life. Accordingly, exposure to stress during gestation in rats has a strong impact on development and can cause long-term abnormalities in adult behavior. Considering that neuronal plasticity has emerged as a major vulnerability element in psychiatric disorders, we investigated the postnatal developmental profile of Brain-Derived Neurotrophic Factor expression (BDNF), an important mediator for long-term functional deterioration associated to mental illness, in male and female rats following exposure to prenatal stress (PNS). Since we found that the majority of alterations became fully manifest at early adulthood, we tried to prevent these abnormalities with an early pharmacological intervention. To address this point, we treated rats during adolescence with the multi-receptor antipsychotic lurasidone, which was proven to be effective in animal models of schizophrenia. Interestingly, we show that lurasidone treatment was able to prevent the reduction of BDNF expression in adult rats that were exposed to PNS. Collectively, our results provide further support to the notion that exposure to early life stress has a negative impact on neuronal plasticity and that pharmacological intervention during critical time windows may prove effective in preventing neuroplastic dysfunction, leading to long-term beneficial effects on brain function.

Prenatal stress leads to changes in IGF-1 binding proteins network in the hippocampus and frontal cortex of adult male rat

Depression is a mental disorder of still unknown origin. Currently, much attention is paid to the potential influence of disturbances in the functioning of neurotrophic factors on the onset of this disease. Insulin-like growth factor 1 (IGF-1) is one of the most important growth agents affecting processes that are crucial for brain development. To date, there are no data showing the impact of prenatal stress on the family of six IGF binding proteins (IGFBP 1-6) that regulate IGF-1 bioactivity. The goal of this study was to investigate whether the decreased expression of IGF-1 in the frontal cortex (FCx) and hippocampus (Hp) of adult male rats following a prenatal stress procedure is related to changes in the IGFBP family. Our results show that rats exposed prenatally to stressful stimuli displayed depression-like behavior based on sucrose preference and elevated plus maze tests. In both cases, in the adult rat brain structures that were examined after the prenatal stress procedure, the IGF-1 protein level was reduced. Moreover, we observed changes of varying degrees in the levels of IGFBPs in stressed animals. A decrease in IGFBP-2 and IGFBP-3 accompanied by an increase in the IGFBP-4 concentration in the Hp and the FCx was detected. There were no differences in IGFBP-1 and IGFBP-6 brain levels between the stressed and control animals, whereas IGFBP-5 concentration was decreased in the Hp of prenatally stressed animals. This study demonstrated that stress during pregnancy may lead not only to behavioral disturbances but also to a decrease in IGF-1 level and the dysregulation of the IGF-1 binding protein network in adult rat offspring.

The selective glucocorticoid receptor antagonist CORT 108297 decreases neuroendocrine stress responses and immobility in the forced swim test

Pre-clinical and clinical studies have employed treatment with glucocorticoid receptor (GR) antagonists in an attempt to limit the deleterious behavioral and physiological effects of excess glucocorticoids. Here, we examined the effects of GR antagonists on neuroendocrine and behavioral stress responses, using two compounds: mifepristone, a GR antagonist that is also a progesterone receptor antagonist, and CORT 108297, a specific GR antagonist lacking anti-progestin activity. Given its well-documented impact on neuroendocrine and behavioral stress responses, imipramine (tricyclic antidepressant) served as a positive control. Male rats were treated for five days with mifepristone (10mg/kg), CORT 108297 (30mg/kg and 60mg/kg), imipramine (10mg/kg) or vehicle and exposed to forced swim test (FST) or restraint stress. Relative to vehicle, imipramine potently suppressed adrenocorticotropin hormone (ACTH) responses to FST and restraint exposure. Imipramine also decreased immobility in the FST, consistent with antidepressant actions. Both doses of CORT 108297 potently suppressed peak corticosterone responses to FST and restraint stress. However, only the higher dose of CORT 108297 (60mg/kg) significantly decreased immobility in the FST. In contrast, mifepristone induced protracted secretion of corticosterone in response to both stressors, and modestly decreased immobility in the FST. Taken together, the data indicate distinct effects of each compound on neuroendocrine stress responses and also highlight dissociation between corticosterone responses and immobility in the FST. Within the context of the present study, our data suggest that CORT 108297 may be an attractive alternative for mitigating neuroendocrine and behavioral states associated with excess glucocorticoid secretion.

Prenatal stress and subsequent exposure to chronic mild stress in rats; interdependent effects on emotional behavior and the serotonergic system

Exposure to prenatal stress (PS) can predispose individuals to the development of psychopathology later in life. We examined the effects of unpredictable chronic mild stress (CMS) exposure during adolescence on a background of PS in male and female Sprague-Dawley rats. PS induced more anxiety-like behavior in the elevated zero maze in both sexes, an effect that was normalized by subsequent exposure to CMS. Moreover, PS was associated with increased depression-like behavior in the forced swim test in males only. Conversely, sucrose intake was increased in PS males, whilst being decreased in females when consecutively exposed to PS and CMS. Hypothalamo-pituitary-adrenal (HPA) axis reactivity was affected in males only, with higher stress-induced plasma corticosterone levels after PS. Markedly, CMS normalized the effects of PS on elevated zero maze behavior as well as basal and stress-induced plasma corticosterone secretion. At the neurochemical level, both PS and CMS induced various sex-specific alterations in serotonin (5-HT) and tryptophan hydroxylase 2 (TPH2) immunoreactivity in the dorsal raphe nucleus, hippocampus and prefrontal cortex with, in line with the behavioral observations, more profound effects in male offspring. In conclusion, these findings show that prenatal maternal stress in Sprague-Dawley rats induces various anxiety- and depression-related behavioral and neuroendocrine changes, as well as alterations in central 5-HT and TPH2 function, predominantly in male offspring. Moreover, CMS exposure partially normalized the effects of previous PS experience, suggesting that the outcome of developmental stress exposure largely depends on the environmental conditions later in life and vice versa.

ADN-1184 a monoaminergic ligand with 5-HT(6/7) receptor antagonist activity: pharmacological profile and potential therapeutic utility

BACKGROUND AND PURPOSE

Many dementia patients exhibit behavioural and psychological symptoms (BPSD) that include psychosis, aggressivity, depression and anxiety. Antipsychotic drugs are frequently prescribed but fail to significantly attenuate mood deficits, may interfere with cognitive function and are associated with motor and cardiac side effects, which are problematic in elderly patients. A need therefore exists for drugs that are better suited for the treatment of BPSD.

EXPERIMENTAL APPROACH

We used in vitro cellular and in vivo behavioural tests to characterize ADN-1184, a novel arylsulfonamide ligand with potential utility for treatment of BPSD.

KEY RESULTS

ADN-1184 exhibits substantial 5-HT6 /5-HT7 /5-HT2A /D2 receptor affinity and antagonist properties in vitro. In tests of antipsychotic-like activity, it reversed MK-801-induced hyperactivity and stereotypies and inhibited conditioned avoidance response (MED = 3 mg·kg(-1) i.p.). Remarkably, ADN-1184 also reduced immobility time in the forced swim test at low doses (0.3 and 1 mg·kg(-1) i.p.; higher doses were not significantly active). Notably, up to 30 mg·kg(-1) ADN-1184 did not impair memory performance in the passive avoidance test or elicit significant catalepsy and only modestly inhibited spontaneous locomotor activity (MED = 30 mg·kg(-1) i.p.).

CONCLUSIONS AND IMPLICATIONS

ADN-1184 combines antipsychotic-like with antidepressant-like properties without interfering with memory function or locomotion. This profile is better than that of commonly used atypical antipsychotics tested under the same conditions and suggests that it is feasible to identify drugs that improve BPSD, without exacerbating cognitive deficit or movement impairment, which are of particular concern in patients with dementia.

Elevated brain glucose and glycogen concentrations in an animal model of depression

INTRODUCTION

Recent data indicate that there is a link between depression and diabetes and that excess glucocorticoids may play an underlying role in the pathogenesis of both of these diseases. The aim of the present study was to determine whether there are any alterations in glucose, glycogen, glucose transporters, insulin, insulin receptors or corticosterone concentrations in the hippocampus and frontal cortex in a prenatal stress rat model of depression.

METHODS

Male rats whose mothers had been subjected to stress and control animals were subjected to the Porsolt test to verify the experimental model. Next, some of the rats were subjected to acute stress and/or were administered glucose. Glucose, glycogen, corticosterone, insulin, insulin receptor, phospho-insulin receptor and glucose transporter (GLUT1, GLUT3 and GLUT4) concentrations were assayed.

RESULTS

Prenatally stressed rats exhibited glucose and glycogen concentrations in both investigated brain structures that exceeded those of the control animals. Prenatal stress also increased the levels of glucose transporters - GLUT1 in both tissues and GLUT4 in the frontal cortex. The changes in the prenatally stressed rats were more prominent in the animals that were subjected to stress or glucose loading in adulthood.

CONCLUSION

The increase in carbohydrate brain concentrations evoked by prenatal stress may result from changes in the amounts of glucose transporters, especially GLUT1. Moreover, the obtained results support the hypothesis that stress during the perinatal period permanently increases the sensitivity of brain tissue to factors that act in adulthood. © 2014 S. Karger AG, Basel.

Vulnerability versus resilience to prenatal stress in male and female rats; implications from gene expression profiles in the hippocampus and frontal cortex

Adverse life events during pregnancy may impact upon the developing fetus, predisposing prenatally stressed offspring to the development of psychopathology. In the present study, we examined the effects of prenatal restraint stress (PS) on anxiety- and depression-related behavior in both male and female adult Sprague-Dawley rats. In addition, gene expression profiles within the hippocampus and frontal cortex (FC) were examined in order to gain more insight into the molecular mechanisms that mediate the behavioral effects of PS exposure. PS significantly increased anxiety-related behavior in male, but not female offspring. Likewise, depression-related behavior was increased in male PS rats only. Further, male PS offspring showed increased basal plasma corticosterone levels in adulthood, whereas both PS males and females had lower stress-induced corticosterone levels when compared to controls. Microarray-based profiling of the hippocampus and FC showed distinct sex-dependent changes in gene expression after PS. Biological processes and/or signal transduction cascades affected by PS included glutamatergic and GABAergic neurotransmission, mitogen-activated protein kinase (MAPK) signaling, neurotrophic factor signaling, phosphodiesterase (PDE)/ cyclic nucleotide signaling, glycogen synthase kinase 3 (GSK3) signaling, and insulin signaling. Further, the data indicated that epigenetic regulation is affected differentially in male and female PS offspring. These sex-specific alterations may, at least in part, explain the behavioral differences observed between both sexes, i.e. relative vulnerability versus resilience to PS in male versus female rats, respectively. These data reveal novel potential targets for antidepressant and mood stabilizing drug treatments including PDE inhibitors and histone deacetylase (HDAC) inhibitors.

Acute and subchronic treatments with selective serotonin reuptake inhibitors increase Nociceptin/Orphanin FQ (NOP) receptor density in the rat dorsal raphe nucleus; interactions between nociceptin/NOP system and serotonin

Nociceptin/Orphanin FQ is the endogenous ligand of NOP receptor, formerly referred to as the Opioid Receptor-Like 1 receptor. We have previously shown that NOP receptors were located on serotonergic neurons in the rat dorsal raphe nucleus, suggesting possible direct interactions between nociceptin and serotonin in this region, which is a target for antidepressant action. In the present study, we investigated further the link between Selective Serotonin Reuptake Inhibitor (SSRI) antidepressant treatments and the nociceptin/NOP receptor system. Intraperitoneal administration of the SSRI citalopram induced an increase in NOP-receptor density, measured by autoradiographic [(3)H] nociceptin binding, in the rat dorsal raphe nucleus, from the first to the 21st day of treatment. This effect was also observed with other SSRIs (sertraline, fluoxetine), but not with two tricyclic antidepressants (imipramine, clomipramine) and was abolished by pre-treatment with para-chlorophenylalanine, an inhibitor of serotonin synthesis. Using microdialysis experiments, we demonstrated that NOP-receptor activation by infusion of nociceptin 10(-6) M or 10(-5) M increased the level of extracellular serotonin in the dorsal raphe nucleus. This effect was abolished by co-infusion of the NOP-receptor antagonist UFP 101. These results confirm the existence of reciprocal interactions between serotonin and nociceptin/NOP transmissions in the dorsal raphe nucleus.

Anxiety-like behavior of prenatally stressed rats is associated with a selective reduction of glutamate release in the ventral hippocampus

Abnormalities of synaptic transmission and plasticity in the hippocampus represent an integral part of the altered programming triggered by early life stress. Prenatally restraint stressed (PRS) rats develop long-lasting biochemical and behavioral changes, which are the expression of an anxious/depressive-like phenotype. We report here that PRS rats showed a selective impairment of depolarization- or kainate-stimulated glutamate and [(3)H]d-aspartate release in the ventral hippocampus, a region encoding memories related to stress and emotions. GABA release was unaffected in PRS rats. As a consequence of reduced glutamate release, PRS rats were also highly resistant to kainate-induced seizures. Abnormalities of glutamate release were associated with large reductions in the levels of synaptic vesicle-related proteins, such as VAMP (synaptobrevin), syntaxin-1, synaptophysin, synapsin Ia/b and IIa, munc-18, and Rab3A in the ventral hippocampus of PRS rats. Anxiety-like behavior in male PRS (and control) rats was inversely related to the extent of depolarization-evoked glutamate release in the ventral hippocampus. A causal relationship between anxiety-like behavior and reduction in glutamate release was demonstrated using a mixture of the mGlu2/3 receptor antagonist, LY341495, and the GABA(B) receptor antagonist, CGP52432, which was shown to amplify depolarization-evoked [(3)H]d-aspartate release in the ventral hippocampus. Bilateral microinfusion of CGP52432 plus LY341495 in the ventral hippocampus abolished anxiety-like behavior in PRS rats. These findings indicate that an impairment of glutamate release in the ventral hippocampus is a key component of the neuroplastic program induced by PRS, and that strategies aimed at enhancing glutamate release in the ventral hippocampus correct the "anxious phenotype" caused by early life stress.

Anxiety-like behaviour and associated neurochemical and endocrinological alterations in male pups exposed to prenatal stress

Epidemiological studies suggest that emotional liability in infancy could be a predictor of anxiety-related disorders in the adulthood. Rats exposed to prenatal restraint stress ("PRS rats") represent a valuable model for the study of the interplay between environmental triggers and neurodevelopment in the pathogenesis of anxious/depressive like behaviours. Repeated episodes of restraint stress were delivered to female Sprague-Dawley rats during pregnancy and male offspring were studied. Ultrasonic vocalization (USV) was assessed in pups under different behavioural paradigms. After weaning, anxiety was measured by conventional tests. Expression of GABA(A) receptor subunits and metabotropic glutamate (mGlu) receptors was assessed by immunoblotting. Plasma leptin levels were measured using a LINCOplex bead assay kit. The offspring of stressed dams emitted more USVs in response to isolation from their mothers and showed a later suppression of USV production when exposed to an unfamiliar male odour, indicating a pronounced anxiety-like profile. Anxiety like behaviour in PRS pups persisted one day after weaning. PRS pups did not show the plasma peak in leptin levels that is otherwise seen at PND14. In addition, PRS pups showed a reduced expression of the γ2 subunit of GABA(A) receptors in the amygdala at PND14 and PND22, an increased expression of mGlu5 receptors in the amygdala at PND22, a reduced expression of mGlu5 receptors in the hippocampus at PND14 and PND22, and a reduced expression of mGlu2/3 receptors in the hippocampus at PND22. These data offer a clear-cut demonstration that the early programming triggered by PRS could be already translated into anxiety-like behaviour during early postnatal life.

Effects of swim stress and fluoxetine on 5-HT1A receptor gene expression and monoamine metabolism in the rat brain regions

Changes in gene expression of the brain serotonin (5-HT) 1A receptors may be important for the development and ameliorating depression, however identification of specific stimuli that activate or reduce the receptor transcriptional activity is far from complete. In the present study, the forced swim test (FST) exposure, the first stress session of which is already sufficient to induce behavioral despair in rats, significantly increased 5-HT1A receptor mRNA levels in the brainstem, frontal cortex, and hippocampus at 24 h. In the brainstem and frontal cortex, the elevation in the receptor gene expression after the second forced swim session was not affected following chronic administration of fluoxetine, while in the cortex, both control and FST values were significantly reduced in fluoxetine-treated rats. In contrast to untreated rats, no increase in hippocampal 5-HT1A receptor mRNA was observed in response to FST in rats chronically treated with fluoxetine. Metabolism of 5-HT (5-HIAA/5-HT) in the brainstem was significantly decreased by fluoxetine and further reduced by swim stress, showing a certain degree of independence of these changes on 5-HT1A receptor gene expression that was increased in this brain region only after the FST, but not after fluoxetine. FST exposure also decreased the brainstem dopamine metabolism, which was unexpectedly positively correlated with 5-HT1A receptor mRNA levels in the frontal cortex. Together, these data suggest that the effects of the forced swim stress as well as fluoxetine involve brain region-dependent alterations in 5-HT1A receptor gene transcription, some of which may be interrelated with concomitant changes in catecholamine metabolism.