Effect of neonatal dexamethasone exposure on growth and neurological development in the adult rat

Developmental Programming by Perinatal Glucocorticoids

Early-life environmental factors can have persistent effects on physiological functions by altering developmental procedures in various organisms. Recent experimental and epidemiological studies now further support the idea that developmental programming is also present in mammals, including humans, influencing long-term health. Although the mechanism of programming is still largely under investigation, the role of endocrine glucocorticoids in developmental programming is gaining interest. Studies found that perinatal glucocorticoids have a persistent effect on multiple functions of the body, including metabolic, behavioral, and immune functions, in adulthood. Several mechanisms have been proposed to play a role in long-term programming. In this review, recent findings on this topic are summarized and the potential biological rationale behind this phenomenon is discussed.

Hormonal Regulation of Oxidative Phosphorylation in the Brain in Health and Disease

The developing and adult brain is a target organ for the vast majority of hormones produced by the body, which are able to cross the blood–brain barrier and bind to their specific receptors on neurons and glial cells. Hormones ensure proper communication between the brain and the body by activating adaptive mechanisms necessary to withstand and react to changes in internal and external conditions by regulating neuronal and synaptic plasticity, neurogenesis and metabolic activity of the brain. The influence of hormones on energy metabolism and mitochondrial function in the brain has gained much attention since mitochondrial dysfunctions are observed in many different pathological conditions of the central nervous system. Moreover, excess or deficiency of hormones is associated with cell damage and loss of function in mitochondria. This review aims to expound on the impact of hormones (GLP-1, insulin, thyroid hormones, glucocorticoids) on metabolic processes in the brain with special emphasis on oxidative phosphorylation dysregulation, which may contribute to the formation of pathological changes. Since the brain concentrations of sex hormones and neurosteroids decrease with age as well as in neurodegenerative diseases, in parallel with the occurrence of mitochondrial dysfunction and the weakening of cognitive functions, their beneficial effects on oxidative phosphorylation and expression of antioxidant enzymes are also discussed.

Rhythm of Fetoplacental 11β-Hydroxysteroid Dehydrogenase Type 2 - Fetal Protection From Morning Maternal Glucocorticoids

CONTEXT

Excess glucocorticoids impact fetal health. Maternal glucocorticoids peak in early morning. Fetoplacental 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) inactivates cortisol to cortisone, protecting the fetus from high glucocorticoids. However, time-specific alterations of human fetoplacental 11β-HSD2 have not been studied.

OBJECTIVE

We hypothesized that fetoplacental 11β-HSD2 activity shows time-specific alteration and acute affective or anxiety disorders impact fetoplacental 11β-HSD2 activity.

METHODS

In this observational study we investigated 78 pregnant European women undergoing amniocentesis (15.9 ± 0.9 weeks of gestation). Amniotic fluid was collected (8:00 to 16:30 hours) for analysis of fetoplacental 11β-HSD2 activity, using cortisol (F):cortisone (E) ratio in amniotic fluid, E/(E + F). Fetoplacental 11β-HSD2 rhythm and association with "acute affective or anxiety disorder" (patients with at least one of: a major depressive episode, specific phobia, panic disorder, generalized anxiety disorder, mixed anxiety and depressive disorder) and "acute anxiety disorder" (one of: panic disorder, generalized anxiety disorder, mixed anxiety, depressive disorder), assessed using Mini International Neuropsychiatric Interview, were investigated.

RESULTS

Activity of 11β-HSD2 correlated with time of amniocentesis, peaking in the morning (r = -0.398; P < 0.001) and increased with acute affective or anxiety disorder (mean [M] = 0.70 vs M = 0.74; P = 0.037) and acute anxiety disorder (M = 0.70 vs M = 0.75; P = 0.016). These associations remained significant when controlling for confounders. 11β-HSD2 activity correlated negatively with pre-pregnancy body mass index (r = -0.225; P = 0.047).

CONCLUSION

Our study indicates a time-specific alteration of fetoplacental 11β-HSD2 activity with peaking levels in the morning, demonstrating a mechanism of fetal protection from the morning maternal glucocorticoid surge.

Do Adolescent Exposure to Cannabinoids and Early Adverse Experience Interact to Increase the Risk of Psychiatric Disorders: Evidence from Rodent Models

There have been growing concerns about the protracted effects of cannabis use in adolescents on emotion and cognition outcomes, motivated by evidence of growing cannabis use in adolescents, evidence linking cannabis use to various psychiatric disorders, and the increasingly perceived notion that cannabis is harmless. At the same time, studies suggest that cannabinoids may have therapeutic potential against the impacts of stress on the brain and behavior, and that young people sometimes use cannabinoids to alleviate feelings of depression and anxiety (i.e., “self-medication”). Exposure to early adverse life events may predispose individuals to developing psychopathology in adulthood, leading researchers to study the causality between early life factors and cognitive and emotional outcomes in rodent models and to probe the underlying mechanisms. In this review, we aim to better understand the long-term effects of cannabinoids administered in sensitive developmental periods (mainly adolescence) in rodent models of early life stress. We suggest that the effects of cannabinoids on emotional and cognitive function may vary between different sensitive developmental periods. This could potentially affect decisions regarding the use of cannabinoids in clinical settings during the early stages of development and could raise questions regarding educating the public as to potential risks associated with cannabis use.

Allium cepa Linn juice protect against alterations in reproductive functions induced by maternal dexamethsone treatment during lactation in male offspring of Wistar rats

Treatment with dams with dexamethasone during lactation has been reported to induce oxidative stress in the testis of the offspring. Allium cepa L (Red Onion) is known to be a potent free radical scavenger. The protective role of Allium cepa against oxidative stress induced in testis following treatment with dexamehasone during lactation in Wistar rats was assessed. Twenty female rats were assigned into four groups (n = 5) during lactation and they were treated as follows: Group 1 serve as Control (distilled water), Group 2, 3, and four were admistered dexamethasone (60 μg/kg), Allium cepa (5 ml/kg) and dexamethasone + Allium cepa respectively. Testicular descent, pubertal age, sperm quality indices, and serum hormonal profile were assessed as indices of reproductive function. Testicular malondialdehyde (MDA) reduced glutathione (GSH) as well as superoxide dismutase (SOD) and catalase activities were assessed as measures of oxidative stress. Results obtained showed that dexamethasone caused significant (P < 0.05) reduction in testes weights, indices of sperm quality, serum testosterone, FSH, LH levels and testicular antioxidant enzyme activities. There was significant delay (P < 0.05) in days of testes descent, preputial separation and increase in testicular MDA. However, maternal treatment with Allium cepa Linn juice significantly (P < 0.05) improved both indices of reproductive function and testicular antioxidant enzymes. These findings suggest that Allium cepa Linn has a protective effect against testicular oxidative stress and reproductive dysfunction following treatment of dams with dexamethasone during lactation.

Mineralocorticoid receptor excessive activation involved in glucocorticoid-related brain injury

The mechanisms involved in brain damage during chronic glucocorticoid exposure are poorly understood. Since mineralocorticoid receptor (MR) activation has been proven to be important in the pathophysiology of vascular damage and MRs are highly expressed in many brain regions, we hypothesized that the cerebral injury observed in subjects with Cushing syndrome is in part associated with the overactivation of MR. The aim of this study was to determine whether the cerebral injury observed in chronic hyperglucocorticoidemia animal models is related to excessive MR activation. Male SD rats were divided into five groups: vehicle, hydrocortisone (HC, 5 mg/kg/day, i.g.), HC + spironolactone (SL, 20 mg/kg/d in chow), dexamethasone (DXM, 0.25 mg/kg/day, i.g.), and DXM + SL (20 mg/kg/d in chow). Compared to the vehicle-treated group, HC-treated rats had higher blood pressure and higher levels of cerebral vascular fibrosis, cortical/hippocampal atrophy, reactive oxygen species (ROS) production and proinflammatory gene expression. However, in HC-treated animals, treatment with SL markedly alleviated ROS production, cerebral and cerebrovascular morphological changes and inflammation but failed to reduce blood pressure. In contrast, DXM induced no cerebral morphological changes except fibrosis in cerebral vessels, an effect that was not ameliorated by SL treatment. These findings demonstrate that the excessive MR activation observed following chronic hyperglucocorticoidemia exposure contributes to cerebrovascular fibrosis and remodeling and promotes neural apoptosis in the cerebral cortex/hippocampus.

Effect of neonatal dexamethasone treatment on cognitive abilities of adult male mice and gene expression in the hypothalamus

The early postnatal period is critical for the development of the nervous system. Stress during this period causes negative long-term effects, which are manifested at both behavioral and molecular levels. To simulate the elevated glucocorticoid levels characteristic of early-life stress, in our study we used the administration of dexamethasone, an agonist of glucocorticoid receptors, at decreasing doses at the first three days of life (0.5, 0.3, 0.1 mg/kg, s.c.). In adult male mice with neonatal dexamethasone treatment, an increase in the relative weight of the adrenal glands and a decrease in body weight were observed, while the basal level of corticosterone remained unchanged. Dexamethasone treatment in early life had a negative impact on the learning and spatial memory of adult mice in the Morris water maze. We analyzed the effect of elevated glucocorticoid levels in early life on the expression of the Crh, Avp, Gr, and Mr genes involved in the regulation of the HPA axis in the hypothalami of adult mice. The expression level of the mineralocorticoid receptor gene (Mr) was significantly downregulated, and the glucocorticoid receptor gene (Gr) showed a tendency towards decreased expression (p = 0.058) in male mice neonatally treated with dexamethasone, as compared with saline administration. The expression level of the Crh gene encoding corticotropin-releasing hormone was unchanged, while the expression of the vasopressin gene (Avp) was increased in response to neonatal administration of dexamethasone. The obtained results demonstrate a disruption of negative feedback regulation of the HPA axis, which involves glucocorticoid and mineralocorticoid receptors, at the level of the hypothalamus. Malfunction of the HPA axis as a result of activation of the glucocorticoid system in early life may cause the development of cognitive impairment in the adult mice.

 

Glucocorticoid receptor activation selectively influence performance of Wistar rats in Y-maze

Glucocorticoid receptors (GR) are ubiquitously expressed in metazoans. Different and contrasting phenotypes have been reported upon their activation. This study investigated the behavioral phenotypes characteristic of GR stimulation in male Wistar rats. Rats in each of the four groups of rats received one of the following treatments: distilled water (control) or one of three doses of dexamethasone (treatment) injected intraperitoneally for 7 days. The Rats were afterwards subjected to the Y maze, the elevated plus maze (EPM), the Morris water maze (MWM), and the novel object recognition (NOR) test. At the end of the study, the animals were anesthetized and neural activity from the prefrontal cortex recorded. Blood was collected via cardiac puncture to evaluate the levels of plasma insulin and glucose, and the prefrontal cortexes excised to determine the levels of insulin, markers of oxidative stress, and calcium in the homogenate. This study showed that treatment with dexamethasone significantly reduced the total and percentage alternation in the Y maze, but had no significant effect on object recognition in the NOR test, long-term and short-term spatial memory in the MWM, or anxiety-like behavior in the EPM. Plasma and brain insulin and calcium levels were elevated moderately following treatment with the lowest dose of dexamethasone. All doses of dexamethasone decreased brain superoxide dismutase and increased lactate dehydrogenase levels. No significant change in neural activity was observed. This study shows that activation of glucocorticoid receptors differentially affects different behavioral paradigms and provides evidence for a role for glucocorticoids in mediating insulin function in the brain.

Glucocorticoids Protect Neonatal Rat Brain in Model of Hypoxic-Ischemic Encephalopathy (HIE)

Hypoxic-ischemic encephalopathy (HIE) resulting from asphyxia in the peripartum period is the most common cause of neonatal brain damage and can result in significant neurologic sequelae, including cerebral palsy. Currently therapeutic hypothermia is the only accepted treatment in addition to supportive care for infants with HIE, however, many additional neuroprotective therapies have been investigated. Of these, glucocorticoids have previously been shown to have neuroprotective effects. HIE is also frequently compounded by infectious inflammatory processes (sepsis) and as such, the infants may be more amenable to treatment with an anti-inflammatory agent. Thus, the present study investigated dexamethasone and hydrocortisone treatment given after hypoxic-ischemic (HI) insult in neonatal rats via intracerebroventricular (ICV) injection and intranasal administration. In addition, we examined the effects of hydrocortisone treatment in HIE after lipopolysaccharide (LPS) sensitization in a model of HIE and sepsis. We found that dexamethasone significantly reduced rat brain infarction size when given after HI treatment via ICV injection; however it did not demonstrate any neuroprotective effects when given intranasally. Hydrocortisone after HI insult also significantly reduced brain infarction size when given via ICV injection; and the intranasal administration showed to be protective of brain injury in male rats at a dose of 300 µg. LPS sensitization did significantly increase the brain infarction size compared to controls, and hydrocortisone treatment after LPS sensitization showed a significant decrease in brain infarction size when given via ICV injection, as well as intranasal administration in both genders at a dose of 300 µg. To conclude, these results show that glucocorticoids have significant neuroprotective effects when given after HI injury and that these effects may be even more pronounced when given in circumstances of additional inflammatory injury, such as neonatal sepsis.

Effects of Neonatal Dexamethasone Exposure on Adult Neuropsychiatric Traits in Rats

The effects of early life stress in utero or in neonates has long-term consequences on hypothalamic-pituitary-adrenal (HPA) stress axis function and neurodevelopment. These effects extend into adulthood and may underpin a variety of mental illnesses and be related to various developmental and cognitive changes. We examined the potential role of neonatal HPA axis activation on adult psychopathology and dopamine sensitivity in the mature rat using neonatal exposure to the synthetic glucocorticoid receptor agonist and stress hormone, dexamethasone. We utilized a comprehensive battery of assessments for behaviour, brain function and gene expression to determine if elevated early life HPA activation is associated with adult-onset neuropsychiatric traits. Dexamethasone exposure increased startle reactivity under all conditions tested, but decreased sensitivity of sensorimotor gating to dopaminergic disruption–contrasting with what is observed in several neuropsychiatric diseases. Under certain conditions there also appeared to be mild long-term changes in stress and anxiety-related behaviours with neonatal dexamethasone exposure. Electrophysiology revealed that there were no consistent neuropsychiatric abnormalities in auditory processing or resting state brain function with dexamethasone exposure. However, neonatal dexamethasone altered auditory cortex glucocorticoid activation, and auditory cortex synchronization. Our results indicate that neonatal HPA axis activation by dexamethasone alters several aspects of adult brain function and behaviour and may induce long-term changes in emotional stress-reactivity. However, neonatal dexamethasone exposure is not specifically related to any particular neuropsychiatric disease.

The Impact of Prenatal Exposure to Dexamethasone on Gastrointestinal Function in Rats

Antenatal treatment with synthetic glucocorticoids is commonly used in pregnant women at risk of preterm delivery to accelerate tissue maturation. Exposure to glucocorticoids during development has been hypothesized to underlie different functional gastrointestinal (GI) and motility disorders. Herein, we investigated the impact of in utero exposure to synthetic glucocorticoids (iuGC) on GI function of adult rats. Wistar male rats, born from pregnant dams treated with dexamethasone (DEX), were studied at different ages. Length, histologic analysis, proliferation and apoptosis assays, GI transit, permeability and serotonin (5-HT) content of GI tract were measured. iuGC treatment decreased small intestine size and decreased gut transit. However, iuGC had no impact on intestinal permeability. iuGC differentially impacts the structure and function of the GI tract, which leads to long-lasting alterations in the small intestine that may predispose subjects prone to disorders of the GI tract.

Maternal treatment with dexamethasone during lactation delays male puberty and disrupts reproductive functions via hypothalamic-pituitary-gonadal axis alterations

The effects of maternal treatment with dexamethasone during lactation on pubertal timing, serum hormonal profile and sperm indices in the male offspring were assessed. Twenty lactating dams were divided into 4 groups (n=5). Group 1 was administered subcutaneously 0.02ml/100g/day normal saline at lactation days 1-21. Groups 2-4 were administered subcutaneously 100μg/kg/day dexamethasone (Dex) at lactation days 1-7, 1-14, and 1-21 respectively. Results showed that there was significant reduction in serum testosterone in the DexLD 1-7 (p<0.05), DexLD 1-14 (p<0.01) and DexLD 1-21 (p<0.001) relative to control. In addition there was a significant reduction in serum FSH and LH in the DexLD 1-7 (p<0.01), DexLD 1-14 (p<0.001) and DexLD 1-21 (p<0.001) when compared with the control. Treatment with dexamethasone during lactation significantly increased the days of preputial separation in the DexLD 1-7 (p<0.05), DexLD 1-14 (p<0.05) and DexLD 1-21 (p<0.001) relative to control. Maternal treatment with dexamethasone throughout lactation period also significantly reduced sperm counts (p<0.001), motility (p<0.01) and increased percentage abnormal sperm (p<0.001) in the offspring when compared with the control. In conclusion, maternal treatment with dexamethasone during lactation may induce delayed puberty and disrupt reproductive functions by altering activities at hypothalamic-pituitary-gonadal axis in the male offspring.

Multiple Antenatal Dexamethasone Treatment Alters Brain Vessel Differentiation in Newborn Mouse Pups

Antenatal steroid treatment decreases morbidity and mortality in premature infants through the maturation of lung tissue, which enables sufficient breathing performance. However, clinical and animal studies have shown that repeated doses of glucocorticoids such as dexamethasone and betamethasone lead to long-term adverse effects on brain development. Therefore, we established a mouse model for antenatal dexamethasone treatment to investigate the effects of dexamethasone on brain vessel differentiation towards the blood-brain barrier (BBB) phenotype, focusing on molecular marker analysis. The major findings were that in total brains on postnatal day (PN) 4 triple antenatal dexamethasone treatment significantly downregulated the tight junction protein claudin-5, the endothelial marker Pecam-1/CD31, the glucocorticoid receptor, the NR1 subunit of the N-methyl-D-aspartate receptor, and Abc transporters (Abcb1a, Abcg2 Abcc4). Less pronounced effects were found after single antenatal dexamethasone treatment and in PN10 samples. Comparisons of total brain samples with isolated brain endothelial cells together with the stainings for Pecam-1/CD31 and claudin-5 led to the assumption that the morphology of brain vessels is affected by antenatal dexamethasone treatment at PN4. On the mRNA level markers for angiogenesis, the sonic hedgehog and the Wnt pathway were downregulated in PN4 samples, suggesting fundamental changes in brain vascularization and/or differentiation. In conclusion, we provided a first comprehensive molecular basis for the adverse effects of multiple antenatal dexamethasone treatment on brain vessel differentiation.

Dexamethasone but not the equivalent doses of hydrocortisone induces neurotoxicity in neonatal rat brain

BACKGROUND

The use of dexamethasone (Dex) in premature infants to treat or prevent chronic lung disease adversely affects neurodevelopment. Recent clinical studies suggest that hydrocortisone (HC) is a safer alternative to Dex. We compared the effects of Dex and HC on neurotoxicity in newborn rats.

METHODS

Rat pups of a neurodevelopmental stage equivalent to premature human neonates were administered Dex or HC either as a single dose on postnatal day (PD) 6, repeated doses on PD 4 to 6 or tapering doses at PD 3 to 6 by i.p. injection. Brain weight, caspase-3 activity, and apoptotic cells were measured at PD 7; learning capability, memory, and motor function were measured at juvenile age.

RESULTS

Dex decreased both body and brain weight gain, while HC did not. Tapering and repeated doses of Dex increased caspase-3 activity, cleaved caspase-3 and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells but HC, except at high doses, did not. Dex impaired learning and memory capability at juvenile age, while the rats exposed to HC showed normal cognitive behavior.

CONCLUSION

HC is probably safer to use than Dex in the immediate postnatal period in neonatal rats. Cautious extrapolation of these findings to human premature infants is required.

Neonatal glucocorticoid treatment increased depression-like behaviour in adult rats

Synthetic glucocorticoid dexamethasone (DEX) is frequently used as a therapeutic agent to lessen the morbidity of chronic lung disease in premature infants. Previous studies suggested that neonatal DEX treatment altered brain development and cognitive function. It has been recognized that the amygdala is involved in emotional processes and also a critical site of neuronal plasticity for fear conditioning. Little is known about the possible long-term adverse effect of neonatal DEX treatment on amygdala function. The present study was aimed to evaluate the possible effect of neonatal DEX treatment on the synaptic function of amygdala in adult rats. Newborn Wistar rats were subjected to subcutaneous tapering-dose injections of DEX (0.5, 0.3 and 0.1 mg/kg) from post-natal day one to three, PN1-PN3. Animals were then subjected to a forced swimming test (FST) and electrophysiological recording aged eight weeks. The results of the FST showed neonatal DEX treatment increased depression-like behaviour in adulthood. After acute stress evoking, the percentage of time spent free floating is significantly increased in the DEX treated group compared with the control animals. Furthermore, neonatal DEX treatment elevated long-term potentiation (LTP) response and the phosphorylation level of MAPK in the lateral nucleus of amygdala (LA). Intracerebroventricular infusion of the MAPK inhibitor, PD98059, showed significant rescue effects including reduced depression-like behaviour and restoration of LTP to within normal range. In conclusion, our results suggested that MAPK signalling cascade in the LA plays an important role in the adverse effect of neonatal DEX treatment on amygdala function, which may result in adverse consequences in adult age, such as the enhancement of susceptibility for a depressive disorder in later life.

Morpho-functional characteristics of rat fetal thyroid gland are affected by prenatal dexamethasone exposure

Thyroid hormones (TH) and glucocorticoids strongly contribute to the maturation of fetal tissues in the preparation for extrauterine life. Influence of maternal dexamethasone (Dx) administration on thyroid glands morpho-functional characteristics of near term rat fetuses was investigated applying unbiased stereology. On the 16th day of pregnancy dams received 1.0mg/Dx/kg/b.w., followed by 0.5mg/Dx/kg/b.w. on the 17th and 18th days of gestation. The control females received the same volume of saline. The volume of fetal thyroid was estimated using Cavalieri's principle; the physical/fractionator design was applied for the determination of absolute number of follicular cells in mitosis and immunohistochemically labeled C cells; C cell volume was measured using the planar rotator. The functional activity of thyroid tissue was provided from thyroglobulin (Tg) and thyroperoxidase (TPO) immunohistochemical staining. Applying these design-based modern stereological methods it was shown that Dx treatment of gravid females led to a significant decrease of fetal thyroid gland volume in 19- and 21-day-old fetuses, due to decreased proliferation of follicular cells. The Tg and TPO immunohistochemistry demonstrated that intensive TH production starts and continues during the examined period in control and Dx-exposed fetuses. Under the influence of Dx the absolute number of C cells was lower in both groups of near term fetuses, although unchanged relation between the two populations of endocrine cells, follicular and C cells suggesting that structural relationships within the gland are preserved. In conclusion maternal glucocorticoid administration at the thyroid gland level exerts growth-inhibitory and maturational promoting effects in near term rat fetuses.

Why Are Childhood Family Factors Associated With Timing of Maturation? A Role for Internal Prediction

Children, particularly girls, who experience early familial adversity tend to go on to reach sexual maturity relatively early. This feature of adolescent development is believed to be an evolved strategy that arose because individuals with genes that caused them to mature relatively early under certain conditions left behind more descendants than those who did not. However, although much has been done to uncover the psychological and physiological mechanisms underlying this process, less attention has been paid to the evolutionary reasons behind why it might be advantageous. It has previously been suggested that this strategy evolved because early familial adversity accurately indicated later environmental adversity, under which conditions early reproduction would likely maximize evolutionary fitness. In this article, we contrast this “external prediction” model with an alternative explanation, which builds on the existing explanation and is mutually compatible with it but also distinct from it. We argue that accelerated development is advantageous because early adversity detrimentally affects the individual’s body, increasing later morbidity and mortality; individuals may adapt to this internal setback by accelerating their development. Unlike the external prediction model, this “internal prediction” relies not on temporal environmental continuity but on long-term effects of early circumstances on the body.

Role of the NMDA receptor in cognitive deficits, anxiety and depressive-like behavior in juvenile and adult mice after neonatal dexamethasone exposure

Postnatal dexamethasone (DEX) therapy has been used to treat or prevent chronic lung disease after premature births. However, there are many reports of long-term negative neurodevelopmental sequelae following this treatment. In contrast, hydrocortisone (HYD), which has fewer neurodevelopment adverse effects, is used as an alternative for DEX. In this study, we report that neonatal DEX exposure (days 1-3) caused alterations of amino acids affecting N-methyl-d-aspartate (NMDA) receptor neurotransmission in mouse brains. Neonatal DEX, but not HYD, exposure (days 1-3) significantly decreased the GluN2B subunit of NMDA receptor in the hippocampus at juvenile and adult stages. Mice treated with DEX showed cognitive deficits, as well as anxiety and depressive-like behavior at juvenile and adult stages. In contrast, mice treated with HYD (days 1-3) showed no behavioral abnormalities at these stages. In the DEX suppression test, plasma levels of corticosterone in mice exposed neonatally to DEX and HYD were significantly higher at juvenile, but not adult stages. Pretreatment with Ro 63-1908, an antagonist at GluN2B subunit, 30min before each injection of DEX, prevented cognitive deficits, as well as anxiety and depressive-like behavior in juvenile and adult mice. Interestingly, subsequent repeated (days 29-33) administration of Ro 63-1908 or L701324, an antagonist of the glycine modulatory site on the NMDA receptor, significantly suppressed behavioral abnormalities in juvenile and adult mice after neonatal DEX exposure. These results indicate that neonatal DEX, but not HYD, exposure produced behavioral abnormalities in juvenile and adult mice by altering glutamatergic neurotransmission via the NMDA receptor. The NMDA receptor antagonists may prevent or treat these DEX-induced neonatal behavioral abnormalities in later life.

Dexamethasone induces apoptosis of progenitor cells in the subventricular zone and dentate gyrus of developing rat brain

The use of dexamethasone in premature infants to prevent and/or treat bronchopulmonary dysplasia adversely affects neurocognitive development and is associated with cerebral palsy. The underlying mechanisms of these effects are multifactorial and likely include apoptosis. The objective of this study was to confirm whether dexamethasone causes apoptosis in different regions of the developing rat brain. On postnatal day 2, pups in each litter were randomly divided into the dexamethasone-treated (n = 91) or vehicle-treated (n = 92) groups. Rat pups in the dexamethasone group received tapering doses of dexamethasone on postnatal days 3-6 (0.5, 0.25, 0.125, and 0.06 mg/kg/day, respectively). Dexamethasone treatment significantly decreased the gain of body and brain weight and increased brain caspase-3 activity, DNA fragments, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, and cleaved caspse-3-positive cells at 24 hr after treatment. Dexamethasone increased cleaved caspse-3-positive cells in the cortex, thalamus, hippocampus, cerebellum, dentate gyrus, and subventricular zone. Double-immunofluorescence studies show that progenitor cells in the subventricular zone and dentate gyrus preferentially undergo apoptosis following dexamethasone exposure. These results indicate that dexamethasone-induced apoptosis in immature cells in developing brain is one of the mechanisms of its neurodegenerative effects in newborn rats.

Dexamethasone administration to the neonatal rat results in neurological dysfunction at the juvenile stage even at low doses

Dexamethasone (DEX), a synthetic glucocorticoid, has been widely used to prevent the development of a variety of poor health conditions in premature infants including chronic lung disease, inflammation, circulatory failure, and shock. Although there are some reports of neurologic complications related to DEX exposure, its full effects on the premature brain have not been examined in detail. To investigate the effects of DEX on neural development, we first administered low doses (0.2 mg/kg bodyweight or less) of the glucocorticoid to neonatal rats on a daily basis during the first postnatal week and examined subsequent behavioral alterations at the juvenile stage. DEX-treated rats exhibited not only a significant reduction in both somatic and brain weights but also learning disabilities as revealed in the shuttle avoidance test. The hippocampi of DEX-treated rats displayed a high apoptotic and a low mitotic cell density compared to control rats on day 7 after birth. In a subsequent experiment, neural stem/progenitor cells were cultured in the presence of DEX for 6 days. The glucocorticoid inhibited cell growth without an increase in cell death. These results suggest that administration of DEX to premature infants induces neurological dysfunction via inhibition of the proliferation of neural stem/progenitor cells.

The role of glucocorticoid receptors in dexamethasone-induced apoptosis of neuroprogenitor cells in the hippocampus of rat pups

Background. Dexamethasone (Dex) has been used to reduce inflammation in preterm infants with assistive ventilation and to prevent chronic lung diseases. However, Dex treatment results in adverse effects on the brain. Since the hippocampus contains a high density of glucocorticoid receptors (GCRs), we hypothesized that Dex affects neurogenesis in the hippocampus through inflammatory mediators. Methods. Albino Wistar rat pups first received a single dose of Dex (0.5 mg/kg) on postnatal day 1 (P1) and were sacrificed on P2, P3, P5, and P7. One group of Dex-treated pups (Dex-treated D1D2) was given mifepristone (RU486, a GCR antagonist) on P1 and sacrificed on P2. Hippocampi were isolated for western blot analysis, TUNEL, cleaved-caspase 3 staining for cell counts, and morphological assessment. Control pups received normal saline (NS). Results. Dex reduced the developmental gain in body weight, but had no effect on brain weight. In the Dex-treated D1D2 group, apoptotic cells increased in number based on TUNEL and cleaved-caspase 3 staining. Most of the apoptotic cells expressed the neural progenitor cell marker nestin. Dex-induced apoptosis in P1 pups was markedly reduced (60%) by pretreatment with RU486, indicating the involvement of GCRs. Conclusion. Early administration of Dex results in apoptosis of neural progenitor cells in the hippocampus and this is mediated through GCRs.

Development of psychophysiological motoric reactivity is influenced by peripubertal pharmacological inhibition of gonadotropin releasing hormone action--results of an ovine model

This study reports the effects of peripubertal GnRH receptor inactivation on development of psychophysiological motoric reactivity (PMR; sometimes also called emotional reactivity), plasma cortisol concentrations and the relationship between plasma cortisol and PMR in male and female sheep. The study formed part of a larger trial and utilised 46 same sex twins. One twin remained untreated (control) while the other received a subcutaneous GnRH agonist (GnRHa Goserelin-Acetate) implant every 4th week, beginning at 8 and 28 weeks of age, in males and females, respectively (different, due to sex specific age of puberty). PMR, a measure of an animals' response to social isolation, was measured over a two minute period at 8, 28 and 48 weeks of age, using a three axis accelerometer. During the test period vocalisation rate was recorded. Cortisol was assayed in blood samples collected on a single day when animals were 40 weeks of age. PMR and vocalisation rate were significantly higher in females than males at all ages tested. At 28 weeks of age (20 weeks treatment) PMR was increased in treated males to the level seen in control females, by 48 weeks of age treated males' PMR was significantly less than controls. In females, 20 weeks of GnRHa treatment (28-48 weeks of age) was not associated with differences in PMR. Cortisol concentrations were significantly higher in females than males but were not affected by treatment. Plasma cortisol concentrations were positively correlated with PMR; this relationship being driven by the treated animals in both sexes. The results demonstrate that PMR is sexually dimorphic and cortisol dependent in sheep from at least 8 weeks of age. Importantly, they also demonstrate that long-term treatment of males with a GnRH agonist results in changes in age-dependent development of PMR.

Neonatal dexamethasone exposure down-regulates GnRH expression through the GnIH pathway in female mice

Synthetic glucocorticoid (dexamethasone; DEX) treatment during the neonatal stage is known to affect reproductive activity. However, it is still unknown whether neonatal stress activates gonadotropin-inhibitory hormone (GnIH) synthesizing cells in the dorsomedial hypothalamus (DMH), which could have pronounced suppressive action on gonadotropin-releasing hormone (GnRH) neurons, leading to delayed pubertal onset. This study was designed to determine the effect of neonatal DEX (1.0mg/kg) exposure on reproductive maturation. Therefore, GnRH, GnIH and GnIH receptors, G-protein coupled receptors (GPR) 147 and GPR74 mRNA levels were measured using quantitative real-time PCR in female mice at postnatal (P) days 21, 30 and in estrus stage mice, aged between P45-50. DEX-treated females of P45-50 had delayed vaginal opening, and irregular estrus cycles and lower GnRH expression in the preoptic area (POA) when compared with age-matched controls. The expression levels of GPR147 and GPR74 mRNA in the POA increased significantly in DEX-treated female mice of P21 and P45-50 compared to controls. In addition, GPR147 and GPR74 mRNA expression was observed in laser captured single GnRH neurons in the POA. Although there was no difference in GnIH mRNA expression in the DMH, immunostained GnIH cell numbers in the DMH increased in DEX-treated females of P45-50 compared to controls. Taken together, the results show that the delayed pubertal onset could be due to the inhibition of GnRH gene expression after neonatal DEX treatment, which may be accounted for in part by the inhibitory signals from the up-regulated GnIH-GnIH receptor pathway to the POA.

Dietary supplementation of female rats with elk velvet antler improves physical and neurological development of offspring

Elk velvet antler (EVA) has a traditional use for promotion of general health. However, evidence of EVA effects at different lifestages is generally lacking. This paper investigated the effects of long-term maternal dietary EVA supplementation on physical, reflexological and neurological development of rat offspring. Female Wistar rats were fed standard chow or chow containing 10% EVA for 90 days prior to mating and throughout pregnancy and lactation. In each dietary group, 56 male and 56 female pups were assessed for physical, neuromotor, and reflexologic development postnatally. Among the examined physical developmental parameters, incisor eruption occurred one day earlier in pups nursing dams receiving EVA. Among neuromotor developmental parameters, duration of supported and unsupported standing was longer for pups nursing EVA supplemented dams. Acquisition of neurological reflex parameters (righting reflex, negative geotaxis, cliff avoidance acoustic startle) occurred earlier in pups nursing dams receiving EVA. Longterm maternal EVA supplementation prior to and during pregnancy and lactation accelerated certain physical, reflexologic, and neuromotor developmental milestones and caused no discernible adverse effects on developing offspring. The potential benefits of maternal EVA supplementation on postnatal development warrants further investigation to determine whether EVA can be endorsed for the promotion of maternal and child health.

Regulation of corticoid and serotonin receptor brain system following early life exposure of glucocorticoids: long term implications for the neurobiology of mood

Potent glucocorticoids (GC) administered early in life have improved premature infant survival dramatically. However, these agents may increase the risk for physical, neurological and behavior alterations. Anxiety, depression and attention difficulties are commonly described in adolescent and young adult survivors of prematurity. In the present study we administered vehicle, dexamethasone, or hydrocortisone to Sprague-Dawley rat pups on postnatal days 5 and 6, mimicking a short term clinical protocol commonly used in human infants. Two systems that are implicated in the regulation of stress and behavior were assessed: the limbic-hypothalamic-pituitary-adrenal axis [LHPA; glucocorticoid and mineralocorticoid receptors within] and the Serotonin (5-HT) system. We found that as adults, male Sprague-Dawley pups treated with GC showed agent specific altered growth, anxiety-related behavior, changes in corticoid response to novelty and gene expression changes within LHPA and 5-HT-related circuitry. The data suggest that prolonged GC-receptor stimulation during the early neonatal period can contribute to the development of individual differences in stress response and anxiety-related behavior later in life.

Effects of motherless rearing on basal and stress-induced corticosterone secretion in rat pups

Rearing of rat pups without a mother, artificial rearing (AR), produces substantial changes in the pups' behavior in later life. These changes are similar to those produced by the stress of repeated mother-pup separations. The predominant interpretation is that the long-term effects of disruptions to the mother-pup relationship are mediated by exposure to elevated levels of corticosterone which affect the development of neurobiological systems underlying cognition and behavior. Indeed, repeated separation of pups from the mother sensitizes the pups' corticosterone response to stress. This study examined basal and stress-induced corticosterone release in AR pups. Corticosterone levels were increased immediately following implantation of feeding cannulae. One day after the start of AR, circulating concentrations of corticosterone were not increased unless AR pups were challenged with an additional stressor (injection). Corticosterone levels were lowest when cannulation and AR started on postnatal day (PND) 5 compared with earlier PNDs. On PND 12, there was no evidence of increased corticosterone levels in AR pups at baseline or in response to stress, indicating that AR did not result in persistent sensitization of corticosterone release. The long-term effects of motherless rearing on rat behavior are mediated by mechanisms that are independent of sustained early corticosterone exposure.

Oxidative stress in the developing brain: effects of postnatal glucocorticoid therapy and antioxidants in the rat

In premature infants, glucocorticoids ameliorate chronic lung disease, but have adverse effects on long-term neurological function. Glucocorticoid excess promotes free radical overproduction. We hypothesised that the adverse effects of postnatal glucocorticoid therapy on the developing brain are secondary to oxidative stress and that antioxidant treatment would diminish unwanted effects. Male rat pups received a clinically-relevant tapering course of dexamethasone (DEX; 0.5, 0.3, and 0.1 mg.kg⁻¹.day⁻¹), with or without antioxidant vitamins C and E (DEXCE; 200 mg.kg⁻¹.day⁻¹ and 100 mg.kg⁻¹.day⁻¹, respectively), on postnatal days 1–6 (P1–6). Controls received saline or saline with vitamins. At weaning, relative to controls, DEX decreased total brain volume (704.4±34.7 mm³ vs. 564.0±20.0 mm³), the soma volume of neurons in the CA1 (1172.6±30.4 µm³ vs. 1002.4±11.8 µm³) and in the dentate gyrus (525.9±27.2 µm³ vs. 421.5±24.6 µm³) of the hippocampus, and induced oxidative stress in the cortex (protein expression: heat shock protein 70 [Hsp70]: +68%; 4-hydroxynonenal [4-HNE]: +118% and nitrotyrosine [NT]: +20%). Dexamethasone in combination with vitamins resulted in improvements in total brain volume (637.5±43.1 mm³), and soma volume of neurons in the CA1 (1157.5±42.4 µm³) and the dentate gyrus (536.1±27.2 µm³). Hsp70 protein expression was unaltered in the cortex (+9%), however, 4-HNE (+95%) and NT (+24%) protein expression remained upregulated. Treatment of neonates with vitamins alone induced oxidative stress in the cortex (Hsp70: +67%; 4-HNE: +73%; NT: +22%) and in the hippocampus (NT: +35%). Combined glucocorticoid and antioxidant therapy in premature infants may be safer for the developing brain than glucocorticoids alone in the treatment of chronic lung disease. However, antioxidant therapy in healthy offspring is not recommended.

The link between perinatal glucocorticoids exposure and psychiatric disorders

The perinatal period is particularly sensitive to a variety of insults during which stress-regulating systems can be permanently altered and psychopathologies ensue. The programming of physiological, endocrinological, and behavioral functions by perinatal adversities is mediated by altered levels of glucocorticoids or the hypothalamic-pituitary-adrenal axis activity in either the mother or offspring. In this article, I review the integrated data from human studies and from animal models that suggest the programming effects of perinatal glucocorticoids exposure. Finally, the concept of developmental origins of psychiatric disorders is discussed.

Early life stress paradigms in rodents: potential animal models of depression?

RATIONALE

While human depressive illness is indeed uniquely human, many of its symptoms may be modeled in rodents. Based on human etiology, the assumption has been made that depression-like behavior in rats and mice can be modulated by some of the powerful early life programming effects that are known to occur after manipulations in the first weeks of life.

OBJECTIVE

Here we review the evidence that is available in literature for early life manipulation as risk factors for the development of depression-like symptoms such as anhedonia, passive coping strategies, and neuroendocrine changes. Early life paradigms that were evaluated include early handling, separation, and deprivation protocols, as well as enriched and impoverished environments. We have also included a small number of stress-related pharmacological models.

RESULTS

We find that for most early life paradigms per se, the actual validity for depression is limited. A number of models have not been tested with respect to classical depression-like behaviors, while in many cases, the outcome of such experiments is variable and depends on strain and additional factors.

CONCLUSION

Because programming effects confer vulnerability rather than disease, a number of paradigms hold promise for usefulness in depression research, in combination with the proper genetic background and adult life challenges.

The role of growth retardation in lasting effects of neonatal dexamethasone treatment on hippocampal synaptic function

BACKGROUND

Dexamethasone (DEX), a synthetic glucocorticoid, is commonly used to prevent or lessen the morbidity of chronic lung disease in preterm infants. However, evidence is now increasing that this clinical practice negatively affects somatic growth and may result in long-lasting neurodevelopmental deficits. We therefore hypothesized that supporting normal somatic growth may overcome the lasting adverse effects of neonatal DEX treatment on hippocampal function.

METHODOLOGY/PRINCIPAL FINDINGS

To test this hypothesis, we developed a rat model using a schedule of tapering doses of DEX similar to that used in premature infants and examined whether the lasting influence of neonatal DEX treatment on hippocampal synaptic plasticity and memory performance are correlated with the deficits in somatic growth. We confirmed that neonatal DEX treatment switched the direction of synaptic plasticity in hippocampal CA1 region, favoring low-frequency stimulation- and group I metabotropic glutamate receptor agonist (S)-3,5,-dihydroxyphenylglycine-induced long-term depression (LTD), and opposing the induction of long-term potentiation (LTP) by high-frequency stimulation in the adolescent period. The effects of DEX on LTP and LTD were correlated with an increase in the autophosphorylation of Ca(2+)/calmodulin-dependent protein kinase II at threonine-286 and a decrease in the protein phosphatase 1 expression. Neonatal DEX treatment resulted in a disruption of memory retention subjected to object recognition task and passive avoidance learning. The adverse effects of neonatal DEX treatment on hippocampal synaptic plasticity and memory performance of the animals from litters culled to 4 pups were significantly less than those for the 8-pup litters. However, there was no significant difference in maternal care between groups.

CONCLUSION/SIGNIFICANCE

Our results demonstrate that growth retardation plays a crucial role in DEX-induced long-lasting influence of hippocampal function. Our findings suggest that therapeutic strategies designed to support normal development and somatic growth may exert beneficial effects to reduce lasting adverse effects following neonatal DEX treatment.

Staging perspectives in neurodevelopmental aspects of neuropsychiatry: agents, phases and ages at expression

Neurodevelopmental risk factors have assumed a critical role in prevailing notions concerning the etiopathogenesis of neuropsychiatric disorders. Staging, diagnostic elements at which phase of disease is determined, provides a means of conceptualizing the degree and extent of factors affecting brain development trajectories, but is concurrently specified through the particular interactions of genes and environment unique to each individual case. For present purposes, staging perspectives in neurodevelopmental aspects of the disease processes are considered from conditions giving rise to neurodevelopmental staging in affective states, adolescence, dopamine disease states, and autism spectrum disorders. Three major aspects influencing the eventual course of individual developmental trajectories appear to possess an essential determinant influence upon outcome: (i) the type of agent that interferes with brain development, whether chemical, immune system activating or absent (anoxia/hypoxia), (ii) the phase of brain development at which the agent exerts disruption, whether prenatal, postnatal, or adolescent, and (iii) the age of expression of structural and functional abnormalities. Clinical staging may be assumed at any or each developmental phase. The present perspective offers both a challenge to bring further order to diagnosis, intervention, and prognosis and a statement regarding the extreme complexities and interwoven intricacies of epigenetic factors, biomarkers, and neurobehavioral entities that aggravate currents notions of the neuropsychiatric disorders.

Neonatal exposure to fenoterol and betamethasone: effects on the behavioral development in the rat

We investigated longitudinally the behavioral development in the rat following exposure to beta-agonists and glucocorticoids (GC). Neonatal rats received either 1 mg/kg fenoterol (FEN), 0.3 mg/kg betamethasone (BET), or saline (SAL). Weanling and young adult rats were tested in the open field, the elevated-plus maze, and the water maze. FEN-treated as well as BET-treated animals displayed increased anxiety-like behavior. Furthermore, BET-treated adult animals showed a reduced locomotor activity. An enhanced 24-h memory in the water maze in both treatment groups may be facilitated by emotional arousal due to the increased anxiety levels. The possible neurobiological underpinnings are discussed in detail.

Glucocorticoids and neuro- and behavioural development

Epidemiological evidence links exposure to stress hormones during fetal or early postnatal development with lifetime prevalence of cardiac, metabolic, auto-immune, neurological and psychiatric disorders. This has led to the concept of 'developmental programming through stress'. Importantly, these effects (specifically, hypertension, hyperglycaemia and neurodevelopmental and behavioural abnormalities) can be reproduced by exposure to high glucocorticoid levels, indicating a crucial role of glucocorticoids in their causation. However, there can be important differences in outcome, depending on the exact time of exposure, as well as duration and receptor selectivity of the glucocorticoid applied. The mechanisms underlying programming by stress are still unclear but it appears that these environmental perturbations exploit epigenetic modifications of DNA and/or histones to induce stable modifications of gene expression. Programming of neuro- and behavioural development by glucocorticoids and stress are important determinants of lifetime health and should be a consideration when choosing treatments in obstetric and neonatal medicine.

Postnatal stress in birds: a novel model of glucocorticoid programming of the hypothalamic-pituitary-adrenal axis

There is growing international interest in how environmental conditions experienced during development can shape adult phenotypes and the extent to which such induced changes are adaptive. One physiological system that links an individual to changes in environmental circumstances during development is the hypothalamic-pituitary-adrenal axis. Mammalian studies have linked early postnatal stress to later changes in the hypothalamic-pituitary-adrenal axis; however, the physiological link [lactational corticosterone (CORT) transfer] between mother and offspring during postnatal development constrains the ability to determine the direct effects of such stressors on subsequent physiology and behavior. Here we present a novel model using an avian species, the zebra finch (Taeniopygia guttata), in which maternal hormonal transfer during postnatal development is likely to be absent. Postnatal exposure of chicks to the stress hormone CORT was manipulated for a 16-d period up until nutritional independence (28 d), and the long-term effects on the physiological response to stress determined. CORT doses were scaled to mimic the physiological response of juvenile birds to a capture-handling-restraint protocol. CORT-fed birds showed exaggerated and prolonged responses to acute stress at 60 d of age. Our results clearly demonstrate that postnatal stress has significant long-term effects on the physiological stress response in birds and provides a potential mechanism underlying long-term behavioural responses to developmental conditions. This study represents the first direct evidence for postnatal glucocorticoid programming of the stress response using this novel model for postnatal stress. This model therefore provides an important tool with which to investigate the role of glucocorticoids in shaping adult phenotypes.

Treating fetal thyroid and adrenal disorders through the mother

Advances in imaging techniques and in molecular diagnosis have enabled the identification in the fetus of disorders of thyroid and adrenal function that can potentially be treated in utero through the mother. In women with Graves disease, the rare instances of autoimmune fetal hyperthyroidism can generally be treated in a noninvasive way by optimizing treatment of the mother. For fetal hypothyroidism with goiter leading to hydramnios, repeated intra-amniotic injections of thyroxine have been reported to decrease the size of the fetal thyroid, but experience is limited and the risk of premature labor is raised. In women who have previously borne a child with severe congenital adrenal hyperplasia, attempts to prevent virilization of the external genitalia of further affected female fetuses involves treatment with high doses of dexamethasone from week 7 of gestation to term, which includes the crucial period of organogenesis. Only one of every eight fetuses treated will, however, benefit from this therapy, meaning that seven are unnecessarily exposed to this potentially harmful agent. In this article, we review the rationale and evidence for efficacy of these approaches, and discuss their potential adverse effects as well as the ethical problems that they raise.

Dexamethasone induces neurodegeneration but also up-regulates vascular endothelial growth factor A in neonatal rat brains

The use of dexamethasone (Dex) in premature infants to prevent and/or treat bronchopulmonary dysplasia can adversely affect early neurodevelopment and probably result in loss of cerebral volume. Vascular endothelial growth factor A (VEGF), specifically VEGF(164) isoform has neurotrophic, neuroprotective and neurogenesis enhancing effects. Previous studies have demonstrated that Dex usually down-regulates VEGF. In the present study we investigated the effect of Dex on brain growth and VEGF in the neonatal rat brain. The pups in each litter were divided into the vehicle (n=84) or Dex-treated (n=98) groups. Rat pups in the Dex group received one of three different regimens of i.p. Dex which included tapering doses on postnatal days 3-6 (0.5, 0.25, 0.125 and 0.06 mg/kg, respectively), or repeated doses of 0.5 or 1 mg/kg/day on postnatal days 4-6 or single dose of 0.031, 0.06, 0.125, 0.25 or 0.5 mg/kg on postnatal day 6. The total VEGF protein and mRNA expression of the three main VEGF splice variants (VEGF(120), VEGF(164), and VEGF(188)) were measured in the rat pup brain using enzyme-linked immunosorbent assay and real-time reverse transcription polymerase chain reaction, respectively. Treatment with Dex significantly decreased the gain of body and brain weight. The tapering and repeated doses of Dex significantly increased caspase-3 activity, VEGF protein and the expression of mRNA of VEGF(164) and VEGF(188) splice variants but the single dose did not. We conclude that Dex is neurodegenerative in the developing brain but also increases VEGF which may play a neurotrophic and neuroprotective role.

Effects of neonatal dexamethasone or methylprednisolone on rat growth and neurodevelopment

BACKGROUND

Clinical studies have demonstrated that premature infants receiving long-term dexamethasone therapy have reduced linear growth, decreased weight gain, and smaller head circumferences. The purpose of the present study was to investigate the effects of the same equivalent doses for anti-inflammatory potency of neonatal dexamethasone and methylprednisolone on rat growth and neurodevelopment.

METHODS

The pups were randomly separated into three treatment groups on postnatal day (PD) 3. At postnatal 3-5 days, tapering doses of corticosteroids or sterile saline were administered subcutaneously. Group 1 was the dexamethasone group (n = 12; PD 3, 0.5 mg/kg; PD 4, 0.25 mg/kg; PD 5, 0.125 mg/kg; PD 6, 0.05 mg/kg s.c.); group 2, methylprednisolone group (n = 12; PD 3, 2.6 mg/kg; PD 4, 1.3 mg/kg; PD 5, 0.650 mg/kg; PD 6, 0.325 mg/kg; group 3, control group (n = 12; normal saline injected). Weight was recorded on PD 3-6, 8, 14, 22, length was recorded on PD 3, 7, 14, 21 for each group. Neurological responses and physical development were tested on PD 7, 14, 21.

RESULTS

On PD 4-6, 8, 14, 22 the weight in the dexamethasone and methylprednisolone groups was lower than in the control group, but the weight in the dexamethasone group was the lowest (P < 0.05). The length in the dexamethasone group was significantly shorter than in the methylprednisolone group on PD 14 and 21. Dexamethasone-treated animals had a reduced total neurological score compared with the methylprednisolone and control groups on PD 7, 14, 21. Although methylprednisolone-treated animals had lower total neurological score than that of the control group on PD 7 and PD 14 (P < 0.05), total neurological scores were not different in the methylprednisolone and control groups on PD 21.

CONCLUSIONS

Postnatal methylprednisolone treatment might be safer than dexamethasone treatment in newborns.

Neonatal dexamethasone administration causes progressive renal damage due to induction of an early inflammatory response

Glucocorticoids (GCs) are widely used to prevent chronic lung disease in immature newborns. Emerging evidence indicates that GC exposure in early life may interfere with kidney function and is associated with hypertension in later life. In this study, we have investigated the effect of neonatal dexamethasone (DEX) administration on renal function in rats. Male rats were treated with DEX in the first 3 days after birth, controls received saline (SAL). Severe renal damage associated with premature death was found at 50 wks upon DEX treatment, while renal function and morphology were normal in controls. A subsequent time-course study was performed from 2 days to 32 wks. Compared with controls, neonatal DEX administration led to significant and persistent growth retardation. Progressive proteinuria and increased systolic blood pressure were found from 8 wks onwards in DEX-treated animals. Renal α-SMA gene expression was elevated from wk 24 onwards and morphological fibrosis was noted at 32 wks of age following DEX treatment. Markedly increased renal gene expression of TNF-α and MCP-1 in DEX -treated rats was observed at day 7, probably contributing to the permanent increase in interstitial macrophage numbers that started at 14 days. Permanently elevated renal TGF-β gene expression was induced by DEX administration from 4 wks onwards. Our data indicate that neonatal DEX administration in rats leads to renal failure in later life, presumably due to an early inflammatory trigger that elicits a persistent pro-fibrotic process that eventually results in progressive renal deterioration.

Corticosteroid receptors and neuroplasticity

The balance in actions mediated by mineralocorticoid (MR) and glucocorticoid (GR) receptors in certain regions of the brain, predominantly in the limbic system, appears critical for neuronal activity, stress responsiveness, and behavioral programming and adaptation. Alterations in the MR/GR balance appear to make nervous tissue vulnerable to damage; such damage can have adverse effects on the regulation of the stress response and may increase the risk for psychopathology. Besides the hippocampal formation, other subpopulations of neurons in extra-hippocampal brain areas have been also shown recently to be sensitive to changes in the corticosteroid milieu. From a critical analysis of the available data, the picture that emerges is that the balance (or imbalance) between MR/GR activation influences not only cell birth and death, but also other forms of neuroplasticity. MR occupation appears to promote pro-survival actions, while exclusive GR activation favors neurodegeneration. Interestingly, the sustained co-activation of both receptors, for example in chronic stress conditions, usually results in less drastic effects, restricted to dendritic atrophy and impaired synaptic plasticity. As our knowledge of the plastic changes underpinning the wide spectrum of behavior effects triggered by corticosteroids/stress growths, researchers should be able to better define new targets for therapeutic intervention in stress-related disorders.

Effect of experimental litter reduction in female rats on parameters of brain and endocrine gland development in the progeny

We studied the relationship between parameters of brain development, elevated plus-maze behavior, and the status of the endocrine glands in the progeny of 4.5-5- and 8-9-month-old females after litter reduction by removal of one uterine tube. The progeny of young experimental females differed from the progeny of control animals by brain weight (at the age of 1 day), morphometrical characteristics of the cortex and its neurons, activity of 3beta-hydroxysteroid dehydrogenase in the adrenal cortex (at the age of 1 and 40 days), and behavioral reactions in the elevated plus-maze (at the age of 30 days). The differences in these parameters between the progeny from old females with experimentally reduced litter size and control females were significantly less pronounced.

Neurodevelopment milestone abnormalities in rats exposed to stress in early life

Manipulation of the corticosteroid milieu by interfering with the mother-newborn relationship has received much attention because of its potential bearing on psychopathology later in life. In the present study, infant rats that were deprived of maternal contact between the 2nd and the 15th postnatal days (MS2-15) for 6 h/day were subjected to a systematic assessment of neurodevelopmental milestones between postnatal days 2 and 21. The analyses included measurements of physical growth and maturation and evaluation of neurological reflexes. Although some somatic milestones (e.g. eye opening) were anticipated, MS2-15 animals showed retardation in the acquisition of postural reflex, air righting and surface righting reflexes, and in the wire suspension test; the latter two abnormalities were only found in males. A gender effect was also observed in negative geotaxis, with retardation being observed in females but not males. To better understand the delay of neurological maturation in MS2-15 rats, we determined the levels of various monoamines in different regions of the brain stem, including the vestibular area, the substantia nigra, ventral tegmental area and dorsal raphe nuclei. In the vestibular region of MS2-15 rats the levels of 5-HT were reduced, while 5-HT turnover was increased. There was also a significant increase of the 5-HT turnover in MS2-15 animals in the raphe nuclei, mainly due to increased 5-hydroxyindoleacetic acid (5-HIAA) levels, and an increase of 3,4-dihydroxyphenylacetic acid (DOPAC) levels in the ventral tegmental area (VTA) of stressed females. No significant differences were found in the immunohistochemical sections for tyrosine and tryptophan hydroxylase in these regions of the brain stem. In conclusion, the present results show that postnatal stress induces signs of neurological pathology that may contribute to the genesis of behavioral abnormalities later in life.

Dexamethasone treatment differentially affects the oxidative energy metabolism of rat brain mitochondria in developing and adult animals

We studied the effect of repeated exposure to dexamethasone (Dex) treatment on rat brain mitochondrial oxidative energy metabolism in developing rats at different postnatal ages, i.e. 2-5 week and in adults. The animals were injected with a dose of 2 mg of Dex/kg body weight at around 7:00 a.m. for three alternative days prior to the day of sacrifice; the control group animals received saline vehicle. We measured rates of respiration with different substrates, viz. glutamate, pyruvate+malate, succinate and ascorbate+TMPD; the contents of individual cytochromes and the dehydrogenases and ATPase activities. Dex treatment, in general, stimulated the state 3 rates of respiration rates in young animals in age-dependent and substrate-specific manner except for the 3 week group, whereas in the adults there was substantial inhibition of the respiration. The pattern of dehydrogenases activities matched with respiration rates. Dex treatment also resulted in uncoupling of the second and third site of phosphorylation in 3-week-old animals and in the adults. The contents of cytochrome aa3, b and ATPase activities decreased significantly after Dex treatment in all the age groups. The results thus emphasize that exposure to repeated Dex treatment can significantly influence the oxidative energy metabolism of brain mitochondria in young growing animals as well as in adults.

Glucocorticoids exacerbate hypoxia-induced expression of the pro-apoptotic gene Bnip3 in the developing cortex

Neonatal administration of the synthetic glucocorticoid, dexamethasone (DEX) retards brain growth, alters adult behaviors and induces cell death in the rat brain, thereby implicating glucocorticoids as developmentally neuroendangering compounds. Glucocorticoids also increase expression of pro-apoptotic Bcl-2 family members and exacerbate expression of hypoxic responsive genes. Bnip3 is a pro-apoptotic Bcl-2 family member that is upregulated in response to hypoxia. In these studies, we investigated the interactions of glucocorticoid receptor and hypoxia in the regulation of Bnip3 mRNA in cortical neurons. Using quantitative real time reverse transcription-polymerase chain reaction, we found that DEX treatment of postnatal days 4-6 rat pups caused a significant increase in Bnip3 mRNA expression compared with vehicle controls. A significant increase in Bnip3 mRNA was also measured in primary cortical neurons 72 h after treatment with RU28362, a glucocorticoid receptor selective agonist. In primary cortical neurons, hypoxia increased Bnip3 mRNA expression and this was exacerbated with RU28362 treatment. To elucidate the mechanism of glucocorticoid- and hypoxia-mediated regulation of Bnip3 transcription, a Bnip3 promoter-luciferase reporter construct was utilized in primary cortical neurons. Upregulation of the Bnip3 promoter was mediated by a single glucocorticoid response element and a hypoxic response element. Bnip3 overexpression in primary cortical neurons significantly increased cell death, which is dependent on the Bnip3 transmembrane domain. However, despite the increased expression of Bnip3 following glucocorticoid and hypoxia treatment, corresponding decreases in cell survival were minimal. These studies identify a novel pathway in the developing cortex through which glucocorticoids may enhance a metabolic insult, such as hypoxia.

Prenatal exposure to betamethasone decreases anxiety in developing rats: hippocampal neuropeptide y as a target molecule

Repeated antenatal administration of betamethasone is frequently used as a life-saving treatment in obstetrics. However, limited information is available about the outcome of this therapy in children. The initial prospective studies indicate that there are behavioral impairments in children exposed to repeated courses of prenatal betamethasone during the third trimester of pregnancy. In this study, pregnant rats received two betamethasone injections on day 15 of gestation. Using immunohistochemistry, the expression of a powerful anxiolytic molecule neuropeptide Y (NPY) was determined on postnatal day (PN) 20 in the hippocampus and basolateral amygdala (structures related to anxiety and fear) of the offspring. Prenatal betamethasone exposure induced significant increases in NPY expression in the hippocampus but not in the amygdala. Indeed, behavioral tests in the offspring, between PN20 and PN22 in the open field, on the horizontal bar, and in the elevated plus maze, indicated decreases in anxiety, without impairments in motor performance or total activity. Decreased body weight in betamethasone-exposed rats confirmed long-lasting effects of prenatal exposure. Thus, prenatal betamethasone treatment consistently increases hippocampal NPY, with decreases in anxiety-related behaviors and hippocampal role in anxiety in rats. Animal models may assist in differentiation between pathways of the desired main effect of the antenatal corticosteroid treatment and pathways of unwanted side effects. This differentiation can lead to specific therapeutic interventions directed against the side effects without eliminating the beneficial main effect of the corticosteroid treatment.

Cognition- and anxiety-related behavior, synaptophysin and MAP2 immunoreactivity in the adult rat treated with a single course of antenatal betamethasone

We investigated the effects of a single course of antenatal betamethasone on cognition- and anxiety-related behavior and synaptophysin and microtubule-associated protein 2 (MAP2) immunoreactivity in the adult rat hippocampus. On d 20 of gestation, pregnant rats were injected with either 1) 170 microg/kg body weight of betamethasone ("clinically equivalent dose," equivalent to 12 mg twice, 24 h apart); 2) half this dose; or 3) vehicle. Cognition- and anxiety-related behavior of the offspring was analyzed at an age of 5 mo using the Morris water maze, object recognition task, and open field test. Subsequently, synaptophysin and MAP2 immunoreactivity were measured in the hippocampus. We report no detrimental effects of antenatal betamethasone on cognition- and anxiety-related behavior and synaptophysin immunoreactivity in the adult rat. On the other hand, MAP2 immunoreactivity was decreased by betamethasone in males, suggesting a permanent impairment in the hippocampus. Interestingly, the lower dose appears to have less influence in terms of growth restriction, known to be associated with an increased risk of disease in adulthood. Further research might elucidate whether the betamethasone effect on hippocampal neurons persists later in life and could affect the aging process increasing the risk for neuropathology of the adult.