Embryonic exposure to corticosterone modifies the juvenile stress response, oxidative stress, and telomere length.

Early embryonic exposure to maternal glucocorticoids can broadly impact physiology and behaviour across phylogenetically diverse taxa. The transfer of maternal glucocorticoids to offspring may be an inevitable cost associated with poor environmental conditions, or serve as a maternal effect that alters offspring phenotype in preparation for a stressful environment. Regardless, maternal glucocorticoids are likely to have both costs and benefits that are paid and collected over different developmental time periods. We manipulated yolk corticosterone (cort) in domestic chickens (Gallus domesticus) to examine the potential impacts of embryonic exposure to maternal stress on the juvenile stress response and cellular ageing. Here, we report that juveniles exposed to experimentally increased cort in ovo had a protracted decline in cort during the recovery phase of the stress response. All birds, regardless of treatment group, shifted to oxidative stress during an acute stress response. In addition, embryonic exposure to cort resulted in higher levels of reactive oxygen metabolites and an over-representation of short telomeres compared with the control birds. In many species, individuals with higher levels of oxidative stress and shorter telomeres have the poorest survival prospects. Given this, long-term costs of glucocorticoid-induced phenotypes may include accelerated ageing and increased mortality.

Yolk Androstenedione in Domestic Chicks (Gallus Gallus Domesticus): Uptake and Sex-Dependent Alteration of Growth and Behavior

In birds, causes and consequences of variation in maternally-derived steroids in egg yolk have been the subject of intense experimentation. Many studies have quantified or manipulated testosterone ("T") and one of its immediate precursors, androstenedione ("A4") - often lumping the two steroids as "androgens" and treating them as functionally equivalent. However, yolk A4 is deposited in substantially higher concentrations than T, binds only weakly to the androgen receptor, and is readily converted into either T or estrone by steroidogenic enzymes present during embryonic development. Thus it may not be appropriate to assume that A4 has the same effect as T. In addition, A4's metabolic fate is likely to differ between females and males. The goals of this study were to examine the sex-specific uptake and metabolism of yolk A4 and consequences of elevated levels of yolk A4 on development and behavior of domestic chicks. Eggs were injected with 2mu Ci of tritiated androstenedione; radioactivity was detected in all tissues of day 7 and day 16 embryos and found in both aqueous and organics phases of day 7 yolk, with no difference between sexes. A second set of eggs was injected with 125ng of A4. A4 increased growth of morphological traits (tarsus, beak) in females, but not males. A4 males had smaller combs than controls; there was no treatment effect in females. A4 reduced tonic immobility behavior in both sexes. The results of this study illustrate the importance of distinguishing both between androgens and between sexes when investigating avian endocrine maternal effects. Copyright 2013 Elsevier Inc. All rights reserved.

Effect Of Yolk Testosterone On Gonadal Testosterone And Aromatase Activity In The Pre-Optic Area Of The Brain In Male Domestic C

Maternal effects are a mother¿s non-genetic contributions to development that alter phenotypic traits in offspring. Maternal effects can take the form of prenatal allocation of resources, such as the deposition of androgens into egg yolks. For example, elevated yolk testosterone increases male sexual behaviors such as copulation solicitation and courtship displays in some avian species, in addition to aggressive behaviors like pecks and intimidating postures towards same-sex competitors. However, the mechanism connecting in ovo testosterone exposure with changes in sexual and aggressive behaviors has yet to be elucidated. While testosterone released by the gonads is important in the activation of sexual behaviors, it must undergo conversion to estrogen by the enzyme aromatase in the pre-optic area (POA) of the avian brain for full expression of sexual activity. POA aromatase is also necessary for the activation of aggressive behaviors in male birds. This experiment tested the hypothesis that elevated yolk testosterone leads to changes in POA aromatase activity and levels of gonadal testosterone, as these two endocrine parameters may mediate the effect of yolk testosterone on the frequency of sexual and aggressive behaviors. The effect of elevated yolk testosterone on gonadal testosterone levels and aromatase activity in the POA of 3-day-old domestic chickens Gallus gallus domesticus was investigated. Unincubated eggs were injected with either 10 ng testosterone in 50 ¿L sesame oil (¿T chicks¿) or 50 ¿L sesame oil (¿C chicks¿). At 3 days post-hatch, gonadal testosterone content was measured after steroid extraction using an EIA, and aromatase activity in the POA was quantified by measuring the production of tritiated water from [1ß-3H]-androstenedione. I predicted that gonadal testosterone levels and brain aromatase activity would be higher in T chicks, however found no difference between treatments. Though juvenile T production peaks at 3 days post-hatch, it is possible that the reproductive systems, including the testes and POA, are not fully developed at this time.

The Effects of Altered Prenatal Melatonin Signaling on Adult Behavior and Hippocampal Gene Expression of the Male Rat: A Circadioneuroendocrine-Axis Hypothesis of Psychopathology

Disturbances in melatonin - the neurohormone that signals environmental darkness as part of the circadian circuit of mammals - have been implicated in various psychopathologies in humans. At present, experimental evidence linking prenatal melatonin signaling to adult physiology, behavior, and gene expression is lacking. We hypothesized that administration of melatonin (5 mg/kg) or the melatonin receptor antagonist luzindole (5 mg/kg) to rats in utero would permanently alter the circadian circuit to produce differential growth, adult behavior, and hippocampal gene expressionin the male rat. Prenatal treatment was found to increase growth in melatonin-treated animals. In addition, subjects exposed to melatonin prenatally displayed increased rearing in the open field test and an increased right turn preference in the elevated plusmaze. Rats administered luzindole prenatally, however, displayed greater freezing and grooming behavior in the open field test and improved learning in the Morris water maze. Analysis of relative adult hippocampal gene expression with RT-PCR revealed increasedexpression of brain-derived neurotrophic factor (BDNF) with a trend toward increased expression of melatonin 1A (MEL1A) receptors in melatonin-exposed animals whereas overall prenatal treatment had a significant effect on microtubule-associated protein 2(MAP2) expression. Our data support the conclusion that the manipulation of maternal melatonin levels alters brain development and leads to physiological and behavioral abnormalities in adult offspring. We designate the term circadioneuroendocrine (CNE)axis and propose the CNE-axis hypothesis of psychopathology.

The Effects of Prenatal Exposure to Altered Melatonin Levels on Hippocampal Gene Expression in the Male Rat

The stability of the circadian rhythm for mammals depends on the levels of serotonin and melatonin, neurohormones that signal for lightness and darkness, respectively. Disruption in the stability of neurohormones has been shown to be a critical factor in psychopathological disorders in humans. For example, altering levels of melatonin in utero through administration of melatonin or the melatonin receptor antagonist, luzindole, has been shown to cause changes in developmental growth and adult behavior in the male rat. Analysis of relative adult hippocampal gene expression with RT-PCR revealed differences in ARNTL expression that suggested abnormality in clock gene expression of the rats that were prenatally exposed to altered levels of melatonin. Differences in the degree of plasticity as suggested by previous behavior testing did not result in differences in gene expression for GABA receptors or NMDA receptors. Morevoer, growth associated protein 43, GAP-43, a protein that is necessary for neuronal growth cones as well as long term learning has been found to be critical for axon and presynaptic terminal formation and retention in other studies, but hippocampal gene expression in our study showed no significant alteration after exposure to various maternal melatonin levels. However, ARNTL is a key regulatory component of clock genes and the circadian cycle so that alterations in the expression of thi critical gene may lead to critical changes in neuronal growth and plasticity. Our data support the conclusion that the manipulation of maternal melatonin levels alters the brain development and the circadian cycles that may lead to physiological and behavioral abnormalities in adult offspring.

EFFECTS OF PRENATAL DEXAMETHASONE ON HIPOPCAMPAL SEROTONIN 1A RECEPTORS IN ADULT MALE RATS

The main activation route for the stress response is the hypothalamo-pituitaryadrenal axis (HPA) and the sympatho-adrenomedullary system. The HPA axis is a neuroendocrine feedback loop mediated by an array of tissue specific hormones, receptors and neurotransmitters that regulate glucocorticoid (GC) release. GCs are steroidal hormones produced by the adrenal glands and are key players in a negativefeedback loop controlling HPA activity. They influence the HPA axis through glucocorticoid receptors in the hypothalamus and pituitary and through both glucocorticoid (GR) and mineralcorticoid receptors (MR) that are co-localized in the hippocampus. Repeated or chronic stress exerts a negative influence on these HPA axis regulatory sites and contributes to potentially pathological conditions, especially during early development. For example, chronic stress promotes increased maternal adrenal gland secretion of glucocortiocoid, leading to abnormally high concentrations of GC inthe fetal environment. The timing and maturation of the HPA axis relative to birth is highly species specific and is closely linked to landmarks in fetal development. In rats this development of the HPA axis takes place in utero and continues even shortly after birth. It is likely that the maternal endocrine environment will affect fetal development during this critical time point and may alter the overall set point for the expression ofgenes and their protein products that mediate fetal HPA axis function. Dexamethasone (DEX) is a synthetic glucocorticoid (sGC) and is a consensus treatment in preterm pregnancies used to expedite fetal lung development. However it has been shown that DEX causes long term physiological and behavioral disorders in prenatally-exposed laboratory animals. Previous studies have also shown that it alters the MR: GR receptor ratio in the hippocampus. Taking into consideration corticosteroid regulation of serotonin receptors, especially 5HT1A receptors and their putative interaction with glucocorticoid receptors in the hippocampus, we hypothesized that prenatal DEX exposure would lead to changes in the expression and function of 5HT1A receptors in the hippocampus. We administered DEX to rat dams during the last trimester of gestation and investigated the changes in these receptors in the adult rat offspring. Radioligand receptor binding assays were used to study hippocampal 5HT1A receptor binding affinity and number. Our results demonstrate that hippocampal 5HT1A receptors are increased in the DEX animalscompared with controls by 36%, with no change in binding affinity. The efficiency of ligand-induced receptor signal transduction via G-protein activation was also studied using [35S]GTPγS incorporation assay. Using this technique, we showed that there was no significant difference in the maximum ligand mediated stimulation (Emax) of 5HT1Areceptors between control and dex exposed animals. However, the intracellular signalling efficiency of hippocampal 5HT1A receptors was diminished, since a significant increase in EC50 values was obtained with the dex exposed group showing a value 51% higherEC50 than controls. Taken together these data illustrate a considerable change in the 5HT1A component of the serotonergic system following prenatal DEX exposure.

Maternal and Postweaning High-Fat Diets Disturb Hippocampal Gene Expression, Learning, and Memory Function

We tested the hypothesis that excess saturated fat consumption during pregnancy, lactation, and/or postweaning alters the expression of genes mediating hippocampal synaptic efficacy and impairs spatial learning and memory in adulthood. Dams were fed control chow or a diet high in saturated fat before mating, during pregnancy, and into lactation. Offspring were weaned to either standard chow or a diet high in saturated fat. The Morris Water Maze was used to evaluate spatial learning and memory. Open field testing was used to evaluate motor activity. Hippocampal gene expression in adult males was measured using RT-PCR and ELISA. Offspring from high fat-fed dams took longer, swam farther, and faster to try and find the hidden platform during the 5-day learning period. Control offspring consuming standard chow spent the most time in memory quadrant during the probe test. Offspring from high fat-fed dams consuming excess saturated fat spent the least. The levels of mRNA and protein for brain-derived neurotrophic factor and activity-regulated cytoskeletal-associated protein were significantly decreased by maternal diet effects. Nerve growth factor mRNA and protein levels were significantly reduced in response to both maternal and postweaning high-fat diets. Expression levels for the N-methyl-D-aspartate receptor (NMDA) receptor subunit NR2B as well as synaptophysin were significantly decreased in response to both maternal and postweaning diets. Synaptotagmin was significantly increased in offspring from high fat-fed dams. These data support the hypothesis that exposure to excess saturated fat during hippocampal development is associated with complex patterns of gene expression and deficits in learning and memory.