Early post-stress administration of MR or GR antagonist in adolescent female rats restored anxiogenic-like behavior and modified the HPA axis response in the adulthood.

Several brain structures responsible for controlling stress responses reach maturity during adolescence. Therefore, acute or chronic stress in prepuberty may negatively affect stress responses as well as behavior in adulthood. The hypothalamus-pituitary-adrenal axis (HPA) is part of the stress system whose inhibitory control is regulated by glucocorticoids through mineralocorticoid (MR) and glucocorticoid (GR) receptors. In this study, we aimed to determine whether MR or GR blockade after stress in adolescence prevents changes in exploratory behavior and HPA axis control in adult female rats. Adolescent female rats (26 days old) were submitted to one or seven daily restraint sessions followed by administration of MR (spironolactone) or GR (RU-486) antagonists. At 60 days old, animals were evaluated in the elevated plus maze and at 61 days old rats were subjected to acute stress to evaluate the HPA response. The chronic restraint in the adolescence induced an anxiogenic effect in the adult animals that was reverted by either MR or GR antagonist. In the same way chronic stress reduced the HPA axis activity by blunted corticosterone (CORT) secretion and decreased the activation of Corticotropin Releasing Hormone (CRH) neurons in the paraventricular nucleus. The post-stress blocking of GR independently restored the CORT secretion without effect on central activation. The acute stress in the adolescence had minor enduring effects. We concluded that the use of RU-486 and spironolactone after stress in the early adolescence can improve behavioral changes induced by stress whereas RU-486 only showed effect on the HPA axis response in adulthood.

Hypothalamic-pituitary-adrenal axis responsivity to an acute novel stress in female rats subjected to the chronic mild stress paradigm.

The chronic mild stress (CMS) paradigm is the most frequently investigated animal model for major depression. The hypothalamic-pituitary-adrenal (HPA) axis participates in the generation of depressive symptomatology. We examined whether the depression-like state induced by CMS is associated with immediate changes in HPA axis activation in response to a novel acute stress and whether this response could be modified by hormonal status. Adult female Wistar rats were ovariectomized and received estrogen or vehicle pellets. After 2 weeks, rats were subjected to CMS (or control) conditions for 2.5 or 4.5 weeks. Rats were subsequently subjected to restraint stress for 1 h, and plasma corticosterone (CT) levels were determined before (2:00 p.m.) and after acute stress induction (3:00 and 4:00 p.m.). CT levels and FOS expression were measured in the medial parvocellular subdivision of the PVN (PaMP), central (CeA) and medial amygdala (MeA) and ventral subiculum of the hippocampus (vSub). Plasma CT levels in animals treated with 6.5 weeks of estrogen were elevated before and 1 h after restraint stress induction. Results indicate that the estrogen chronicity and CMS exposure impacted CT secretion. Neuronal PaMP, CeA, MeA and vSub activity decreased after 4.5 weeks of CMS in all groups. No differences were detected between CMS and non-CMS groups. These data suggest that the HPA central hyporesponsiveness observed in the experimental groups subjected to a longer protocol period was independent to CMS paradigm and estrogen treatment restored partially its activity. These data suggest that additional stressors could be responsible for the observed alterations of the HPA axis.

Adaptogenic potential of royal jelly in liver of rats exposed to chronic stress.

Restraint and cold stress increase both corticosterone and glycemia, which lead to oxidative damages in hepatic tissue. This study assessed the effect of royal jelly (RJ) supplementation on the corticosterone level, glycemia, plasma enzymes and hepatic antioxidant system in restraint and cold stressed rats. Wistar rats were allocated into no-stress, stress, no-stress supplemented with RJ and stress supplemented with RJ groups. Initially, RJ (200mg/Kg) was administered for fourteen days and stressed groups were submitted to chronic stress from the seventh day. The results showed that RJ supplementation decreases corticosterone levels and improves glycemia control after stress induction. RJ supplementation also decreased the body weight, AST, ALP and GGT. Moreover, RJ improved total antioxidant capacity, SOD activity and reduced GSH, GR and lipoperoxidation in the liver. Thus, RJ supplementation reestablished the corticosterone levels and the hepatic antioxidant system in stressed rats, indicating an adaptogenic and hepatoprotective potential of RJ.

Dexamethasone Prevents Lipopolysaccharide-Induced Epithelial Barrier Dysfunction in Rat Ileum.

Inflammatory mediators have been postulated as elementary inducing factors to the disruption of the intestinal tight junctions (TJ) and consequently, gut permeability and bacterial translocation. Corticosteroids are considered the mainstay in the treatment of septic shock; however, the impact of this therapy on the intestinal epithelial barrier dysfunction during septic shock remains unknown. Our aims were to demonstrate the role of low dexamethasone (DEX) doses in modulation of the inflammatory response, as well as the expression and the arrangement of TJ proteins in endotoxemic rats. One hour before the endotoxemia induction by lipopolysaccharide (LPS) administration, rats were pretreated with DEX at two low-doses (0.1 and 1.0 mg/kg). The parameters assessed included intestinal permeability, bacterial translocation, cytokines production, histology injury, localization, and expression of TJ proteins. Endotoxemic rats displayed intestinal epithelial barrier dysfunction, characterized by increased permeability and bacterial translocation, TJ disruption (opening and changes to its constituent proteins expression) and hyperactivation of the inflammatory response. On the other hand, the pretreatment with DEX attenuated the systemic and mucosal production of inflammatory mediators and also reverted the LPS-induced ileal injuries, increasing the expression of occludin and claudin-1, but also reducing claudin-2. Moreover, the histological damages and the morphology of the TJ were preserved by the DEX administration, therefore reducing their LPS-induced opening. The present study sheds light on the fact that early DEX treatment breaks the vicious cycle of local gut inflammation and barrier dysfunction in endotoxemia, especially preserving an essential structure of this monolayer epithelium, the TJ.

Royal jelly decreases corticosterone levels and improves the brain antioxidant system in restraint and cold stressed rats.

Restraint and cold stress induces the hypothalamic-pituitary-adrenal (HPA) axis to release corticosterone from the adrenal gland, which can worsen the antioxidant defense system in the central nervous system. Here, we investigated the corticosterone levels and the antioxidant defense system in the cerebellum and brain, as well as in its isolated regions, such as cerebral cortex, striatum and hippocampus of stressed rats supplemented with royal jelly (RJ). Wistar rats were supplemented with RJ for 14days and the stress induction started on the 7th day. Stressed rats increased corticosterone levels, glycemia and lipid peroxidation in the brain and cerebellum, cerebral cortex and hippocampus besides reduced glutathione defense system in the brain and striatum. Rats supplemented with RJ decreased corticosterone, maintained glycemia and decreased lipid peroxidation in the brain, cerebellum, as well as striatum and hippocampus, besides improved glutathione defense system in cerebral cortex and striatum. This study suggests an anti-stress and neuroprotective effect of RJ under stress conditions.

Estrogen receptors ERα and ERß participation in hypothalamus-pituitary-adrenal axis activation by hemorrhagic stress.

The sympato-adrenal-system and hypothalamus-pituitary-adrenal (HPA) axis are anatomically and functionally connected with participation of several brain areas that express estrogen receptors (ERα and ERß). We assessed the neuronal activity of these areas for FOS expression and the action of PPT (ERα agonist) or DPN (ERß agonist) in HPA axis activity during hemorrhagic stress. Ovariectomized Wistar rats treated with vehicle (DMSO) or ER agonists were catheterized for blood collection. Animals received (control) or not (hemorrhagic) immediate reposition with the same volume of saline. Immunohistochemistry was performed for FOS, tyrosine hydroxylase (TH) and corticotropin releasing hormone (CRH) in the brain areas. In vehicle-treated animals, hemorrhage enhanced: plasma corticosterone (CORT), oxytocin (OT) and vasopressin (AVP) measured by radioimmunoassay; the expression of TH-FOS co-localized neurons in ventrolateral medulla (A1C1) and FOS expression in medial parvocellular paraventricular nucleus (mpPVN). In controls, PPT decreased: plasma CORT; FOS expression at locus coeruleus (LC); FOS and CRH-FOS at mpPVN, compared to vehicle. After hemorrhage, PPT decreased: plasma CORT; FOS expression at LC and mpPVN; TH-FOS at LC, solitary tract nucleus (NTS), A1C1; CRH-FOS at mpPVN, compared to vehicle. After hemorrhage DPN decreased: plasma CORT; FOS expression at LC and mpPVN; TH-FOS at LC, A1C1; CRH-FOS at mpPVN, compared to vehicle. PPT blocked the increase of OT secretion and increased AVP secretion, after hemorrhage. DPN reduced OT and increased AVP levels, regardless hemorrhage. In hemorrhagic stress, ERα and ERß reduced the HPA axis activation and neuronal activity in brain areas involved in the HPA axis control.

STAT5 signaling in kisspeptin cells regulates the timing of puberty.

Previous studies have shown that kisspeptin neurons are important mediators of prolactin's effects on reproduction. However, the cellular mechanisms recruited by prolactin to affect kisspeptin neurons remain unknown. Using whole-cell patch-clamp recordings of brain slices from kisspeptin reporter mice, we observed that 20% of kisspeptin neurons in the anteroventral periventricular nucleus was indirectly depolarized by prolactin via an unknown population of prolactin responsive neurons. This effect required the phosphatidylinositol 3-kinase signaling pathway. No effects on the activity of arcuate kisspeptin neurons were observed, despite a high percentage (70%) of arcuate neurons expressing prolactin-induced STAT5 phosphorylation. To determine whether STAT5 expression in kisspeptin cells regulates reproduction, mice carrying Stat5a/b inactivation specifically in kisspeptin cells were generated. These mutants exhibited an early onset of estrous cyclicity, indicating that STAT5 transcription factors exert an inhibitory effect on the timing of puberty.

Recovery of normal testicular temperature after scrotal heat stress in rams assessed by infrared thermography and its effects on seminal characteristics and testosterone blood serum concentration.

Reestablishment of testicular normal temperature after testicular heat stress is unknown and its effect varies widely. The aim of this study was to investigate the impact of scrotal insulation (IN) on testicular temperature and its relation to semen quality and testosterone blood serum concentration. For this, 33 rams were used; 17 submitted to IN for 72 hours (using bags involving the testes) and 16 not submitted to IN (control group). The experiment was performed between August and December 2013 in Pirassununga, Brazil (21°56″13″ South/47°28'24″ West). Seminal characteristics, testosterone blood serum concentration, rectal temperature (RT), respiratory frequency, scrotal superficies mean temperature (SSMT), and eye area mean temperature (EAMT) were analyzed 7 days before IN and 21, 35, 49, 63, and 90 days afterward. Scrotal superficies mean temperature and EAMT were measured by thermography camera FLIR T620. Testosterone was evaluated by radioimmunoassay. Analysis of variance was used to determine the main effects of treatment, time, and treatment-by-time interaction using PROC MIXED of SAS software adding command REPEAT. Pearson correlation test was used to verify correlation between SSMT, EAMT, RT, and respiratory frequency. Significant difference was considered when P ≤ 0.05. At the end of IN, SSMT was higher (P < 0.05) in insulated group (32.26 ± 0.19(o)C) than in control group (30.58 ± 0.18(o)C), and the difference between rectal and testicular (deduced from SSMT) temperatures was 1.12 °C; in the other times of the evaluation this difference was between 2.91 and 4.25 °C in IN group. Scrotal superficies mean temperature was reestablished 24 hours after IN. Rectal temperature and EAMT presented correlation (r = 0.59; P < 0.0001). There was time-by-treatment interaction for total sperm (P = 0.0038) and progressive motility (P = 0.01), abnormal spermatozoa (P < 0.0001), membranes integrity (P < 0.0001), induced thiobarbituric acid reactive substances (TBARSs; P = 0.05), and DNA integrity (P = 0.0004). These semen characteristics were negatively affected 21 days after IN, and excluding induced TBARSs and abnormalities, recovered 35 days afterward; induced TBARSs just were affected after 49 days of IN; sperm abnormalities just recovered after 63 days. Testosterone blood serum concentration was lesser in insulated rams (P = 0.03). Thus, the difference of 1.12 °C between RT and testicular temperature impacts semen quality and testosterone blood serum concentration. Moreover, this study shows that rams can recover testes temperature efficiently toward IN and that infrared thermography is an efficient tool to identify differences on SSMT.

Low-level laser therapy to recovery testicular degeneration in rams: effects on seminal characteristics, scrotal temperature, plasma testosterone concentration, and testes histopathology.

The aim of this study was to investigate the efficiency of low-level laser therapy (LLLT) to recovery testicular degeneration in rams. In the first study, rams were induced to testicular degeneration by scrotal insulation, and then, they were treated using LLLT at 28 J/cm(2) (INS28) or 56 J/cm(2) (INS56) energy densities. Sperm kinetics, morphology, and membranes integrity as well as proportion of lumen area in seminiferous tubule were assessed. In the second study, rams were submitted or not to scrotal insulation and treated or not by the best protocol of LLLT defined by experiment 1 (INS28). In this study were evaluated sperm kinetics, morphology, membranes integrity, ROS production, and DNA integrity. Testosterone serum concentration and proportion of lumen area in seminiferous tubule were also analyzed. Insulation was effective in promoting sperm injuries in both experiments. Biostimulatory effect was observed in experiment 1: INS28 presented smaller proportion of lumen area (P = 0.0001) and less degeneration degree (P = 0.0002). However, in experiment 2, there was no difference between the groups (P = 0.17). In addition, LLLT did not improve sperm quality, and there was a decreasing for total and progressive motility (P = 0.02) and integrity of sperm membranes (P = 0.01) in LLLT-treated groups. Moreover, testosterone concentration was not improved by LLLT (P = 0.37). Stimulation of aerobic phosphorylation by LLLT may have led to a deregulated increase in ROS leading to sperm damages. Thus, LLLT at energy of 28 J/cm(2) (808 nm of wavelength and 30 mW of power output) can induce sperm damages and increase the quantity of cells in seminiferous tubule in rams.

[Blockade of AT1 receptor of Angiotensin II reduces the number of antral follicles in female rats with obesity induced by cafeteria diet]. / Bloqueio do receptor AT1 da Angiotensina II reduz o número de folículos antrais em ratas com obesidade induzida por dieta de cafeteria.

PURPOSE: To evaluate the follicular development of female Wistar rats with obesity induced by the cafeteria diet, submitted to the administration of losartan (LOS), an antagonist of the AT1 receptor of Angiotensin II. METHODS: At weaning (21 days of age), female Wistar rats were randomly divided, into two groups: control (CTL) that received standard chow and cafeteria (CAF) that received a cafeteria diet, a highly palatable and highly caloric diet. At 70 days of age, at the beginning of the reproductive age, animals of the CAF group were subdivided into two groups (n = 15/group): CAF, that received water, and CAF+LOS, that received LOS for 30 days. The CTL group also received water by gavage. At 100 days of age, the animals were euthanized and body weight (BW) as well as the retroperitoneal, perigonadal and subcutaneous fat weights were analyzed. The right ovaries were isolated for counting the number of primary, secondary, antral and mature follicles. Plasma levels of FSH, LH, prolactin and progesterone hormones were analyzed. The results were expressed as mean ± standard error of the mean. Data were analyzed statistically by one-way ANOVA followed by the Newman-Keuls post-test (p < 0.05). RESULTS: BW and fat weight, as well as the number of antral follicles, were higher in the CAF group compared to the CTL group. However, FSH and LH levels were lower in CAF animals compared to CTL animals. LOS administration attenuated the reduction of FSH and LH levels. Progesterone and PRL levels were similar among groups. CONCLUSION: LOS could improve follicular development in obese females and could be used as an adjunctive drug in the treatment of infertility associated with obesity.

Bloqueio do receptor AT1 da Angiotensina II reduz o número de folículos antrais em ratas com obesidade induzida por dieta de cafeteria / Blockade of AT1 receptor of Angiotensin II reduces the number of antral follicles in female rats with obesity induced by cafeteria diet

OBJETIVO: Avaliar o desenvolvimento folicular em ratas Wistar com obesidade induzida por dieta de cafeteria (DCAF) submetidas à administração de losartan (LOS), um antagonista do receptor AT1 da Angiotensina II. MÉTODOS: Aos 21 dias de vida, as ratas foram separadas aleatoriamente em dois grupos: controle (CTL), que recebeu ração padrão, e cafeteria (CAF), que recebeu a DCAF, altamente palatável e calórica. Aos 70 dias de vida, início da idade reprodutiva, animais do grupo CAF foram subdivididos em dois grupos (n=15/grupo): CAF, que recebeu água, e CAF+LOS, que recebeu 30 mg/kg de peso corporal (PC) de LOS por gavagem durante 30 dias. O grupo CTL também recebeu água por gavagem. Aos 100 dias de vida foi realizada a eutanásia dos animais e o PC e das gorduras retroperitoneal, perigonadal e subcutânea foi avaliado. Os ovários direitos foram retirados para contagem do número dos diferentes tipos de folículos ovarianos. As concentrações plasmáticas dos hormônios folículo-estimulantes (FSH), luteinizante (LH), prolactina (PRL) e progesterona foram avaliadas. Os resultados foram expressos como média±erro padrão da média. Para análise estatística, foi utilizado one-way ANOVA, seguido pelo pós-teste de Newman-Keuls (p<0,05). RESULTADOS: O PC e das gorduras, assim como o número de folículos antrais, foi elevado no grupo CAF em relação ao CTL. Todavia, as concentrações de FSH e LH foram mais baixas entre os animais CAF. A administração de LOS reduziu o PC e das gorduras retroperitoneal e subcutânea, bem como o número de folículos antrais. O tratamento com LOS atenuou a redução das concentrações de FSH e de LH. As concentrações de progesterona e PRL foram semelhantes entre os grupos estudados. CONCLUSÃO: O uso de LOS pode favorecer o desenvolvimento folicular em fêmeas obesas e pode possibilitar sua utilização como fármaco coadjuvante no tratamento da infertilidade associada à obesidade. .

PURPOSE: To evaluate the follicular development of female Wistar rats with obesity induced by the cafeteria diet, submitted to the administration of losartan (LOS), an antagonist of the AT1 receptor of Angiotensin II. METHODS: At weaning (21 days of age), female Wistar rats were randomly divided, into two groups: control (CTL) that received standard chow and cafeteria (CAF) that received a cafeteria diet, a highly palatable and highly caloric diet. At 70 days of age, at the beginning of the reproductive age, animals of the CAF group were subdivided into two groups (n=15/group): CAF, that received water, and CAF+LOS, that received LOS for 30 days. The CTL group also received water by gavage. At 100 days of age, the animals were euthanized and body weight (BW) as well as the retroperitoneal, perigonadal and subcutaneous fat weights were analyzed. The right ovaries were isolated for counting the number of primary, secondary, antral and mature follicles. Plasma levels of FSH, LH, prolactin and progesterone hormones were analyzed. The results were expressed as mean±standard error of the mean. Data were analyzed statistically by one-way ANOVA followed by the Newman-Keuls post-test (p<0.05). RESULTS: BW and fat weight, as well as the number of antral follicles, were higher in the CAF group compared to the CTL group. However, FSH and LH levels were lower in CAF animals compared to CTL animals. LOS administration attenuated the reduction of FSH and LH levels. Progesterone and PRL levels were similar among groups. CONCLUSION: LOS could improve follicular development in obese females and could be used as an adjunctive drug in the treatment of infertility associated with obesity. .

Estrogen, but not progesterone, induces the activity of nitric oxide synthase within the medial preoptic area in female rats.

The control of gonadotropin-releasing hormone (GnRH) secretion depends on the action of ovarian steroids and several substances, including nitric oxide (NO). NO in the medial preoptic area (MPOA) stimulates the proestrus surge of luteinizing hormone (LH). We studied the effect of estrogen (Tamoxifen-TMX) and progesterone (RU-486) antagonists on mRNA and protein expression of NO synthase (NOS), the enzyme that produces NO, as well as its activity within MPOA. Female rats received s.c. injections of TMX (3mg/animal) on first and second days of the estrous cycle (9 am), RU-486 (2mg/animal) on first, second, (8 am and 5 pm) and third days of the estrous cycle (8 am) or oil (controls) and were killed on the third day (5 pm). Real time-PCR and western blotting were performed to study NOS mRNA and protein expressions. The NOS activity was indirectly assessed by measuring the conversion from [(14)C]-L-arginine into [(14)C]-L-citrulline. TMX significantly decreased neuronal NOS (nNOS) mRNA expression (90%), and the activity of NOS, but did not alter nNOS protein expression. Also, TMX significantly decreased LH, FSH, estrogen and progesterone plasma levels. RU-486 nor affected NOS mRNA and protein expressions neither the NOS activity in the MPOA, but reduced FSH levels. The nitrergic system in the MPOA can be stimulated by estrogen whereas TMX decreased NOS activity and mRNA expression. In conclusion, the involvement of the nitrergic system in the MPOA to induce the surge of LH on proestrus depends on the estrogen action to stimulate the mRNA-nNOS expression and the activity of nNOS but it does not seem to depend on progesterone action.

Early adolescent stress alters behavior and the HPA axis response in male and female adult rats: the relevance of the nature and duration of the stressor.

Adolescence is a period of transition from childhood to adulthood that involves the maturation of social and cognitive behavior. The activation of the stress system during this phase can lead to long-lasting adverse effects. We aimed to verify whether the nature and duration of stressors applied in adolescent female and male rats would alter their exploratory behavior and stress responses as adults. Wistar rats on day P26 were divided into groups that were subjected to 1 (acute) or 7 (chronic) insulin or lipopolysaccharide (LPS) injections or restraint stress for 1 h. At P60, the rats were subjected to the elevated plus-maze, and at P61, they were subjected to 30 min of restraint stress after which plasma samples and brains were collected. LPS acute injection promoted anxiolytic effects in male adults. Acute LPS treatment and acute or chronic restraint induced anxiolytic behavior in female adults. The administration of adolescent chronic stimuli to males decreased the adult plasma corticosterone (CORT) and progesterone levels after restraint. Adolescent acute restraint or LPS injection decreased the CORT response in female adults. The adult neuronal activation of the corticotrophin-releasing hormone and vasopressin on the paraventricular nucleus did not vary according to the type of adolescent stress or sex. Our results indicate that both adult behavior and the glucocorticoid stress response are affected differently in males versus females by adolescent stress. The duration of stressors had a greater effect on the CORT and progesterone response in males, whereas the nature of the stressor had a greater effect on exploratory behavior in females.

Differential immunoreactivity of glucocorticoid receptor and GABA in GABAergic afferents to parvocellular neurons in the paraventricular nucleus.

We assessed the distribution of glucocorticoid receptors (GR), GABA (γ-aminobutyric acid) neurons and co-localization of GR in GABA-positive neurons for four hypothalamic sources of GABAergic projections to the parvocellular neurons in the paraventricular nucleus (PVH) from normal, sham-surgery and adrenalectomized male rats subjected to intraperitoneal injections of saline or dexamethasone. Blood samples were collected to measure corticosterone by radioimmunoassay. The distribution of GR, GABA-positive neurons and co-localization of GR in GABA-positive neurons were analyzed by immunofluorescence in sections from the paraventricular nucleus (PVH). In intact and sham rats, dexamethasone induced expression of GABAergic neurons in the regions of the anterior periventricular nucleus (PVa) coincident with anterior (PVHap) and medial (PVHmp) parvocellular subdivisions of thePVH. However, the co-expression of GR in GABAergic neurons was found only in the region of the PVa coincident with PVHmp. These findings confirm that glucocorticoids may directly act on GABAergic neurons through GR. PVHap and PVHmp present differentiated patterns of GABA and GR expression between then. The co-localization of GR in GABA-positive neurons in the region of the PVa coincident with PVHmp demonstrates a critic importance of this region to control the hypothalamus-pituitary-adrenal axis through GABAergic mediation.

Divergent roles of the CRH receptors in the control of gonadotropin secretion induced by acute restraint stress at proestrus.

CRH has been implicated as a mediator of stress-induced effects on the hypothalamus-pituitary-gonad axis, acting via CRH receptors in various brain regions. We investigated whether the effects of restraint stress on the secretion of gonadotropins on the morning of proestrus are mediated by the CRH-R1 or CRH-R2 receptors in the oval subdivision of the anterolateral BST, the central amygdala, the locus coeruleus (LC), or the A1 and A2 neuron groups in the medulla. At proestrus morning, rats were injected with antalarmin (a CRH-R1 antagonist), asstressin2-B (a CRH-R2 antagonist) or vehicles. Thirty minutes after the injection, the animals were placed into restraints for 30 min, and blood was sampled for 2 h. At the end of the experiment, the brains were removed for immunofluorescence analyses. Restraint stress increased the levels of FSH and LH. Antalarmin blocked the stress-induced increases in FSH and LH secretion, but astressin2-B only blocked the increase in FSH secretion. LC showed intense stress-induced neuronal activity. FOS/tyrosine-hydroxylase coexpression in LC was reduced by antalarmin, but not astressin2-B. The CRH-R1 receptor, more than CRH-R2 receptor, appears to be essential for the stimulation of the hypothalamus-pituitary-gonad axis by acute stress; this response is likely mediated in part by noradrenergic neurons in the LC. We postulate that the stress-induced facilitation of reproductive function is mediated, at least in part, by CRH action through CRH-R1 on noradrenaline neurons residing in the LC that trigger GnRH discharge and gonadotropin secretion.

The role of AT1 receptor-mediated reproductive function in renovascular hypertension in male rats.

There is an association between hypertension and reproductive dysfunction. Angiotensin II (Ang II) is involved in the pathogenesis of hypertension and the regulation of reproduction. The present study aimed to determine whether the angiotensinergic system mediates the effects of hypertension on reproductive function in male rats subjected to a two-kidney, one-clip (2K1C) model. Sexual behavior parameters, gametogenesis and plasma concentrations of Ang II, testosterone, prolactin and corticosterone were evaluated in male rats 28days after 2K1C or sham surgery and losartan (Los) treatment (a type 1 angiotensin II (AT1) receptor antagonist) or vehicle (V) treatment. The animals were divided into Sham+V, 2K1C+V, Sham+Los and 2K1C+Los groups. The 2K1C+V group showed a hypertensive response, inhibition of sexual behavior, spermatogenesis dysfunction, and increases in plasma Ang II and prolactin. Conversely, plasma testosterone decreased, and plasma corticosterone remained constant. Losartan treatment normalized blood pressure and prevented the changes in plasma testosterone and prolactin, sexual behavior and spermatogenesis in the 2K1C+Los group. In addition, losartan treatment caused an additional increase in circulating Ang ll in both groups (Sham+Los and 2K1C+Los). Together, these results suggest that Ang ll, acting through the AT1 receptor, modulates behavioral and endocrine parameters of reproductive function during renovascular hypertension. In addition, the effects of circulating Ang II on plasma testosterone and prolactin seem to contribute to the spermatogenic and sexual dysfunctions in hypertensive rats.

The CRH-R1 receptor mediates luteinizing hormone, prolactin, corticosterone and progesterone secretion induced by restraint stress in estrogen-primed rats.

Acute stress has been shown to modify hypothalamus-pituitary-gonadal (HPG) axis activity. Corticotropin-releasing hormone (CRH), the principal regulator of the hypothalamus-pituitary-adrenal (HPA) axis, has been implicated as a mediator of stress-induced effects on the reproductive axis. The role of the specific CRH receptor subtypes in this response is not completely understood. In the current study, we investigated the role of the CRH-R(1) receptor on luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), progesterone (P) and corticosterone (CT) secretion in stress-induced responses under the influence of estrogen (E(2)). Estrogen-primed ovariectomized rats (estradiol cypionate, 10 µg sc) received an i.v. administration of antalarmin (0.1 or 1mg/kg), a selective CRH-R(1) antagonist, or vehicle before restraint stress for 40 min. Seven blood samples were collected from two experimental groups (one from 10:00 h to 14:00 h and the other from 10:00 h to 18:00 h). An increase of plasma LH induced by restraint acute-stress was followed by alteration of the secretion pattern in the estrogen-induced afternoon surge. In a similar manner, we observed a suppression of the afternoon surge in plasma FSH, a delay of E(2)-induced PRL secretion, and an increase in plasma P and CT. Antalarmin attenuated stress-induce LH increase, decreased CT and P secretion and blocked the stress effects on PRL secretion. These findings suggest that CRH-R(1) mediates, at least in part, the restraint stress effects on the HPA, PRL, and reproductive axes.

Progesterone production in superovulated holstein heifers and in crossbred recipient of embryo supplemented with betacarotene and tocopherol / Produção de progesterona em novilhas Holandesas superovuladas e receptoras de embrião mestiças suplementadas com betacaroteno e tocoferol

Two experiments were conducted to evaluate the effect of the intramuscular injection of betacarotene associated to tocopherol on the plasma concentration progesterone of superovulated Holstein heifers (experiment 1) and in crossbred (Bos taurus x Bos indicus) heifers submitted to fixed-time embryo transfer (FTET, experiment 2). In experiment 1, after estrus synchronization and superovulation animals were inseminated 12 and 24 hours after estrus onset and embryos flushed 7 days later. Heifers were allocated randomly to one of three treatments: Control; T800 (800 mg of betacarotene plus 500 mg of tocopherol) and T1200 (1,200 mg of betacarotene plus 750 mg of tocopherol). The treatments were given on the day of ear implant placement and repeated on the first day of superovulation. Blood samples were collected on D0, D5, D9, D12 and D16. In experiment 2, treatments were imposed at intravaginal device insertion (D0). The same experimental design, as in experiment 1, was used. Blood samples were collected on D17 (embryos implanted) for progesterone determination by radioimmunoassay. In experiment 1, average plasma progesterone concentrations after corpora lutea formation (D12 plus D16 means) were 13.7±1.8 ng/ml, 14.5±2.3 ng/ml and 10.8±2.3 ng/ml for control, T800 and T1200, respectively, and did not differ (P=0.44). In experiment 2, progesterone concentrations on D17 in Control (8.88±0.57 ng/ml), T800 (7.48±0.64 ng/ml) and T1200 (5.90±1.33 ng/ml) groups were similar (P=0.11). Results indicate that the supplemental betacarotene and tocopherol injections did not influence peripheral progesterone concentrations in superovulated Holstein donors and crossbreed recipients heifers.

Dois experimentos foram conduzidos para avaliar o efeito da injeção intramuscular de betacaroteno associada ao tocoferol, na concentração plasmática de progesterona de novilhas Holandesas superovuladas (Experimento 1) e em novilhas cruzadas (Bos taurus x Bos indicus) submetidas à transferência embrionária em tempo fixo (TETF, experimento 2). No experimento 1, após a sincronização do estro e superovulação, os animais foram inseminados entre 12 a 24 h após o início do estro e os embriões recuperados após 7 dias. As novilhas foram divididas, aleatoriamente, em 1 de 3 tratamentos: Controle (duas injeções de soro); T800 (800 mg de betacaroteno mais 500 mg de tocoferol) e T1200 (1.200 mg de betacaroteno mais 750 mg de tocoferol). Os tratamentos foram administrados no dia da colocação do implante de progesterona e repetido no primeiro dia da superovulação. As colheitas de sangue foram realizadas no D0, D5, D9, D12 e D16. No experimento 2, os tratamentos foram realizados no momento da inserção do dispositivo de progesterona (D0). Utilizou-se o mesmo delineamento do experimento 1. A colheita de sangue para a determinação da progesterona por radioimunoensaio foi realizada no D17 (inovulação embrionária). No experimento 1, a concentração plasmática média, após formação do corpo lúteo (média da soma de D12 com D16) foi de 13,7±1,8 ng/ml, 14,5±2,3 ng/ml e 10,8±2,3 ng/ml para os grupos Controle, T800 e T1200, respectivamente, e não diferiram (P=0,44) entre os tratamentos. No experimento 2, a concentração de progesterona nas receptoras, no dia 17, foi semelhante (P=0,11) entre os grupos controle (8,88±0,57 ng/ml), T800 (7,48±0,64 ng/ml) e T1200 (5,90±1,33 ng/ml). Os resultados indicaram que as injeções de suplemento com betacaroteno e tocoferol não influenciaram na concentração plasmática de progesterona em novilhas Holandesas doadoras de embriões e em novilhas cruzadas, receptoras de embrião.

Effect of social instigation and aggressive behavior on hormone levels of lactating dams and adult male Wistar rats

Among rodents, maternal aggression in the postpartum period represents a species-typical adaptation, but when aggressive behavior increases beyond this adaptive level, it can represent a model of excessive aggression. This study assessed the neuroendocrine response of lactating rats and socially instigated male rats. The aim of the present study was to assess neuroendocrine responses and the behavioral pattern of lactating rats and males that were subjected to an emotional stressor using the social instigation protocol. We measured plasma corticosterone levels as the key hormonal parameter of the hypothalamic-pituitary-adrenal (HPA) axis and oxytocin, prolactin, and progesterone, which are released in response to several types of stressors. Our results showed that lactating rats that were subjected to only social instigation or aggressive confrontation in the presence of their pups had lower plasma corticosterone levels, and this response was similar to oxytocin, prolactin, and progesterone levels. By contrast, male rats showed increased corticosterone levels after being subjected only to social instigation. Male rats also engaged in aggressive behavior compared with the control group. In conclusion, this study demonstrated that lactating rats subjected to social instigation exhibited an attenuation of the HPA axis response, which is considered to be crucial to the dam's welfare so that it can care for its offspring. Thus, we can infer that lactation is a relevant factor in neuroendocrine responses to stress because of the increased levels of corticosterone in males.(AU)

Effect of social instigation and aggressive behavior on hormone levels of lactating dams and adult male Wistar rats

Among rodents, maternal aggression in the postpartum period represents a species-typical adaptation, but when aggressive behavior increases beyond this adaptive level, it can represent a model of excessive aggression. This study assessed the neuroendocrine response of lactating rats and socially instigated male rats. The aim of the present study was to assess neuroendocrine responses and the behavioral pattern of lactating rats and males that were subjected to an emotional stressor using the social instigation protocol. We measured plasma corticosterone levels as the key hormonal parameter of the hypothalamic-pituitary-adrenal (HPA) axis and oxytocin, prolactin, and progesterone, which are released in response to several types of stressors. Our results showed that lactating rats that were subjected to only social instigation or aggressive confrontation in the presence of their pups had lower plasma corticosterone levels, and this response was similar to oxytocin, prolactin, and progesterone levels. By contrast, male rats showed increased corticosterone levels after being subjected only to social instigation. Male rats also engaged in aggressive behavior compared with the control group. In conclusion, this study demonstrated that lactating rats subjected to social instigation exhibited an attenuation of the HPA axis response, which is considered to be crucial to the dam's welfare so that it can care for its offspring. Thus, we can infer that lactation is a relevant factor in neuroendocrine responses to stress because of the increased levels of corticosterone in males.