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.

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.

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.

Dehydroepiandrosterone protects against oxidative stress-induced endothelial dysfunction in ovariectomized rats.

Cardiovascular disease is less frequent in premenopausal women than in age-matched men or postmenopausal women. Moreover, the marked age-related decline in serum dehydroepiandrosterone (DHEA) level has been associated to cardiovascular disease. The aim of this study was to evaluate the effects of DHEA treatment on vascular function in ovariectomized rats. At 8 weeks of age, female Wistar rats were ovariectomized (OVX) or sham (SHAM) operated and 8 weeks after surgery both groups were treated with vehicle or DHEA (10mg kg⁻¹ week⁻¹) for 3 weeks. Aortic rings were used to evaluate the vasoconstrictor response to phenylephrine (PHE) and the relaxation responses to acetylcholine (ACh) and sodium nitroprusside (SNP). Tissue reactive oxygen species (ROS) production and SOD, NADPH oxidase and eNOS protein expression were analysed. PHE-induced contraction was increased in aortic rings from OVX compared to SHAM, associated with a reduction in NO bioavailability. Furthermore, the relaxation induced by ACh was reduced in arteries from OVX, while SNP relaxation did not change. The incubation of aortic rings with SOD or apocynin restored the enhanced PHE-contraction and the impaired ACh-relaxation only in OVX. DHEA treatment corrected the increased PHE contraction and the impaired ACh-induced relaxation observed in OVX by an increment in NO bioavailability and decrease in ROS production. Besides, DHEA treatment restores the reduced Cu/Zn-SOD protein expression and eNOS phosphorylation and the increased NADPH oxidase protein expression in the aorta of OVX rats. The present results suggest an important action of DHEA, improving endothelial function in OVX rats by acting as an antioxidant and enhancing the NO bioavailability.

A calcium-induced calcium release mechanism supports luteinizing hormone-induced testosterone secretion in mouse Leydig cells.

Leydig cells are responsible for the synthesis and secretion of testosterone, processes controlled by luteinizing hormone (LH). Binding of LH to a G protein-coupled receptor in the plasma membrane results in an increase in cAMP and in intracellular Ca(2+) concentration ([Ca(2+)](i)). Here we show, using immunofluorescence, that Leydig cells express ryanodine receptors (RyRs) and inositol 1,4,5-trisphosphate receptors (IP(3)Rs). Measurements of intracellular calcium changes using the fluorescent calcium-sensitive dye fluo-3 and confocal microscopy show that both types of receptors are involved in a calcium-induced calcium release (CICR) mechanism, which amplifies the initial Ca(2+) influx through plasma membrane T-type calcium channels (Ca(V)3). The RyRs and IP(3)Rs are functional, as judged from both their activation by caffeine and IP(3) and block by ryanodine and 2-aminoethoxydiphenyl borate (2-APB), respectively. RyRs are the principal players involved in the release of Ca(2+) from the endoplasmic reticulum, as evidenced by the fact that global Ca(2+) changes evoked by LH are readily blocked by 100 muM ryanodine but not by 2-APB or xestospongin C. Finally, steroid production by Leydig cells is inhibited by ryanodine but not by 2-APB. These results not only broaden our understanding of the role played by calcium in Leydig cells but also show, for the first time, that RyRs have an important role in determining testosterone secretion by the testis.

Neonatal handling reduces renal function in adult rats.

BACKGROUND/AIMS: To evaluate the effects of neonatal handling on hydroelectrolytic balance in adult rats. METHODS: The litters were divided into two groups: nonhandled and handled. The procedure consisted of handling the pups for 1 min/day in the first 10 days postnatally. When adults, animals had their body weight verified and were housed in individual metabolic cages. After a 24-hour period, urine samples were collected and the urinary and water intake volumes measured. Blood samples to determine osmolality, aldosterone, corticosterone, angiotensin II, creatinine, urea, sodium and potassium levels were collected. The kidneys were removed for histological assessment. Urinary osmolality, sodium, urea and creatinine were also measured and the creatinine clearance (CC) calculated. RESULTS: No difference between groups was found in the body weight. Handled animals showed a reduction in the total kidney wet weight, water intake, urinary volume, CC, plasma angiotensin II, corticosterone and aldosterone when compared to the nonhandled and an increase in the urinary osmolality and sodium excretion fraction. No differences in serum potassium and no evidence of structural changes were demonstrated by histological analysis. CONCLUSION: Neonatal handling induced long-lasting effects decreasing renal function without evidence of kidney structural changes.

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.

Effects of neonatal handling on central noradrenergic and nitric oxidergic systems and reproductive parameters in female rats.

Early-life environmental events that disrupt the mother-pup relationship may induce profound long-lasting changes on several behavioral and neuroendocrine systems. The neonatal handling procedure, which involves repeated brief maternal separations followed by experimental manipulations, reduces sexual behavior and induces anovulatory estrous cycles in female rats. On the afternoon of proestrus, neonatally handled females show a reduced surge of luteinizing hormone (LH) and an increased content of gonadotropin-releasing hormone in the medial preoptic area (MPOA). In order to detect the possible causes for the reduced ovulation and sexual behavior, the present study aimed to analyze the effects of neonatal handling on noradrenaline (NA) and nitric oxide (NO) levels in the MPOA on the afternoon of proestrus. Neonatal handling reduced MHPG (NA metabolite) levels and MHPG/NA ratio in the MPOA, indicating decreased NAergic activity. Additionally, neonatal handling decreased NO levels, as measured by the metabolites (NO(x)), nitrite and nitrate in the same period. We may conclude that the neonatal handling procedure decreased activity of the NAergic and NOergic systems in the MPOA during proestrus, which is involved in the control of LH and FSH secretion, and this may possibly explain the anovulatory estrous cycles and reduced sexual behavior of the neonatally handled female rats.

GABAergic mediation of stress-induced secretion of corticosterone and oxytocin, but not prolactin, by the hypothalamic paraventricular nucleus.

The hypothalamus-pituitary-adrenal axis (HPA) participates in mediating the response to stressful stimuli. Within the HPA, neurons in the medial parvocellular region of paraventricular nucleus (PVN) of the hypothalamus integrate excitatory and inhibitory signals triggering secretion of corticotropin-releasing hormone (CRH), the main secretagogue of adrenocorticotropic hormone (ACTH). Stressful situations alter CRH secretion as well as other hormones, including prolactin and oxytocin. Most inputs to the PVN are of local origin, half of which are GABAergic neurons, and both GABA-A and GABA-B receptors are present in the PVN. The objective of the present study was to investigate the role of GABA-A and GABA-B receptors in the PVN's control of stress-induced corticosterone, oxytocin and prolactin secretion. Rats were microinjected with saline or different doses (0.5, 5 and 50 pmol) of GABA-A (bicuculine) or GABA-B (phaclofen) antagonists in the PVN. Ten minutes later, they were subjected to a stressor (ether inhalation) and blood samples were collected 30 min before and 10, 30, 60, 90 and 120 min after the stressful stimulus to measure hormone levels by radioimmunoassay. Our results indicate that GABA acts in the PVN to inhibit stress-induced corticosterone secretion via both its receptor subtypes, especially GABA-B. In contrast, GABA in the PVN stimulates oxytocin secretion through GABA-B receptors and does not alter prolactin secretion.

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.

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.

Pargyline effect on luteinizing hormone secretion throughout the rat estrous cycle: correlation with serotonin, catecholamines and nitric oxide in the medial preoptic area.

The neurons that produce gonadotrophin-releasing hormone (GnRH) are mainly found in the medial preoptic area (MPOA) and constitute a common final pathway to the control of luteinizing hormone (LH) surge on proestrus. The control of GnRH secretion depends on several neurotransmitters, such as serotonin (5-HT), noradrenaline (NA), dopamine (DA) and nitric oxide (NO). The aim of this work was to study the profile of 5-HT, catecholamines and their main metabolites in the MPOA throughout the estrous cycle and their interactions with NO system in this area to control LH surge. For this purpose, the following were evaluated: (I) the effect of pargyline (a monoamine oxidase inhibitor) acute treatment on plasma LH secretion throughout the estrous cycle, correlated with changes of 5-HT, DA and NA content as well as activity and expression of neuronal NO synthase (nNOS) within MPOA; (II) the effect of 5,7-dihydroxitriptamine (a drug that depletes 5-HT) microinjection into MPOA on plasma LH in ovariectomized rats treated with oil, estradiol (E(2)) or E(2) plus progesterone (P(4)). Pargyline prevented LH surge on proestrus without altering its basal secretion. Throughout the estrous cycle, pargyline augmented both 5-HT and DA contents in approximately 300% and NA content in 50% in the MPOA. During proestrus, pargyline stimulated nNOS activity at 9 h and inhibited it at 11 h. nNOS expression was inhibited by pargyline at 15 h. Depletion of 5-HT content in the MPOA increased LH secretion in ovariectomized rats treated with E(2) plus P(4), but it did not modify in rats treated with either oil or E(2). Therefore, the present data show that pargyline treatment can inhibit proestrus LH surge through a mechanism that may involve 5-HT and NO systems in the MPOA. Moreover, the effect of 5-HT in the MPOA for limiting LH surge seems to depend on plasma levels of E(2) and P(4).

Effects of acute stress on the day of proestrus on sexual behavior and ovulation in female rats: participation of the angiotensinergic system.

Physical or emotional stress can affect the female reproductive physiology and angiotensin II (Ang II) is a hormone that participates in the stress response and also in the control of reproductive hormones. The present study aimed at evaluating the effects of acute stress in the morning and afternoon of proestrus on sexual behavior and ovulation and the participation of Ang II in the stress-induced effects. Female rats with regular estrous cycles were used. Several different stress protocols were tested in the morning and in the afternoon of proestrus: restraint stress 10 min; restraint stress 1 h and ether stress, respectively. The participation of Ang II was evaluated by injecting Ang II receptor antagonists (losartan and PD123319) 15 min before stress. The lordosis quotient was recorded and the number of oocytes was counted. Plasma levels of luteinizing hormone, progesterone, prolactin and corticosterone were measured. All types of stress in the morning of proestrus induced a reduction in the number of oocytes. Restraint stress (1 h) in the afternoon of proestrus induced a significant reduction in the lordosis quotient. Peripheral and central losartan, but not PD123319, injections partly reverted the effects of stress on ovulation in the morning of proestrus. Acute stress in the morning of proestrus also reduced luteinizing hormone, progesterone and prolactin surges later on the same day. In conclusion, acute stress on the day of proestrus can affect female reproductive physiology. Moreover, the angiotensinergic system, through AT(1) receptors, participates in the effects of acute stress in the morning of proestrus.

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.

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.

Changes in alpha-estradiol receptor and progesterone receptor expression in the locus coeruleus and preoptic area throughout the rat estrous cycle.

We have previously shown that the locus coeruleus (LC) is essential for triggering surges of LH. Since LC neurons are responsive to estradiol, which induces progesterone receptor (PR) expression, this study aimed to investigate whether LC neurons express the alpha-estradiol receptor (alphaER) and PR as well as comparing such responses to that observed in the preoptic area (POA). Female rats were perfused at 10, 14 and 16 h on each day of the estrous cycle, and a blood sample was collected for estradiol, progesterone and LH measurements. alphaER- and PR immunoreactive (ir) neurons were detected in POA and LC by immunocytochemistry (ICC). Higher plasma estradiol levels were observed on the day of proestrus, when a smaller number of alphaER-ir POA neurons were detected. An increase in the number of alphaER-ir neurons were observed at 16 h of proestrus and estrus. The number of PR-ir neurons increased in POA only at 16 h of proestrus, and remained unchanged during all other days and times. The profile of alphaER-ir and PR-ir neurons in LC changed over the estrous cycle, with a lower expression on metestrus morning and reaching a peak on diestrus afternoon before declining on the day of proestrus. However, on estrus afternoon, alphaER-ir neurons increased, while PR-ir neurons decreased which may be related to the prolactin surge of estrus. These data show that LC neurons express alphaER and PR and seem to be more sensitive to variations in estradiol than POA. Also, the fluctuation in alphaER and PR observed for LC neurons seems to accompany the hormonal events that occur during the estrous cycle. This profile of alphaER and PR expression might be related to the ability of estradiol and progesterone in regulating the activity of LC neurons, which could be associated to the control mechanisms of LH and prolactin release.

Estradiol and progesterone modulation of angiotensin II receptors in the arcuate nucleus of ovariectomized and lactating rats.

The expression of angiotensin II (Ang II) receptors in the brain is modulated by estradiol and progesterone. Considering that Ang II plays a critical role in controlling prolactin secretion and that neurons in the arcuate nucleus (ARC) are the main regulator of this function, the present study aimed to evaluate ARC Ang II receptor binding in 2 experimental models with different estradiol and progesterone plasma levels. Animals were divided into 4 groups: ovariectomy (OVX) plus oil vehicle, OVX plus estradiol and progesterone replacement, lactating rats on day 7 postpartum, and lactating rats on day 20. Animals were killed by decapitation, and the brains were removed. Ang II receptors were quantified by autoradiography in ARC. Trunk blood samples were collected, and plasma estradiol and progesterone were measured by radioimmunoassay. Treatment of OVX rats with estradiol and progesterone increased Ang II receptor binding when compared to OVX vehicle-treated animals. Plasma estradiol (r = +0.77) and progesterone (r = +0.87) were highly correlated with Ang II receptors in ovariectomized animals. Lactating rats (day 20) showed a significant decrease in Ang II receptor binding and plasma progesterone when compared to lactating rats (day 7), however, no difference was seen in plasma estradiol. Plasma levels of progesterone (r = +0.81), but not estradiol (r = +0.32), were highly correlated with Ang II receptors in lactating rats. In conclusion, present results show that ARC Ang II receptors decreases on day 20 of lactation compared to day 7 and are highly correlated with plasma progesterone, indicating a pivotal role for progesterone in this regulation.

Neonatal handling reduces angiotensin II receptor density in the medial preoptic area and paraventricular nucleus but not in arcuate nucleus and locus coeruleus of female rats.

Neonatal handling alters the hypothalamic-pituitary-adrenal (HPA) axis and the hypothalamic-pituitary-gonads axis (HPG) in adult animals, and angiotensin II (Ang II) modulates the functions in these axes. We tested whether neonatal handling could change the density of Ang II receptors in some central areas in female rats. Results showed decreased density of the Ang II receptors in the medial preoptic area (MPOA) and hypothalamic paraventricular nucleus (PVN) of the neonatal handled group.

Neonatal handling induces alteration in progesterone secretion after sexual behavior but not in angiotensin II receptor density in the medial amygdala: implications for reproductive success.

Neonatal handling affects the hypothalamus-pituitary-gonadal axis in female rats. Indeed, postnatal handling induces anovulatory estrous cycles and decreases sexual receptiveness. On the other hand, Angiotensin II (Ang II) infused into the medial amygdala (MeA) reduces sexual behavior in male and female rats. Considering this, and that gonadal steroid secretion after copulatory behavior is important for reproductive success, the purpose of the present study was to investigate whether the reduction in sexual receptiveness in neonatally handled female rats is mediated by changes in Ang II receptor density in MeA. Moreover, gonadal steroid secretion after sexual behavior was analyzed. Two groups of female Wistar rats were studied: nonhandled (pups were left undisturbed) and handled (pups were handled for 1 min once a day during the first 10 days of life). Once they were 80-85 days old in the evening of the proestrus day, sexual receptiveness was recorded and after that the animals were killed by decapitation. Trunk blood samples were collected, and plasma estradiol and progesterone were measured by radioimmunoassay. The brains were removed for Ang II receptor autoradiography in MeA. The decreased lordosis quotient in the neonatally handled group was confirmed in the present study. Neonatal handling also reduced the progesterone concentration in the plasma, but did not change the estradiol and the density of Ang II receptors in MeA. The reduced progesterone could be due to the decreased lordosis frequency of handled females. However, this decreased sexual receptiveness is not mediated by changes in Ang II receptors in MeA.