Effects Of Estradiol Benzoate Research Articles

Role of Membrane Estrogen Receptor Alpha on the Positive Feedback of Estrogens on Kisspeptin and GnRH Neurons.

Estrogens act through nuclear and membrane-initiated signaling. Estrogen receptor alpha (ERα) is critical for reproduction, but the relative contribution of its nuclear and membrane signaling to the central regulation of reproduction is unclear. To address this question, two complementary approaches were used: estetrol (E4) a natural estrogen acting as an agonist of nuclear ERs, but as an antagonist of their membrane fraction, and the C451A-ERα mouse lacking mERα. E4 dose- dependently blocks ovulation in female rats, but the central mechanism underlying this effect is unknown. To determine whether E4 acts centrally to control ovulation, its effect was tested on the positive feedback of estradiol (E2) on neural circuits underlying luteinizing hormone (LH) secretion. In ovariectomized females chronically exposed to a low dose of E2, estradiol benzoate (EB) alone or combined with progesterone (P) induced an increase in the number of kisspeptin (Kp) and gonadotropin-releasing hormone (GnRH) neurons coexpressing Fos, a marker of neuronal activation. E4 blocked these effects of EB, but not when combined to P. These results indicate that E4 blocked the central induction of the positive feedback in the absence of P, suggesting an antagonistic effect of E4 on mERα in the brain as shown in peripheral tissues. In parallel, as opposed to wild-type females, C451A-ERα females did not show the activation of Kp and GnRH neurons in response to EB unless they are treated with P. Together these effects support a role for membrane-initiated estrogen signaling in the activation of the circuit mediating the LH surge.

Effect of Estradiol Benzoate on Epididymis Duct in Male Wistar Ratsat Pre-Puberty

Effect of Estradiol Benzoate on Epididymis Duct in Male Wistar Ratsat Pre-Puberty

FSH and estradiol benzoate administration recover spermatogenesis and sexual hormone levels in a busulfan-injured rat model

Busulfan induces azoospermia and testicular atrophy, while follicle stimulating hormone (FSH) and estradiol benzoate (EB) may improve spermatogenesis. Our objective was to determine the effects of FSH and EB on the recovery of spermatogenesis, histology, sexual hormones, and testicular gene expression in the testis of a busulfan-injured rat model. Forty adult rats were assigned into eight groups. Half received a single intraperitoneal saline or 30 mg/kg busulfan injection, and 42 days after, the animals received intramuscular injections for 10 days: 1 ml saline, 7.5 IU FSH, and 12 μg/kg EB or FSH+EB. One day after, blood plasma was obtained for hormone analysis, sperm was recovered from epididymis, and testes were processed for histology and RNA extraction. Busulfan decreased sperm count, motility, and viability; induced seminiferous tubular atrophy; and decreased blood testosterone, FSH, and luteinizing hormone. Hormonal treatments partially recovered spermatogenesis, decreasing tubular atrophy. They also decreased caspase 3 and iNOS expression while increasing Bcl-2 expression, compared with the busulfan treatment. FSH+EB was the most efficient treatment, also increasing the concentration of sexual hormones close to no-busulfan levels. Thus, busulfan has a clear negative effect in spermatogenesis in the rat model, and FSH and EB, especially combined, could help to reverse these effects.

Effects of Hindbrain Infusion of an Estrogen Receptor Antagonist on Estrogenic Modulation of Eating Behavior

Estradiol (E2) inhibits eating behavior in females via activating estrogen receptors (ERs) within the brain. Activation of hindbrain ERαs has been shown to be sufficient to inhibit eating behavioral pattern. To investigate the involvement of hindbrain ERαs in estrogenic control of eating behavior, intracerebroventricular infusion (4th i.c.v.) of an estrogen receptor antagonist, ICI 182780 (ICI), was performed in ovariectmized female rats. Significantly lower daily food intake was observed in rats after estradiol benzoate (EB) injections. The effect of EB on food intake was significantly compromised by 4th i.c.v. infusions of both 4 and 8 nM ICI solutions. The results suggest that hindbrain infusions of ICI can significantly attenuate the inhibitory effect of E2 on food intake. Importantly, 4th i.c.v. infusions during 12 days exerted no effect per se on eating. Further, there was no difference in the number of ERα immunopositive neurons in the selected hypothalamic nuclei and nucl. tractus solitarius. We conclude that the 4th i.c.v. infusions with ICI attenuated the exogenous estrogenic effect on food intake in ovariectomized rats, and the hindbrain is an important site pro viding estrogenic control of food intake.

Effects of estradiol benzoate on proliferation and differentiation of in vitro cultured hippocampal neural stem cells

Objective To explore the potential mechanism of action of estradiol benzoate on proliferation and differentiation of rat hippocampal neural stem cells. Methods Hippocampus tissues from SD rats were dissociated and plated into culture flasks.Neural stem cells were identified by immunofluorescence against Nestin.After treatment with different concentration of estradiol benzoate(10-10, 10-9, 10-8, 10-7, 10-6 mol/L), the proliferation and differentiation of neural stem cells were assessed by MTT assay and the proportion of neurons and astrocytes in differentiated cells was assessed by flow cytometry.Western blot assay was performed to detect the expression levels of protein in neural stem cells. Results (1)The neural stem cells formed neurospheres and grew in floating, and were Nestin-positive.Estrogen receptors, including ERα and ERβ, were expressed in neural stem cells; (2)After treatment with 10-8 mol/L estradiol benzoate versus in the control group, the cell viability was significantly increased(t=5.36, P=0.003), and the ratio of neuron-specific nuclear protein(NeuN)-positive neuron cells in total cells was significantly increased(t=4.32, P=0.02), but the ratio of glial fibers acidic protein(GFAP)-positive cell in total cells was decreased(t=4.65, P=0.008). The expression levels of GDNF, GFRal and Ret proteins were enhanced in the estradiol benzoate group compared with the control group. Conclusions Appropriate concentration of estradiol benzoate promotes proliferation and differentiation ofin vitrocultured hippocampal neural stem cells and elevates the ratio between neurons and glial cells differentiated from neural stem cells. Key words: Estradiol; Stem cells; Hippocampus

Effect of estradiol benzoate injection to male rabbits on glucose, total protein, albumin, calcium concentrations and prostate tissue

Objective: This study was carried out to investigate the effects of estradiol benzoate (EB) injection to male rabbits on glucose, total-protein, albumin, calcium concentrations and prostate tissue, and the role of prolactin as an important mediator of estrogen action in prostate. Materials and methods: Fifty four adult male rabbits were used in this study. The rabbits were randomly divided into two groups. Group A contained 36 male rabbits, which were further randomly divided into four sub-groups, three of them contained 10 rabbits and one sub-group contained 6 rabbits as control. Group B contained 18 male rabbits, which were divided randomly into three equal sub-groups. Three sub-groups of Groups A and B were treated once each on alternative day with the intramuscular injections of EB dosed at 40, 80 and 120 µg/rabbit, respectively for 20 days, whereas the fourth sub-group of Group A received no estradiol, and Group B received 1 mg Bromocriptine Mesilate in addition to EB through oral route on each alternative day. Blood samples were collected for measuring glucose, t-protein, albumin and calcium levels. Prostate tissue samples were collected from all the rabbits for histological studies. Results: Glucose was significantly ( P ?0.05) increased as a result of 80 µg EB injection, while significantly ( P ?0.05) decreased due to 40 and 120 µg EB injection. Total protein significantly ( P ?0.05) increased due to injection of 40 µg EB, however t-protein was not changed due to 40 and 120 µg injection. On the other hand, the results of albumin and calcium were not affected ( P ?0.05) by EB. In prostate tissues, EB induced hyperplasia with dysplasia or dysplasia only, but this effect was mild due to inhibition of prolactin. Conclusion: The injection of EB to male rabbits increased or decreased glucose level, increased t-protein level mildly or not changed, while albumin and calcium levels were not affected. EB induced hyperplasia on prostate tissue, and this effect was reduced by prolactin inhibition indicating that prolactin might have a role on the action of estrogen. http://doi.org/10.5455/javar.2017.d184

Incorporation of estradiol benzoate to CIDR protocol improves the reproductive responses in crossbred dairy heifers.

The present study was designed to determine the effect of estradiol benzoate (EB) on reproductive response following a controlled internal drug release (CIDR) protocol in crossbred (Sahiwal × Friesian) dairy heifers. In the first trial, a total of 100 crossbred dairy heifers were treated with CIDR protocol for 7days and injected with the PGF2α on day 6. After 24h of CIDR removal, one group (EB = 50) was injected with estradiol benzoate whereas the other (control = 50) remained untreated. Estrus intensity and response were recorded visually and ovulation rate was recorded by ultrasonography. All heifers were artificially inseminated at 48 and 60h following CIDR removal. Heifers were scanned for pregnancy within days 30-40 of artificial insemination (AI). In the second trial, two subgroups of heifers were included to observe the estrus and ovulatory events. The results of the first trial revealed that estrus response was achieved 100% in both the treatment groups. Estrus intensity (2.9 ± 0.1 vs. 2.0 ± 0.7) and ovulation rate (100 vs. 88%) differed significantly (P < 0.05) between the EB and control groups. However, a tendency for higher pregnancy per AI was observed (54 vs. 36%; P = 0.07) in EB than that in control groups. The results of the second trial revealed that a significantly (P < 0.05) shorter estrus and earlier ovulatory events were observed in EB-treated heifers. It is concluded that the incorporation of estradiol benzoate to the CIDR protocol is helpful to improve the estrus signs and enhance the ovulation and the pregnancy per AI in crossbred dairy heifers.

Estradiol Increases Choice of Cocaine over Food in Male Rats

Women present more severe cocaine addiction profiles than men on some measures. Similarly, female rodents display greater cocaine intake under a variety of cocaine self‐administration schedules, including a choice self‐administration procedure in which subjects can choose between cocaine and food. Estradiol has been shown to largely mediate many of these sex effects, including cocaine choice. However, the effects of estradiol on male cocaine behavior are less studied. Male brains express estrogen receptors, and estradiol has been shown to modulate behaviors that share underlying neurobiology with cocaine reinforcement. Therefore, we sought to characterize the effects of estradiol in males, on choice behavior and on motivation for both cocaine and food in single‐reinforcer progressive ratio (PR) tests.MethodsMale castrated rats were treated daily with estradiol benzoate (EB) (5ug/0.1, S.C., n=23) or vehicle (peanut oil, n=23) throughout choice testing (3 grain food pellets, 1 mg/kg/infusion I.V. cocaine) and single‐reinforcer food and cocaine PR testing. Additionally, a subset of rats were tested in a modified choice procedure, in which the “cost” of the reinforcers were manipulated by escalating the fixed‐ratio (FR) requirement of the preferred reinforcer while maintaining the FR requirement of the non‐preferred reinforcer constant.ResultsEB increased cocaine intake in the choice test. EB subjects also demonstrated greater cocaine PR breakpoints, but had similar food PR breakpoints to controls. However, after a switch from home‐cage food restriction to ad libitum feeding, EB subjects increased food PR breakpoints while food PR breakpoints dropped in the control group. In the cost escalation test, cocaine preferring rats defended their cocaine intake to a greater degree than food preferring rats. There was no effect of EB on this measure. This suggests that, although estradiol increases the proportion of cocaine preferring rats in the choice procedure, EB does not further affect this measure.ConclusionThese results indicate that the effects of estradiol on choice behavior are not sex‐specific, estradiol increases the allocation of behavior towards cocaine in both sexes. Considering this concordant effect on behavior, the underlying neurobiology of choice behavior may be similarly affected by estradiol in both sexes.Support or Funding InformationNIDA (5R01DA027525‐05)

Metabolic Effects of Temporally Targeted Food Restriction in Female Rats with or without Estrogen

To lose weight, overweight people limit calories by reducing food intake and/or number of meals, typically eating in the evening when activity is less. We use rats to model this pattern by providing food for 2 hr/day during the inactive period. In previous work, estrogen decreased body weight and food intake during temporally targeted food restriction as it does during ad libitum feeding. Thus, the goal of this study was to investigate mechanisms that underlie estrogen effects on feeding during temporally targeted food restriction. Ovariectomized rats were given estradiol benzoate (EB) or vehicle twice weekly for 3 wks of ad libitum feeding, or for 2 wks of ad libitum feeding followed by 1 wk of access to food for only 2 hr/d. On the last day of food restriction, some rats were allowed to eat before sacrifice (FED) and others were not (FASTED). Rats then were sacrificed to collect blood, livers, adrenals, and uteri. In both hormone groups, 1-hr food intake increased during targeted food restriction; however EB-treated rats ate less. Insulin and leptin were reduced in FASTED rats in both hormone groups. Liver glycogen was elevated in ad libitum rats of both hormone groups but decreased in both FED and FASTED food restricted groups. Glucose was reduced, while triglycerides and free fatty acids were elevated in EB-treated rats that were food restricted. Adrenal weights and plasma corticosterone were greater in EB-treated rats, but increased in both groups with food restriction, suggesting that temporally targeted restriction is a potent stressor. Together, these results suggest that EB influences metabolic patterns during temporally targeted food restriction, which may contribute to EB effects on eating and body weight during that restriction. Support: OCAST HR12-196

Different effects of bisphenol-A on memory behavior and synaptic modification in intact and estrogen-deprived female mice.

Bisphenol-A (BPA) has the capability of interfering with the effects of estrogens on modulating brain function. The purpose of this study was to investigate the effects of BPA on memory and synaptic modification in the hippocampus of female mice under different levels of cycling estrogen. BPA exposure (40, 400 μg/kg/day) for 8 weeks did not affect spatial memory and passive avoidance task of gonadally intact mice but improved ovariectomy (Ovx)-induced memory impairment, whereas co-exposure of BPA with estradiol benzoate (EB) diminished the rescue effect of EB on memory behavior of Ovx mice. The results of morphometric measurement showed that BPA positively modified the synaptic interface structure and increased the synaptic density of CA1 pyramidal cell in the hippocampus of Ovx females, but inhibited the enhancement of EB on synaptic modification and synaptogenesis of Ovx mice. Furthermore, BPA up-regulated synaptic proteins synapsin I and PSD-95 and NMDA receptor NR2B but inhibited EB-induced increase in PSD-95 and NR2B in the hippocampus of Ovx mice. These results suggest that BPA interfered with normal hormonal regulation in synaptic plasticity and memory of female mice as a potent estrogen mimetic and as a disruptor of estrogen under various concentrations of cycling estrogen.

A Possible Non-genomic Epileptogenic Properties of Estradiol Attenuated by MK801 and DNQX in Amygdala Kindled Rats.

Although the epileptogenic properties of estrogens have been widely demonstrated in several models and species, the mechanism(s) by which estrogens can acutely change seizure parameters including after discharge and seizure durationremains to be determined. In the present study, we examined the role of NMDA (N-methyl-D-aspartate), non-NMDA andestrogen receptors in estradiol benzoate(EB) effects on kindled seizure parameters. Different groups of fully kindled male rats received either EB (30 μg /Kg); EB plus MK801 (2 mg/Kg, as NMDA antagonist); DNQX (7.5 mg/Kg);tamoxifen (TAM, 0.1 mg/Kg, as non- NMDA antagonist) or intra-amygdala injection of anisomycine (30 mmol/mL, a protein synthesis inhibitor). Kindled seizure parameters including after discharge duration (ADD) and stage 5 duration(S5D) were determined at 0.25 and 3 h post sesame oil (EB solvent) or EB treatment. While pretreatment with either MK801 or DNQX could block the ADD prolongation induced by EB at 0.25 h, they had no effect on S5D prolongation at 3 h. Moreover, application of anisomycine or TAM had no effect on estradiol induced ADD and S5D prolongation. These results indicate that both NMDA and non-NMDA receptors could be involved in EB induced ADD prolongation. The observed short termnon-estrogenic receptor or protein synthesis dependent effects of EB may provide a non-genomic mechanism for the stimulatory effects of the steroid on seizure activity.

Pre- and/or Postsurgical Administration of Estradiol Benzoate Increases Skin Flap Viability in Female Rats

It has been shown that estrogens have a protective effect with regard to tissue ischemia. Therefore, in this macroscopic and histological investigation, the effect of estradiol benzoate on skin flap viability was studied in sham-operated and ovariectomized Sprague-Dawley rats. Three months prior to flap surgery a group of rats underwent ovariectomy, while the remaining animals underwent a sham operation. Subsequently, all rats had a 2 × 8-cm skin flap created on the dorsum. Rats were randomly divided into estradiol- or saline-treated groups. Treatment started either on the day of flap excision or 3 days prior to the surgery. Our results showed that administration of estradiol benzoate prior to and after flap surgery significantly decreases skin flap necrosis in both sham-operated and ovariectomized rats, with the highest survival rate in animals where treatment started 3 days prior to flap surgery. In conclusion, the observed protective effect of estradiol on skin flap viability could potentially be applied to plastic and reconstructive surgery in postmenopausal women. Nevertheless, further research is needed to explain the exact underlying mechanism and to find the optimal treatment protocol for human clinical practice.

Neonatal exposure to zearalenone induces long term modulation of ABC transporter expression in testis

Mycotoxin zearalenone (ZEN) is a cereal contaminant produced by various species of Fusarium fungi. When interacting with estrogen receptors, ZEN leads to animal fertility disturbances and other reproductive pathologies. Few data are available on the effects of perinatal exposure to ZEN, particularly in the blood–testis barrier. The aim of this study was to assess the impact of ZEN in adult rats exposed neonatally. We focused on the expression and cellular localization of major ABC transporters expressed in adult rat testis, comparing ZEN effects with those of Estradiol Benzoate (EB) neonatal exposure. Dose-dependent and long term modulations of mRNA and protein levels of Abcb1, Abcc1, Abcg2, Abcc4 and Abcc5 were observed, along with Abcc4 protein cellular delocalization. ZEN exposure of SerW3 Sertoli cells showed modulation of Abcb1, Abcc4 and Abcc5. Comparison with EB exposure showed similar modulation profiles for Abcg2 but differential modulations for Abcb1, Abcc1, Abcc4 and Abcc5 in vivo, and a similar profile for Abcb1 modulation by ZEN and EB, but differential modulation for Abcc4 and Abcc5 in vitro. ZEN and EB effects were inhibited by in vitro addition of the pure anti-estrogen ICI 182.780, suggesting the at least partial implication of ZEN estrogenic activity in these modulations. These results suggested that ZEN neonatal exposure could affect the exposure of testis to ABC transporter substrates, and negatively influence spermatogenesis and male fertility.

Sensitization of sexual behavior in ovariectomized rats by chronic estradiol treatment

The ovariectomized (OVX) rat treated with estradiol benzoate (EB) is used to elucidate neuroendocrine mechanisms of sexual behavior. Chronic behavioral and pharmacological manipulations can be confounded by rising baselines, since females are behaviorally more sensitive to repeated EB injections. The literature lacks a systematic examination of chronic effects of EB administered alone to the sexually experienced OVX rat. Long–Evans rats were repeatedly treated (8 tests) with s.c. injections of 2, 5, or 10μg EB at different time intervals (4 or 8days). Female sexual behaviors as well as receipt of mounts, intromissions and ejaculations from the male were observed in the unilevel 4-hole pacing chamber. The effects of adrenalectomy (ADX) and strain (Long–Evans vs. Wistar) were also assessed. Long–Evans OVX rats treated with 5μg EB every 8days showed persistently low levels of sexual behavior. Sensitization was most robust following 10μg EB at 4-day intervals. Very few sexual behaviors were ever induced by 2μg EB. ADX did not affect the development of behavioral sensitization by 10μg EB. Therefore, to achieve a low steady state of sexual behaviors in sexually experienced Long-Evans OVX rats 5μg of EB administered every 8days is optimal, whereas a persistently high level of sexual behaviors is induced with 10μg EB administered every 4days. OVX Wistar rats are behaviorally more sensitive to EB. Behavioral sensitization to EB may serve as a mechanism to optimize reproductive success.

Effects of estradiol benzoate and trenbolone acetate, alone or in combination at dose levels present in Synovex Choice, on performance by feedlot heifers1

Trials were conducted with beef heifers at 4 sites to evaluate feedlot performance and carcass characteristics in response to implants containing 14 mg estradiol benzoate and 100 mg trenbolone acetate (EB/TBA; Synovex Choice, Zoetis LLC, New York, NY), 14 mg estradiol benzoate (EB), 100 mg trenbolone acetate (TBA), or a sham-implanted control (SC). The study design at each site was a randomized complete block with 12 blocks and 4 treatments. Blocks of cattle at each site were harvested in commercial abattoirs when masked personnel estimated at least 60% of animals would yield carcasses with USDA quality grades of Choice or Prime. Data were pooled across sites for statistical analysis. Initial BW averaged 374 kg, and days on feed ranged from 98 to 126 d (mean 112 d). Heifers implanted with EB/TBA, EB, and TBA had greater ADG and G:F (P < 0.05) than SC; ADG and G:F were greater for EB/TBA than EB or TBA (P < 0.05). Heifers treated with TBA had greater G:F than EB (P < 0.05). Feed intake was not affected by treatments. Mean HCW and LM area for EB/TBA were greater than for other treatments (P < 0.05). Mean HCW for TBA was greater than SC (P < 0.05) but not different from EB. Mean LM area for EB and TBA were greater than SC (P < 0.05) but not different from each other. There were no treatment differences (P > 0.05) for KPH, 12th-rib fat thickness, or yield grade. Dressing percent was greater for EB/TBA than SC (P < 0.05) but not different from EB or TBA. Marbling score was decreased by EB/TBA (P < 0.05) compared with other treatments, but no other differences were noted. Despite the effect of EB/TBA on marbling scores, there were no significant (P > 0.05) treatment differences on proportions of carcasses with quality grades ≥ Choice vs. < Choice. With respect to ADG and G:F, implants containing EB, TBA, or EB/TBA produced improved responses over SC. Furthermore, EB/TBA induced greater ADG and G:F responses than EB and TBA. Results confirmed that EB and TBA have additive effects, as evidenced by the observation that calves implanted with EB/TBA had significantly greater ADG and G:F than heifers implanted with either EB or TBA alone or compared with SC heifers.

Effect of Varying Doses of Estradiol Benzoate on the body weight and blood picture in Turkeys

A present study was carried out to investigate the effects of Estradiol benzoate 2 (mg/ml) hormone doses on the body weight and blood picture of Turkeys birds through studying the following parameters: body weight, RBC count , total WBC, MCV, MCH, MCHC, and platelet PLT. Forty growing Turkeys (30 days age) weighting between (250-350)gm were randomly divided into four groups (ten each group) treated as follows: Turkeys in the first group were injected with single dose of Estradiol benzoate (1 mg) on the first day of experiment (30 day post hatching) subcutaneously in the neck and termed as G1 group, the Turkeys in the 2nd group (G2) were injected Estradiol benzoate (2 mg) on the first day of experiment subcutaneously in the neck while the Turkeys in the third group (G3) were injected Estradiol benzoate (0.3 ml) at the first day of experiment subcutaneously in the neck the fourth group (G4) served as control, body weight was determined on (0, 15 and 30) days of experiment and blood samples were collected on 15th and 30th day of the experiment from groups to evaluate the blood parameters. Results revealed a significant increase (P&lt;0.05) in body weight of G1, G2 and G3 in a comparison with control group at (15 and 30) days of experiment. Furthermore, in comparison among treated groups G2 and G3 also showed a significant increase (P&lt;0.05) in the body weight as compared with G1 group during periods. Moreover, data revealed that all treated groups showed non-significant differences in blood parameters experiment as compared with control group.

16 STRATEGIES OF FOLLICULAR WAVE SYNCHRONIZATION WITH ESTRADIOL BENZOATE IN GYR (BOS TAURUS INDICUS) CATTLE

Physiological and behavioral differences between Bos taurus and Bos indicus can influence the response to a fixed AI protocol. The objective of this study was to examine the reduction of the usual dose of 2 mg of estradiol benzoate (EB) to 1 mg at the beginning of a fixed-time AI protocol, aiming at follicular regression. In a second step, we evaluated the effect of EB on follicle development during follicular pre-deviation and dominance. The experiment was performed at Monte Verde Farm (Uberaba, MG, Brazil). Twenty-two cows (n = 10 heifers and n = 12 nonlactating cows) underwent an estrous synchronization protocol with a progesterone-releasing intravaginal device (P4; Sincrogest®, Ouro Fino Animal Health, São Paulo, Brazil) and received 1 (G1mg, n = 11) or 2 mg (G2mg, n = 11) of EB (Sincrodiol®, Ouro Fino Animal Health), on a random day (designated Day 0). Follicular dynamics was monitored once per day by ultrasonography from Day 0 to 4 with blood sample collections. In a second step, females received 2 mg of EB on Day 3 (GD3, pre-deviation, n = 4) or Day 5 (GD5, dominance, n = 4) of the estrous cycle (Day 0 was the ovulation). Following these treatments, follicular development was monitored daily for 6 days with blood sample collections. The statistical analysis was conducted using the SAS System for Windows 2 (2003; SAS Institute Inc., Cary, NC, USA). The explanatory variables included in the statistical model were the dose of EB, animal category (cows and heifers), and their interaction. The mean test was used to compare intervals from EB treatment to follicular atresia and follicular wave emergence using ANOVA. Progesterone concentrations between groups were compared using the Wilcoxon test. Independently of animal category or stage of the estrous cycle, both EB doses (1 or 2 mg) induced follicular atresia in 2.2 ± 0.9 and 2.1 ± 1.2 days (P &gt; 0.05), respectively. Emergence of a new follicular wave was observed, from Day 0 to 4, in 64% (7/11) of females from G1mg and in 45% (5/11) from G2mg, and the interval between treatment and follicular emergence was 3.4 ± 0.8 and 3.0 ± 1.0 days (P &gt; 0.05), respectively. Plasma progesterone concentrations of the 22 animals increased from 2.1 ± 2.0 ng mL–1 to 7.6 ± 3.0 ng mL–1 by 24 h after the device insertion (P &lt; 0.05), reaching peak concentration (8.0 ± 3.0 ng mL–1) by 48 h after treatment beginning, decreasing to 6.4 ± 2.5 ng mL–1 by 72 h, and remaining constant up to 96 h. Estradiol benzoate injection at follicle pre-deviation (GD3) caused follicular atresia (2.0 ± 1.4 days) and emergence of a new follicular wave in 3.7 ± 0.1 days in all animals (4/4). However, EB injection during follicle dominance (GD5) did not synchronize a new follicular wave and follicles persisted during the time of monitoring. Furthermore, EB applied at dominance hastened luteolysis in 50% (2/4) of the treated animals. In conclusion, a reduced dose of EB (1 mg) at the beginning of the protocol with P4 effectively induces follicular atresia. To synchronize a wave emergence at any stage of the estrous cycle, EB must be associated with an exogenous source of progesterone.

The role of ovarian hormones in sexual reward states of the female rat

To what extent does the reward value of sexual stimulation in females depend on ovarian hormones? The effects of estradiol benzoate (EB) and progesterone (P) were examined on the acquisition and expression of sexual reward induced by paced copulation and clitoral stimulation (CLS) in ovariectomized (OVX) rats. In experiment 1 we examined the expression of a pacing‐induced conditioned place preference (CPP). Ovariectomized, hormone-primed rats were given experience with paced copulation associated with one side of a CPP apparatus. Changing hormonal status prior to the final CPP test did not alter pacing-induced CPP. However, subsequent partial extinction of CPP was observed only in rats primed with EB+P, a treatment previously shown to induce sexual desire and receptivity. In Experiment 2, significant CLS-induced CPP developed in ovariectomized rats regardless of hormone priming. Our results show that the expression of the sexual reward state induced by paced copulation, and CLS in particular, is independent of hormone priming. We propose that ovarian hormones sensitize sensory and motor pathways necessary for sexual behavior and stimulation to induce reward.

Effects of two estradiol esters (benzoate and cypionate) on the induction of synchronized ovulations in Bos indicus cows submitted to a timed artificial insemination protocol

The effects of estradiol benzoate (EB) and estradiol cypionate (EC) on induction of ovulation after a synchronized LH surge and on fertility of Bos indicus females submitted to timed AI (TAI) were evaluated. In Experiment 1, ovariectomized Nelore heifers were used to evaluate the effect of EB (n = 5) and EC (n = 5) on the circulating LH profile. The LH surge timing (19.6 and 50.5 h; P = 0.001), magnitude (20.5 and 9.4 ng/mL; P = 0.005), duration (8.6 and 16.5 h; P = 0.001), and area under the LH curve (158.6 and 339.4 ng/mL; P = 0.01) differed between the EB and EC treatments, respectively. In Experiment 2 (follicular responses; n = 60) and 3 (pregnancy per AI; P/AI; n = 953) suckled Bos indicus beef cows submitted to an estradiol/progesterone-based synchronization protocol were assigned to receive one of two treatments to induce synchronized ovulation: 1 mg of EB im 24 h after progesterone (P4) device removal or 1 mg of EC im at P4 device removal. There was no difference (P > 0.05) between EB and EC treatments on follicular responses (maximum diameter of the ovulatory follicle, 13.1 vs. 13.9 mm; interval from progesterone device removal to ovulation, 70.2 vs. 68.5 h; and ovulation rate, 77.8 vs. 82.8%, respectively). In addition, P/AI was similar (P < 0.22) between the cows treated with EB (57.5%; 277/482) and EC (61.8%; 291/471). In conclusion, despite pharmacologic differences, both esters of estradiol administered either at P4 device removal (EC) or 24 h later (EB) were effective in inducing an LH surge which resulted in synchronized ovulations and similar P/AI in suckled Bos indicus beef cows submitted to TAI.

Comparison of early morphological and molecular changes induced by 17-alpha-methyltestosterone and estradiol benzoate in the rat ovary

Repeated exposure to 17-α-methyltestosterone (17MT) and estradiol benzoate (EB) for 28 or 90 days in rats induce similar ovarian atrophy. The objective of the present work was to identify and compare the early effects induced by 17MT and EB on the ovary using molecular and histopathological tools. Female rats were evaluated after 1, 3 or 7 days following an oral exposure by gavage at a daily dose of 600 mg/kg/day for 17MT and 5 mg/kg/day for EB. All animals were found to be acyclic after 3 or 7 days of treatment with 17MT and EB. Histopathological changes were present in the ovary, uterus, vagina and mammary gland after both treatments. Ovarian atrophy known as the long term effect of 17MT and EB was not yet detected after 7 days of treatment. But non regressive corpora lutea and cystic follicles were identically observed in the ovary of 17MT and EB treated females. Both compounds induced a decrease of LH transcripts together with an increase of plasma progesterone and prolactin levels. Differences in the profile of regulation of the aromatase were noted after 1 and 3 days of treatment in 17MT treated animals (upregulated) when compared to EB treated animals (downregulated). In summary, we have shown that despite the different nature of hormonal activity, EB and 17MT induce very early endocrine perturbation which presents several similarities. Our work indicated that the detection of early key hormonal markers in short term studies can help to predict the adverse long term effects on target tissues.