Administration Of Estradiol Benzoate Research Articles

Different Critical Perinatal Periods and Hypothalamic Sites of Oestradiol Action in the Defeminisation of Luteinising Hormone Surge and Lordosis Capacity in the Rat

Female rats show a gonadotrophin-releasing hormone (GnRH)/luteinising hormone (LH) surge in the presence of a preovulatory level of oestrogen, whereas males do not because of brain defeminisation during the developmental period by perinatal oestrogen converted from androgen. The present study aimed to identify the site(s) of oestrogen action and the critical period for defeminising the mechanism regulating the GnRH/LH surge. Animals given perinatal treatments, such as steroidal manipulations, brain local implantation of oestradiol (E(2) ) or administration of an NMDA antagonist, were examined for their ability to show an E(2) -induced LH surge at adulthood. Lordosis behaviour was examined to compare the mechanisms defeminising the GnRH/LH surge and sexual behaviour. A single s.c. oestradiol-benzoate administration on either the day before birth (E21), the day of birth (D0) or day 5 (D5) postpartum completely abolished the E(2) -induced LH surge at adulthood in female rats, although the same treatment did not inhibit lordosis. Perinatal castration on E21 or D0 partially rescued the E2-induced LH surge in genetically male rats, whereas castration from E21 to D5 totally rescued lordosis. Neonatal E(2) implantation in the anterior hypothalamus including the anteroventral periventricular nucleus (AVPV)/preoptic area (POA) abolished the E(2) -induced LH surge in female rats, whereas E(2) implantation in the mid and posterior hypothalamic regions had no inhibitory effect on the LH surge. Lordosis was not affected by neonatal E(2) implantation in any hypothalamic regions. In male rats, neonatal NMDA antagonist treatment rescued lordosis but not the LH surge. Taken together, these results suggest that an anterior hypothalamic region such as the AVPV/POA region is a perinatal site of oestrogen action where the GnRH/LH regulating system is defeminised to abolish the oestrogen-induced surge. The mechanism for defeminisation of the GnRH/LH surge system might be different from that of sexual behaviour, in terms of the site(s) of oestrogen action and critical period, as well as the neurotransmitter system involved.

320 INFLUENCE OF PROGESTERONE AND MOMENT OF ESTRADIOL BENZOATE INJECTION ON MULTIPLE-OVULATION EMBRYO TRANSFER RESULTS

Current superovulatory treatment combines progesterone as well as oestradiol injection at the moment of CIDR insertion to improve synchronization of follicular wave emergence [reviewed by Bo et al. 2002 Theriogenology 57, 53–172; and Mapletoft et al. 2003 J. Anim. Sci. 81 (E. Suppl.), E28–E36] The aim of the present work was to study if delaying oestradiol benzoate (EB) injection 24 or 48 h from CIDR insertion would have the same outcome on embryo production after superovulatory treatment as additional progesterone administered at CIDR insertion. One hundred and eleven superovulatory treatments conducted during the same period (5 consecutive collection days) at random stages of the oestrus cycle at the same location were retrospectively evaluated. Holstein cycling heifers of 18 months of age (body condition score 3.2 ± 0.28, 1–5 range; weighing 357 ± 28 kg) were divided according to the following treatments: control group (n = 24): Day 0: CIDR insertion (Pfizer Animal Health, New York, NY, USA), 50 mg of progesterone, and 2 mg of oestradiol benzoate (Benzadiol, Universal Laboratory, Montevideo, Uruguay); Group BE24 (n = 47): Day –1: CIDR insertion and Day 0: 2 mg of oestradiol benzoate; Group BE48 (n = 40): Day –2: CIDR insertion and Day 0: 2 mg of oestradiol benzoate. All heifers were superstimulated on Day 3.5 (Day 0 = EB injection) with 290 NIH units of FSH (Folltropin, BionicheAnimal Health, Belleville, ON, Canada) in twice-daily decreasing doses over 4.5 days. On Day 6, all cows received 2 doses (a.m. and p.m.) of a prostaglandin F2α analogue (800 µg, Delprostenate, Glandinex, Universal Laboratory), and CIDR were removed on the morning of Day 7. Cows were injected with 10 µg of GnRH (Receptal, Intervet, Boxmeer, the Netherlands) on Day 8 a.m. and were inseminated 12 and 24 h later with semen of 3 bulls of proven fertility. On Day 15, ova/embryos were collected nonsurgically and evaluated in accordance with IETS guidelines. Data were analysed with a negative binomial regression model (Table 1). Administration of EB 24 or 48 h after CIDR insertion produced similar numbers of transferable and freezable embryos as well as total ova/embryos compared with addition of progesterone and EB at the moment of CIDR insertion. According to these results, EB could be administrated without progesterone injection either 24 or 48 h after CIDR insertion without compromising embryo production. Table 1.Embryo production of heifers superstimulated after additional progesterone (P4) and different times (24 or 48 h after CIDR insertion) of oestradiol benzoate administration (results are mean ± SE)

63 EVALUATION OF HYPOTHALAMIC–PITUITARY RESPONSIVENESS DURING THE POSTPARTUM NELLORE COWS

The presence of calf, body condition score, energy balance, number of births (multiparous vs primiparous) and breed are factors that influence the duration of postpartum anoestrus in beef cows. The objective of the present study was to evaluate, during early postpartum, the time of re-establishment of pituitary LH stocks, measured by the hypothalamic-pituitary-axis responsiveness to exogenous administration of gonadotropin-releasing hormone (GnRH) or oestradiol benzoate (EB). Multiparous lactating Nellore cows (Bos indicus, n = 65) were randomly allocated into 6 groups, according to the hormonal treatment: EB group (1.0 mg of EB, IM, n = 7), GnRH group (50 μg of lecireline, IM, n = 16). The EB-supplemented (SUP; n = 9) and GnRH-SUP (n = 16) groups received the same treatments specified above and were SUP with a balanced diet, based on cotton meal and ground corn (3.5 kg cow–1 per day). Additionally, animals from EB-calf removed (CR; n = 4) and GnRH-CR (n = 13) groups received the same treatments of EB and GnRH group, respectively and had their CR shortly after parturition. The hormones were administered weekly, from 7 days postpartum (±5 days) until the occurrence of the first ovulation, which was determined by the presence of corpus luteum during ovarian ultrasonography performed weekly. Blood samples were collected just before and 2 h (GnRH groups) or 18 h (EB groups) after hormone administration, in order to determine LH concentration by radioimmunoassay. Data were analysed by ANOVA. Mean values in days (± standard error of the means) for the first postpartum LH surge were EB (73.0 ± 5.2); EB-CR (16.7 ± 5.8); EB-SUP (41.7 ± 6.7); GnRH (32.3 ± 3.0); GnRH-CR (11.0 ± 3.5); GnRH-SUP (15.6 ± 2.8). There were significant differences (P < 0.05) between groups EB vs EB-CR; EB vs EB-SUP; BE vs GnRH; GnRH vs GnRH-CR; GnRH vs GnRH-SUP and a tendency between EB-SUP vs EB-CR (P < 0.10). Results indicate that from the second week postpartum, there is sufficient LH in the pituitary to induce ovulation after GnRH or EB administration. However, the cows from the EB group ovulated later than animals from the other groups, possibly due to the sensitivity of the hypothalamus to negative feedback of estrogens, inhibiting the pre-ovulatory LH surge. Additionally, CR and food SUP reduced in 2 to 4 weeks the time of the first postpartum LH surge induced by GnRH or EB in Nellore cows. A fellowship was received from FAPESP. Support was received from FAPESP.

Effect of Oophorectomy and Estrogen Administration on Diabetic Pathogenesis in Female Spontaneously Diabetic Torii Rats

In order to examine the effect of sex hormones on diabetic pathogenesis in female Spontaneously Diabetic Torii (SDT) rats, we performed oophorectomy on female SDT rats, administered female hormones after the oophorectomy, and measured body weight changes, plasma glucose concentration, and pancreatic histopathology. At 26 weeks of age, the body weight was significantly heavier in the oophorectomized group and significantly lighter in the estradiol benzoate (EB) administration group than in the sham-operated control group. Although glucose concentration did not significantly change in the oophorectomized group, it was significantly lower in the EB administration group than in both control and the oophorectomized group. Severe histopathological change was observed in the oophoretomized group but not in the EB administration group. Thus, EB blocked weight gain and pancreatic islet change that was induced by oophoretomy and it also lowered glucose concentration. These results suggest that estrogen plays a preventive role for diabetic pathogenesis in female SDT rats.

Estrogen receptor ligands counteract cognitive deficits caused by androgen deprivation in male rats

Androgen deprivation causes impairment of cognitive tasks in rodents and humans, and this deficit can be reverted by androgen replacement therapy. Part of the effects of androgens in the male may be mediated by their local metabolism to estradiol or 3-alpha androstanediol within the brain and the consequent activation of estrogen receptors. In this study we have assessed whether the administration of estradiol benzoate, the estrogen receptor β selective agonist diarylpropionitrile or the estrogen receptor α selective agonist propyl pyrazole triol affect performance of androgen-deprived male Wistar rats in the cross-maze test. In addition, we tested the effect of raloxifene and tamoxifen, two selective estrogen receptor modulators used in clinical practice. The behavior of the rats was assessed 2 weeks after orchidectomy or sham surgery. Orchidectomy impaired acquisition in the cross-maze test. Estradiol benzoate and the selective estrogen receptor β agonist significantly improved acquisition in the cross-maze test compared to orchidectomized animals injected with vehicle. Raloxifene and tamoxifen at a dose of 1 mg/kg, but not at doses of 0.5 or 2 mg/kg, also improved acquisition of orchidectomized animals. Our findings suggest that estrogenic compounds with affinity for estrogen receptor β and selective estrogen receptor modulators, such as raloxifene and tamoxifen, may represent good candidates to promote cognitive performance in androgen-deprived males.

Fertility Following CIDR Based Synchronization Regimens in Anoestrous Nili‐Ravi Buffaloes

The objective of this study was to compare oestrus expression and fertility rate in used and new controlled internal drug releasing (CIDR) device treated anoestrous buffaloes. Furthermore, to determine the timing of ovulation, and fertility rate in estradiol benzoate (EB) and GnRH-administered CIDR-treated anoestrous Nili-Ravi buffaloes. In experiment 1, buffaloes received either a used CIDR (UCIDR, n = 35) or a new CIDR (NCIDR, n = 36) for 7 day and PGF2α on day 6. Oestrous expression was similar (p > 0.05) between UCIDR (88.5%) and NCIDR (96.6%) buffaloes. The pregnancy rate did not differ (p > 0.05) because of treatment (37.1% in UCIDR vs 36.6% in NCIDR). In experiment 2, buffaloes (n = 55) received CIDR device for 7 days and PGF2α, on day 6 and randomly assigned into three treatment groups: (i) CIDR-EB (n = 17) received EB on day 8, (ii) CIDR-GnRH (n = 18) received GnRH on day 9 and (iii) control (n = 20) received no further treatment. Mean interval from CIDR removal to ovulation in CIDR-EB, CIDR-GnRH and CIDR group were 61.3 ± 0.8, 64.9 ± 1.8 and 65.1 ± 16.7 h, respectively. However, the buffaloes in the CIDR-EB and CIDR-GnRH group had lesser variability in the timing of ovulation compared to control. The pregnancy rate of both CIDR-EB group (58%) and CIDR-GnRH group (61%) were tended to be higher (p < 0.1) than control (30%). In conclusion, compared to NCIDR devices, previously UCIDR devices are equally effective to induce oestrus in anoestrous buffaloes resulting optimal pregnancy rate. Administration of EB and GnRH after CIDR removal results in tighter synchrony (less variability) and improved fertility in anoestrous buffaloes. CIDR based synchronization regimens have great potential in fertility improvement in anoestrous buffaloes.

Androgen inhibition of sexual receptivity is modulated by estrogen

Sexual receptivity induced in ovariectomized rats by the long-term administration of estradiol benzoate (EB) can be inhibited by concurrent administration of androgens. Experiment 1 examined the role of time course and dose of androgens in the inhibition of estrogen-induced sexual receptivity. Ovariectomized rats were treated with EB (2.0 microg per rat per day) for 6 days and tested for sexual receptivity (Test Day I). EB treatment continued for 15 days concomitant with daily administration of one of three doses of dihydrotestosterone propionate (DHTP; 7.5, 0.75, 0.075 mg/kg) or 3α-androstanediol (3α-Adiol; 3.75, 1.0, 0.375 mg/kg). Four tests for sexual receptivity were conducted on days 3, 6, 14, and 15 of the androgen/vehicle treatment period (Test Days II-V). On Day 15 (Test Day V), the rats received progesterone (1.0 mg per rat) 4 h before testing. Using the same experimental design, Experiment 2 examined the effect of increasing the dose of estrogen on the androgenic inhibition of sexual receptivity. Ovariectomized rats were treated with one of two doses of EB (2.0 or 10.0 microg per rat per day) concomitant with daily administration of DHTP (7.5 mg/kg) or 3α-Adiol (3.75 mg/kg). In Experiment 1, the highest doses of both DHTP and 3α-Adiol significantly inhibited estrogen-induced sexual receptivity. Data from Experiment 2 indicate that the inhibitory effects of DHTP but not 3α-Adiol can be moderated by an increased dose of EB.

Role of neural afferents as mediators of estrogen effects on the hypothalamic ventromedial nucleus

The effects of estrogens on the ventrolateral division of the hypothalamic ventromedial nucleus (VMNvl) are essential for its role in the regulation of female sexual behavior. Enhanced synaptogenesis and induction of progesterone receptors (PRs) are hallmarks of the actions of estrogens on the VMNvl. To investigate the influence of neural afferents in mediating these effects, we estimated the number of spine and dendritic synapses per neuron and the total number of PR-immunoreactive neurons in ovariectomized rats treated with either estradiol benzoate or vehicle, after unilateral VMN deafferentation. The estimates were performed independently in the VMNvl of the deafferented and contralateral sides, and in the VMNvl of unoperated rats (controls). The administration of estradiol benzoate did not induce any increase in the number of synapses of the deafferented VMNvl. In the contralateral VMNvl, the synaptogenic effects of estrogen were apparent, but still reduced relative to the control VMNvl, where a 25% increase in the total number of synapses was observed after estrogenic stimulation. In the absence of estrogenic stimulation, i.e., in basal conditions, deafferentation reduced the number of dendritic and spine synapses, but particularly the latter. The reduction was also visible, but less marked, in the contralateral VMNvl. Contrary to synapses, the estrogen induction of PRs was unaffected by deafferentation, and the total number of PR-immunoreactive neurons was similar in the control, deafferented and contralateral VMNvl. The results show that estrogens enhance synaptogenesis in the VMNvl by acting through neural afferents and induce PR expression by acting directly upon VMN neurons.

D-003 does not possess oestrogenic potential in-vivo: findings of the uterotrophic assay

D-003 is a mixture of long-chain fatty acids purified from sugarcane wax that inhibits both cholesterol synthesis prior to mevalonate formation, and lipid peroxidation. D-003 has been shown to prevent bone loss and bone resorption in ovariectomized rats, and significantly improves bone resorption markers in postmenopausal women with reduced bone mineral density. As hormone-replacement therapy, D-003 displays cholesterol-lowering and anti-resorptive effects. We have studied its potential oestrogenic activity in-vivo using the uterotrophic assay. Rats were randomly distributed into five groups: a sham-operated group and four groups of ovariectomized rats, one treated with vehicle, one with D-003 (50 mg kg(-1)), one with oestradiol benzoate (30 microg kg(-1)) and one with D-003 (50 mg kg(-1)) plus oestradiol benzoate (30 microg kg(-1)). Treatments were administered for 14 days. Ovariectomy decreased the values of relative uterus weight, epithelium cell height and endometrial thickness compared with sham-operated rats, and these effects were all significantly reduced with oestradiol benzoate, but not with D-003. Concurrent administration of D-003 and oestradiol benzoate had statistically similar effects on all variables as oestradiol benzoate alone. In conclusions, D-003 orally given at 50 mg kg(-1), a dose that prevents bone loss and bone resorption in ovariectomized rats, did not display oestrogenic/anti-oestrogenic activity in-vivo, as assessed in the uterotrophic assay.

Effect of estrogen and tamoxifen on the shell gland AVT and VT3R of scotosensitive and scotorefractory Japanese quail

The neurohypophyseal hormone arginine vasotocin (AVT) found in most vertebrate species is known to modulate different aspects of reproduction in quail. AVT system is sensitive to gonadal steroids. Previous studies have shown that estradiol benzoate stimulates the proliferation of shell gland and increases the AVT and the vasotocin 3 receptor (VT3R) in long day length. This study was undertaken to investigate the effect of estrogen and tamoxifen on AVT as well as its receptor VT3 under the short day condition (6L:18D). Estradiol benzoate (EB) was administered daily in sexually quiescent (scotosensitive) condition for 15 days. After the initial period of sexual quiescence, the quail of control group exhibited sexual development (scotorefractory condition). Thereafter, scotorefractory quail were administered with anti-estrogen tamoxifen, which eliminated the reoccurrence of scotosensitivity. Immunohistochemical and in-situ hybridization studies indicate the expression of AVT and VT3R transcripts in both scotosensitive as well as scotorefractory conditions. Administration of EB to scotosensitive female quail produced an increase in AVT and VT3 while tamoxifen suppressed them in scotorefractory quail. The results indicate that in quail myometrium the expression of VT3R is upregulated by estrogen when kept under short day condition.

Non-invasive methods of oestrus detection in captive southern hairy-nosed wombats ( Lasiorhinus latifrons)

In order to develop a reliable method of oestrus detection in captive southern hairy-nosed (SHN) wombats, the reproductive behaviour of four groups of adult animals (1♂:2♀) was monitored using video surveillance and activity using movement-sensitive radio transmitters for a period of 12 months. During this time faecal samples were collected every 3 days and subsequently analysed for progesterone and oestradiol-17β metabolites. In an attempt to induce and characterise oestrus-specific behaviour, each female was administered a subcutaneous injection of either 0.01 ( n = 2), 0.1 ( n = 4) or 0.2 mg/kg ( n = 2) of oestradiol benzoate in one of two hormone trials. Remote video surveillance was an effective tool for detecting the reproductive behaviour of the captive SHN wombat. Courtship ( n = 426) and mating ( n = 46) was observed in five wombats and consisted of 13 distinctive behaviours in six consecutive phases: (1) investigation, (2) attraction, (3) chase, (4) restraint, (5) copulation and (6) recovery. Female sexual receptivity occurred at night and lasted for approximately only 13-h. Faecal progesterone metabolite analysis proved to be a reliable method for mapping oestrous cycle activity, but was not useful for the prediction of oestrus. Six out of the eight female wombats displayed periods of elevated progesterone secretion, corresponding to a mean (±SE) luteal phase of 20.9 ± 1.1 days ( n = 23). Oestrous cycle length, defined as the interval between two successive luteal phases separated by a follicular phase was 31.8 ± 1.1 days ( n = 12) and consisted of a follicular phase of 11.6 ± 0.6 days ( n = 12). Changes in the secretion of faecal oestradiol-17β metabolites provided little instructive information on oestrous cycle activity and were not associated with oestrus. Administration of oestradiol benzoate resulted in a spike of oestradiol-17β metabolites in the faeces 3–4 days later, but was not dose dependent nor did it facilitate reproductive behaviour in either sex. Activity was not linked to key events in the oestrous cycle and appears not to be suitable as a method for detecting oestrus in the SHN wombat. We therefore recommend the use of 24-h video surveillance as the most reliable method for oestrus detection in captive SHN wombats.

132 INDUCTION OF FIRST POSTPARTUM OVULATION AFTER ADMINISTRATION OF GnRH, ESTRADIOL BENZOATE, OR LH ASSOCIATED OR NOT WITH CALF REMOVAL IN NELORE COWS

There are reports in the literature indicating that the presence of calf, body condition score, energy balance, number of births (multiparous v. primiparous), and breed are factors that influence the duration of postpartum anoestrus in beef cows. The purpose of the present study was to evaluate, during early postpartum, the time necessary for reestablishment of pituitary LH stocks, determined by the hypothalamic-pituitary axis responsiveness to exogenous administration of GnRH and estradiol benzoate (EB). Multiparous lactating Nelore cows (n = 51) were kept in Brachiaria brizantha pasture. The animals were randomly allocated in 8 groups, according to the hormonal treatment: EB Group (1.0 mg of EB, i.m. Estrogin®, Farmavet, Sao Paulo, Brazil; n = 7), EB and calf removal (CR) group (EB/CR, calves were removed at the time of birth, n = 4), EB/SUP group (cows were supplemented with a balanced diet, based on cotton meal and ground corn, from the beginning of the experiment until ovulation), GnRH group (100 μg, licereline, i.m. Gestran Plus®, ARSA SLR, Buenos Aires, Argentina; n = 7), GnRH/CR group (n = 4), GnRH/SUP group (n = 8), LH group (12.5 mg, i.m. Lutropin® Bioniche, Ontario, Canada; n = 7), and control group (did not receive any hormone to induce ovulation or diet supplementation, n = 5).The hormones were administered weekly, from 7 days postpartum (±5 days) until the occurrence of the first ovulation, which was determined by the presence of CL during weekly ovarian ultrasonography (Aloka 900, Tokyo, Japan, 7.5 MHz probe). The data were analyzed by ANOVA. On average (±SEM) the first ovulation occurred 86.7 ± 0.5 (EB); 19.7 ± 0.6 (EB/CR); 57.8 ± 0.4 (EB/SUP); 44.7 ± 0.5 (GnRH); 25.9 ± 0.6 (GnRH/CR); 32.8 ± 0.4 (GnRB/SUP); 42.4 ± 0.5 (LH); and 59.3 ± 0.5 (control) days postpartum. There were significant differences between groups: EB v. EB/SUP (P &lt; 0.01), EB v. EB/CR (P &lt; 0.01), EB v. control (P &lt; 0.04), EB v. GnRH (P = 0.01), and there was a tendency between groups: GnRH v. GnRH-SUP (P = 0.10) and LH v. control (P = 0.10). The first ovulations were detected from the second week postpartum (animals from Groups GnRH and EB/CR) until the last ultrasound examination on Day 120 postpartum (Group EB). The results indicate that from the second week postpartum there is sufficient LH in the pituitary to induce ovulation after GnRH or EB administration. However, the cows from EB group ovulated later than animals from the other groups, possibly due to the sensitivity of hypothalamus to negative feedback of estrogens, inhibiting the pre-ovulatory LH surge. Additionally, calf removal and food supplementation reduced in 2 to 4 weeks the time of the first postpartum ovulation induced by GnRH or EB. Fellowship from FAPESP. Supported from FAPESP (Sao Paulo, Brazil).

6-Hydroxydopamine lesions enhance progesterone-facilitated lordosis of rats and hamsters, independent of effects on motor behavior

The Ventral Tegmental Area (VTA) is an important brain area for progesterone (P 4)'s effects to facilitate female sexual behavior of rodents. We investigated the importance of dopaminergic neurons in the VTA, and two dopaminergic projection sites, the Nucleus Accumbens (NAc), and Caudate Nucleus of the Striatum (CN), in modulating P 4-facilitated sex and motor behavior. Ovariectomized (ovx) rats and hamsters, administered estradiol benzoate (10 µg) and P 4 (0, 50, 100, 200, or 500 µg), were tested for motor behavior in a chamber that automatically records horizontal beam breaks, and for sexual behavior in response to a sexually-experienced male. Animals were tested once a week until each P 4 dosage was received; animals then had bilateral 6-hydroxydopamine (6-OHDA) or sham lesions to the VTA, NAc, or CN and were re-tested at each P 4 dosage on subsequent weeks. Fixed brains were stained with cresyl violet and processed for dopamine transporter (DAT) immunoreactivity. The number of cresyl violet stained cells was significantly lower in all 6-OHDA infusion sites compared to non-6-OHDA infusion sites of rats and hamsters. Also, in rats, the number of DAT-immunoreactive neurons was lower in all 6-OHDA infusion sites compared to non-6-OHDA infusion sites. In rats, 6-OHDA but not sham, lesions to the VTA, NAc, or CN produced P 4-dependent increases in lordosis quotients and resulted in modest increases in motor behavior. In hamsters, 6-OHDA, but not sham, lesions to the VTA, NAc, or CN produced P 4-dependent increases in total lordosis durations and produced modest decreases in motor behavior. This suggests that the dopaminergic output neurons of midbrain VTA may play an important role in modulation of P 4-facilitated sexual lordosis among rodents.

Neonatal oxytocin alters subsequent estrogen receptor alpha protein expression and estrogen sensitivity in the female rat

In most species, the effects of oxytocin (OT) on female reproductive behavior are dependent upon estrogen, which increases both OT and OT receptor expression. It is also becoming apparent that OT neurotransmission can influence estrogen signaling, especially during development, as neonatal OT manipulations in prairie voles alter ERα expression and estrogen-dependent behaviors. We tested the hypothesis that OT developmentally programs ERα expression and estrogen sensitivity in female Sprague-Dawley rats, a species previously used to establish the estrogen-dependence of OT signaling in adulthood. OT treatment for the first postnatal week significantly increased ERα-immunoreactivity in the ventromedial nucleus of the hypothalamus (VMH), but not in the medial preoptic area (MPOA). Conversely, neonatal OT antagonist (OTA) treatment significantly reduced ERα-immunoreactivity in the MPOA, but not in the VMH. Both treatments increased OT-immunoreactivity in the paraventricular nucleus of the hypothalamus (PVN) and reduced estrogen sensitivity, indicated by reduced sexual receptivity following chronic estradiol benzoate (EB) administration. Behavioral deficits in OTA-treated females were apparent during both paced and non-paced tests with 0.5 μg EB (but not 5.0 or 10.0 μg EB), whereas deficits in OT-treated females were only observed during the initial paced test with 0.5 and 5.0 μg EB (but not 10.0 μg EB). The current results demonstrate that OT can positively regulate ERα expression within the MPOA and VMH during development; however, endogenous OT selectively programs ERα expression within the MPOA. Thus, exogenous OT or OTA exposure during development may have long-term consequences on behavior through stable changes in ERα and OT expression.

Effect of estradiol benzoate on rat testis and adrenal.

The effects of in vivo administration of estradiol benzoate at a dose of 50 micrograms/rat/day for 15 days on testosterone production of testis and adrenal in vitro were investigated in rats. The data revealed that the androgen synthesis of both the steroidogenic organs were reduced by the treatment. The decrease in androgen production by testis was related to its reduced sperm count and weight. On the contrary, accumulation of cholesterol occurred in treated rat testis indicating inhibition of its steroidogenesis. This data confirm our earlier reports on the direct effect of estrogen on testis.

Estrogen receptor alpha and beta specific agonists regulate expression of synaptic proteins in rat hippocampus

Changes in hippocampal CA1 dendritic spine density and synaptic number across the estrous cycle in female rats correlate with increased hippocampal-dependent cognitive performance in a manner that is dependent on estrogen receptors (ERs). Two isoforms of the estrogen receptor, α and β are present in the rat hippocampus and distinct effects on cognitive behavior have been described for each receptor. The present study generated a profile of synaptic proteins altered by administration of estradiol benzoate, the ERα selective agonist PPT (1,3,5-tris (4-hydroxyphenyl)-4-propyl-1H-pyrazole) and the ERβ selective agonist DPN (2,3-bis (4-hydroxyphenyl) propionitrile) alone and in combination in comparison to vehicle in the CA1 region of the dorsal hippocampus. In the stratum radiatum, estradiol, DPN, and PPT increased PSD-95 and AMPA-type glutamate receptor subunit GluR1. Only DPN administration regulated expression of AMPA receptor subunits GluR2 and GluR3, increasing and decreasing levels respectively. DPN also increased GluR2 expression in the other lamina of the CA1. These results support previous reports that estradiol and isoform specific agonists differentially activate ERα and ERβ to regulate protein expression. The distinct effects of DPN and PPT administration on synaptic proteins suggest that the desired therapeutic outcome of estrogen may be accomplished by using specific estrogen receptor agonists. Moreover, the effects of estradiol treatment on PSD-95 expression are consistent with a growing body of evidence that this postsynaptic protein is a key marker of estrogen action related to spine synapse formation.

Ovarian steroids alter mu opioid receptor trafficking in hippocampal parvalbumin GABAergic interneurons

The endogenous hippocampal opioid systems are implicated in learning associated with drug use. Recently, we showed that ovarian hormones regulate enkephalin levels in the mossy fiber pathway. This pathway overlaps with parvalbumin (PARV)-basket interneurons that contain the enkephalin-activated mu opioid receptors (MORs) and are important for controlling the “temporal timing” of granule cells. Here, we evaluated the influence of ovarian steroids on the trafficking of MORs in PARV interneurons. Two groups of female rats were analyzed: cycling rats in proestrus (relatively high estrogens) or diestrus; and ovariectomized rats euthanized 6, 24 or 72 h after estradiol benzoate (10 μg, s.c.) administration. Dorsal hippocampal sections were dually immunolabeled for MOR and PARV and examined by light and electron microscopy. As in males, in females MOR-immunoreactivity (-ir) was in numerous PARV-labeled perikarya, dendrites and terminals in the dentate hilar region. Variation in ovarian steroid levels altered the subcellular distribution of MORs in PARV-labeled dendrites but not terminals. In normal cycling rats, MOR-gold particles on the plasma membrane of small PARV-labeled dendrites (area < 1 μm 2) had higher density in proestrus rats than in diestrus rats. Likewise, in ovariectomized rats MORs showed higher density on the plasma membrane of small PARV-labeled dendrites 72 h after estradiol exposure. The number of PARV-labeled cells was not affected by estrous cycle phase or estrogen levels. These results demonstrate that estrogen levels positively regulate the availability of MORs on GABAergic interneurons in the dentate gyrus, suggesting cooperative interaction between opioids and estrogens in modulating principal cell excitability.

Efeito do eCG ou benzoato de estradiol associado ao norgestomet na taxa de concepção de vacas de corte submetidas à IATF no pós-parto

Este estudo objetivou comparar as taxas de concepção, em vacas de corte no período pós-parto (PPP), tratadas com Gonadotrofina Coriônica Eqüina (eCG) ou Benzoato de Estradiol (BE), após o uso de Norgestomet submetidas à inseminação artificial em tempo fixo (IATF). A hipótese é que a administração de eCG ou BE aumenta as taxas de concepção. Vacas Nelore (n=138) e Brangus (n=63), lactantes, entre 26 e 118 dias do PPP, foram divididas em três grupos homogêneos e dentro de cada grupo subdivididas em dois blocos, um com um PPP &lt; 45 dias (PPP1; n=107) e outro &gt;; 45 dias (PPP2; n=94). Todas as fêmeas receberam um implante auricular contendo 3mg de Norgestomet (Crestar®), seguido pela administração de 5mg de Valerato de Estradiol. Os implantes auriculares foram mantidos durante 10 dias. Na retirada dos implantes, as fêmeas receberam 1mL de solução fisiológica (n=68; Grupo Controle) ou 500UI de eCG (Folligon®; n=67; Grupo eCG) ou 1mg de Benzoato de Estradiol (Index; n=66; Grupo BE) 24 horas após a retirada do implante. A IATF foi realizada 54 horas após a retirada do implante. O diagnóstico de gestação foi realizado por ultra-sonografia 30 dias após a IATF. Houve interação entre os tratamentos e o PPP. No PPP1, a taxa de concepção foi maior no grupo eCG comparado ao BE (47,22% vs. 15,38%; P&lt;0,01). No PPP2, as taxas de concepção dos grupos eCG e BE foram maiores que no grupo controle (41,93%, 44,44% vs. 22,22%; P&lt;0,01). Conclui-se que vacas, com até 45 dias do PPP, o eCG associado ao Norgestomet aumenta as taxas de concepção.

Sex and regional differences in estradiol content in the prefrontal cortex, amygdala and hippocampus of adult male and female rats

In general, the behavioral and neural effects of estradiol administration to males and females differ. While much attention has been paid to the potential structural, cellular and sub-cellular mechanisms that may underlie such differences, as of yet there has been no examination of whether the differences observed may be related to differential uptake or storage of estradiol within the brain itself. We administered estradiol benzoate to gonadectomized male and female rats, and compared the concentration of estradiol in serum and brain tissue found in these rats to those of gonadectomized, oil-treated rats and intact rats of both sexes. Long-term gonadectomy (3 weeks) reduced estradiol concentration in the male and female hippocampus, but not in the male or female amygdala or in the female prefrontal cortex. Furthermore, exogenous treatment with estradiol increased estradiol content to levels above intact animals in the amygdala, prefrontal cortex and the male hippocampus. Levels of estradiol were undetectable in the prefrontal cortex of intact males, but were detectable in all other brain regions of intact rats. Here we demonstrate (1) that serum concentrations of estradiol are not necessarily reflective of brain tissue concentrations, (2) that within the brain, there are regional differences in the effects of gonadectomy and estradiol administration, and (3) that there is less evidence for local production of estradiol in males than females, particularly in the prefrontal cortex and perhaps the hippocampus. Thus there are regional differences in estradiol concentration in the prefrontal cortex, amygdala and hippocampus that are influenced by sex and hormone status.

Estrogen pretreatment modulates morphine-induced conditioned place preference in ovariectomized mice

Estrogen is known to modulate the neurotransmission in the brain. The main aim of this study was to investigate the effects of estrogen on the rewarding properties of morphine using conditioned place preference (CPP) paradigm in adult female mice. The possible rewarding effect of estrogen was also examined in ovariectomized mice. Following a 6-day conditioning procedure, sham operated animals showed a significant preference towards the side previously paired with a range of morphine doses (2, 5 and 10—but not 20—mg/kg, SC). However, ovariectomized mice showed decreased CPP compared to gonadally intact mice with a right shift in their morphine dose–response curve. These effects were reversed by chronic daily administration of estradiol benzoate (EB; 20 µg/kg, SC). Furthermore, in ovariectomized mice, EB per se was able to induce CPP. In conclusion, our findings indicate that estradiol has a facilitating effect on morphine reward while its deficiency increases the threshold dose of morphine to induce CPP.