Structural and histomorphometric evaluations of ferutinin effects on the uterus of ovariectomized rats during osteoporosis treatment

AimsThe effects of chronic administration of Ferutinin (phytoestrogen found in the plants of genus Ferula), compared with those elicited by estradiol benzoate, were evaluated, following ovariectomy, on the uterus of ovariectomized rats as regard weight, size, structure and histomorphometry.Main methodsThe experimental study included 40 female Sprague–Dawley rats, assigned to two different protocols, i.e. preventive and recovering. In the preventive protocol, ferutinin (2 mg/kg/day) was orally administered for 30 days, starting from the day after ovariectomy; in the recovering protocol, ferutinin was administered, at the same dosage, for 30 days starting from the 60th day after ovariectomy, when osteoporosis was clearly established. Its effects were compared with those of estradiol benzoate (1.5 μg per rat twice a week, subcutaneously injected) vs. vehicle-treated ovariectomized controls and vehicle-treated sham-operated controls. Uteri were removed, weighed and analysed under both the structural and histomorphometrical points of view.Key findingsOur data show that ferutinin acts, similarly to estradiol benzoate, on the uterus stimulating endometrial and myometrial hypertrophy; this notwithstanding, the phytoestrogen ferutinin, in contrast to estrogen treatment, appears to increase apoptosis in uterine luminal and glandular epithelia.SignificanceFerutinin, used in osteoporosis treatment primarily for bone mass recovering, seems in line with an eventual protective function against uterine carcinoma, unlike estrogens so far employed in hormone replacement therapy (HRT).     

Paced mating behavior in female rats in response to different hormone priming regimens

A female rat will display a repertoire of behaviors during a sexual encounter with a male rat including sexually receptive (the lordosis response) and proceptive (hopping, darting) behaviors. In addition, when given the opportunity, a sexually receptive female rat will approach and withdraw from the male rat, controlling the timing of the receipt of mounts, intromissions, and ejaculations, a behavior known as paced mating behavior. The present experiments tested the hypotheses (1) that progesterone regulates paced mating behavior, and (2) that multiple hormone regimens used previously to induce sexual receptivity have the same effect on paced mating behavior. Paced mating behavior was assessed in sexually receptive ovariectomized female rats after treatment with: (1) estradiol benzoate (EB; 30.0 mg/kg) followed by a range of doses of progesterone (P; 1.0-8.0 mg/kg), (2) two pulses of unesterified estradiol (E2; 2.0 microg/rat) followed by 1.0 mg/rat of P, and (3) EB alone (5.0 microg/rat) for 6 days. No differences in sexual receptivity or in paced mating behavior were observed across doses of P (1.0-8.0 mg/kg). In contrast, the number of hops and darts per min increased with the dose of P administered. E2 + P administration resulted in slightly, but significantly, lower levels of sexual receptivity along with significantly longer contact-return latencies following an intromission in relation to the other treatment conditions. In addition, female rats exhibited fewer hops and darts per min in response to E2 + P than in response to EB + 8.0 mg/kg of P. The administration of EB alone for 6 days induced levels of receptivity and paced mating behavior indistinguishable from EB + P, while eliciting significantly fewer hops and darts per min than the EB + 8.0 mg/kg P treatment condition. Hormone priming regimen had no effect on the percentage of exits displayed during the paced mating tests in any experimental phase. Dose of P had no effect on paced mating behavior in sexually receptive rats. In addition, P does not appear to be necessary for the display of paced mating behavior following long-term treatment with EB. In contrast, the pulsatile administration of E2 + P induced a different pattern of paced mating behavior in sexually receptive rats.     

Olfactory conditioned same-sex partner preference in female rats: Role of ovarian hormones

The dopamine D2-type receptor agonist quinpirole (QNP) facilitates the development of conditioned same-sex partner preference in males during cohabitation, but not in ovariectomized (OVX) females, primed with estradiol benzoate (EB) and progesterone (P). Herein we tested the effects of QNP on OVX, EB-only primed females. Females received a systemic injection (every four days) of either saline (Saline-conditioned) or QNP (QNP-conditioned) and then cohabited for 24 h with lemon-scented stimulus females (CS +), during three trials. In test 1 (female-female) preference was QNP-free, and females chose between the CS + female and a novel female. In test 2 (male-female) they chose between the CS + female and a sexually experienced male. In test 1 Saline-conditioned females displayed more hops & darts towards the novel female, but QNP-conditioned females displayed more sexual solicitations towards the CS + female. In test 2 Saline-conditioned females displayed a clear preference for the male, whereas QNP-conditioned females displayed what we considered a bisexual preference. We discuss the effect of dopamine and ovarian hormones on the development of olfactory conditioned same-sex preference in females.     

Different doses of estradiol benzoate induce conditioned place preference after paced mating

The ovarian hormones estrogen and progesterone are required for the complete display of sexual behavior in female rats. Paced mating produces a reward state in intact cycling and ovariectomized (OVX), hormonally primed females as evaluated by the conditioned place preference (CPP) paradigm. Most of the studies that have evaluated CPP induced by paced mating in OVX females have used relatively high doses of estradiol benzoate (EB). In the present study we determined if different doses of EB, combined with progesterone (P), could induce CPP after paced mating. For this purpose OVX female rats were divided in five groups that received one of different doses of estradiol benzoate (5, 2.5, 1.25 or 0.625 μg estradiol + 0.5 mg of progesterone) before being allowed to pace the sexual interaction and conditioned in a CPP paradigm. We found that the lowest dose of EB used (0.625 μg) significantly reduced the lordosis quotient and the lordosis coefficient. Even though these females paced the sexual interaction, they didn't change its original preference, suggesting that sexual interaction did not induce a positive affective, reward state. Females allowed to pace the sexual interaction with higher doses of EB developed CPP after paced mating. These results indicate that a threshold of estradiol is required for paced mating to induce CPP.     

Administration of an oxytocin receptor antagonist attenuates sexual motivation in male rats

In male rats, oxytocin impacts both sexual arousal and certain types of consummatory sexual behaviors. However, the role of oxytocin in the motivational aspects of sexual behavior has received limited attention. Given the role that oxytocin signaling plays in consummatory sexual behaviors, it was hypothesized that pharmacological attenuation of oxytocin signaling would reduce sexual motivation in male rats. Sexually experienced Long-Evans male rats were administered either an oxytocin receptor antagonist (L368,899 hydrochloride; 1 mg/kg) or vehicle control into the intraperitoneal cavity 40 min prior to placement into the center chamber of a three-chambered arena designed to assess sexual motivation. During the 20-minute test, a sexually experienced stimulus male rat and a sexually receptive stimulus female rat were separately confined to smaller chambers that were attached to the larger end chambers of the arena. However, physical contact between test and stimulus rats was prevented by perforated dividers. Immediately following the sexual motivation test, test male rats were placed with a sexually receptive female to examine consummatory sexual behaviors. Although both drug and vehicle treated rats exhibited a preference for the female, treatment with an oxytocin receptor antagonist decreased the amount of time spent with the female. There were no differences between drug and vehicle treated rats in either general activity, exploratory behaviors, the amount of time spent near the stimulus male rat, or consummatory sexual behaviors. Extending previous findings, these results indicate that oxytocin receptors are involved in sexual motivation in male rats.     

The inhibitory effects of corncob bedding on sexual behavior in the ovariectomized Long–Evans rat treated with estradiol benzoate are overcome by male cues

The mechanisms underlying the sensitization of sexual behaviors by repeated administration of estradiol benzoate (EB) to ovariectomized (OVX) rats are not well understood. Here we tested whether two housing conditions play a role. Sexual behavior in the female rat is dependent on the activation of ERα (estrogen receptor alpha) by estradiol. Corncob (CC) bedding has been reported to have adverse effects on the reproductive behavior and physiology of rats, and to disrupt ERα signaling in mice. In addition, some rodent behaviors are stimulated by olfactory stimuli and enhanced in the presence of estradiol. Upon arrival to the facilities OVX Long–Evans rats were housed on either Sani-Chips (SC) or CC in a room that housed only females (F) or males and females (M). Females were first given four sexual training sessions with 10 μg EB + 500 μg progesterone (P; administered 48 h and 4 h prior to training, respectively), followed by a 2-week hormone washout period. Next, 10 μg EB was administered s.c. every 4 days, 48 h prior to each of 8 test sessions in a unilevel 4-hole pacing chamber. On the final training day (i.e., when primed with EB + P), no inhibitory effects of corncob bedding were found, however a facilitation of the lordosis quality occurred in SC/F. Although all groups appear to have sensitized to the repeated administration of EB, CC/F animals displayed fewer high quality lordosis magnitudes and hop/darts, and received fewer mounts and intromissions overall. They also had a lower lordosis quotient (LQ) on tests 2–4 although this effect disappeared by test 5. These results suggest that although CC may inhibit some components of female sexual behavior when primed with EB alone, cues from sexually vigorous males can overcome that inhibition. Moreover, they suggest that male cues can facilitate mechanisms of estradiol sensitization. We recommend that quality control studies be conducted at individual institutions to assess any impact of corncob bedding on animal physiology and behavior.     

Long-term ovariectomy and hormone-induced sexual behavior, progestin receptors, and hypothalamic morphology in female rats

Long-term ovariectomy reduces the ability of estradiol and progesterone treatment to induce sexual receptivity in female rats. Previous researchers suggested that this effect may be due to a decreased induction of neural progestin receptors by estradiol in the long-term ovariectomized rats. The present study was designed to replicate and extend this finding, and to search for neuroanatomical correlates by measuring the volume of the ventromedial nucleus (VMN) of the hypothalamus, a putative site of action of estradiol and progesterone for the induction of female sexual behavior. Long-term ovariectomy (5 to 6 weeks) as compared to short-term ovariectomy (1 week) reduced the ability of estradiol-17 beta and progesterone treatment to induce sexually receptive and proceptive behaviors. Consistent with previous reports, our data show that the reduced levels of cytosol progestin receptors after long-term ovariectomy and estradiol treatment are related to a reduced ability of estradiol to induce the receptors. Long-term ovariectomy did not affect the concentration of cytosol progestin receptors in the preoptic area, suggesting a neuroanatomical specificity to this effect. Contrary to our predictions, long-term ovariectomy did not affect the volume of the VMN. In fact, estradiol treatment, while blocking the effect of long-term ovariectomy on sexual behavior, decreased the volume of the VMN. Therefore, the measurement of the volume of the VMN is not a good predictor of the responsiveness to steroid hormone induction of sexual behavior.     

A soy supplement and tamoxifen inhibit sexual behavior in female rats

In addition to displaying proceptive (hopping and darting) and receptive (lordosis) behaviors during a sexual encounter with a male, female rodents will regulate the timing of the encounter by engaging in a series of approaches and withdrawals from the male, a behavior termed paced mating behavior. Proceptive, receptive, and paced mating behaviors are all regulated by, and sensitive to, estrogen and progesterone, suggesting that compounds capable of disrupting these critical hormones may also perturb the display of female sexual behavior. The present experiments examined the impact of the selective estrogen receptor modulator (SERM) tamoxifen and a popular soy phytoestrogen dietary supplement on female sexual behavior in rats. Ovariectomized female rats were given either tamoxifen (TAMOX) by implant or the soy supplement through the diet then injected with estradiol benzoate (EB, 10 microg) or oil followed 48 h later with an injection of progesterone (P, 500 microg). Animals were then tested for sexual behavior 4 h after the P injection. Neither compound had any effect on sexual behavior when administered in conjunction with P alone; however, both significantly diminished receptive behavior, as measured by the lordosis quotient (LQ), in animals primed with both EB and P. Similarly, the hopping and darting rate was also significantly depressed in both the soy- and TAMOX-treated animals, compared to the EB- and P-treated controls, with the soy-treated animals showing significantly less proceptive behavior than the TAMOX-treated animals. Finally, soy but not TAMOX significantly attenuated paced mating behavior in animals compared to the EB- and P-treated controls. These results demonstrate that both the soy supplement and TAMOX act as estrogen antagonists on both proceptive and receptive behavior in female rats.     

Effects of ovariectomy and estradiol replacement therapy upon the sexual and aggressive behavior of the greater galago (Galago crassicaudatus crassicaudatus)

The effects of ovariectomy and estradiol treatment upon sexual and aggressive behavior were studied in a prosimian primate, the greater galago. Ovariectomized galagos were sexually unreceptive and frequently aggressive, but retained their sexual attractiveness to males. When females were treated with estradiol monobenzoate, however, their aggression and refusals of males' mounting attempts decreased markedly. Although males mounted these females, they usually failed to copulate, possibly because the females did not perform certain postural adjustments which assist males to intromit. Estradiol benzoate alone, even in large doses, does not fully restore patterns of mating behavior in ovariectomized female greater galagos. These observations on a prosimian primate are in striking contrast to the results of similar work on Old World monkeys and chimpanzees.     

RU486 facilitates or disrupts the sensitization of sexual behaviors by estradiol in the ovariectomized Long–Evans rat: Effect of timecourse

An acute injection of estradiol benzoate (EB) to the ovariectomized (OVX) rat activates low levels of lordosis, and subsequent progesterone (P) administration augments lordosis and recruits a complete pattern of sexual behavior including appetitive behaviors (e.g., hops/darts and solicitations). However, repeated injections of 5 μg or 10 μg EB (but not 2 μg EB), administered every 4 days to sexually-experienced OVX rats results in a behavioral sensitization, such that lordosis quotients (LQs) and appetitive behaviors progressively increase. We have shown that adrenal P does not play a critical role because behavioral sensitization to EB is not prevented by adrenalectomy. Here we tested whether P receptors play a role by examining the effect of chronic administration of the P receptor antagonist RU486 at a dose that reliably inhibits sexual behavior in fully primed OVX rats. Females were treated with EB (5 or 10 μg), and 5 mg RU486 dissolved in 0.4 mL vehicle (VEH; 80% sesame oil, 15% benzyl benzoate, 5% benzyl alcohol) 48 h and 5 h prior to each of 7 tests, respectively, occurring at 4-day intervals in unilevel 4-hole pacing chambers. Control animals were treated with 2, 5, or 10 μg EB + VEH. As expected, sensitization did not occur in females treated with 2 μg EB + VEH, and those females received fewer intromissions and ejaculations than all other groups. RU486 did not prevent the sensitization of LQ, moderate and high lordosis magnitudes (LM2 and LM3) or appetitive sexual behaviors on early tests, and in fact potentiated appetitive behaviors, LQ, LM2 and LM3, consistent with its facilitative actions in females treated with EB-alone, as we and others have reported previously. However, despite the initial facilitation, blocking P receptors by chronic administration of RU486 inhibited the maintenance of behavioral sensitization to EB.     

Sexual receptivity in aged female rats : Behavioral evidence for increased sensitivity to estrogen

Lordosis behavior and behavioral patterns indicative of sexual receptivity or nonreceptivity were evaluated in 3- and 25-month-old female rats. Intact, 25-month-old females revealing a pattern of prolonged vaginal cornification (PVC) were highly receptive, whereas 25-month-old pseudopregnant (PL) females were nonreceptive. These measures did not differ as a result of previous sexual experience (i.e., sexually naive vs retired breeders). Following ovariectomy, sexual behavior persisted significantly longer in 25-month-old PVC females than in 3-month-old females ovariectomized during vaginal proestrus. No difference was observed in the rate at which the vaginal smears of 25-month-old PVC and young ovariectomized females became leukocytic. When tested 5, 19, and 20 days after ovariectomy, sexual behavior was absent in all females. Following treatment with estradiol benzoate (0.5 or 1.0 μg/kg), the latency for the reappearance of sexual behavior in 25-month-old females was significantly shorter than that in similarly treated 3-month-old females. This was the case regardless of prior ovarian condition (PVC or PL) and breeding experience. In addition, the mean lordosis quotient (LQ) of 25-month-old females receiving either dose of EB was significantly greater than that of similarly treated 3-month-old females on at least 5 days of a 10-day treatment period. These results are discussed in terms of possible age-related changes in central and peripheral estrogen metabolism.     

Estrogen receptor α and β are involved in the activation of lordosis behavior in estradiol-primed rats

The present study was designed to assess the participation of estrogen receptors alpha (ERα) and beta (ERβ) in the short-term facilitation of lordosis behavior in ovariectomized (ovx), estradiol (E₂) primed rats. In experiment 1, dose response curves for PPT and DPN (ERα and ERβ agonists, respectively) facilitation of lordosis behavior (lordosis quotient and lordosis score) were established by infusing these agonists into the right lateral ventricle (icv) in female rats injected 40 h previously with 5 μg of E₂ benzoate. PPT doses of 0.08 and 0.4 ng produced high lordosis quotients starting at 30 min and continuing at 120 and 240 min post-injection. DPN induced high levels of lordosis behavior at all times tested. However, the intensity of lordosis induced by both agonists was weak. In experiment 2, we tested the involvement of each ER in facilitation of lordosis by icv infusion of MPP (ERα-selective antagonist) or PHTPP (ERβ-selective antagonist) prior to infusion of 2 ng of free E₂. Icv infusion of either MPP or PHTPP 30 min before free E2 significantly depressed E₂ facilitation of lordosis. The results suggest that both forms of ER are involved in the short-latency facilitation of lordosis behavior in E₂-primed rats.     

The display of sexual behaviors by female rats administered ICI 182,780

ICI 182,780 (ICI) is a pure antiestrogen that when administered systemically does not cross the blood-brain barrier, thus its actions are limited to the periphery. Four experiments were conducted to test the effects of ICI on the display of sexual behaviors in ovariectomized rats. Experiment 1 examined the effects of three doses of ICI (250, 500, and 750 μg/rat) on sexual receptivity and paced mating behavior in rats primed with estradiol benzoate (EB) in combination with progesterone (P). Experiments 2 and 3 compared the display of sexual behaviors in rats primed with EB+P or EB alone and administered either 250 μg ICI (Experiment 2) or 500 μg ICI (Experiment 3). Experiment 4 tested the effects of ICI (250 and 500 μg) on the expression of estrogen-induced progestin receptors in the uterus. ICI did not affect the display of sexual receptivity in any experiment. In rats primed with EB+P, paced mating behavior was altered by the 500 and 750 μg, but not the 250 μg, doses of ICI. The lowest (250 μg) dose of ICI did alter paced mating behavior in rats primed with EB alone. The effects of ICI on paced mating behavior were manifested by a substantial lengthening of contact-return latencies following intromissions and ejaculations. The percentage of exits were not affected by ICI. Estrogen stimulation of uterine weight and induction of uterine progestin receptors was suppressed by ICI (250 and 500 μg). ICI effects on paced mating behavior in hormone-primed female rats are likely to reflect antiestrogenic actions in the periphery, including interference with the estrogen induction of progestin receptors.     

Vaginocervical stimulation attenuates the sensitization of appetitive sexual behaviors by estradiol benzoate in the ovariectomized rat

The acute administration of estradiol benzoate (EB) to the ovariectomized (OVX) rat induces low levels of lordosis while sexually appetitive behaviors (e.g., hops, darts, solicitations) are absent, yet the repeated administration of EB results in a behavioral sensitization in which lordosis is potentiated and sexually appetitive behaviors are induced. We have shown that repeated copulation attenuates the sensitization of appetitive sexual behaviors. Here, we assessed which component of male stimulation during copulation is involved in the attenuation. On 8 occasions, sexually experienced OVX Long–Evans rats were treated with 10 μg EB and 48 h later assigned to one of six groups that differed in their experience on intermediates tests (2–7). One was given repeated access to a male (EB/Male), and another was placed in the copulation chamber alone (EB/Alone) on intermediate tests. Three groups were given one of three somatosensory stimuli by the experimenter: manual flank stimulation (FLS), clitoral stimulation (CLS), or vaginocervical stimulation (VCS). Finally, the control group was left undisturbed in the animal care facility (ACF). Sexual behaviors were measured on Tests 1 and 8. VCS received from the experimenter (VCS) or from the male during copulation (EB/Male) attenuated the magnitude of the sensitization of appetitive sexual behaviors compared with those that were not brought to the testing rooms (ACF), and the effect was most pronounced on sexual solicitations. These results suggest that VCS received during penile intromission inhibits the sensitization of sexually appetitive behaviors by repeated administration of EB. As such, repeated administration of EB may oppose those mechanisms that induce estrous termination, perhaps by sensitizing inhibitory processes within the ventromedial hypothalamus that typically prevent the display of sexual behaviors (i.e., by facilitating disinhibition).     

Effects of neonatal testosterone treatment on pacing behaviors and development of a conditioned place preference

Two experiments assessed the effects of neonatal testosterone treatment on paced mating behavior and conditioned place preference in female rats. In both experiments, females received s.c. injections of 5.0 microg testosterone propionate or oil vehicle at three days postpartum. As adults, females were ovariectomized and given s.c. injections of 10 microg estradiol benzoate and 500 microg progesterone, 48 and 4 h before mating, respectively. In Experiment 1, TP- and Oil-treated females exhibited similar high levels of lordosis responsiveness, but TP-treated females showed increased intervals between mounts and between intromissions in paced and non-paced mating conditions compared to control females. The effect was particularly pronounced during paced mating, when contact return latencies were increased approximately 2-fold by TP treatment. TP-treated females showed exaggerated pacing behavior, showing significantly greater return latencies after intromissions than Oil-treated females. In Experiment 2, TP- and Oil-treated groups were tested in a conditioned place preference paradigm to determine if the behavioral changes observed in Experiment 1 were in part a result of changes in the perceived reward produced by paced mating. TP treated and control females developed equivalent preferences for places associated with paced but not non-paced mating, indicating that neonatal TP treatment at this dosage does not disrupt or enhance the conditioned place preference induced by paced mating. The results of the two experiments demonstrate that neonatal TP treatment alters the display of pacing behavior but not the reward state induced by paced mating, and suggest that TP affects neural substrates involved in performance of paced mating without effects on those controlling lordosis or place preference conditioning.     

Hormonal status and test condition, but not sexual experience, modulate partner preference in female rats

A series of experiments was conducted to determine the contributions of hormonal status, test condition, and sexual experience to the display of partner preference by female rats. Preference for a sexually active male rat over a sexually receptive female rat was assessed in independent groups of female rats tested in a condition limiting physical contact (No Contact) and a condition allowing for sexual interaction (Contact). Although hormonal status and test condition influenced the preference for a sexually active male, repeated testing and sexual experience had no effect. Experiment 1 demonstrated that independent of test condition, preference for the male is stronger in estrogen- and progesterone-primed rats than in rats receiving the vehicle. Moreover, independent of hormone condition, rats tested in the No Contact condition exhibit a stronger preference for the male than rats tested in the Contact condition, reflecting in part the active pacing of mating stimulation by sexually receptive rats tested in the Contact condition. Experiment 2 showed that the overall pattern of partner preference in proestrous and diestrous rats was similar to that observed in ovariectomized, estrogen- and progesterone-primed, and oil-treated rats, respectively. In Experiment 3, rats primed with estrogen alone did not exhibit a preference for the male even though fully receptive. Experiments 4 and 5 demonstrated that sexual experience does not affect the expression of preference for the male in estrogen- and progesterone-primed rats. The present findings demonstrate that the female rat's preference for the male is stable across repeated tests and is not affected by sexual experience. Our results also confirm that gonadal hormones influence the expression of a preference for a sexually active male versus a sexually receptive female and demonstrate that the magnitude of preference is modulated by test conditions.     

Non-ovarian aromatization is required to activate female sexual motivation in testosterone-treated ovariectomized quail

Although aromatase is expressed in both male and female brains, its functional significance in females remains poorly understood. In female quail, sexual receptivity is activated by estrogens. However it is not known whether sexual motivation is similarly estrogen-dependent and whether estrogens locally produced in the brain contribute to these behavioral responses. Four main experiments were designed to address these questions. In Experiment 1 chronic treatment of females with the anti-estrogen tamoxifen decreased their receptivity, confirming that this response is under the control of estrogens. In Experiment 2 chronic treatment with tamoxifen significantly decreased sexual motivation as treated females no longer approached a sexual partner. In Experiment 3 (a) ovariectomy (OVX) induced a significant decrease of time spent near the male and a significantly decreased receptivity compared to gonadally intact females, (b) treatment with testosterone (OVX + T) partially restored these responses and (c) this effect of T was prevented when estradiol synthesis was inhibited by the potent aromatase inhibitor Vorozole (OVX + T + VOR). Serum estradiol concentration was significantly higher in OVX + T than in OVX or OVX + T + VOR females. Together these data demonstrate that treatment of OVX females with T increases sexual motivation and that these effects are mediated at least in part by non-gonadal aromatization of the androgen. Finally, assays of aromatase activity on brain and peripheral tissues (Experiment 4) strongly suggest that brain aromatization contributes to behavioral effects observed here following T treatment but alternative sources of estrogens (e.g. liver) should also be considered.     

Integrity of mating behaviors and seasonal reproduction in coyotes (Canis latrans) following treatment with estradiol benzoate

Coyotes (Canis latrans) are seasonally monestrous and form perennial pair-bonds. Breeding is dominated by each pack's alpha male and female, and both sexes share responsibility for territory defense and pup-rearing. They are also opportunistic predators on domestic livestock and pets. But while dominant adults have been implicated as primary killers, depredation is reduced when coyotes are without pups. Contraception, therefore, may represent a non-lethal solution for conflicts between coyotes and humans. Steroid hormones successfully control fertility in some species, but have been considered contraindicated in wildlife and canids in particular; specific concerns include possible induction of aberrant behavior, or uterine and hematopoietic pathologies. Herein we describe a study examining the physiological effectiveness, health safety, and behavioral consequences following treatment of estrous coyotes with exogenous estrogen. We treated captive adult female coyotes in estrus with 0.01 mg/kg estradiol benzoate (EB), either before (n = 5) or immediately after ovulation (n = 6), then documented reproductive outcome, physiological variables and behavioral responses, during and after treatment. Pregnancy was averted in six females treated after ovulation, suggesting that appropriate timing of treatment proved crucial. A transient suppression of sexual behavior was observed, and in some cases, estrus appeared slightly lengthened. However, neither ovulation nor mating behavior was fully suppressed. Importantly, non-pregnant females (and their mates) displayed diestrous socio-sexual behavior similar to pregnant coyotes (behavioral pseudopregnancy). Furthermore, non-pregnant coyotes did not mate again until the next native breeding season, and we observed no deleterious physiological effects during diestrus or subsequent ovarian cycles.     

A prenatal source for defeminization of female rats is the maternal ovary

Sexual behavior in laboratory rats is influenced by a variety of factors in the perinatal environment. Male rats are masculinized and defeminized in response to circulating testosterone perinatally. Females undergo a process of feminization but in some cases are exposed to testosterone. Previous work has shown that during prenatal development female rats normally undergo a partial masculinization and defeminization of sexual behavior as reflected by altered responsiveness to gonadal hormones in adulthood. In the present study we investigated whether the maternal ovary influences adult females' responsiveness to gonadal hormones. Pregnant rats were ovariectomized on Day 10 of pregnancy and their offspring tested for sexual behavior in adulthood. Following ovariectomy pregnancies were maintained by administration of systemic progesterone. In addition the ovariectomized pregnant rats were given one of three daily treatments (Days 10-21): 0.2 microgram estradiol benzoate in sesame oil and 0.1 cc propylene glycol, 5 mg of the aromatase inhibitor 1,4,6-androstatriene-3,17-dione (ATD) in 0.1 cc propylene glycol, or 0.1 cc propylene glycol. A control group was generated from SHAM operated mothers given daily control injections of propylene glycol and sesame oil. Offspring were ovariectomized in adulthood and tested for display of feminine sexual behavior in response to estradiol benzoate and progesterone or estradiol benzoate alone. Masculine sexual behavior was measured in response to testosterone propionate (TP). Feminine sexual behavior was enhanced in offspring from ovariectomized mothers given only progesterone replacement during pregnancy. Offspring from mothers treated with ATD displayed the greatest elevations in feminine sexual behavior. Estradiol treatments of ovariectomized mothers prevented the increase in feminine potential seen in offspring in the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Behavioral defeminization by prenatal androgen treatment in rats can be overcome by sexual experience in adulthood

Exposure to testosterone during a critical period of prenatal development disrupts the normal display of sexual behaviors in adult ovariectomized (OVX) rats treated with estradiol benzoate (EB) followed by progesterone (P). The organizational hypothesis posits that prenatally androgenized females (PNAFs) are desensitized to EB. We tested this hypothesis by first treating PNAFs with varying doses of EB (2.5, 5, 10, 20 μg) followed by P (500 μg), and second by subjecting females to an established EB behavioral sensitization paradigm where females are first given sexual experience with EB (10 μg) and P prior to repeated sexual behavior testing with EB alone. Long-Evans females were androgenized in utero by a s.c. injection of 500 μg testosterone propionate or the oil control to pregnant dams on gestational day 18. Female offspring were OVX on postnatal day 80 and tested one week later in the unilevel 4-hole pacing chamber. Genital tissue was defeminized in PNAFs, and the lordosis quotient (LQ) and partial (i.e., hops/darts) and full solicitations were significantly lower, while defensive behaviors were higher, in PNAF females, relative to non-PNAF females regardless of the acute EB priming dose. However, repeated testing with EB alone (10 μg), or EB and P eliminated the differences between groups on LQ and hops/darts, indicating that the behavioral deficit can be overcome by sexual experience. These results suggest that PNAFs are not desensitized to EB, and despite disruptions in sexual differentiation of anatomical structures, the deficiency in sexual behavior in response to acute EB and P can be experientially overcome. PNAFs appear, however, to have a chronic deficit in the expression of full solicitations.