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.     

Lack of effect of vaginal lavages and aliphatic acids on ejaculatory responses in rhesus monkeys: Behavioral and chemical analyses

Four behavioral experiments involving a total of 19 adult male and 27 adult spayed female rhesus monkeys failed to reveal significant sexual stimulatory properties of vaginal lavages obtained from estrogen-treated donor females when the material was applied to spayed nonestrogenized recipient females. However, all but one of the males copulated to ejaculation when paired with estrogenized females. Two of three males showed moderate increases in sexual behavior with recipients when the vaginal lavage tested was contaminated with 24-hr-old ejaculate. When purified aliphatic acids were applied to spayed nonestrogenized recepients, one of two males showed increased frequencies of mounting behavior, but intromissions and ejaculations were not displayed.Quantitative analyses of short chain aliphatic acids in vaginal lavages, the hypothesized active component, revealed that (a) spayed females had nondetectable levels of aliphatic acids; (b) daily estradiol benzoate treatment for 6–10 days (25 μg/day i.m.) induced detectable levels of acetic, propionic, and butyric acids; (c) exposure to estradiol for six months resulted in a fairly constant plateau of aliphatic acid concentrations; and (d) ejaculate from the male caused up to fivefold elevations in the aliphatic acid concentrations.Three intact females were studied throughout a menstrual cycle, and the peak values of aliphatic acids occurred in the luteal phase, several days after presumed ovulation. Three spayed females treated chronically with estradiol were given four daily injections of 5 mg progesterone, and the mean concentrations of aliphatic acids increased from 199.7 to 801.0 μg/ml. However, the endocrine conditions associated with maximum concentrations of aliphatic acids in either intact or spayed females are known from other studies to be associated with decreased likelihood of copulation.We conclude that for the majority of males studied, the application of vaginal lavages obtained from estrogenized donors did not significantly increase copulatory behavior with spayed, nonestrogenized recipient females. Moreover, the data from aliphatic acid determinations suggest that increases in concentrations of these substances are not always associated with facilitation of copulation, since the largest increases were found either (1) following copulation to ejaculation, (2) during the luteal phase in cycles free of copulation, or (3) following progesterone treatment of spayed, estrogenized females. Finally, comparison of our results with those from other laboratories suggests that the mechanism involved in positive effects may depend upon associative learning or upon extinction and disinhibition of sexual interest.     

Ovarian hormones,copulatory stimuli,and female sexual behavior in the Mongolian gerbil

The effects of repeated estradiol benzoate (1.0 or 3.3 μg) and progesterone (0.5 mg) injections and mating experiences (10 min or 4 hr) were examined in ovariec-tomized female Mongolian gerbils (Meriones unguiculatus) paired with sexually vigorous but unfamiliar males. Estradiol benzoate alone for 2 days did not elicit female sexual responses. Estradiol benzoate for 2 days followed by progesterone facilitated lordosis in the female. In females injected daily with 1.0 μg estradiol benzoate, progesterone exposure for approximately 1 day produced a significant inhibition in subsequent lordosis, although these females continued to respond to the male with lordosis quotients of approximately 60. A 4-hr mating experience produced a nearly complete elimination of sexual activity in tests observed 24 hr later with a fresh male. Footstomping was positively associated with sexual activity in both sexes, although females footstomped more often in the 1.0 rather than the 3.3-μg estradiol benzoate condition. Fighting was most frequent in tests in which lordosis quotients were low. Interactions among copulatory experiences and inhibitory effects of progesterone summed to terminate female sexual receptivity and alter other social interactions in the gerbil.     

Periovulatory changes in female sexual behavior and patterns of ovarian steroid secretion in group-living rhesus monkeys

The behavior of nine intact group-living adult female rhesus was observed for 30 min daily with each of four adult male rhesus across a verified ovulatory menstrual cycle. Blood samples collected from females daily or on alternate days were analyzed for estradiol, testosterone, and progesterone. Female patterns of approach, follow, and initiate proximity increased several days prior to the estradiol peak, peaked on the day of the estradiol peak, then declined completely or to very low frequencies. Mounts, intromissions, and ejaculations increased significantly on the day of the estradiol peak, remained elevated for 2 more days, then declined completely by the fifth day after peak estradiol. Ejaculations never occurred outside of a 10-day period starting 4 days before the estradiol peak and ending 5 days after the estradiol peak. During this period females initiated over 90% of all approaches. Female hand slap, threaten away, and stand up increased significantly on the first day of increased copulation, remained elevated while copulation was significantly elevated, then decreased along with the decline in copulation. Ten of eleven patterns of female behavior correlated significantly with estradiol level prior to the estradiol peak. All were significantly inversely correlated with progesterone level after the estradiol peak. No pattern of female behavior correlated significantly with testosterone either before or after the estradiol peak. Similarly, male patterns of behavior correlated with female levels of estradiol and progesterone, but not testosterone. These results demonstrate a relationship between increased serum estradiol and increased female initiation of sexual behavior. The finding that some patterns of female behavior increase several days prior to copulation, whereas other behaviors increase coincident with increased copulation suggests that the behavior of group-living rhesus females serves two functions. The first is to communicate sexual interest and the second is to maintain the consort pair and increase the probability that ejaculation will occur. In addition, the strong correlation between preovulatory female behavior and estradiol level suggests that the female's behavior provides precise information about her reproductive state and could thus coordinate copulation with maximal fertility.     

Duration of hormonal deprivation: influences on physiological and behavioral responsiveness to estradiol

A total of 54 ovariectomized female guinea pigs were divided into three groups and tested six times at 2-week intervals for their responsiveness to exogenous ovarian hormones (3 days of 4 micrograms/kg estradiol benzoate plus 1 day of 0.4 mg/kg progesterone) or control injections (0.2 ml oil vehicle). Two weeks after ovariectomy, treatment with estradiol significantly reduced food intake and body weight, and also produced vaginal membrane rupture in 98.1% of the females. When tested for sexual behavior at 4, 6, and 8 hr after the progesterone injection, 29 of the subjects (53.7%) displayed lordosis in response to manual stimulation. Twelve weeks after ovariectomy, the effects of estradiol on food intake, body weight, and vaginal membrane condition had not diminished. However, the overall proportion of females from which lordosis could be elicited declined to 27.8%. Biweekly injections of estradiol benzoate plus progesterone to one of the groups of females did not prevent this decline in the sexual response. Based on these results, it was concluded that the observed reduction in behavioral lordosis does not represent a general decline in the responsiveness of ovariectomized guinea pigs to estrogenic stimulation, but may involve changes in their responsiveness to progesterone or in other mechanisms more specifically associated with sexual behavior.     

Role played by the ovary and adrenals in early receptivity during 4-day cycle in the female rat

The mechanisms involved in the control of precocious sexual receptivity were studied in 4-day cyclic female Wistar rats injected with 10 μg estradiol benzoate (EB) and caged with a male during the night from diestrus II to proestrus. Early mating frequencies were compared in intact females, in animals ovariectomized on the morning of diestrus I, in adrenalectomized and in adrenalectomized-ovariectomized females. No change in early sexual receptivity occurred either in ovariectomized, or in adrenalectomized animals. On the contrary, a significant decrease of precocious mating frequencies was noted in adrenalectomized-ovariectomized females. The role played by the ovary in the control of precocious receptivity was supposed to be due to the secretion of progesterone which has been evidenced on the late afternoon of diestrus II in estrogen treated females.Concerning the mechanisms by which the adrenals may compensate for the ovaries in the control of early sexual receptivity in estrogen-primed females it was observed that notwithstanding an inhibitory action exerted by EB on the adrenal progesterone secretion, a low rate of progesterone was maintained in the peripheral plasma which was compatible with early mating in ovariectomized animals.     

Sexual experience interacts with steroid exposure to shape the partner preferences of rats

A three-phase experiment manipulated sexual experience and hormone exposure (perinatally and in adulthood) in female rats housed individually from weaning so as to limit peripubertal social and sexual experience. Noncontact partner preference for a male or estrous female rat was measured both before and after sexual experience, first while rats were under the influence of circulating testosterone propionate (TP) and later after priming them with ovarian hormones (estradiol benzoate and progesterone; EB & P). When implanted with TP capsules and tested while sexually naive, all groups of female rats preferred females to males without differing statistically. However, following three sexual experience sessions with estrous females, differences emerged between the masculinized and control groups in the magnitude of their female-directed preference, with masculinized females demonstrating a significantly greater preference for estrous females. Sexual experience with male rats under EB & P did not result in a significant shift in preference in any group. Histological assessment indicated that the volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) was increased by exposure to TP postnatally, and SDN-POA volume correlated positively with partner preference scores but only when rats were both sexually experienced and exposed to circulating TP in adulthood. These results suggest that sexual experience interacts with steroid exposure to shape partner preference.     

Only Self-Paced Mating Is Rewarding in Rats of Both Sexes

When rats are mated in a traditional mating chamber (with one male and one female) in which the male dictates the pace of the copulatory sequence, males develop a reward state as evaluated by conditioned place preference (CPP). In this mating situation no reward state is induced in females. However, when female rats are able to control (pace) the rate of sexual stimulation, thereby reducing the aversive consequences associated with mating, a clear CPP is observed. In the present study the CPP paradigm was used to determine whether if the reinforced state induced by coital interactions in male rats can be maintained when females pace the sexual interaction. Adult male and female rats were mated in one of two different conditions: (1) where subjects were able to pace their coital interactions or (2) where subjects were not able to pace their sexual contacts. The results showed that when males had control over the sexual interaction they developed a clear place preference while males that mated with females that paced their coital contacts did not develop CPP. Similarly, only females that were able to pace their sexual contacts developed place preference. These results suggest that coital interactions in males, as well as in females, can induce a reward state only when they are able to control the sexual interaction. Under seminatural conditions sexual behavior in rats is highly promiscuous, they mate in groups and repeatedly change partners in the middle of copulation. This behavioral sequence allows both, male and female to control the rate of sexual interaction, assuring the induction of a reward state outlasting the actual performance of coital responses.     

Natural or hormone-induced sexual and social behaviors in the female brown lemming (Lemmus trimucronatus)

The behaviors of intact or ovariectomized, estradiol benzoate-treated or estradiol benzoate followed by progesterone-treated female brown lemmings were compared. Intact, diestrous females engaged in more social interactions with a male than did ovariectomized females (Experiment 1). In the first 5 min of a 1-hr mating exposure (Experiment 2, Test A) intact females in natural estrus engaged in more social and sexual behaviors than did ovariectomized females in estrogen-induced estrus. However, during the last 5 min of the 1-hr exposure (Test B) ovariectomized females receiving estrogen alone continued to show high levels of sexual activity with a male partner, while intact estrous females or females receiving estrogen followed by progesterone showed an apparent drop in sexual receptivity and an increase in aggressivity. Aggressive behaviors, as indexed by threat-leap behaviors on the part of the female may increase in the presence of progesterone. Declines in sexual activity, occurring within 1 hr of progesterone injection, were apparently dependent on the interaction of progesterone and copulatory events which may affect both the male and female.     

Differential hormonal control of aggression and sexual behavior in female Syrian hamsters

These experiments were designed to test the effects of chronic estradiol treatment on aggression and sexual behavior in female hamsters. Isolated female hamsters were ovariectomized and tested for their behavioral responses to a group-housed, ovariectomized female hamster (aggression test) and a group-housed, intact male hamster (sexual behavior test). Following these baseline tests, the experimental females were implanted sc with Silastic capsules containing different concentrations of estradiol (100, 25, 10, or 0%) diluted with cholesterol and retested 3, 7, 10, and 14 days after implantation. High levels of aggression were observed on the baseline test, with no changes in aggression toward an intruder female observed for any implant group on subsequent tests. Despite these high levels of aggression toward another female, most of the estradiol-treated females (80% at 14 days) were sexually responsive in the presence of a male. There was no effect of Silastic estradiol concentration on sexual behavior, even though a range of serum estradiol levels (39–105 pg/ml) resulted. Lordosis latencies decreased and lordosis durations increased over the extent of estradiol treatment. Seventeen days after Silastic implantation, all females were injected with progesterone and retested. Estradiol-treated females showed an extreme reduction in aggression toward a stimulus female, as well as a further stimulation of sexual behavior after progesterone treatment. High levels of aggression in cholesterol-treated females (0% estradiol) were maintained even after progesterone injection, and these females never displayed any sexual responsivity. These results suggest that sexual behavior in the female hamster is sensitive to estradiol alone, whereas the inhibition of aggression requires the combination of estradiol plus progesterone.     

Progesterone facilitation of lordosis in male and female Sprague-Dawley rats following priming with estradiol pulses

Adult male Sprague-Dawley rats rarely exhibit progesterone-facilitated lordosis following steroid treatments which are effective in females. In contrast, progesterone-facilitated lordosis has been observed following priming with estradiol pulses in another strain. The aim of this study was to compare progesterone-facilitated feminine sexual behavior in adult male and female Sprague-Dawley rats following priming with estradiol benzoate (EB) or estradiol pulses. Female sexual behavior was measured in adult, gonadectomized males and females treated as follows: Two pulses of estradiol followed by progesterone or oil the next day; EB (two doses) for 3 days, and progesterone or oil the next day. These protocols were repeated at 4- or 6-day intervals, respectively. Progesterone-facilitated lordosis was observed consistently in both sexes treated with estradiol pulses. By the fifth test, lordosis quotients did not differ between the sexes, but the lordosis ratings in progesterone-treated males remained lower than those observed in females. Proceptivity (hop-darting) was facilitated by progesterone in females, but was never observed in males. Lordosis was induced in both sexes by 15 micrograms EB, but was not reliably facilitated by progesterone. Treatment with the lower dose of EB (1.5 micrograms) induced high levels of receptivity in females (occasionally facilitated by progesterone), but not in males regardless of subsequent treatment (i.e, progesterone or oil). These data suggest that progesterone-facilitated lordosis can be induced in male Sprague-Dawley rats, if a regimen of estradiol pulses is used. Thus, the brain of the adult male is not inflexibly differentiated with regard to progesterone facilitation of feminine receptive behavior.     

Hormones and social behavior of squirrel monkeys. (Saimiri sciureus). I. Effects of endocrine status of females on behavior within heterosexual pairs.

Intact male squirrel monkeys were paired with ovariectomized females given either oil vehicle, estradiol benzoate (10 μg) alone, or estradiol benzoate combined with progesterone (5 mg). Affiliative behaviors, including social contacts, female grasping of the male, male and female approaches, and following by the male were observed more frequently, and social distance decreased when females received estradiol as compared to oil. Furthermore, when progesterone was combined with estradiol, some of the effects seen with estradiol alone, such as grasping by the female and following by the male, were reversed. These results support the hypothesis that seasonal changes between sex-segregated and sex-integrated forms of social organization reported for this species are influenced by endocrine conditions of the female.     

Interactions of social,spatial and hormonal factors on the behavior of rhesus monkeys (Macaca mulatta)

In a three year study, the interactions of social, spatial and hormonal variables on the behavior of rhesus monkeys were investigated. Observations were made on (1) an oppositelysexed pair alone in a cage; (2) the pair alone in a large room; and (3) the pair together with three ovariectomized females in the same large room. Each of four males was tested with the same group of four ovariectomized females (16 pairs, 480 1-hr tests). Each female served in turn as the focal female, namely, the hormone-treated one, and received first estradiol benzoate (EB) alone and then in combination with progesterone (P). The presence of three other females (the social variable) had a marked effect on all aspects of the behavior of the focal pair, and reduced the male's ejaculations as well as other sexual and affiliative interactions with the focal female. This was due to an inhibitory influence exerted by the dominant female on the interactions of subordinate females with the male. Comparing data from two groups of females showed that female dominance rank, and not male sexual preference, was the critical factor, and that mate competition between female rhesus monkeys was operating. Decreasing the space available for the interactions of the pair appeared to imitate a bonding effect in the male, increasing male grooming and tending to increase male sexual activity. In the group setting, treating the female with EB increased sexual activity, and additional progesterone decreased it in all three test settings. The effects of progesterone were most clearly apparent when the pair was tested alone in a large area.     

The inhibitory actions of progesterone: effects on male and female sexual behavior of the hamster

A series of three experiments compared the inhibitory effects of progesterone on estrogen- or androgen-induced sexual behavior in male and female hamsters. In the first experiment chronic progesterone treatment was found to have no effect on male copulatory behavior maintained after castration with testosterone propionate or estradiol benzoate. However, testosterone propionate was more effective at maintaining male behavior than estradiol benzoate. In the second experiment progesterone was found to have a slight inhibitory effect on the rate of the restoration of the intromission response after androgen treatment in males which had been castrated for 8 weeks. In the final experiment, chronic progesterone treatment markedly inhibited sexual receptivity in male and female hamsters which had been given 4 weeks of androgen or estrogen treatment and a single pretest injection of progesterone. Thus, progesterone was shown to be a potent inhibitor of androgen- or estrogen-induced estrus in both male and female hamsters. Due to the large difference in effectiveness on these two behavioral systems, we suggest that progesterone affects steroid-induced male copulatory behavior and female receptivity by different mechanisms of action.     

Effects of ovarian hormones on the behavior of captive Macaca fascicularis

To examine the effects of ovarian hormones on the behavior of female Macaca fascicularis and their male partners, daily 1-hr behavior tests were conducted while ovariectomized females were (1) untreated, (2) given estradiol benzoate (EB) (5 μg subcutaneously [s.c.]/day), (3) given estradiol benzoate together with increasing doses of progesterone (P) (5 mg, 10 mg, and 20 mg. s.c./day), and (4) given testosterone propionate (TP) (0.25 mg s.c./day) (six pairs, 540 tests). Weekly blood samples were analyzed by radioimmunoassay for plasma hormone levels (81 samples). Estrogen treatment produced plasma estradiol levels similar to those of intact females during the late follicular phase of the menstrual cycle. Additional progesterone at the lowest dose produced plasma progesterone levels similar to or somewhat higher than those during the midluteal phase, while higher doses produced supraphysiological levels. Androgen treatment resulted in plasma levels well above the physiological range. Hormone treatments produced highly significant effects on the sexual, social, and aggressive interactions of the pairs. As in rhesus monkeys, estrogen increased male and female sexual activity, and increasing doses of additional progesterone reversed these effects. Unlike in rhesus monkeys, testosterone propionate increased both female sexual motivation (invitations) and also male sexual activity and ejaculatory performance. The direction of the hormone-dependent changes in grooming and aggressive interactions confirmed earlier results with intact females and indicated that aggressive interactions and male grooming times were highest, and female grooming times were lowest, when copulatory activity was at its height.     

Estrogenic effects of zearalenone on the expression of progestin receptors and sexual behavior in female rats

Zearalenone is a resorcylic acid lactone compound that is produced by fungal infection of edible grains and is believed to influence reproduction by binding to estrogen receptors. In order to study the potential estrogenic effects of this compound in the brain, we examined the effects of zearalenone on the expression of neuronal progestin receptors and feminine sexual behavior in female rats. Ovariectomized rats were treated with zearalenone (0.2, 1.0, or 2.0 mg), estradiol benzoate, or vehicle daily for 3 days. They were then either perfused, and progestin receptors visualized by immunocytochemistry, or injected with progesterone and tested for sexual receptivity with male rats. Progestin receptor-containing cells were counted in the medial preoptic area and ventromedial hypothalamus. The two highest doses of zearalenone increased the concentration of neuronal progestin receptors, as did 10 microg of estradiol. The highest dose of zearalenone (2 mg) also induced progestin receptor staining density comparable to that of 10 microg of estradiol benzoate. In behavioral tests, ovariectomized animals treated with 2 mg of zearalenone followed by progesterone showed levels of sexual receptivity comparable to females treated daily with estradiol benzoate (2 microg) followed by progesterone. These studies suggest that, although structurally distinct and less potent than estradiol, zearalenone can act as an estrogen agonist in the rat brain.     

Perinatal exposure to progesterone, estradiol, or mifepristone affects sexual differentiation of behavior in opossums (Monodelphis domestica)

The effects of perinatal exposure to progesterone (P) and estradiol (E) on sexual differentiation of behavior and morphology were examined by treating male and female gray short-tailed opossums on postnatal day 8 with progesterone alone (P), P plus estradiol (E) (PE), the P receptor antagonist mifepristone/RU486 (MIF), or corn oil control (C) and gonadectomizing them before puberty. When given female hormone replacement therapy in adulthood and tested with intact stimulus males, MIF animals showed less female-typical aggressive threat behavior than animals in other treatment groups. Stimulus males scent marked in more tests involving females than males and in more tests involving MIF animals than animals in other treatment groups. Body weight was lower in females than in males and was lower in MIF animals than in animals in other treatment groups, and P females failed to show female-typical genital locks after copulation. Sexual receptivity was similar in males and females and, while not decreased by any perinatal hormone treatment, was higher in PE males than in animals of either sex in any treatment group. These findings suggest that perinatal exposure to P is associated with the organization of feminine threat behavior and the defeminization of attractivity, body weight and genital anatomy in this marsupial. Reasons for these findings and for why female sexual receptivity is enhanced by perinatal exposure to exogenous E only in an endogenous masculine environment are discussed.     

Silent or Vocalizing Rats Copulate in a Similar Manner

Both male and female rats produce 50 kHz ultrasonic vocalizations (USVs) in the presence of a sexual partner and during copulation. Previous studies showed that USVs have no incentive value for rats. In this study, we evaluated the role of USVs in behavior during copulation. Three groups of rats were used: sham males paired with sham females, devocalized females paired with sham males, and sham females paired with devocalized males. During the copulation test, the USVs emitted by the sham rat were recorded and the sexual behavior of both the male and the female were observed. The results revealed that devocalized and sham females showed similar patterns of sexual behavior and no difference was found in the copulatory behavior of devocalized and sham males. Also the behavior of the partner of a sham rat was comparable to the partner of a devocalized rat. In addition, almost no changes in USVs emission were found in the 5 seconds before and/or after a copulatory behavior. It can be concluded that USVs play no important role in rat copulatory behavior at least in sexually naïve rats.     

Ovarian hormones and the duration of sexual receptivity in the female golden hamster

The induction of sexual receptivity and its maintenance after copulation in ovariectomized female golden hamsters (Mesocricetus auratus) was found to be a function of the levels of ovarian hormones administered. Various combinations of estradiol benzoate (between 0.6 and 666 μg) and progesterone (between 0.05 and 5.0 mg) were administered in two experiments. Although some animals responded at 0.6 μg, higher levels of estradiol benzoate (1–6 μg or more) were more effective in inducing levels of lordosis equivalent to those seen in intact females in natural estrus. After mating, a depression in lordosis was observed in both ovariectomized and intact females. However, in ovariectomized females (excluding animals that did not respond initially) the duration of postcopulatory receptivity was a function of the level of progesterone administered. High levels of progesterone tended to prolong slightly the duration of postcopulatory receptivity.     

Female sexual behavior displayed by androgenized female rhesus macaques

Adult, prenatally androgenized female rhesus macaques (female pseudohermaphrodites) that had been ovariectomized were treated with estradiol benzoate (20 micrograms/day) and paired with males at weekly intervals for 4 weeks beginning on Day 12 of injection. Their sexual behavior was compared to that of a control group of females. The sexual behavior of the males toward the two groups of genetic females (control females with normal female genitalia and hermaphrodites with well-formed male genitalia) was also observed. Females and hermaphrodites were equally receptive to male invitations to copulate. Although there were some differences in the specific components of proceptive behavior displayed by the two groups, the overall differences were negligible. Earlier studies had shown that infant and juvenile hermaphrodites resemble males in patterns of play and sexual behavior. When treated with testosterone as adults and paired with receptive females, they displayed mounting patterns typical of males--one of seven hermaphrodites achieved intromission and ejaculated. It has now been demonstrated that when treated with estrogen and paired with males, they responded as females. Hence, the capacity to behave sexually as males is not incompatible with the capacity to respond sexually as females under certain hormonal and environmental conditions.