Forebrain implants of estradiol stimulate maternal nest-building in ovariectomized rabbits

In rabbits, estradiol and progesterone (P) stimulate digging a maternal burrow while P withdrawal promotes straw-carrying. To investigate where such hormones act to regulate those activities, ovariectomized rabbits were implanted with estradiol benzoate (EB; Experiment 1) in the nucleus accumbens (ACC), the principal nucleus of the medial preoptic area or the dorsal hippocampus. Implants were combined with s.c. P injections. In Experiment 2, P (in crystals or dissolved in oil) was implanted in the same regions as in Experiment 1, combined with s.c. injections of EB. Implants of EB into the ACC or MPOA-bed nucleus of the stria terminalis (BNST) stimulated significant digging across the period of P injections in 72% and 67% of females, respectively. Neither EB implants in the hippocampus nor cholesterol implants in the MPOA-BNST were effective in eliciting digging. P withdrawal provoked a rapid decline of digging in all animals; it also stimulated straw-carrying in 53% of females implanted with EB in the MPOA-BNST. P implants failed to stimulate digging in most females injected with EB. Removal of P crystals did not promote straw-carrying. Results support an action of estradiol on the ACC and MPOA-BNST to promote digging while only the MPOA-BNST is involved in stimulating straw-carrying. The failure of P implants to stimulate digging or straw-carrying in EB-treated females suggests that the stimulation of other or additional brain areas by P is necessary to fully activate maternal nest-building.     

Effects of gonadal hormones on eating and body weight in mongolian gerbils (Meriones unguiculatus)

The effects of gonadal steroids on food intake and body weight were studied in Mongolian gerbils. Orchiectomy of adult male gerbils caused significant increases in body weight but had no detectable effect on food intake. Treatment with testosterone propionate or 5α-dihydrotestosterone propionate (100 μg/day) had no effect on food intake or body weight of orchiectomized males, but withdrawal of exogenous androgen treatment had the same effect as orchiectomy, increased body weight with no increase in food intake. Treatment with estradiol benzoate (EB; 2 μg/day) increased food intake and body weight of ovariectomized gerbils, but progesterone (1 mg/day) had no effect on these measures when given by itself. However, when progesterone was given concurrently with EB it synergized with the estrogen and further increased eating and body weight. These results are contrasted with previous work in other mammalian species.     

Occurrence of permanent changes in vaginal and uterine epithelia in mice treated neonatally with progestin, estrogen and aromatizable or non-aromatizable androgens.

Female mice of the C57 Black/Tw strain were injected daily with 100 microng testosterone, 50 microng testosterone propionate (TP), 100 microng 5 alpha-dihydrotestosterone (DHT) or 50 microng 5 alpha-dihydrotestosterone propionate (DHTP), for 10 days from the day of birth. Two other groups of female mice were given neonatal injections with 20 microng estradiol-17 beta and 100 microng progesterone for 10 days, respectively. All mice were ovariectomized at 60 days of age and killed at 90 days. In 100% of neonatally estrogenized or androgenized, ovariectomized mice, the cranial part of the vagina was lined with stratified epithelium with either cornification or parakeratosis or mucification. Stratification only or stratification with superficial squamous metaplasia or cornification took place in the uterine epithelia of 18% of the TP-treated, 75% of the DHT-treated and 50% of the DHTP-treated, ovariectomized mice. In contrast, neonatally estrogenized, ovariectomized mice did not show the estrogen-independent, persistent uterine changes. Neonatal progesterone treatment failed to induce the permanent changes in the vaginal and uterine epithelia.     

Hormone profiles and nest-building behavior during the periparturient period in rabbit does

This study was done to elucidate the relationship between the hormones beta-estradiol, progesterone, prolactin and beta-endorphin and nest-building behavior in rabbit does during the periparturient period. Beta-estradiol increased as parturition approached with a significant increase starting 2 days before parturition (day -2). Progesterone decreased with the progress of gestation, but a significant decrease was observed starting on day -2. Prolactin concentration started to increase on day -2 prepartum but a significant increase in prolactin concentration was not noted until the last day of pregnancy. The concentration of beta-endorphin was highly variable during the sampling period and could not be correlated with the other hormones or nest-building behavior. To assess the role of prolactin in nest-building behavior, groups of rabbits were treated with bromocryptine, bromocryptine plus prolactin or saline (controls). Treatment with 4 mg bromocryptine or 4 mg bromocryptine + 1.5 mg bovine prolactin on days 25 and 27 of pregnancy did not affect the number of live kits born or the gestation length. The mean nest scores, a measure of the nest quality, were not affected by bromocryptine treatment, but treatment with bromocryptine plus prolactin resulted in lower nest scores (P < 0.05). Injection of 8 mg bromocryptine from day 28 of gestation to kindling resulted in an extended gestation (P < 0.05). Injection of 4 or 8 mg bromocryptine resulted in fewer live kits born (P < 0.05), reduced nest scores (P < 0.01) and blocked milk production, as determined from the palpable mammary tissue. These results indicate that prolactin has less influence on nest-building behavior than on milk production. The hormones most likely to influence nest building are beta-estradiol and progesterone because the levels of these hormones started to change at the time when the rabbits started to prepare nests. Further study is required to determine the influence of these hormones on nest-building behavior.     

Effects of androgens on body weight, feeding, and courtship behavior in the pigeon

Adult male pigeons, some intact and some castrated in adulthood, were housed in individual cages kept in an isolated room with temperature and lighting controlled. Weekly measurements were made of ad lib. food intake and body weight for 4 mo after surgery. Castration was followed by a significant depression in body weight and by initially depressed but then progressively enhanced feeding. Food deprivation elicited an increase in food intake proportional to body weight loss, but castrates consumed less food at 100%, 90%, and 80% of ad lib. feeding weight than either intact birds or castrates treated daily with testosterone propionate (TP). Castrates gained weight and ate more than controls in response to daily treatments (im) with TP (6 mg/400 g) or 5a-dihydrotestosterone (DHT, 6 mg/400 g), while androstenedione (15 mg/400 g) and androsterone (15 mg/400 g) were ineffective. Administration of 100 mg DHT (sc) to castrates produced a significant enhancement of body weight without elevating the level of food intake. The biological potency of these diverse androgens on male courtship behavior was reciprocal to that for weight-promoting potency. The results suggest that the structural requirements of the androgen molecule for promoting body weight differ from those for stimulating sexual behavior.     

Mothers and offspring: The rabbit as a model system in the study of mammalian maternal behavior and sibling interactions

This article is part of a Special Issue “Parental Care”.Jay Rosenblatt effectively promoted research on rabbit maternal behavior through his interaction with colleagues in Mexico. Here we review the activities of pregnant and lactating rabbits (Oryctolagus cuniculus), their neuro-hormonal regulation, and the synchronization of behavior between mother and kits. Changing concentrations of estradiol, progesterone, and prolactin throughout gestation regulate nest-building (digging, straw-carrying, fur-pulling) and prime the mother's brain to respond to the newborn. Nursing is the only mother–young contact throughout lactation. It happens once/day, inside the nest, with ca. 24 h periodicity, and lasts around 3 min. Periodicity and duration of nursing depend on a threshold of suckling as procedures reducing the amount of nipple stimulation interfere with the temporal aspects of nursing, though not with the doe's maternal motivation. Synchronization between mother and kits, critical for nursing, relies on: a) the production of pheromonal cues which guide the young to the mother's nipples for suckling; b) an endogenous circadian rhythm of anticipatory activity in the young, present since birth. Milk intake entrains the kits' locomotor behavior, corticosterone secretion, and the activity of several brain structures. Sibling interactions within the huddle, largely determined by body mass at birth, are important for: a) maintaining body temperature; b) ensuring normal neuromotor and social development. Suckling maintains nursing behavior past the period of abundant milk production but abrupt and efficient weaning occurs in concurrently pregnant-lactating does by unknown factors. Conclusion: female rabbits have evolved a reproductive strategy largely dissociating maternal care from maternal presence, whose multifactorial regulation warrants future investigations.     

Hormonal correlates of 'masculinization' in female spotted hyaenas (Crocuta crocuta). 2. Maternal and fetal steroids.

Concentrations of androgens (androstenedione, testosterone, 5 alpha-dihydrotestosterone), oestrogen and progesterone were measured in relation to pregnancy in the spotted hyaena (Crocuta crocuta). The gestation period was estimated to be about 110 days. There was a marked progressive rise in all the steroids starting in the first third of gestation. Chromatographic separation of plasma showed that much of the oestrogen is not oestradiol (only 12% of total measured) and that a significant fraction of the 'testosterone' may be dihydrotestosterone. In the final third of pregnancy, concentrations of androgen (especially testosterone plus dihydrotestosterone) in the female circulation reached the maximal values of adult males; the percentage of dihydrotestosterone relative to total testosterone plus dihydrotestosterone was higher in females (44 +/- 3.9%, n = 20) than in males (29.5 +/- 3.5%, n = 17). Plasma androstenedione was also significantly higher in females, but the increment was less than for oestrogen, testosterone and progesterone, and the temporal pattern was less clear. Samples from the maternal uterine and ovarian circulation showed that androstenedione is largely of ovarian origin and metabolized by the placenta, while testosterone, progesterone and oestrogen are primarily of placental or uterine origin. Fetal samples were taken from two mixed-sex sets of twins and one male singleton. Gradients across the placenta measured in the fetal circulation confirmed that the placenta metabolizes androstenedione and is a source of testosterone for the female fetus; there were no consistent differences in androgens between male and female fetuses. It is suggested that the conspicuous masculinization of the female spotted hyaena, especially evident in the external genitalia at birth, is a result, at least in part, of high placental production of testosterone or dihydrotestosterone derived from the metabolism of high maternal androstenedione.     

Neuroendocrinology of maternal behavior in the rabbit

Rabbit maternal behavior consists of building an underground nest of straw and body hair during late pregnancy and displaying, with circadian periodicity, a single 3-min nursing bout/day across lactation. Estrogen, androgen, progesterone, and prolactin regulate specific aspects of nest-building and promote the onset of maternal responsiveness. However, the maintenance of this behavior relies on stimuli from the litter: by preventing mother/young contact at parturition or during early lactation maternal responsiveness is altered or abolished. The brain areas controlling the expression of nest-building and nursing were investigated by implanting estradiol, locating the distribution of estrogen and prolactin receptors, quantifying the expression of immediate-early genes, and lesioning structures of the olfactory system. These studies revealed that: (a) estrogen receptor-alpha, alpha, present in the preoptic region, may mediate the stimulation of nest-building by estradiol; (b) prolactin binding sites, located mainly in periventricular structures, are more abundant in late pregnancy and early lactation; (c) the number of FOS-immunoreactive neurons increases in the lateral septum, but not in the mediobasal hypothalamus, following nursing; (d) the accessory olfactory bulb tonically inhibits the expression of maternal behavior because its removal promotes maternal responsiveness in virgins, which are otherwise unresponsive to daily pup exposure. In summary, rabbits rely on the same hormonal and extrahormonal factors that stimulate maternal behavior in other mammals, yet the way in which such factors promote elaborate nest-building and the unfailing display of circadian nursing is unique to rabbits and warrants future investigation.     

Decidualization in rats given 5alpha-dihydrotestosterone or its propionate neonatally.

In Experiment 1, female rats were given a single subcutaneous injection of 1.25 mg 5alpha-dihydrotestosterone (DHT) or its propionate (DHTP) on day 5 of postnatal life. All of them showed regular estrous cycles as adults like untreated control animals. At about 60 days of age, the rats were ovariectomized and given 7 daily injections of 2 mg progesterone (P) plus 0.2 mug estradiol-17beta (ED). Uterine trauma applied on the 4th day of P-ED injections resulted in well developed deciduomata in all animals by the day after the last injection. This made a sharp contrast to the failure of female rats receiving testosterone propionate (TP) neonatally to give a positive response under similar experimental conditions (Takewaki and Ohta, 1974). The mean weight of traumatized horns was significantly larger in DHTP-treated rats (but not in DHT-treated rats) than in controls. In Experiment 2, rats were ovariectomized on day 4 and given a dose of 1.25 mg DHT or DHTP on day 5. Controls were ovariectomized on day 4 but not given any steroid on the next day. A series of 7 daily injections of 2 mg P plus 0.2 mug ED was started at about 60 days of age, after the animals had received 3 daily injections of 0.2 mug ED or 30 daily injections of 0.1 mug ED. Incidence of deciduomata following uterine traumatization was markedly lowered only in animals treated with DHTP neonatally and given 0.1 mug ED for 30 days as adults, no significant differences being found in both incidence and size of deciduomata among the other groups. It was suggested that the effects of neonatal steroid administration on uterine responsiveness in adulthood are specific to the steroid. The previous conclusion that persistent estrus in androgen-sterilized rats plays a part in the reduction of uterine responsiveness was confirmed. An exposure of rats to estrogen for a prolonged postpuberal period was without effect, unless the animals had received enough androgen neonatally.     

The effect of testosterone propionate, 5 alpha-dihydrotestosterone and 5 alpha-androstan-3 beta, 17 beta-diol on acid phosphatase activity in the prostate of castrated rats

The acid phosphatase is studied in the prostate gland of rats. It is shown that 10 days after gonadectomy the activity of acid phosphatase lowered considerably. Administration of testosterone propionate or 5 alpha-dihydrotestosterone to castrated animals restored the enzyme activity whereas 5 alpha-androstan-3 beta,17-diol was not effective. Administration of testosterone propionate with one of its metabolites increased the activity of acid phosphatase in the prostate gland, however to a less extent than with the use of the hormone itself. The lowest activity is detected with the simultaneous application of three androgens.     

Androgen binding to ammonium sulfate precipitates of human adipose tissue cytosols

Although androgens are believed to influence the distribution of human adipose tissue and have been detected in human fat, receptors for these sex hormones have yet to be identified. These studies demonstrate that a high-affinity, limited-capacity binding component for the synthetic androgen methyltrienolone (R1881) exists in ammonium sulfate precipitates of human adipose tissue cytosols. The equilibrium dissociation constant (Kd = 0.1 to 0.4 nmol/L, n = 6) and the number of binding sites (2 to 26 fmol/mg protein, n = 22) are consistent with those reported for androgen receptors in rat prostate, human prostatic carcinoma, MCF-7 cells, and baboon myocardium. The relative steroid-binding specificities of the human adipose tissue androphile (R1881 approximately 5 alpha-dihydrotestosterone greater than testosterone greater than estradiol approximately progesterone much greater than dexamethasone) are similar, but not identical, to those reported for androgen receptors in rat prostate (R1881 greater than 5 alpha-dihydrotestosterone approximately testosterone greater than estradiol greater than progesterone much greater than cortisol) and baboon myocardium (R1881 greater than 5 alpha-dihydrotestosterone greater than testosterone greater than progesterone greater than estradiol much greater than cortisol). The function of the androgen-binding component in human adipose tissue is not known.     

Effects of neonatal gonadal steroids on adult CA3 pyramidal neuron dendritic morphology and spatial memory in rats

The hippocampus is implicated in spatial cognition, which is sexually dimorphic and developmentally sensitive to gonadal steroids. Previously we have shown a sex difference in CA3 pyramidal cell layer volume and neuronal soma size that was reversible with neonatal castration in males or prenatal treatment of females with either testosterone propionate (TP) or a nonaromatizable androgen, dihydrotestosterone propionate, but not estradiol benzoate, all of which correlated with adult water maze navigation. The present study further investigates developmental androgen sensitivity of CA3 pyramidal neurons by measuring dendritic morphology and its relation to adult spatial ability. Female rats were injected with TP on postnatal day (P) 3 and P5 or ovariectomized (OVX) on P2, and male rats were castrated on P2, with or without testosterone replacement (Cas+T). Sham surgery controls were also included. Animals were tested on a water maze in adulthood, sacrificed, and CA3 pyramidal neurons were Golgi-stained and reconstructed in three dimensions using a computer-interfaced morphometry system. High-androgen groups (control males, Cas+T, TP females) performed better in spatial navigation and exhibited CA3 neurons with longer dendrites, a larger number of dendritic branches, and volumes of influence compared to low-androgen groups (control females, castrated males, OVX). Collectively, these findings indicate that the critical time period for organizational effects of androgens on the CA3 pyramidal neurons includes both prenatal and postnatal life, during which time androgens regulate developmental events such as somal growth and neuronal differentiation, all of which significantly contribute to establishing the sex difference in adult spatial navigation.     

Pretreatments with 5 alpha-dihydrotestosterone and the uptake of testosterone by cell nuclei in the brains of male rhesus monkeys

An in vivo competition method was used in adult male rhesus monkeys to determine if testosterone binds to high affinity binding agents, notably androgen receptors, in brain cell nuclei. Castrated males received 5 alpha-dihydrotestosterone propionate (DHTP, 20 mg, N = 6), testosterone propionate (TP, 100 mg, N = 3) or oil vehicle (controls, N = 6) followed 3 h later by 5 mCi [3H]testosterone [( 3H]T) as an intravenous bolus. Brain and peripheral tissue samples were removed after 60 min, homogenized and separated into supernatant and purified nuclear fractions. Radioactive metabolites of [3H]T [( 3H]estradiol, [3H]DHT) and unchanged [3H]T were identified by high performance liquid chromatography (HPLC). Androgen pretreatments reduced the nuclear uptake of [3H]T by 67-98% in hypothalamus (HYP), preoptic area (POA) and pituitary gland (PIT). This blockade was presumed to be due to prior occupation of nuclear androgen receptors by unlabeled androgens because pretreatments had no effects on levels of [3H]T in supernatants. Since [3H]T was the major radioactive androgen present in brain cell nuclei, results strongly suggested that the principal nuclear androgen receptor ligand in HYP, POA and PIT was unchanged [3H]T rather than [3H]DHT as occurs in the genital tract. In the amygdala the situation was quite different. Here, nuclear concentrations of [3H]T were reduced by 67% following TP pretreatment but were not changed following DHTP pretreatment, indicating a different uptake mechanism in this region that could have particular relevance for testosterone's central actions on behavior.     

Gonadal hormones stimulate ultrasound production by female hamsters.

Two studies were conducted to examine the role of sex hormones in ultrasound production by female hamsters. Ovariectomized hamsters were treated with estradiol benzoate (EB), testosterone propionate (TP), progesterone (P), estradiol plus progesterone (EB + P), testosterone plus progesterone (TP+P), or oil vehicle. Rates of ultrasound production by these females were observed in response to brief male-female contact, and during exposure to synthetic ultrasounds. Maximal rates of ultrasound production required EB + P or TP+P replacement therapy. Intermediate call rates were stimulated by EB and TP individually, whereas P alone had no significant effect. These results support the hypothesis that ovarian estrogens and progesterone control proceptive as well as receptive behaviors in female hamsters.     

Oral testosterone self-administration in male hamsters: dose-response, voluntary exercise, and individual differences

Although testosterone was declared a controlled substance in 1990, the potential for steroid dependence is largely unexplored. The present study used food-induced drinking with oral testosterone self-administration in hamsters to determine (1) the dose-response for testosterone reward, (2) links between testosterone self-administration and voluntary exercise, and (3) factors predicting individual differences in androgen intake. Testosterone (1-4 mg/ml) was presented in aqueous solution 3 h/day for 35 days, with and without food. At 3 mg/ml, testosterone maintained fluid intake, even without food (3.0 +/- 0.2 ml/3h). At 4 mg/ml, fluid intake declined to 2.4 +/- 0.3 ml/3h in the presence of food. However, no dose-response relationship between testosterone self-administration and reward was observed. To test the interaction of testosterone and exercise, males drinking testosterone (RUN + T) or vehicle received a running wheel. Additional males self-administered testosterone without exercise. Testosterone intake correlated positively with exercise and negatively with body weight in RUN + T males. Experiment 3 determined the relationship between testosterone self-administration and mating or saccharin preference. There were no statistically significant correlations. However, testosterone self-administration increased mating behavior. These data demonstrate that testosterone is a mild reinforcer. Although preference for androgens is not predicted by mating or saccharin intake, testosterone intake is linked with voluntary exercise.     

Regulation of hormonally mediated maternal nest structure in the mouse (Mus musculus) as a function of neonatal hormone manipulation

Nest building in mice was evaluated by amount of hay used daily and type of nest constructed. Increased amounts of hay were utilized and maternal style nests constructed following treatment with appropriate ratios of oestrogen plus progesterone. This response occurred only in the female. Following neonatal injection of testosterone propionate the female no longer showed the maternal nest building response. When males were castrated on day 1, they showed a response to oestrogen and progesterone which was similar to the female response. Thus, the hormonally elicited maternal nest style is sex limited due to early exposure to androgens and therefore resembles sexual responsiveness and the ovulatory mechanism which can similarly be suppressed as a result of the presence of androgen.     

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.     

Androgenic modulation of progesterone metabolism by rat granulosa cells in culture

Effects of androgens on progesterone accumulation, utilization of exogenous progesterone and accumulation of [4-14C]progesterone metabolites by rat granulosa cells in culture were studied. Androgen increased progesterone accumulation in cultures without exogenous progesterone and slowed the overall decline of progesterone concentration in cultures supplemented with exogenous progesterone. Both aromatizable testosterone and nonaromatizable 5 alpha-dihydrotestosterone decreased [4-14C]progesterone utilization by granulosa cells by 12 to 30%. This effect was observed irrespective of whether the cells were continuously exposed to androgens or only pre-exposed. In he same experiments, androgens decreased conversion of radiolabeled progesterone to 20 alpha-hydroxy-4-pregnen-3-one by 11 to 50% and to 5 alpha-pregnane-3 alpha, 20 alpha-diol by 26 to 49%. Accumulation of 3 alpha-hydroxy-5 alpha-pregnan-20-one was not altered in 3 h incubations and was increased by up to 43% in 24 h incubations by androgen treatment. It is suggested that androgens alter progesterone catabolism by granulosa cells by decreasing 20 alpha-hydroxysteroid dehydrogenase activity and that this effect may contribute to overall stimulatory action of androgens on progesterone accumulation.     

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)     

Androgens stimulate sex change in protogynous grouper,Epinephelus coioides: spawning performance in sex-changed males

We examined the efficacy of androgens (1.0 mg/kg body mass), testosterone (T), 11-ketotestosterone (11-KT), 17alpha-methyltestosterone (MT), testosterone propionate (TP) or androgen mixture (T, MT and TP in an equal ratio), for induction of sex change in protogynous orange-spotted grouper, Epinephelus coioides. The spawning performance in sex-changed males was also investigated. MT and androgen mixture at a dose of 1.0 mg/kg BW induced a sex transition and completion of spermatogenesis up to the functional male phase. The androgen mixture was most effective. Significantly, higher plasma T levels were found in MT and androgen mixture groups compared to control and other androgen implantation (T, TP or 11-KT) groups. We found that plasma levels of estradiol-17beta (E2) or 11-KT were not different among treated groups. Sex-changed males could successfully fertilize mature eggs. Fertilization and hatching rates were of 23.5-70.4% and 8.4-44.6%, respectively. The data demonstrated that induction of sex change by exogenous androgens in groups could apply to the aquaculture field for seed production.