Inhibition of adult social behaviour in ducks induced by juvenile administration of gonadal hormones

This experiment was designed to study the long-term behavioural effects of gonadal hormone injections into domestic ducklings. Ten male and four female ducklings were injected daily from their 4th day onwards: the males with testosterone propionate and the females with oestradiol benzoate. Five males were injected for 40 days, the other ducklings (5♀ + 4♂) for 80 days. Behavioural effects of these treatments were assessed when the birds were six months old. Social displays were strongly inhibited in the injected males as compared with control birds but no general significant effect was observed for the aggressive and sexual behaviour. The inhibition of social displays is consistent with the view that these behaviour patterns are regulated by the pituitary-gonadal axis and the different levels at which the functional inhibition could have occured are discussed. Far fewer social displays were performed by the males presented with injected females which, on the other hand, showed less sexual behaviour than the control females. This supports the idea that the female plays an important part in the social display of ducks.     

Daily variations of behavioural activities and of plasma testosterone levels in the domestic duck Anas platyrhynchos

The daily variation of various behavioural activities and of plasma testosterone levels have been studied simultaneously in two groups of five domestic ducks. The social displays and sexual behaviour are essentially exhibited by the birds during the early morning (and to a lesser extent in the late afternoon for major displays). The morning corresponds precisely with the highest testosterone levels observed in the blood. As testosterone propionate injections are known to elicit social displays and sexual behaviours in ducks, it is suggested that the correlation observed between the variations of testosterone levels and of behaviour could be due to a direct effect of the variations of hormone levels on behaviour. The theoretical possibility of such a short-term hormonal effect is briefly discussed.     

Intracranial androgenic and estrogenic stimulation of male-typical behaviors in house mice (Mus domesticus).

Two experiments in house mice (Mus domesticus) examined the neural sites at which steroid hormones activate the following male-typical behaviors: 70 kHz ultrasonic mating vocalizations in response to stimulus females or their urine, urinary marking in response to stimulus males or stimulus females, mounting of estrous females, and intermale aggression. In the first experiment, four groups of castrated males received bilateral intracranial implants of testosterone (T) into either the septum (SEPTUM), medial preoptic area (MPO), anterior hypothalamus (AHA), or ventromedial hypothalamus (VMH). Two control groups received subcutaneous silastic capsules of T (TSIL) or empty silastic capsules (BSIL). The TSIL males performed all behaviors at male-typical levels while the BSIL males were unresponsive. MPO males emitted ultrasonic mating vocalizations at high levels while few vocalizations were seen in males of the other brain implant groups. The VMH, AHA, and MPO males urine marked at higher levels than the BSIL males but did not exhibit the high levels of the TSIL males. Mounting was observed only in MPO and TSIL males. Aggression was rare in males from any of the brain implant groups. In the second experiment, the hormone activity of the implants was increased by using testosterone propionate (TP) or a 50% mixture of estradiol (E2) and cholesterol. The six groups were SEPTUMTP, SEPTUME2, MPOTP, MPOE2, TPSIL, and BSIL. The TPSIL males performed all behaviors at male-typical levels while the BSIL males were unresponsive. TP was effective at restoring vocalizations and urine marking only when placed in the MPO; however, E2 was effective at both sites. Again aggression and mounting were less evident in the brain implanted males. In conclusion, implants of T or TP were effective in restoring ultrasonic mating vocalization when placed into the MPO. MPO implants of T and TP were also effective in stimulating urine marking, although VMH and AHA implants also showed some effectiveness. The restorative effects of E2 were not localized which is probably related to the greater hormonal activity of this treatment. Comparisons of the properties of the various brain implants to restore more than one behavior were discussed.     

Wood duck hatch date: relationship to pairing chronology, plasma luteinizing hormone, and steroid hormones during autumn and winter

We examined variation in courtship activity and hormone levels of male and female wood ducks (Aix sponsa) in relation to hatch date. Young wood ducks were assigned in groups of 8 (4 males and 4 females) to 4 experimental pens; 2 pens contained early-hatched ducks (3-12 April) and 2 pens contained late-hatched ducks (7-16 June). Courtship behaviors occurred less frequently in October and November than in December and January-February for both early- and late-hatched groups. Early-hatched wood ducks participated in courtship more frequently and formed pair bonds sooner than late-hatched individuals. Testosterone (T) and androstenedione (AD) levels of males did not differ between treatment groups; however, average levels of luteinizing hormone (LH) were greater for early-hatched males. Differences in LH occurred in 2 of 12 samples (6 October and 3 November); otherwise, LH did not vary by treatment. Levels of T and LH in males varied temporally, but there was no significant temporal variation in AE levels. Temporal variation in hormone levels was similar for early- and late-hatched males. Estradiol (E), progesterone (P), and LH levels of females did not differ between treatment groups. There was temporal variation in levels of E and LH, but not of P; this variation was similar for early- and late-hatched females. These data indicate that behavioral differences occurring temporally and between early- and late-hatched wood ducks were not related to corresponding differences in hormone levels.     

Androgens, aggressive behaviour and social relationships in higher mammals

This paper reviews the relationships between androgen levels, aggressive behaviour and social relationships in ungulates and primates. In these and most other mammalian species, aggressive behaviour is sexually dimorphic with males being generally more aggressive than females. This difference is evident very early in play behaviour. In males, and sometimes also in females, aggressive behaviour varies in relation with reproductive cycles and the hormonal changes which are involved in these cycles. The experimental manipulation of hormonal levels by castration or administration of exogenous hormones gives results that vary according to the species, sex, type of hormone (e.g. aromatizable or non-aromatizable androgens), and other factors (e.g. antlers state in stags). Nevertheless, it has generally been shown that aggressive behaviour in male ungulates depends largely on androgens and that in female ungulates androgen treatment consistently raises social rank, with or without modification in aggressiveness. Primates, on the other hand, seem to be less dependent on androgens for the expression of aggressive behaviour and social status.     

Effects of estradiol benzoate, estrone, and propionates of testosterone or dihydrotestosterone on sexual and related behaviors of ovariectomized rhesus monkeys

Ovariectomized adult rhesus monkeys were injected daily for 10 days with either 1 mg of dihydrotestosterone propionate (DHTP), 1 mg of testosterone propionate (TP), 10 μg of estradiol benzoate (EB), or 500 μg of estrone (El). On the 5th and 10th days of treatment, females received two 24-min behavioral tests with each of two adult males. All females received every hormonal treatment during the course of the study, with the order of treatments counterbalanced. Prior to the initiation of an hormonal treatment, each subject received two tests with no hormone treatment (NORX). Three behaviors related to female proceptivity were recorded. Treatment with DHTP had no influence on any aspect of proceptivity measured, in comparison to the NORX condition, whereas El or TP treatment augmented the frequencies of two of the proceptive behaviors and EB increased all three. The response of the male toward the female was influenced by the female's hormonal condition. Treatment with TP or DHTP did not increase the frequency of male contact or the mount rate in comparison to the NORX condition, whereas EB or El treatment did. In addition, DHTP was the only steroid which failed to increase the percentage of tests with intromission or ejaculation when compared to NORX. Female receptivity, as measured by acceptance or rejection of male contacts, was not different for the NORX-, TP-, EB-, or El-treated conditions. DHTP treatment, however, reduced female receptivity in comparison to all other conditions. Treatment with DHTP or TP resulted in an increase in the frequency of female yawning behavior, whereas neither estrogen treatment showed any effect on this behavior. The influences of TP on female proceptive and male sexual behavior were never duplicated or even approximated by treatment of females with the nonaromatizable DHTP. Nor was there any evidence that TP inhibited female receptivity below the level characteristic of NORX females, as was true for DHTP.     

Testosterone increases singing and aggression but not male-typical sexual partner preference in early estrogen treated female zebra finches

Female zebra finches given estradiol benzoate (EB) as nestlings and testosterone propionate (TP) as adults show masculinized sexual partner preference, preferring females instead of males. This suggests an organizational effect of EB on sexual partner preference in a socially monogamous species that pairs for life. It is not known whether there is an activational hormone effect on sexual partner preference in this species, or whether adult testosterone treatment is necessary for masculinized preference to be expressed. In this experiment females were injected with EB daily for the first 2 weeks posthatching. As adults they were given TP filled or empty implants. Subjects were then given two-choice preference tests with male vs female stimuli, in which singing as well as proximity to the stimuli was recorded, followed by tests in a group aviary for social behavior and pairing preference. Females with TP implants sang more than females with empty implants and were more aggressive toward other females. They did not, however, differ from females with empty implants in any measure of sexual partner preference. Neither group showed a marked preference for males; instead both groups were equally interested in males and females. Thus adult testosterone treatment is not necessary for early estrogen treated females to show a shift in sexual partner preference in the male-typical direction.     

Effects of testosterone propionate on the social behaviour of groups of male comestic ducklings Anas platyrhynchos L.

One-month old testosterone-injected ducklings were observed in groups of three males and their social behaviour compared to that of oil-injected control birds. Most elements of adult sexual behaviour and one pattern of aggressive behaviour (chest fight) occurred more frequently in the experimental animals. It was shown that the same hormonal treatment induces different behavioural responses in different animals. Unlike previous studies, no social displays were observed in the testosterone-injected ducklings. Possible explanations of this fact are discussed.     

Effect of implanting bull calves with testosterone propionate, dihydrotestosterone propionate or oestradiol-17 beta prepubertally on the pituitary-testicular axis and on postpubertal social and sexual behaviour.

Twelve non-implanted crossbred bull calves served as controls and 30 crossbred bull calves (10/treatment) were implanted for 82 days, beginning at 34 days of age, to determine the influence of testosterone propionate (TP), dihydrotestosterone propionate (DHTP) and oestradiol-17 beta (E2) on prepubertal and pubertal pituitary-testicular function and on postpubertal social and sexual behaviour. Compared with control bulls, concentrations of serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and inhibin concentrations were suppressed (P less than 0.01) in all implanted bulls. Testosterone (T) concentration increased (P less than 0.001) in TP-implanted, but decreased (P less than 0.01) in DHTP and E2 bulls during the implant period. LH response to gonadotrophin-releasing hormone (GnRH) challenge during the implant period (2.5 months of age) was less (P less than 0.01) in TP, E2 and DHTP bulls than in controls. A small but significant T response to GnRH occurred in control bulls at 2.5 months of age. LH and T responses to GnRH challenge at 7 months of age (100 days after implant removal) was similar (P greater than 0.20) in control and implanted bulls. Steroid implants administered prepubertally had no effect (P greater than 0.10) on postpubertal social and sexual behaviours, including number of flehmen responses, abortive mounts, services and competitive order score. Body weight did not differ (P greater than 0.10) between treatment groups, but testis size was reduced (P less than 0.01) during the implant period and up to 10 months of age in treated bulls compared with controls. Testes remained smaller in E2-treated bulls up to the end of the study (23 months of age), but daily sperm production and epididymal weight did not differ (P greater than 0.10) between treatment groups at slaughter. Control bulls reached puberty earlier (P less than 0.01; 270 +/- 11 days of age) than did TP (302 +/- 11 days), DHTP (309 +/- 11 days) or E2 (327 +/- 11 days) bulls. Although puberty was delayed in all implant groups, there was no difference in scrotal circumference at puberty (average 28.4 +/- 0.4 cm) between treatment groups. Our findings indicate that TP, DHTP and E2 implants administered prepubertally result in acute suppression of serum LH, FSH and inhibin during the implant period and in post-implant suppression of testis size and delayed puberty in bulls. The lack of treatment effect on behaviour suggests that steroidal programming of sexual behaviour occurs before 1 month of age in bulls.     

Sexual differentiation of behavior in the zebra finch: effect of early gonadectomy or androgen treatment

Treatment of nestling zebra finches with estradiol benzoate (EB) has been shown to masculinize singing in females and demasculinize copulatory behavior in males, suggesting that sexual differentiation of these behaviors is under hormonal control such that testicular hormones induce the capacity for song and ovarian hormones suppress the capacity for mounting. Two experiments were carried out to obtain a more complete picture of sexual differentiation in this species. In Experiment 1, nestlings were injected daily for the first 2 weeks after hatching with testosterone propionate (TP), dihydrotestosterone propionate (DHTP), or a combination of DHTP and EB. As adults, birds were gonadectomized and implanted with TP prior to testing, then tested again after implantation with EB. Singing was not increased in females by any of the treatments. The only effect of either TP or DHTP given alone was defeminization of female proceptive behavior by DHTP. Thus androgens appear to have less influence than estrogens on sexual differentiation of behavior in this species. The combination of DHTP and EB demasculinized mounting in males. In Experiment 2, nestlings were gonadectomized at 7-9 days of age and implanted with TP prior to testing in adulthood. Early gonadectomy had little effect on later behavior; early castrated males sang, danced, and copulated normally and early ovariectomized females neither sang nor mounted.     

Prenatal flutamide treatment eliminates the adult male rat's dependency upon vasopressin when forming social-olfactory memories.

The sexually dimorphic number of cells expressing arginine vasopressin (AVP) in the bed nucleus of the stria terminalis and the density of AVP fibers within the lateral septum appear to be organized by pre- and postnatal androgens. Social recognition behaviors are also sexually dimorphic and AVP-dependent. Whereas AVP antagonists prevent males from recognizing familiar intruders by olfactory investigation of the anal-genital area, they have no effect in females. To test the hypothesis that the male's dependency upon AVP to form social recognition memories begins prior to birth, we compared the effectiveness of an AVP antagonist to block social recognition in control males and females with that seen in male offspring whose mothers were treated prenatally with an androgen antagonist (flutamide). In an initial study we showed that while sexual experience may enhance social recognition in males, virgin males exhibit the ability to recognize conspecifics and are sensitive to the memory blocking actions of AVP antagonists. In a second experiment, pregnant rats were treated daily for the last 10 days of gestation with either flutamide (10 mg) or control vehicle. Within 12 h of birth, male offspring from flutamide litters were injected with either testosterone proprionate (50 microg TP) or vehicle control. AVP-antagonist treatment in adults eliminated the ability of control males to recognize familiar juvenile intruders, but had no effect on males exposed prenatally to flutamide, regardless of whether these males were treated with TP or vehicle on day 1 of life. These data support the hypothesis that the development of the male's dependency upon AVP to express social recognition memories begins with the organizational actions of prenatal androgens.     

Senescence and steroid hormone receptor reactivities in accessory sex glands of elderly rats (Sprague-Dawley) following exogenous hormonal therapy

The aim of this study was to characterize the stromal and epithelial distribution of AR, ERα and ERβ reactivities in the different accessory sex glands of elderly rats and during strong hormonal changes. Ten month old male rats were divided into six senile groups and submitted to treatment: Senile/Control group (SC); Senile/Testosterone group (ST): Senile/Estrogen group (SE); Castrated group (CA); Castrated/Testosterone group (CT); Castrated/Estrogen group (CE). After a 30-day treatment, the prostatic ventral lobe (VL), dorsal lobe (DL) and coagulating gland (CG) samples were processed for immunohistochemistry and Western Blotting. The results showed that AR immunoreactivity was characterized in the epithelium of VL and DL in senile/control rats and senile rats submitted to exogenous hormonal therapy. AR reactivity in the coagulating gland was verified predominantly in the stromal cells in the different experimental groups. ERα reactivity occurred predominantly in the stromal compartment in all accessory sex glands. In the DL and CG, ERα immunoreactivities were intense in the groups which received testosterone (ST) and estrogen (SE). ERβ immunoreactivity in the CG was verified in the stromal compartment in the different experimental groups, showing a positive response to both increased testosterone and estrogen levels. ERβ reactivity, in the DL, was intensified in the stroma of senile rats with higher serum testosterone levels, and in senile rats with increased serum estrogen levels, especially in the glandular epithelium. Thus, the results revealed different distribution pattern of steroid hormone receptors in each one of the prostatic lobes in senescence, especially in the prostate dorsal lobe and coagulating gland, which is a fundamental factor due to the fact that major prostatic diseases occur in a later period of life.     

Early androgen treatment and male and female sexual behavior in mice

To investigate the role of neonatal androgen stimulation in the development of the potential for masculine and feminine sexual behavior in the mouse, different groups of mice were hormonally manipulated early in life. One group of female mice was administered testosterone propionate (TP) within 24 hr of birth; a second group of females was given a control injection of oil on the day of birth; a third group of females received an injection of TP on the 10th day after birth. A group of males received a control injection of oil on the day of birth. All mice were gonadectomized at about 30 days of age. At 60 days of age, mice were injected with estrogen and progesterone and tested for sexual receptivity; several weeks later all mice were injected with TP and tested for male sexual behavior. Female behavior: Females given oil at birth and females given TP on the 10th day after birth showed high levels of sexual receptivity as adults following estrogen-progesterone treatment. Females given TP on the day of birth, and male mice, rarely exhibited lordosis following estrogen-progesterone treatment. Male behavior: Most mice, regardless of genetic sex or neonatal treatment, mounted in adulthood following administration of exogenous androgen. There was little difference in mounting frequency between groups, suggesting that exogenous or endogenous androgen stimulation of the neonatal mouse does not facilitate adult mounting behavior. These data for the mouse are in essential agreement with existing data for the rat, and indicate that sexual behavioral differentiation induced by androgen stimulation in infancy is best characterized as an inhibition of the potential to display feminine sexual behavior in adulthood.     

The social display of the Chilean teal Anas flavirostris flavirostris

Filmed episodes of social display in the Chilean teal were analysed in order to throw light on the function of social display in surface-feeding ducks and the role the female plays in this activity. Four different methods were used to study the associations between different behaviour patterns in several individuals. It appears that the behaviour patterns comprising social display fall into three groups which are described as "attention getting", "close-range" and aggressive. It is proposed that social display allows unpaired males to attract the attention of females in an attempt to establish a pair-bond through the use of the "close-range" behaviour patterns. This forces paired males to compete in "attention-getting" behaviour patterns. Aggression results from this competition and from the threatening presence of unpaired males when the paired males try to strengthen their pair-bonds with the use of the "close-range" behaviour patterns.
Females play an influential role as their behaviour links the "attention-getting" behaviour with the "close-range" and aggressive behaviour. Their "close-range" behaviour suppresses that of other females.     

Regulation of urine marking in male and female mice: effects of sex steroids

Effects of sex steroids on urine-marking activity were studied in male, female, and neonatally androgenized female mice. Urine marking was estimated by suspending ceramic tubes that were connected in a horizontal row with a steel rod into the home cage of an isolated mouse. Intact males showed high marking activity, which was diminished after castration. Both testosterone propionate (TP) and estradiol benzoate (EB) were effective in restoring the marking activity of castrated males, while 5-alpha-dihydrotesterone (DHT) did not have any stimulative effects. Intact normal females showed quite low marking activity and ovariectomy further depressed it. TP and DHT enhanced the marking of ovariectomized females, but EB restored the activity only to the preovariectomy level. In intact females which were neonatally androgenized, the marking activity was much higher than that of normal females. The pattern of the change induced by gonadectomy and hormone treatment in these females resembled that in males. Thus, ovariectomy reduced the activity and both TP and EB restored the level. These results indicate that the sexual dimorphism in the urine marking in mice is primarily determined by hormonal environment during early postnatal age. Hormonal control of scent marking is discussed in relation to the studies in other rodents.     

Sexually dimorphic basal water absorption at the isolated pelvic patch of Japanese tree frog, Hyla japonica

Frogs ingest little water orally, but absorb the majority of the water needed for normal physiological performance through a specific region of the ventral skin, the pelvic patch. We observed non-stimulated (basal water absorption, BWA) water flux through the isolated pelvic patch in vitro in Japanese tree frog (Hyla japonica). We found that water flux through non-stimulated skin from the pelvic patch was greater in males than females. This water flux was confirmed as BWA by observing no effect following the in vitro administration of propranolol and [adamantaneacetyl(1), O-Et-D-Tyr(2), Val(1), aminobutyryl(6), Arg(8, 9)] vasopressin, which are a beta-adrenergic receptor antagonist and a vasopressin V2 receptor antagonist, respectively. We further examined this phenomenon following gonadectomy, treatment with sex hormones (E2, 17beta-estradiol; TP, testosterone propionate), estrogenic chemicals (BPA, bisphenol A; MTX, methoxychlor) or prolactin (PRL, a hormone regulated by sex hormones that has osmoregulatory activity). Ovariectomy increased BWA in females. Injection (in vivo treatment) of E2 or PRL reduced BWA in males, whereas TP injection increased BWA in females. However, the in vitro addition of E2, TP, or PRL to the Ringer's solution on the serosal side of the ventral skin patch did not alter BWA. Subsequently, we injected (in vivo treatment) BPA or MTX, environmental chemical contaminants with known hormonal actions in mammals. Injection of BPA or MTX reduced BWA in males as observed following treatment with E2. These results provide the first evidence of sexual dimorphism in BWA through the isolated pelvic patch. The gonad appears essential for observed sexual dimorphism in BWA, and we hypothesize that sex hormones regulate the release of PRL, that in turn influences BWA indirectly. E2 is known to exert a specific stimulatory effect on PRL secretion. In addition, we have observed that some endocrine disrupting contaminants also eliminate the sexual dimorphism in BWA observed in the Japanese tree frog.     

A Juvenile Hormone analogue enhances homosexual behaviour in female‐deprived males of the migratory locust

In laboratory colonies of crowded migratory locusts Locusta migratoria (L.), homosexual behaviour (i.e. males mounting other males) is commonly observed. Female‐deprived males of Locusta migratoria migratorioides R. & F. mount each other in a characteristic mating position, often forming a group of several insects. When allatectomized males are placed together with intact, female‐deprived males, the former are usually mounted by the latter, demonstrating some degree of control involving the corpora allata over homosexual behaviour. This may be related to the positive effects of Juvenile Hormone (JH) or Juvenile Hormone analogues (JHAs) in enhancing male sexual behaviour, as is shown in some other insects. In the present study, a potent JHA (i.e. pyriproxyfen) is injected into a group of young, crowded L. m. migratorioides males, and an equivalent group of control males is maintained in a separate cage. Both groups are deprived of females. Three times a week, during 2‐h observation periods, JHA‐injected and control males are placed together in the absence of females, and homosexual mountings, per group and per individual, are recorded every 10 min. Observations are performed for 10 weeks. Analysis of these data, including the time spent in mounting behaviour, the percentage of individuals within a group involved in the behaviour during the observation periods and the identity of both partners, reveals that the JHA‐treated males show a more intense homosexual mating behaviour than control males in all quantified parameters. This is the first report of the enhancement of homosexual behaviour by an endocrine factor in insects.     

Central and peripheral action of testosterone propionate on scent gland morphology and marking behaviour in the Mongolian gerbil

Scent gland size and activity and frequency of marking under standard conditions were compared in five groups of male and female gerbils: (1) intact, sham-operated controls, (2) intact with scent glands excised, (3) gonadectomized, (4) gonadectomized injected with 1000 μg testosterone propionate (TP) on alternate days, and (5) gonadectomized with a low dose (25 μg) TP applied topically to the ventral scent gland on alternate days. The animals were housed in individual cages and tested for marking in an open field arena with plastic pegs.The scent gland is not required in either sex for the behavioural act of marking. Topical application of a dose of TP too low to exert a systematic effect restored the scent gland but not marking. Injection of sufficient TP to restore seminal vesicle weight restored marking, as well as the scent glands.It was concluded that in the male, both marking behaviour and scent gland size are controlled by the testes. The effect of androgens on marking is mediated directly through the central nervous system, and not through peripheral stimulation of the glands.Females have smaller glands and mark less than males. The ovaries appear to have little control over marking frequency, and some control over scent gland size. It is possible to stimulate marking behaviour to supernormal levels by TP injection, but not by topical application.     

Neonatal androgenization in ground squirrels: influence on sex differences in body mass and luteinizing hormone levels

Female squirrels were injected at birth with 50 or 1000 micrograms testosterone propionate (TP); control males and females were treated with oil vehicle. Squirrels were gonadectomized at 47 days of age. Body mass was recorded weekly and plasma luteinizing hormone (LH) was determined once monthly over the next year. Marked annual cycles in body mass were manifested by 30 out of 31 squirrels. Peak body mass and peak-to-trough differences were greater for control male and TP-female squirrels than for control female squirrels. Trough body weights did not differ among the groups. Luteinizing hormone was detectable in all male and most androgenized females but not in any control female squirrels during the first 4 mo after gonadectomy. Peak LH values were significantly greater for control male than for control female squirrels and were not influenced by neonatal androgenization in females. Testosterone propionate treatment also did not affect sex differences in timing of LH peaks or the total number of months in which LH was detectable. We conclude that testicular hormones secreted during the early postnatal period induce sex differences in the circannual pattern of weight change and some aspects of LH secretion. Complete masculinization, however, either requires more extensive action of gonadal hormones, perhaps both pre- and postnatally, or occurs through some androgen-independent mechanism.