Effects of prenatal antiandrogen treatment on masculinization and defeminization of guinea pigs

Neurobiological and Hormonal Mechanisms Regulating Women's Sleep

Sleep is crucial for optimal well-being, and sex differences in sleep quality have significant implications for women's health. We review the current literature on sex differences in sleep, such as differences in objective and subjective sleep measures and their relationship with aging. We then discuss the convincing evidence for the role of ovarian hormones in regulating female sleep, and survey how these hormones act on a multitude of brain regions and neurochemicals to impact sleep. Lastly, we identify several important areas in need of future research to narrow the knowledge gap and improve the health of women and other understudied populations.

Effects of Long-Term Flutamide Treatment During Development on Sexual Behaviour and Hormone Responsiveness in Rams

Testosterone exposure during midgestation differentiates neural circuits controlling sex-specific behaviours and patterns of gonadotrophin secretion in male sheep. Testosterone acts through androgen receptors (AR) and/or after aromatisation to oestradiol and binding to oestrogen receptors. The present study assessed the role of AR activation in male sexual differentiation. We compared rams that were exposed to the AR antagonist flutamide (Flu) throughout the critical period (i.e. days 30-90 of gestation) to control rams and ewes that received no prenatal treatments. The external genitalia of all Flu rams were phenotypically female. Testes were positioned s.c. in the inguinal region of the abdomen, exhibited seasonally impaired androgen secretion and were azospermic. Flu rams displayed male-typical precopulatory and mounting behaviours but could not intromit or ejaculate because they lacked a penis. Flu rams exhibited greater mounting behaviour than control rams and, similar to controls, showed sexual partner preferences for oestrous ewes. Neither control, nor Flu rams responded to oestradiol treatments with displays of female-typical receptive behaviour or LH surge responses, whereas all control ewes responded as expected. The ovine sexually dimorphic nucleus in Flu rams was intermediate in volume between control rams and ewes and significantly different from both. These results indicate that prenatal anti-androgen exposure is not able to block male sexual differentiation in sheep and suggest that compensatory mechanisms intervene to maintain sufficient androgen stimulation during development.

The Effects of a Single Developmentally Entrained Pulse of Testosterone in Female Neonatal Mice on Reproductive and Metabolic Functions in Adult Life

Early postnatal exposures to sex steroids have been well recognized to modulate predisposition to diseases of adulthood. There is a complex interplay between timing, duration and dose of endocrine exposures through environmental or dietary sources that may alter the sensitivity of target tissues to the exogenous stimuli. In this study, we determined the metabolic and reproductive programming effects of a single developmentally entrained pulse of testosterone (T) given to female mice in early postnatal period. CD-1 female mice pups were injected with either 5 μg of T enanthate (TE) or vehicle (control [CON] group) within 24 hours after birth and followed to adult age. A total of 66% of T-treated mice exhibited irregular cycling, anovulatory phenotype, and significantly higher ovarian weights than vehicle-treated mice. Longitudinal nuclear magnetic resonance measurements revealed that TE group had greater body weight, whole-body lean, and fat mass than the CON group. Adipose tissue cellularity analysis in TE group revealed a trend toward higher size and number than their littermate CONs. The brown adipose tissue of TE mice exhibited white fat infiltration with down-regulation of several markers, including uncoupling protein 1 (UCP-1), cell death-inducing DNA fragmentation factor, α-subunit-like effector A, bone morphogenetic protein 7 as well as brown adipose tissue differentiation-related transcription regulators. T-injected mice were also more insulin resistant than CON mice. These reproductive and metabolic reprogramming effects were not observed in animals exposed to TE at 3 and 6 weeks of age. Collectively, these data suggest that sustained reproductive and metabolic alterations may result in female mice from a transient exposure to T during a narrow postnatal developmental window.

Sexual behavior in male rodents

The hormonal factors and neural circuitry that control copulation are similar across rodent species, although there are differences in specific behavior patterns. Both estradiol (E) and dihydrotestosterone (DHT) contribute to the activation of mating, although E is more important for copulation and DHT for genital reflexes. Hormonal activation of the medial preoptic area (MPOA) is most effective, although implants in the medial amygdala (MeA) can also stimulate mounting in castrates. Chemosensory inputs from the main and accessory olfactory systems are the most important stimuli for mating in rodents, especially in hamsters, although genitosensory input also contributes. Dopamine agonists facilitate sexual behavior, and serotonin (5-HT) is generally inhibitory, though certain 5-HT receptor subtypes facilitate erection or ejaculation. Norepinephrine agonists and opiates have dose-dependent effects, with low doses facilitating and high doses inhibiting behavior.

Hypothalamus region-specific global gene expression profiling in early stages of central endocrine disruption in rat neonates injected with estradiol benzoate or flutamide

To identify genes linked to early stages of disruption of brain sexual differentiation, hypothalamic region-specific microarray analyses were performed using a microdissection technique with neonatal rats exposed to endocrine-acting drugs. To validate the methodology, the expression fidelity of microarrays was first examined with two-round amplified antisense RNAs (aRNAs) from methacarn-fixed paraffin-embedded tissue (PET) in comparison with expression in unfixed frozen tissue (UFT). Decline of expression fidelity when compared with the 1x-amplified aRNAs from UFTs was found as a result of the preferential amplification of the 3' side of mRNAs in the second round in vitro transcription. However, expression patterns for the 2x-amplified aRNAs were mostly identical between methacarn-fixed PET and UFT, suggesting no obvious influence of methacarn fixation and subsequent paraffin embedding on expression levels. Next, in the main experiment, neonatal rats at birth were treated subcutaneously either with estradiol benzoate (EB; 10 microg/pup) or flutamide (FA; 250 microg/pup), and medial preoptic area (MPOA)-specific microarray analysis was performed 24 h later using 2x-amplified aRNAs from methacarn-fixed PET. Numbers of genes showing constitutively high expression in the MPOA predominated in males, implying a link with male-type growth supported by perinatal testosterone. Around 60% of genes showing sex differences in expression demonstrated altered levels after EB treatment in females, suggesting an involvement of genes necessary for brain sexual differentiation. When compared with EB, FA affected a rather small number of genes, but fluctuation was mostly observed in females, as with EB. Moreover, many selected genes common to EB and FA showed down-regulation in females with both drugs, suggesting a common mechanism for endocrine center disruption in females, at least at early stages of post-natal development.

The effects of prenatal social stress on behaviour: mechanisms and function

In this review, we summarise experimental animal studies on the effects of the social environment during pregnancy on the offsprings' behaviour, brain, and neuroendocrine function. We show that in non-human mammals the stability of the social environment in which the pregnant females live is critical for the offsprings' social and sexual behaviour later in life as well as for reproductive functioning, endocrine state and androgen and estrogen receptor distribution in specific parts of the brain. Based on these findings, we discuss different neuroendocrine mechanisms mediating the influence of the social environment during pregnancy on the offsprings' behaviour. We conclude that maternal steroids play a decisive role in shaping foetal brain development. However, a pituitary adrenocortical pathway need not always be involved. At least in some cases an involvement of the sympathetic adrenomedullary system seems to be possible. Concerning function, we favour the hypothesis that the behavioural effects of prenatal social stress are not necessarily the 'pathological' consequences of adverse social conditions (non-adaptive explanation). Contrarily, mothers could be adjusting their offspring to the environment in which they live during pregnancy in an efficient way (adaptive explanation).

Application of an antiandrogen during pregnancy infantilizes the male offsprings' behaviour

The present study was conducted to test the hypothesis that an application of an antiandrogen during pregnancy causes an infantilization of the male offsprings' behaviour later in life. The subjects studied were male guinea pigs whose mothers were either treated with an antiandrogen (flutamide and carrier) or a placebo (carrier only) during pregnancy. The mothers lived in groups of five females and one male. Application of the antiandrogen or the placebo took place on days 30, 32, 34, and 36 of pregnancy, the sensitive phase of foetal CNS sexual differentiation in guinea pigs. After weaning three groups of sons, whose mothers had received the antiandrogen (FT-sons) and five groups of sons, whose mothers had received the placebo (PT-sons) were established. Each group consisted of two males. From their 20th through their 100th day of age, the spontaneous behaviour of the males was recorded in their home cages in 5-day intervals. Additionally, blood samples were collected to determine serum cortisol concentrations. FT-sons and PT-sons did not differ in serum cortisol concentrations. However, distinct differences in behaviour occurred: FT-sons rested significantly longer with bodily contact than PT-sons. Additionally, FT-sons displayed more play-behaviour than PT-sons. These results point to a behavioural infantilization in males prenatally treated with antiandrogen. The behavioural differences between FT- and PT-sons are in accordance with previous studies in which a decrease of serum androgen concentrations in pregnant females living in an unstable social environment [Psychoneuroendocrinology 2001;26:503] and an infantilization of their sons' behaviour was described [Psychoneuroendocrinology 2003;28:67]. Thus, our study supports the hypothesis, that the decrease of androgen concentrations during pregnancy, caused by an unstable social environment, is responsible for the infantilization of the male offsprings' behaviour.

Exposure to naturally circulating androgens during foetal life incurs direct reproductive costs in female spotted hyenas, but is prerequisite for male mating

Among all extant mammals, only the female spotted hyena (Crocuta crocuta) mates and gives birth through the tip of a peniform clitoris. Clitoral morphology is modulated by foetal exposure to endogenous, maternal androgens. First births through this organ are prolonged and remarkably difficult, often causing death in neonates. Additionally, mating poses a mechanical challenge for males, as they must reach an anterior position on the female's abdomen and then achieve entry at the site of the retracted clitoris. Here, we report that interfering with the actions of androgens prenatally permanently modifies hyena urogenital anatomy, facilitating subsequent parturition in nulliparous females who, thereby, produce live cubs. By contrast, comparable, permanent anatomical changes in males probably preclude reproduction, as exposure to prenatal anti-androgens produces a penis that is too short and has the wrong shape necessary for insertion during copulation. These data demonstrate that the reproductive costs of clitoral delivery result from exposure of the female foetus to naturally circulating androgens. Moreover, the same androgens that render an extremely unusual and laborious process even more reproductively costly in the female are apparently essential to the male's physical ability to reproduce with a normally masculinized female.

Influence of gonadal hormones on the development of parental behavior in adult virgin prairie voles (Microtus ochrogaster)

Prairie voles (Microtus ochrogaster) are a socially monogamous species and both sexes are parental after the birth of pups. In contrast, sexually inexperienced adult prairie voles differ in their behavior towards pups such that virgin males are paternal whereas virgin females are often infanticidal. To test whether there exists a discrete perinatal 'sensitive period' during which gonadal hormones influence this behavior, and to distinguish between the relative contributions of estrogenic and androgenic mechanisms to this influence, prairie voles were exposed to testosterone propionate (TP), the anti-androgen flutamide, or the aromatase inhibitor 1,4,6-androstatriene-3,17-doine (ATD) either prenatally via their pregnant dam for the last 15-19 days of the 22-day gestational period or postnatally on days 1-7. None of the treatments altered the high paternal responsiveness of males or the high infanticide rate in females when compared with controls. Females exposed prenatally to ATD, however, had levels of parental behavior that were significantly higher than the lowest levels observed in prenatally TP-treated females. These results suggest that sex differences in the parental behavior of adult virgin prairie voles are not generated exclusively by androgenic or estrogenic mechanisms during a restricted prenatal or early postnatal 'sensitive period' and that the parental behavior of virgin females may be more susceptible to any influence of gonadal hormones during development than males.

Timing of prenatal androgen exposure: anatomical and endocrine effects on juvenile male and female rhesus monkeys

Prenatal androgen shapes genital differentiation. In humans, genital anatomy determines sex of rearing and subsequent behavioral development. Rhesus monkey genital anatomy and neuroendocrine function are sexually differentiated, and behavioral development occurs in a complex social environment. We investigated prenatal hormonal influences on sexual differentiation by suppressing or increasing androgens in male and female rhesus monkeys. Pregnant multiparous female rhesus monkeys received 35-40 days of testosterone enanthate (TE) treatment, androgen antagonist (flutamide, FL) treatment, or vehicle starting on gestation day (GD) 35 or 40 (early) or GD 110 or 115 (late). Exogenous androgen increased neonatal LH secretion in females when given early and altered female genital differentiation when administered either early or late. TE treatment, early or late in gestation, had no measurable effects on male genital differentiation or neuroendocrine function. Early FL treatment, however, radically altered male genital differentiation, producing in two cases males with a urethral opening separate from the glans. In females, early FL treatment produced detectable alterations in genitalia consistent with a reduced exposure to prenatal androgen, suggesting that female rhesus monkeys are naturally exposed prenatally to meaningful levels of T. Late FL treatment reduced male penis size and increased neonatal T secretion, but had no effect in females. This is the first study to block endogenous prenatal testosterone in rhesus monkeys, thereby altering sexual differentiation. These findings illustrate the complexity of prenatal influences on anatomical and neuroendocrine development. The relationship between the anatomical changes reported here and sex differences in behavior is currently under investigation.

Sex differences in EEG in adult gonadectomized rats before and after hormonal treatment

EEG activity was recorded from the left and right parietal cortex in adult male and female Wistar rats that were gonadectomized (GNX) after puberty during 2 days without and 3 days with hormonal treatment (either testosterone propionate, 5 alpha-DHT or vehicle in males and progesterone, estradiol benzoate or vehicle in females). In contrast to EEG characteristics reported for intact rats, GNX abolished right over left parietal activation in both sexes and, sex differences in EEG interhemispheric correlation and in theta and delta relative power in the right parietal; additionally GNX males showed higher absolute power than females. Hormonal treatment reestablished interparietal asymmetry in both sexes and a lack of sex differences in absolute power, however, it was not enough to reestablish sex differences in delta and theta proportion in the right parietal nor in interhemispheric correlation. Differential effects were obtained with testosterone propionate and 5 alpha-DHT in males suggesting that activational effects of testosterone on EEG are probably exerted through testosterone or its aromatized metabolites. The results of our study indicate that the activational effects of gonadal steroids after puberty are necessary for maintaining sex differences in the EEG of the adult rat.

Prenatal social stress masculinizes the females' behaviour in guinea pigs

This study investigated the influence of the social environment during pregnancy and lactation on the female offsprings' behaviour and body weight. The subjects studied were daughters whose mothers had lived: a) in a stable social environment (SSE) during pregnancy and lactation; b) in an unstable social environment (USE) during pregnancy and lactation; c) in a SSE during pregnancy but in an USE during lactation; d) in an USE during pregnancy but in a SSE during lactation. The SSE was made by keeping the group composition (one male, five females) constant; in the USE situation every third day two females from different groups were exchanged. After weaning (n = 4 x 3 = 12), groups of daughters, consisting of four females each, were established, originating from the different categories of mothers. From their 41st through their 80th day of age the spontaneous behaviour of the daughters was recorded in their home cages. When the mothers had lived in an USE during pregnancy, the daughters displayed significantly higher amounts of male-typical courtship, play, and social orientation behaviour compared to daughters whose mothers had lived in a SSE during pregnancy. The stability and instability, respectively, of the social environment during lactation, however, had no significant influence on the daughters' prospective behaviour. The four categories of daughters did not differ in their body weights either at birth or at 80 days of age. Thus, the instability of the social environment during pregnancy obviously represented a mild stressor that nevertheless caused a distinct masculinization of the daughters' behaviour.