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PubMed1989

Embryonic sex steroids affect mating behavior and plasma LH in adult chickens.

Chicken embryos of both sexes were treated with either antiestrogen (tamoxifen = T), antiandrogen (flutamide = F), aromatization inhibitor (ATD = A), estradiol (E), or oil (control = C). Before puberty, some males of each group were castrated. At puberty, birds were tested under the following regimes: castrated males injected daily with testosterone propionate (CAS + TP) or estradiol benzoate (CAS + EB), intact males (M-INT), intact females (F-INT), and females injected daily with TP (F-TP). In the M-INT and CAS + TP males, E treatment suppressed masculine mating behavior. The embryonic treatments with T, F, and A demasculinized only the frequency of copulations. None of the antihormone treatments caused any masculinization of the sexual activity in the F-TP birds. Untreated males had higher plasma LH than females. The embryonic treatment with E reduced (feminized) the LH levels in CAS + EB birds. This effect was less pronounced in M-INT birds. The results suggest that in chickens, estradiol plays a role in the masculinization of copulatory behavior potential in the developing male embryo. High embryonic estradiol reduces the potential for displaying male sexual behavior at puberty. Feminization of LH secretion requires a high level of estradiol in both embryonic and adult life.

Androstatrienes↗
PubMed1994

SDN-POA volume, sexual behavior, and partner preference of male rats affected by perinatal treatment with ATD.

The present study investigated 1) the importance of the aromatization process during the perinatal period for the development of the sexually dimorphic nucleus in the preoptic area of the hypothalamus (SDN-POA) of male rats, and 2) the relationship between SDN-POA volume and parameters of masculinization in male rats that were treated perinatally with the aromatase-inhibitor ATD. Males were treated with ATD either prenatally or pre- and neonatally, or with the vehicle. Masculine sexual behavior and partner preference were investigated in adulthood. Thereafter, animals were sacrificed and SDN-POA volume was measured. The SDN-POA volume was reduced in both the prenatally and the pre- and neonatally treated group, with a larger reduction in the latter than in the former group. Combined pre- and neonatal ATD treatment resulted in reduced frequency of mounts, intromissions, and ejaculations, as well as a reduced preference for a female over a male. The SDN-POA size was significantly and positively correlated with frequency of masculine sexual behavior, as well as preference for a female over a male.

Androstatrienes↗
PubMed1993

Behavioral effects of neonatal treatment with clomipramine, scopolamine, and idazoxan in male rats.

It has been suggested that REM sleep deprivation due to the administration of clomipramine, during early developmental stages, results in dramatic behavioral changes during adulthood. One of the main alterations is the impairment of masculine sexual behavior (MSB). Clomipramine increase monoaminergic availability at the synaptic level and also suppresses REM sleep. This study was performed to compare the effect on masculine sexual behavior of three different neonatal treatments: clomipramine, which increases monoaminergic availability at the synaptic level and suppresses REM sleep; scopolamine, a cholinergic antagonist that suppresses REM sleep; and idaxozan, a selective adrenergic agonist. Subjects (Ss) were treated neonatally and tested for masculine sexual behavior during adulthood with standard techniques. Results obtained with clomipramine administration showed a marked impairment of MSB, mainly reflected by the decrease in the percentage of active Ss and the decrease in the percentage of Ss reaching ejaculation. In contrast, idaxozan and scopolamine produce a facilitation of MSB. The effect of idaxozan was not significantly different when compared to saline control rats. The effect of scopolamine was greater, and the percentage of Ss reaching ejaculation was significantly larger than saline control. These results suggest that the alterations of sexual behavior induced with neonatally administered clomipramine are not due to early REM sleep deprivation. As idaxozan did not replicate clomipramine results, it is also possible that noradrenergic transmission is not involved in the generation of these effects. It remains possible that the serotonin system could be responsible for the impairment of sexual behavior due to neonatal clomipramine treatment.

Adrenergic alpha-2 Receptor Antagonists↗
PubMed1995

Estrogen promotes neuron addition to an avian song-control nucleus by regulating post-mitotic events.

Only male zebra finches sing and several telencephalic song control regions exhibit sex differences in neuron number that presumably reflect effects of estrogen (E2) exerted during the first few posthatch weeks. That is, implanting females with E2 during this time masculinizes neuron number and instills the capacity for vocal behavior. In certain song regions, E2 masculinizes neuron number by preventing the naturally-occurring death of neurons, long after their production, migration and process outgrowth are complete. However, in the Higher Vocal Center (HVC), the cellular mechanisms by which E2 establishes sex differences in neuron number are poorly understood. In contrast with other song regions, HVC neurogenesis overlaps with sexual differentiation and the incorporation of new neurons is greater in young males and E2-treated females, than in normal females. However, it is not known whether E2 promotes the addition of HVC neurons by stimulating their production, specification, and/or survival. To address this issue we injected males and females with [3H]thymidine on days 15 and 16 to label a small group of sexually dimorphic HVC neuronal cohorts born during sexual differentiation. Afterwards, on day 17, females were implanted with Silastic pellets filled with estradiol benzoate (EB) or left empty. We report here that EB exposure on day 17 masculinized (increased) the number of neurons in the HVC at day 35 that were labeled by [3H]thymidine injections on days 15/16. Thus, EB was able to increase cell number among at least some HVC neuronal cohorts after their final division, implying estrogenic regulation of post-mitotic events.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

The effect of medial preoptic--anterior hypothalamic lesions on bisexual behavior of the male rat.

The effects of bilateral radiofrequency lesions in various parts of the medial preoptic area (mPOA) and anterior hypothalamus (AH) on masculine and hormone induced feminine sexual behavior was studied in male rats. Anatomical as well as statistical analysis of the extent and location of the lesions and the consequent behavioral changes indicated that different parts of the mPOA-AH continuum are involved in masculine and feminine sexual behavior in different ways. Bilateral destruction at the transition of the mPOA and AH resulted in a large reduction of masculine sexual activity while lesions concentrated in the AH slightly facilitated feminine sexual behavior in males. These results are consistent with the notion that the mPOA-AH continuum is divided into anatomically and functionally different parts.

Animals↗
PubMed1988

Effects of lesions of the sexually dimorphic nucleus on sexual behavior of testosterone-treated female Wistar rats.

Discrete bilateral lesions were placed into the sexually dimorphic nucleus (SDN) of the medial preoptic area (MPOA) of ovariectomized female Wistar rats, chronically treated with testosterone (T). Effects of these lesions upon masculine and feminine sexual behavior were studied by comparing the results of pre- and postoperative tests, using sham-operated and unoperated females as controls. Bilaterally-lesioned and, to a lesser extent, unilaterally-lesioned females, showed a marked and significant reduction of masculine sexual behavior (i.e., mounting), especially in the first postoperative tests. Feminine sexual responses, i.e., receptive and proceptive behavior, although slightly lower in bilaterally-lesioned females, did not change significantly. Sexual partner preference, operationalized as the choice between a receptive female and a sexually active male, remained unaffected by the lesions. Plasma levels of testosterone were similar in the various groups. It is concluded that the SDN may be functionally implicated in the control of masculine sexual behavior in T-treated females.

Animals↗
PubMed1989

Lesions of the SDN-POA inhibit sexual behavior of male Wistar rats.

Discrete bilateral lesions in the SDN-POA of sexually naive adult male rats were found to decrease the number of animals ejaculating and/or to increase latencies to the first mount, intromission and ejaculation. The deleterious effects of the lesions disappeared after 4 tests for sexual behavior but were reinstated when the males were tested under suboptimal conditions, i.e., when they were tested with a marginally receptive female or when they had only limited access to the stimulus female. It was subsequently shown that males with a bilaterally lesioned SDN-POA still showed an increase in plasma testosterone. LH and prolactin levels in response to sexual stimulation. Effects of the lesions on scent marking were not found. Together with previous data indicating that SDN-POA-lesions disrupt masculine sexual behavior in females, these data are taken as evidence that the SDN-POA plays a role in the regulation of masculine sexual behavior. The data further suggest that previously reported negative results of SDN-POA-lesions on masculine sexual behavior in male rats might be attributed to the use of sexually experienced instead of sexually inexperienced animals.

Animals↗
PubMed2006

fMRI of parents of children with Asperger Syndrome: a pilot study.

BACKGROUND: People with autism or Asperger Syndrome (AS) show altered patterns of brain activity during visual search and emotion recognition tasks. Autism and AS are genetic conditions and parents may show the 'broader autism phenotype.' AIMS: (1) To test if parents of children with AS show atypical brain activity during a visual search and an empathy task; (2) to test for sex differences during these tasks at the neural level; (3) to test if parents of children with autism are hyper-masculinized, as might be predicted by the 'extreme male brain' theory. METHOD: We used fMRI during a visual search task (the Embedded Figures Test (EFT)) and an emotion recognition test (the 'Reading the Mind in the Eyes' (or Eyes) test). SAMPLE: Twelve parents of children with AS, vs. 12 sex-matched controls. DESIGN: Factorial analysis was used to map main effects of sex, group (parents vs. controls), and sexxgroup interaction on brain function. An ordinal ANOVA also tested for regions of brain activity where females>males>fathers=mothers, to test for parental hyper-masculinization. RESULTS ON EFT TASK: Female controls showed more activity in extrastriate cortex than male controls, and both mothers and fathers showed even less activity in this area than sex-matched controls. There were no differences in group activation between mothers and fathers of children with AS. The ordinal ANOVA identified two specific regions in visual cortex (right and left, respectively) that showed the pattern Females>Males>Fathers=Mothers, both in BA 19. RESULTS ON EYES TASK: Male controls showed more activity in the left inferior frontal gyrus than female controls, and both mothers and fathers showed even more activity in this area compared to sex-matched controls. Female controls showed greater bilateral inferior frontal activation than males. This was not seen when comparing mothers to males, or mothers to fathers. The ordinal ANOVA identified two specific regions that showed the pattern Females>Males>Mothers=Fathers: left medial temporal gyrus (BA 21) and left dorsolateral prefrontal cortex (BA 44). CONCLUSIONS: Parents of children with AS show atypical brain function during both visual search and emotion recognition, in the direction of hyper-masculinization of the brain. Because of the small sample size, and lack of age-matching between parents and controls, such results constitute a pilot study that needs replicating with larger samples.

Asperger Syndrome↗
PubMed2004

A model for environmental sex reversal in fish.

A mathematical model is presented which combines genetic XX-female/XY-male sex determination with environmental pressure for phenotypic sex reversal. This may occur when fishes are exposed to endocrine disrupters, specifically masculinization by exposure to androgens and feminization by exposure to estrogens. A generic model is derived for the sex ratio in successive generations and three special cases, with chronic and constant pressure to sex reverse, are discussed in detail. These show that, with extreme environmental pressure to masculinize, the male genotype is at risk of dying out but with less extreme pressure, masculinization will not be detectable since the proportion of phenotypic males becomes one-half. With feminization at any pressure to sex reverse, the male and female genotypes will be maintained in a stable sex ratio in which the proportion of genotypic males exceeds one-half and is close to one-half if YY offspring (eggs) are not viable. In converse, the model is also applicable to the genetic ZZ-male/ZW-female system of sex determination in fish. At present suitable data are not available with which to validate the model, but proposals are made for relevant experimental studies.

Androgens↗
PubMed2004

A comparison of breast, testicular and prostate cancer in mass print media (1996-2001).

This paper compares the portrayal of breast, testicular and prostate cancer in mass print English language magazines in the United States and Canada from 1996 to 2001. It is a follow-up of three papers that examined each of these three diseases separately in high circulating magazines up to 1995. It includes both quantitative and qualitative analyses of magazine stories and notes the continuing dominance of a medical perspective regarding disease as well as the association of each type of cancer examined with stereotypically individualized yet feminine and masculine characteristics and pursuits. It notes the conflation of breast cancer, since the discovery of BRCA1 and BRCA2, with the family. To be a 'feminine' woman is to be vulnerable to breast cancer and to be a 'masculine' man is to be vulnerable to testicular cancer when young and prostate cancer when older. The association of disease not just with personhood but also with the specifics of stereotyped masculinity and femininity may construct a more intimate, more personal link between disease and identity. This close attachment of gender and disease may shore up and exacerbate a fear reaction. It may also serve to diminish the awareness of other, more prevalent, causes of death for men and women. The social control consequences of potentially exacerbated disease-specific fear are discussed.

Attitude to Health↗
PubMed2005

Barriers to healthy eating amongst men: a qualitative analysis.

Currently, little is known about the meanings men attach to food or to the links between food and health. The burgeoning literature on men's health highlights forms of masculinity (e.g. risk-taking, invulnerability) as a factor (negatively) influencing men's health practices. The aim of this study was to provide an analysis of men's accounts of food and health using concepts pertaining to masculinity. We report on a qualitative analysis of a dataset comprising 24 interviews with UK men from a range of age and social class groups. Our findings suggest two principal barriers to healthy eating in men: cynicism about government health messages and a rejection of healthy food on grounds of poor taste and inability to satisfy. These findings are discussed in relation to masculine ideals such as rationality, autonomy and strength. The implications of our analysis for future research and men's health promotion policy are discussed.

Adult↗
PubMed1976

Neonatal androgen and mounting behaviour in female house mice.

Strains of intact, mature female mice were found to differ appreciably in their levels of performance of masculine copulatory patterns when presented with a stimulus oestrous female. Balb/c and DBA/2 strains, which showed few responses to stimulus females, were still unresponsive when given exogenous androgen, whereas the C57BL/6Fa strain and its R1 hybrids with the DBA/2 strain, showed more pre-injection masculine responses which increased to consistent and very high levels following androgen treatment. In a second study, injection of Balb/c females with testosterone propionate on the day of birth did not increase the number of masculine responses displayed, even after androgen treatment at maturity.

Animals↗
PubMed2002

Post-hatching hormonal modulation of a sexually dimorphic neuromuscular system controlling song in zebra finches.

Sexual dimorphisms are present throughout the zebra finch song system, from forebrain centers to the tracheosyringeal portion of the hypoglossal nucleus (nXIIts) to the muscles of the syrinx (vocal organ). In females, gonadal steroids administered during development can partially masculinize the telencephalic areas, and in adulthood can increase the size of syrinx muscles. In the present study, two experiments were designed to investigate the role of early androgen and estrogen in the development of nXIIts and the ventralis and dorsalis muscles of the syrinx. In experiment one, males and females were treated with testosterone, estradiol, dihydrotestosterone, the anti-androgen flutamide, or a vehicle control for 21 days after hatching. At day 60, nXIIts volume, motoneuron soma size and number were assessed, as well as syrinx weight and the size of ventralis and dorsalis fibers. In experiment two, animals were administered either the estrogen synthesis inhibitor, fadrozole, or vehicle, and the syrinx measurements were taken at day 60. Male-biased sex differences were detected on all measures in both experiments, and several right-side biases were detected. In females, dihydrotestosterone masculinized soma size in nXIIts and testosterone slightly increased syrinx weight. E2 feminized the syrinx of males. However, flutamide did not prevent masculine development of either structure, and fadrozole did not inhibit feminine syrinx development. These results are consistent with the idea that, as in the forebrain, steroid hormones can stimulate aspects of sexual differentiation, but they may not be direct triggers for the process.

Aging↗
PubMed2003

Sex differences in interest in infants in juvenile rhesus monkeys: relationship to prenatal androgen.

Yearling rhesus monkey females interact more with infants than do males. However, the continuity of this sex difference throughout the juvenile period is unknown. Human females display similar sexually differentiated interest in infants, and studies of girls with congenital adrenal hyperplasia suggest that this sex difference may be modulated by prenatal androgen exposure. We investigated infant interest in 1- to 3-year-old juvenile rhesus monkeys. Hormonal influences on this behavior were investigated by treating pregnant females with an androgen-receptor blocker (flutamide), testosterone enanthate, or vehicle, early or late in gestation. Subjects were reared in their well-established natal groups, composed of species-typical matrilineal social structures, including members of all ages. Yearling control females interacted with infants more than did yearling control males. At 2 and 3 years of age, the magnitude of the sex difference in interactions with infants increased markedly, producing effect sizes of more than 2.5 standard deviations. These effects are larger than those reported in humans. Androgen treatment did not affect male or female interactions with infants, but late gestation flutamide masculinized aspects of females' interest in infants. Although early flutamide prevented complete masculinization of male genitalia, this treatment was not accompanied by any alterations in the masculine pattern of infant interest. We found no evidence that the robust juvenile sex difference in frequency of infant interactions results from socialization. However, it was largely unaffected by our hormone manipulations. Whether this reflects characteristics of our specific treatments or is evidence of nonhormonal influences on infant interest remains unanswered.

Age Factors↗
PubMed2002

Effect of prenatal androgen receptor antagonist or aromatase inhibitor on sexual behavior, partner preference and neuronal Fos responses to estrous female odors in the rat accessory olfactory system.

Many socially relevant odors are detected in rodent species by the vomeronasal organ and subsequently processed by the accessory olfactory system (AOS). We previously found that gonadectomized male and female rats treated in adulthood with testosterone propionate (TP) showed equivalent Fos responses in the AOS to odors derived from estrous females. Likewise, in contrast with numerous other mammalian species, gonadectomized female rats show surprisingly high levels of male-typical mounting behavior in response to adult TP. We tested the hypothesis that prenatal testosterone (T) exposure, acting via androgen receptors (ARs) or via estrogen receptors, masculinizes the AOS in rats of both sexes. Pregnant dams were treated with either the AR blocker, Flutamide, the aromatase inhibitor, 1,4,6-androstatriene-3,17-dione (ATD), or nothing (control) to assess the role of prenatal androgen and estradiol receptor activation, respectively, in this masculinization. Beginning at birth, male and female offspring were injected subcutaneously (sc) every other day with either ATD (pre- and neonatal ATD group) or oil vehicle (Flutamide and control groups) until postnatal Day 12. Subjects were gonadectomized as adults, hormonally treated and tested for different behaviors before having their AOS Fos responses to estrous female odors assessed. Prenatal treatment with Flutamide (but not ATD) significantly decreased anogenital distance and severely impaired intromissive and ejaculatory behaviors in males tested after TP replacement without disrupting mounting capacity in either sex. Pre- and neonatal treatment with ATD (but not Flutamide) enhanced lordosis responsiveness in males tested after sc injections of estradiol and progesterone, whereas these perinatal treatments had no effect on any aspect of masculine coital performance in either sex. After TP treatment, male and female control subjects preferred to approach a tethered stimulus female as opposed to a male, and prenatal Flutamide or perinatal ATD treatments did not modify this pattern of partner preference. Neuronal Fos responses to estrous odors were (as in previous studies) identical in the AOS of gonadectomized TP-treated control males and females. Prenatal Flutamide or perinatal ATD treatments failed to disrupt consistently this profile of Fos responses to estrous odors in the AOS of rats of either sex. These behavioral and neuroanatomical findings raise the possibility that the similar level of male-typical responsiveness to social odors that occurs in male and female rats after adult TP treatment results from nonsteroid-hormone-dependent, species-specific factors that act perinatally in the brains of rats of both sexes.

Androgen Antagonists↗
PubMed2003

Play, copulation, anatomy, and testosterone in gonadally intact male rats prenatally exposed to flutamide.

The role of prenatal androgen on the differentiation of sexually dimorphic juvenile play and adult copulatory patterns was evaluated in male offspring of rats injected with 5 mg of the androgen receptor blocker flutamide (4'-nitro-3'-trifluoromethylisobutyranilide) from Days 11-21 of pregnancy. Rough-and-tumble play was incompletely masculinized in flutamide-exposed males at 31 days of age. The copulatory potential tested at 70 days of age was severely attenuated by prenatal flutamide. There was no ejaculatory behavior, low levels of intromissions, and depressed levels of nonintromittive mounting when the animals were tested while gonadally intact. Adult plasma levels of testosterone (T) were not different in flutamide-exposed males and controls, but testicular and epididymal weight, anogenital (AG) distance, and penile length were reduced. While reductions in intromittive mounting and ejaculatory behavior may be due to the abnormalities in the external genitalia, the incomplete masculinization of play and the reduction in nonintromittive mounting probably resulted from effects the androgen antagonist exerted on sexual differentiation of the central nervous system. These data suggest that androgen released prior to birth is needed for the full masculinization of juvenile play behaviors in the rat, just as it is for the adult copulatory pattern.

Androgen Antagonists↗
PubMed1997

Sexual differentiation in prairie voles: the effects of corticosterone and testosterone.

Prairie voles (Microtus ochrogaster) exhibit low levels of physical sexual dimorphism and have endogenous basal corticosterone levels that are 5-10 times higher than those measured in rats; prairie voles also do not show a postnatal period of adrenal hyporesponsivity. On the basis of studies in rats suggesting that adrenal hyperactivity during the perinatal period could reduce masculinization or feminize sexual behavior, we hypothesized that adrenal hormones might influence sexual differentiation in prairie voles. We also examined the hypothesis that the effects of testosterone in prairie voles might differ from those reported in other rodents. Treatments with either corticosterone or testosterone propionate (TP) were given prenatally (gestational Days 12-20), via maternal injection, or postnatally (Days 1-6), by directly injecting the pups. Additional groups of males were castrated or sham-operated on postnatal Day 1, and a subgroup of castrated males received postnatal TP. Male and female sexual behavior was observed in adulthood following gonadectomy and hormone treatments. Corticosterone treatment was associated with high levels of mounting in both sexes and did not inhibit lordosis behavior in females. Postnatal TP treatment inhibited lordosis in females but did not facilitate mounting in either sex. Males that were castrated at birth showed unexpectedly high levels of mounting in response to adult androgens. The results of this study suggest that in prairie voles corticosterone is capable of masculinizing without defeminizing sexual behavior, whereas postnatal testicular secretions are not essential for, and may actually inhibit, masculinization in this species.

Animals↗
PubMed1998

Aromatase activity and regulation of sexual behaviors in the green anole lizard.

Sexual behaviors in green anoles are regulated by steroid hormones. Androgens activate the display of masculine courtship and copulatory behaviors, and estradiol activates feminine receptivity. Testosterone can also facilitate receptivity in females. The present study was conducted to test the role of converting testosterone to estradiol (aromatization) in the regulation of sexual and aggressive behaviors. Adult males and females were gonadectomized and implanted with a Silastic capsule containing either testosterone propionate (T) or estradiol benzoate (E) or with an empty (blank, BL) capsule. T- and BL-treated animals were then given injections of either Fadrozole (FAD, an aromatase inhibitor) or saline (SAL). E-treated animals received saline injections. Each individual was then tested alternately with male and female stimulus animals. Overall, T stimulated masculine sexual behaviors and receptivity, but the androgen had little effect on the display of aggressive behaviors. The inhibition of aromatase activity by treatment with Fadrozole eliminated the effect of T on receptivity. In contrast, Fadrozole treatment had no effect on mounting behavior or the frequency of courtship bouts. The inhibition of aromatase activity did increase the number of dewlap extensions (the display of a red throat fan) during courtship. These results suggest that the metabolism of testosterone to estradiol is a mechanism through which androgens can facilitate receptivity, and that such aromatization of testosterone is not required for the display of masculine sexual behaviors. In addition, females performed courtship and mounting behaviors less frequently than males, suggesting that an organizational component to steroid hormone regulation of sexual behaviors may exist in the anole.

Aggression↗