The sexual behaviour of prenatally androgenized ewes observed in the field

Clarke, I. J.

doi:10.1530/jrf.0.0490311

Cited by 53 publications

(26 citation statements)

References 12 publications

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“…It has been suggested that genital virilization in CAH girls does not correlate to male typical patterns of motor behavior (Dittmann, 1992). Indeed it has been shown in female ewes and female rhesus macaques that behavioral masculinization can occur independently of genital virilization (Clarke, 1977;Goy, Bercovitch, & McBrair, 1988). These observations support our findings in rats, and suggest that at least some of the sex differences in movement arise from sex differences in neural organization, rather than as a byproduct of differences in body morphology.…”

Section: Implications For Sex Differences In Humanssupporting

confidence: 89%

The Brain as the Engine of Sex Differences in the Organization of Movement in Rats

Field

2007

Arch Sex Behav

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Sex differences in the kinematic organization of non-reproductive behavior are often relegated to byproducts of sex differences in body morphology. We review evidence showing not only that male and female rats organize their posture and stepping differently during a variety of actions, but that these differences arise from sex differences in the organization of movement in the central nervous system (CNS). Indeed, the expression and choice of sex-typical patterns of movement can be altered by CNS injury. The pattern of hormonal regulation of these sex differences is also not organized as commonly held theory would predict. As expected, males castrated shortly after birth are female-typical in their motor organization. Females ovariectomized at birth, however, are male-typical in their patterns of movement. Thus, female-typical patterns of movement organization are not the default form, but rather are dependent on the effects of gonadal steroids to feminize the developing CNS. The implications of these findings are discussed with regards to our understanding of the evolution of sex differences in CNS anatomy and behavior both for animals and humans.

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Section: Implications For Sex Differences In Humanssupporting

confidence: 89%

The Brain as the Engine of Sex Differences in the Organization of Movement in Rats

Field

2007

Arch Sex Behav

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“…In contrast, both T and DHT treatment advances the pubertal rise in LH, suggesting that the tonic mode of gonadotropin secretion is masculinized by androgen. In sheep, androgens also appear to masculinize juvenile play behavior [36] and to masculinize sexual behavior [7,10,37]. However, to our knowledge, nothing is yet known about the role of aromatization in these processes.…”

Section: Discussionmentioning

confidence: 99%

“…2 Correspondence: Charles E. Roselli [5]. As initially determined by Short [6] and later refined by Clarke et al [7][8][9][10], sexual differentiation in sheep occurs from approximately Days 30 to 100 of the 145-day gestation.…”

Section: Introductionmentioning

confidence: 99%

Estrogen Synthesis in Fetal Sheep Brain: Effect of Maternal Treatment with an Aromatase Inhibitor1

Roselli

Resko

Stormshak

2003

Biology of Reproduction

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The aim of the present study was to determine whether the fetal lamb brain has the capacity to aromatize androgens to estrogens during the critical period for sexual differentiation. We also determined whether administration of the aromatase-inhibitor 1,4,6-androstatriene-3,17-dione (ATD) could cross the placenta and inhibit aromatase activity (AA) in fetal brain. Eight pregnant ewes were utilized. On Day 50 of pregnancy, four ewes were given ATD-filled Silastic implants, and the other four ewes received sham surgeries. The fetuses were surgically delivered 2 wk later (Day 64 of gestation). High levels of AA (0.8-1.4 pmol/h/mg protein) were present in the hypothalamus and amygdala. Lower levels (0.02-0.1 pmol/h/mg protein) were measured in brain stem regions, cortex, and olfactory bulbs. The Michaelis-Menten dissociation constant (K(m)) for aromatase in the fetal sheep brain was 3-4 nM. No significant sex differences in AA were observed in brain. Treatment with ATD produced significant inhibition of AA in most brain areas but did not significantly alter serum profiles of the major sex steroids in maternal and fetal serum. Concentrations of testosterone in serum from the umbilical artery and vein were significantly greater in male than in female fetuses. No other sex differences in serum steroids were observed. These data demonstrate that high levels of AA are found in the fetal sheep hypothalamus and amygdala during the critical period for sexual differentiation. They also demonstrate that AA can be inhibited in the fetal lamb brain by treating the mother with ATD, without harming fetal development.

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“…Clarke and colleagues (Clarke et al, 1976b;Clarke, 1977) assessed the effects of maternal testosterone treatment in sheep over several different gestational periods on estrous cyclicity and the display of male-typical mounting behavior. The greatest degree of genital masculinization was achieved in ewes exposed to testosterone over days G30 -G80, whereas the greatest behavioral masculinization and defeminization was seen in ewes exposed to testosterone over either G50 -G100 or G70 -G120.…”

Section: Sexual Differentiation Of Reproductive Behavior In Sheepmentioning

confidence: 99%

The ram as a model for behavioral neuroendocrinology

Perkins

Roselli

2007

Hormones and Behavior

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The sheep offers a unique model to study male sexual behavior and sexual partner preference. Rams are seasonal breeders and show the greatest libido during short days coincident with the resumption of ovarian cyclicity in the ewe. Threshold concentrations of testosterone are required for the acquisition and display of adult sexual behavior. In addition, estrogens produced from circulating testosterone by cytochrome P450 aromatase in the preoptic area are critical for the maintenance of sexual behaviors in rams. Sex differences in adult reproductive behaviors and hormone responsiveness are the result of permanent organizational effects exerted by testosterone and its metabolites on brain development. Early exposure to ewes enhances ram sexual performance, but cannot prevent some rams from exhibiting male-oriented sexual partner preferences. Neurochemical and neuroanatomical studies suggest that male-oriented ram behavior may be a consequence of individual variations in brain sexual differentiation.

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The sexual behaviour of prenatally androgenized ewes observed in the field

Cited by 53 publications

References 12 publications

The Brain as the Engine of Sex Differences in the Organization of Movement in Rats

The Brain as the Engine of Sex Differences in the Organization of Movement in Rats

Estrogen Synthesis in Fetal Sheep Brain: Effect of Maternal Treatment with an Aromatase Inhibitor1

The ram as a model for behavioral neuroendocrinology

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