Role of the developing rat testis in differentiation of the neural tissues mediating mating behavior.

Abstract

Male rats castrated at 1, 5, 10, 20, 30, and 90 days of age and females ovariectomized at 90 days of age were compared as adults for female mating behavior when given estradiol and progesterone. The Day-1 and Day-5 castrates displayed more feminine behavior than those castrated after Day 5. When males castrated at similar ages received testosterone as adults, Day 1 and Day-5 castrates displayed fewer intromissions and ejaculations than Ss castrated later. The data support the hypothesis that the action of gonadal hormones on differentiating genital tracts and neural tissues is analogous. Feminization occurs in genotypic females or in either sex when gonads are absent. Masculinization occurs when androgen is present, regardless of genotypic sex.

Role for estradiol in female-typical brain and behavioral sexual differentiation

“…Thus presumably when the ovaries start to secrete estrogens at day 7 after birth [53], AFP no longer plays a significant role. Consistent with a postnatal role of estradiol in feminization of the brain is the observation by Steward and Cygan [93] of an enhanced of female receptivity in neonatally gonadectomized male and female rats treated with estradiol over postnatal days [30][31][32][33][34][35][36][37][38][39][40]. We propose thus that the defeminizing action of estradiol normally occurs prenatally in males and is avoided in fetal females because of the protective actions of AFP.…”

“…Thus female guinea pigs treated with testosterone propionate in utero showed elevated levels of male-typical mounting behavior together with reduced levels of female-typical lordosis behavior in adulthood [75]. Supportive evidence for a role of perinatal testosterone in the development of the male brain came from subsequent studies by Feder and Whalen [31], and Grady et al [40], and many others (reviewed in [10]) showing that removal of testosterone by neonatal castration reduced males' later capacity to show male sexual behaviors while enhancing their ability to show female sexual behaviors. Additional evidence suggested that testosterone secreted by the testes acts perinatally, either directly via androgen receptors or after being aromatized into estradiol and stimulating estradiol receptors ( [58,68]) to masculinize (enhance male-typical sexual responses) and/or defeminize (suppress femaletypical responses) the neural substrate that controls sexual behavior (Fig.…”

“…We propose thus that the defeminizing action of estradiol normally occurs prenatally in males and is avoided in fetal females because of the protective actions of AFP. We further propose that the feminizing action of estradiol normally occurs in genetic females between birth and the age of puberty (postnatal days [40][41][42][43][44][45][46][47][48][49][50]. Accordingly, several studies in which estrogen exposure was manipulated in both sexes during the perinatal developmental period have suggested that different critical periods exit for male-and female-typical organization of the brain [80,82].…”

Studies on the pathogenesis of the pseudohermaphroditism in the mouse with testicular feminization

“…Serum luteinizing hormone was assayed and Chaikoff by Doctors Robert Eskay and John Porter using a radioion 1-2 weeks immunoassay technique and NIAMD Rat LH-RP-I (Na- (27), in contrast to the testicular feminization syndrome in man (9,28,29), has a defect in testosterone biosynthesis and low testosterone blood levels. Since early castration in the rat has been reported to lead to a variety of secondary changes, including partial androgen insensitivity (30,31), it was necessary to characterize the hormonal status of the Tfmn mice. Therefore, testosterone values were compared in pooled samples of serum from normal male, normal female and Tfmin mice, all between 6 and 8 wk of age (Fig.…”

Effect of hour of operation on feminization of neonatally castrated male rats

“…Males castrated at 1 day of age and injected with estrogen and progesterone as adults have been reported by Grady, Phoenix, & Young (1965) to displayas many lordotic responses as similarly injected spayed females. Gerali, Hendricks, Johnson, & Bounds (1968), usingamethod ofscoring receptivity which included quality as weil as frequency of lordosis and soliciting behaviors, found that I-day castrated males' behavior was inferior to that of fern ales spayed within a short time after birth_ Neither study specified the time within the 24-h period after birth at which castration occurred.…”