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Laboratoire de Chimie Hormonale Maternité de Port-Royal, 75014 Paris, France and †Centre de Recherches Endocrinologiques, Hôpital Cochin, 27 rue du Faubourg St-Jacques, 75014 Paris, France
(Received 31 January 1977)
It has been suggested that testosterone production by the foetal testis is under gonadotrophin control (Catt, Dufau, Neaves, Walsh & Wilson, 1975; Warren, Haltmeyer & Eik-Nes, 1975), but the particular roles of foetal pituitary and/or chorionic gonadotrophin are not clearly understood. We have previously demonstrated that a substance with both the biological and radioimmunological properties of luteinizing hormone (LH) is present in the pituitary gland of the male mouse foetus at 18 days of gestation (Pointis & Mahoudeau, 1976a, b). In the present work, we attempted to determine whether the pituitary gland of the male mouse foetus exhibits gonadotrophic activity during earlier stages of genital tract differentiation.
On days 14-18 of gestation, the gonads and pituitary glands of male foetuses (Albino
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Adult male rats which had been castrated at birth and treated with the non-aromatizable androgen dihydrotestosterone propionate (DHTP) showed incomplete copulatory behaviour. When tested with oestrous female rats during treatment with testosterone propionate (TP) they readily mounted these females and showed frequent penile intromissions but rarely ejaculated. In a long series of observations the proportion of ejaculating rats in tests of 30 min did not exceed 50%. Neonatally castrated rats treated with DHTP during infancy thus seemed to be capable of ejaculation in adulthood during treatment with TP, but the threshold for the occurrence of the ejaculatory reflex seemed to be higher than in normal male rats.
By replacing treatment in adulthood with TP by a combined treatment with DHTP and oestradiol benzoate (OB), the frequency of ejaculation was not increased. It was concluded that the incomplete copulatory behaviour was not due to reduced efficiency of aromatization of androgen within the brain of these rats.
The addition of OB to DHTP during the neonatal period of treatment enhanced the frequency of ejaculation in adulthood. The combined treatment of 0·1 mg DHTP on days 1, 3 and 5 with 0·01 mg OB on day 1 made adult copulatory behaviour during treatment with TP indistinguishable from that of rats castrated on day 10 or rats castrated at birth and treated with TP during infancy.
It was concluded that the masculine organization of systems and structures involved in the display of male copulatory behaviour occurs under the influence of both non-aromatizable androgen and oestrogen, oestrogen being most likely the substance required to 'organize' the central nervous aspects of the regulation of this behaviour. The absence neonatally of nonaromatizable androgen and/or oestrogen results in specific deficiencies in adult copulatory behaviour as compared with the behaviour of normal male rats.
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Levels of testosterone in plasma and concentrations of LH in both plasma and pituitary glands of fetal mice aged 14, 16 and 18 days were measured by radioimmunoassays in a representative number of fetuses. During this period levels of testosterone in the plasma of male mice were significantly higher than those in the females. Levels of testosterone in plasma of male mice increased from day 14 to day 16 of gestation and decreased on day 1 before parturition. Plasma concentrations of LH remained undetectable in male and female fetuses until day 16 of gestation. Levels of LH rose slightly in both sexes in later gestation, but still remained significantly lower in the plasma of male fetuses on days 17–18. In contrast, higher but not significantly different concentrations of LH were observed in pituitary glands from days 14 to 18 in male compared with female mice. These observations suggest that the high levels of testosterone in the plasma of male fetal mice might be responsible for feedback inhibition of LH secretion during the last days of gestation.
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Untreated male and female rat pups were killed 1–5 days post partum and the serum concentrations of testosterone, oestrogens, LH and FSH were determined by radioimmunoassay. At all five sampling times, the serum concentrations of testosterone in male rats were about three times higher than those in female rats, but serum levels of oestrogens did not differ between the sexes. Serum concentrations of LH and FSH were lower in male than in female pups. In another study, rats were decapitated 1–10 days after birth and serum concentrations of testosterone were determined with a different radioimmunoassay. Again, at all four sampling times, the concentration of testosterone was significantly higher in the male than in the female pups.
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SUMMARY
Groups of neonatal female rats were treated for the first 5 days of life with oestradiol-17β, oestradiol benzoate or a synthetic oestrogen, 11β-methoxy-17-ethynyl-1,3,5(10)-oestratriene-3,17β-diol (RU 2858), in daily doses ranging from 0·5 to 1000 ng. Oestradiol-17β had no effect on adult ovarian cyclicity or sexual receptivity after ovariectomy and oestrogen + progesterone treatment. Ovarian cyclicity was prevented by 100 ng or more oestradiol benzoate/day, and by all doses of RU 2858. Only rats receiving 50 ng oestradiol benzoate/ day or 0·5 ng RU 2858/day showed normal receptivity. The defeminizing action of RU 2858 was at least 100 times greater than that of oestradiol benzoate; it is suggested that this greater potency is due to the low affinity of RU 2858 for the oestradiol-binding protein in the plasma of neonatal rats. These results indicate that defeminization of the neonatal rat brain can be induced by physiological amounts of oestrogen, and are discussed with reference to the action of testosterone.
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The number of prolactin and growth hormone cells was estimated in the mouse anterior pituitary gland. During postnatal development in females, the number of prolactin cells showed a rectilinear increase from about 0·3 × 104 at 20 days of age to about 21 × 104 in adult female mice, while growth hormone cells gradually increased from about 7 × 104 on day 20 to about 20 × 104 on days 60–70, with a plateau level of about 14 × 104 cells around puberty. Prolactin cells were more abundant in adult female (about 21 × 104) than in male (about 5 × 104) mice, while there were fewer growth hormone cells in adult females (about 20 × 104) than in males (about 25 × 104). Ovariectomy before puberty induced the male pattern of pituitary development by inhibition of the increase in the number of prolactin cells and stimulation of that of growth hormone cells. In animals ovariectomized just before puberty (30–35 days of age) or 5 days after vaginal opening (40–45 days of age) the number of prolactin cells showed no further increase after the day of operation. On the other hand, when animals were ovariectomized at 10 days of age, the number of prolactin cells increased to the level found in 30-day-old normal control females. This implies that the increase in prolactin cells between 10 and 30 days of age is not dependent on the ovary, although after puberty the increase does depend on the presence of the ovary.
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SUMMARY
The incorporation of [35S]methionine into protein in various regions of the brain and in the anterior pituitary, and serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels were measured at 6 h intervals throughout a 24 h period in the following groups of Wistar rats: (1) normal adult males and females; (2) adult genetic males or females which had been respectively 'feminized' or 'masculinized' by androgen deprivation or administration in neonatal life. Similar measurements were made at 12 h intervals in adult male rats which had been castrated at 7 or 15 days of age.
Serum LH levels showed a circadian rhythmicity in normal adult animals of both sexes, with peak levels in the male occurring 6 h earlier than those in the female. There was no statistically significant circadian rhythm in FSH levels in any group of animals. In all groups of castrated animals LH and FSH levels were raised but no circadian rhythms were observed.
Incorporation of [35S]methionine into protein in all cerebral areas showed circadian rhythms, the peak values of which, in the adult males, were almost 8 h (120°) out of phase with those of the adult females. In the 'feminized' genetic males or 'masculinized' genetic females the rhythmic phase was reversed to that of the opposite genetic sex. Animals castrated at 7 days or 15 days of age did not appear to show a rhythm.
A 12 h rhythm of incorporation was apparent in the anterior pituitary of the normal adult male and the adult 'masculinized' female; no significant rhythm was seen in the normal adult female and the 'feminized' male.
It is suggested that a 'female type' rhythm of incorporation in the brain may be associated with the maintenance of oestrous cycles.
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Stimulation of the uterine cervix (CS) induced a nocturnal surge of prolactin at 04.00 h and a diurnal surge at 17.00 h in normal ovariectomized rats. However, the CS-induced prolactin surges did not occur in ovariectomized rats which had been treated with 250 μg testosterone propionate during the neonatal period. Chronic bilateral lesions of the suprachiasmatic nucleus (SCN) completely abolished the CS-induced nocturnal and diurnal surges of prolactin release which were observed in sham-lesioned, ovariectomized rats. Furthermore, bilateral lesions of the medial basal part of the suprachiasmatic area (MBSC), lying rostral to the SCN, were also effective in blocking the CS-induced nocturnal and diurnal surges. Lesions which destroyed mainly the optic chiasma and extended partially into the MBSC and SCN did not block the CS-induced prolactin surges.
These results suggest that one reason for the failure of ovary-grafted male rats and neonatally androgenized female rats to maintain pseudopregnancy is the extinction of the circadian rhythm of the two daily prolactin surges, and that the MBSC, in addition to the SCN which is known to be a generator of other circadian rhythms, is involved in generation of the rhythm of prolactin surges.
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penis and scrotal sac ( George & Wilson 1994 , Griffin et al. 2001 ), as well as later, sexually differentiated behaviours ( Phoenix et al. 1959 ), have been explored in efforts to explain the genesis of the external genitalia of the female spotted
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/2 in some brain areas of young and adult hamsters displayed an evident sexually dimorphic expression pattern, suggesting that hibernators could very well be a useful model for unveiling the sexually differentiated neurobiological role of the classical
