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We have demonstrated that sexual activity produces transient sympathoadrenal activation and a pronounced, long-lasting increase in prolactin in men and women. However, by analyzing endocrine alterations at 10-min intervals, a precise assignment of these changes to the pre-, peri- and postorgasmic periods was not possible. Thus, the current study aimed to accurately differentiate the endocrine response to sexual arousal and orgasm in men using an automatic blood collection technique with 2-min sampling intervals. Blood was drawn continuously before, during and after orgasm over a total period of 40 min in 10 healthy subjects and were compared with samples obtained under a control condition. Sexual activity induced transient increases of plasma epinephrine and norepinephrine levels during orgasm with a rapid decline thereafter. In contrast, prolactin levels increased immediately after orgasm and remained elevated throughout the experiment. Although oxytocin was acutely increased after orgasm, these changes were not consistent and did not reach statistical significance. Vasopressin, LH, FSH and testosterone plasma concentrations remained unaltered during sexual arousal and orgasm. These data confirm that prolactin is secreted after orgasm and, compared with oxytocin, seems to represent a more reliable and sustained marker for orgasm in man. The results further reinforce a role for prolactin either as a neuroendocrine reproductive reflex or as a feedback mechanism modulating dopaminergic systems in the central nervous system that are responsible for appetitive behavior.
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Levels of adrenal and peripheral plasma corticosterone are higher in the adult female than in the adult male rat and variations in oestrogen and androgen levels can alter corticotrophin and adrenocortical hormone metabolism (Troop, 1954; Coyne & Kitay, 1969; Ruhmann-Wennhold, Lauro & Nelson, 1970). Some studies conducted in male and female prepuberal animals at various ages have demonstrated no significant sexual differences in adrenal corticosteroids (Critchlow, Liebelt, Bar Sela, Mountcastle & Lipscomb, 1963); other investigators such as Troop (1954) and Yates, Herbst & Urquhart (1958) have suggested higher corticosteroid metabolism in males and in females respectively. During the first few days of life, sexual differentiation of the hypothalamus occurs, and the presence of androgens, as in the normal male or in the female injected with testosterone, induces a male pattern of gonadotrophin secretion. In contrast, low levels of androgens in the normal female or the male castrated at birth, induce
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Department of Anatomy, Juntendo University School of Medicine, Hongo, Tokyo 113, Japan
(Received 18 October 1977)
Differentiation of sexual behaviour patterns in male rats is dependent on the internal secretion of the testes during neonatal life. Removal of the testes at this time causes feminization and results in male rats which display female patterns of sexual behaviour (Gorski, 1971). Female patterns of behaviour are usually rare in normal male rats but recently we found that transection of the dorsal afferent neurones to the preoptic and anterior hypothalamic areas potentiated the display of lordosis in hormonally primed male rats (Yamanouchi & Arai, 1975). In the present study, further neuroanatomical analysis was carried out to clarify the localization of the afferent pathway involved in the regulation of lordosis behaviour.
Anterior or posterior roof deafferentation (ARD or PRD) was performed by lowering an L-shaped Halasz knife (2-5 mm horizontal blade) to the level
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ABSTRACT
Serum concentrations of testosterone, 5α-dihydrotestosterone, oestradiol and progesterone were measured by radioimmunoassay combined with Celite chromatography in male and female Japanese quail (Coturnix coturnix japonica) during the second half of embryonic life (days 9–17 of incubation) and during the first 5 weeks after hatching. The mean level of each of the four steroids was significantly affected by the age of the birds. An overall effect of sex was detected by analysis of variance only on oestradiol concentrations, with females having higher serum concentrations than males during most of the age range studied. Significant peaks of testosterone and progesterone were also detected around hatching time. These results are consistent with the view that oestradiol is the major hormone implicated in the sexual differentiation of reproductive behaviour in the quail. The relationships between the circulating concentrations of oestradiol during ontogeny and the critical period of differentiation as postulated by currently accepted models is also discussed.
J. Endocr. (1988) 118, 127–134
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ABSTRACT
There is sexual dimorphism of specific species of mRNA in the neonatal rat brain and this sexual dimorphism may be imprinted by steroids of testicular origin during the perinatal period. According to current theories, only aromatizable androgens may cause sexual differentiation of sexual behaviour and function in the adult. The effects of oestradiol benzoate on mRNA synthesis in the neonatal female limbic system were therefore studied. In addition, cytosolic and nuclear oestrogen receptors were measured after administration of testosterone propionate, oestradiol benzoate or dihydrotestosterone (DHT). An attempt was made to distinguish between the brain oestrogen receptor and the plasma oestrogen-binding protein, alphafoetoprotein (AFP) by isoelectric focussing. After injection of 50 μg oestradiol benzoate s.c. to neonatal female rats, the expression of mRNA coding for sexually dimorphic proteins appeared to be changed to a male-type pattern. The overall density of labelling was noticeably greater and specific changes in labelled proteins were observed. These effects were observed within 3 h of injection. Both testosterone and oestradiol caused a marked depletion of cytosolic oestrogen receptors in the limbic system whereas DHT was ineffective in this respect. Nuclear receptors were present in equal abundance in male- and female-derived nuclei and only oestradiol was able to cause a significant (P < 0·025) increase in nuclear oestrogen receptors. The receptor and AFP could be distinguished by isoelectric focussing, since the pI of the receptor was 7·05, while that of AFP was 4·5. These results are consistent with the possibility that oestradiol alters transcription in the neonatal rat brain and may do this through the oestrogen receptor. Nevertheless, it is also possible that oestradiol could alter post-transcriptional events such as the stability of mRNA or the binding of tRNA to the polysomal complex.
Journal of Endocrinology (1989) 120, 83–88
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SUMMARY
Testosterone and androstenedione levels in plasma and testicular tissue of developing rats were measured using gas—liquid chromatography with electron capture detection. The major androgen of both the adult and early postnatal period of development was testosterone. Pooled plasma from 230 one-day-old male rats contained 0·027 μg. testosterone/100 ml. The concentration of testosterone in the testes at this age was 0·328 μg./g. wet tissue. With increasing age there was a decline in testosterone concentration in plasma as well as in gonadal tissue which lasted until about the age of 30 days. The period from 40 to 60 days was characterized by an increasing concentration of testosterone in the plasma and gonads. During adulthood, testosterone reached concentrations as high as 0·202 μg./100 ml. peripheral plasma.
Androstenedione could not be detected in the circulation during the critical period of neonatal neural sexual differentiation, but it was present in the testes at this stage. In the pubertal and adult stages androstenedione was found in the plasma and testes. Its concentration, particularly in adulthood, was not as great as that of testosterone.
These results indicate that testosterone is present in plasma and testicular tissue of the rat during the neonatal period when behavioural and physiological sexual differentiation is presumed to occur.
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ABSTRACT
The effects of testosterone propionate (TP) on brain mechanisms involved in the sexual differentiation of ultrasonic vocalizations were examined in Mongolian gerbils (Meriones unguiculatus). Treatment of neonatal females with TP fully masculinized the rate of emission of the upsweep precopulatory ultrasound during adult sexual interactions with oestrous females. Intracranial implantation of small crystals of TP mixed with cholesterol (65 ng) into females 1–15 h after birth also masculinized the upsweep vocalization emitted in adulthood. Implants of TP positioned in the hypothalamic area had a significantly greater masculinizing effect than TP implants outside this region, or pure cholesterol implants. Two other sexually dimorphic vocalizations, the modulated (mainly precopulatory) and unmodulated (mainly copulatory) calls were masculinized by systemic TP, but intracranial TP had no significant masculinizing action on these calls. Genital structures of females which received neonatal injections of TP were strongly virilized in that their clitorides were lengthened and male-type cornified spines were present on the glans. Females which had received intracranial implants of TP were not virilized peripherally in adulthood. We conclude that testosterone or its metabolites have a direct hypothalamic effect on the development of masculine upsweep vocalizations. Because the other vocalizations were insensitive to intracranial TP, the underlying neural tissues may have different thresholds of response to androgen.
J. Endocr. (1985) 107, 355–363
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It has long been recognized that one of the advantages of sexual reproduction, consisting of the fusion between a male and a female gamete derived from two different individuals, is the increased genetic diversity of the offspring resulting in improved adaptability to environmental changes (Maynard Smith, 1978).
The different genetic strategies
The existence of functional male and female individuals is essential for reproduction in mammals as well as the majority of species (though not all – parthenogenetic lizards are known; Cole, 1984) in other vertebrates. It might be supposed that the mechanisms of sex differentiation would be basically similar in all vertebrates. Instead of this, several variations on a theme exist for achieving what is effectively the same end. In both mammals and birds, sex is determined by specific, visibly distinguishable chromosomes. In mammals, males (the heterogametic sex) have an X and a Y chromosome, while females (homogametic) have two
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Abstract
Treatment of developing embryos of two diverse species of reptiles with fadrozole (a potent and specific nonsteroidal inhibitor of aromatase activity in mammals) resulted in the induction of male sex determination. In the first experiment, males were produced in an all-female parthenogenic species of lizard (Cnemidophorus uniparens). In the second experiment, male sex determination was induced in a turtle (Trachemys scripta) with temperature-dependent sex determination. The results support the hypothesis that the endogenous production of oestrogen may represent a pivotal step in the sex determination cascade of reptiles. Further, the production of male C uniparens indicates that the genes required for male sexual differentiation have not been lost in this parthenogenic lizard.
Journal of Endocrinology (1994) 141, 295–299
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ABSTRACT
Testosterone metabolism was studied by an in-vitro technique in the brain and cloacal gland of young male and female quail at different ages ranging from 7 days of incubation to 2 days after hatching. Very active metabolism, leading almost exclusively to the production of 5β-reduced compounds, was observed. 5β-Reductase activity remained high throughout the incubation period in the hypothalamus, decreased around the time of hatching in the cerebellum and decreased progressively between days 7 and 15 of incubation in the cloacal gland. These changes could be involved in the control of sexual differentiation: the high 5β-reductase in the brain possibly protects males from being behaviourally demasculinized by their endogenous testosterone while the decreasing 5β-reductase in the cloacal gland would progressively permit the masculinization of that structure.
J. Endocr. (1984) 102, 77–81
