Intrahypothalamic Implants of Testosterone or Estradiol and Resumption of Masculine Sexual Behavior in Long-term Castrated Male Rats

Christensen, L. W.; Clemens, Lynwood G.

doi:10.1210/endo-95-4-984

Cited by 211 publications

(61 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Testosterone secreted from the testes reaches the brain largely as a prohormone [1, 2], and exerts its effects mainly via conversion to estrogen in the neural tissues in many male mammals [3, 4]. This local conversion to estrogen is catalyzed by aromatase (P450arom), which is highly expressed in specific brain regions including the hypothalamus and limbic areas during the period of development [5, 6]and adulthood [7, 8].…”

Section: Introductionmentioning

confidence: 99%

Alteration in Sex-Specific Behaviors in Male Mice Lacking the Aromatase Gene

2003

View full text Add to dashboard Cite

Brain aromatase (P450arom) is a key enzyme in estrogen biosynthesis from testicular androgens. This local aromatization in neural tissues is thought to be an important process for sexual differentiation and activation of sexual behavior in male rodents. To determine the functional significance of the aromatase gene in development and activation of sex-specific behavior, we analyzed a series of behavioral profiles in gonadally intact male mice with targeted disruption of exons 1 and 2 of the aromatase gene (ArKO). In most cases, ArKO males were infertile and showed deficits in male sexual behavior including mount, intromission and ejaculation. Noncontact penile erection was not significantly affected by deletion of the aromatase gene. A great reduction of aggressive behavior against male intruders was also observed in ArKO males, while they tended to exhibit aggression toward estrous females during male copulatory tests. Furthermore, 73% of ArKO males showed infanticide toward pups, whereas characteristic parental behavior, but not infanticide, was observed in wild-type males. These results support the brain aromatization hypothesis and indicate that aromatase gene expression is a critical step not only for motivational and consummatory aspects of male sexual behavior, but also for aggressive and parental behaviors in male mice.

show abstract

Section: Introductionmentioning

confidence: 99%

Alteration in Sex-Specific Behaviors in Male Mice Lacking the Aromatase Gene

2003

View full text Add to dashboard Cite

show abstract

“…In addition, drugs that inhibit aromatization block male sexual behaviour ( 5 , 7, 16) and when anti-hormones are administered along with T replacement the blockade of oestrogen receptors inhibits sexual behaviour (14,17,18). (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23).…”

mentioning

confidence: 99%

Evidence that Neural Aromatization of Androgen Regulates the Expression of Sexual Behaviour in Female Musk Shrews

Rissman

1991

J Neuroendocrinology

View full text Add to dashboard Cite

The experiments reported on here were conducted to test the hypothesis that sexual behaviour in the female musk shrew (Suncus murinus) is regulated by the neural aromatization of testosterone to oestradiol. In the first experiment ovariectomized animals received subcutaneous hormone implants containing either an aromatizable androgen (testosterone or androstenedione), a nonaromatizable androgen (dihydrotestosterone or methyltrienolone), or cholesterol. Only females that received an aromatizable androgen exhibited significant amounts of sexual behaviour as compared with controls (cholesterol). To examine the role of the oestrogen receptor, the anti-oestrogen, tamoxifen (200 or 400 pg daily) was given to ovary intact or ovariectomized females treated with testosterone. Tamoxifen treatment had significant negative effects both on female sexual behaviour and on the weights of several peripheral tissues as compared with control treatments. A similar set of experiments was conducted to examine the effect of an anti-androgen on female sexual behaviour. The androgen receptor blocker, flutamide, had no effect on sexual behaviour or weights of peripheral tissues. To determine whether flutamide can act as an anti-androgen in this species two final experiments were conducted in male musk shrews. Flutamide treatment in males did affect several measures of sexual behaviour. In summary, these data demonstrate that the oestrogen receptor is involved in the control of female copulatory behaviour. The androgen receptor plays a role in the expression of male, but not female, sexual behaviour. Female musk shrews display copulatory behaviour in advance of follicular development when oestradiol concentrations in plasma are very low. Thus, they may have evolved a strategy of aromatizing peripherally produced androgens in the brain to concentrate the oestrogen required for the expression of sexual behaviour.The steroid hormone testosterone (T) can enter its many target tissues via one of two avenues. T can either bind to androgen receptors directly or after it has been reduced to one of its androgenic metabolites. Alternatively, T may be aromatized in the cytoplasm to oestradiol (E2) and the nucleus can be accessed via binding to oestrogen receptors (1 -3). Somewhat paradoxically, peripherally produced T appears to require neural aromatization (and subsequent binding to oestrogen receptors) in order to promote copulatory behaviour in a number of male animalsThe largest data sets that test the aromatization hypothesis have been generated in male rats and quail. The evidence supporting the hypothesis is that first, after castration and hormone replacement, either T or pharmacological doses of E, are able to reinstate male sexual behaviour (13,15,22,23). Second, only androgens that can be aromatized to oestrogens are behaviourally effective after castration (6,13,15,16,22). In addition, drugs that inhibit aromatization block male sexual behaviour ( 5 , 7, 16) and when anti-hormones are administered along with T replacement the blo...

show abstract

“…These results suggest that androgens exert motivational effects necessary for the display of male sexual behavior presumably by acting within the central nervous system. This interpretation was confirmed by studies in which direct CNS steroid manipulations were performed [23, 24]. …”

Section: Discussionmentioning

confidence: 68%

Sex Differences in Male-Typical Copulatory Behaviors in Response to Androgen and Estrogen Treatment in Rats

Roselli

Chambers

1999

Neuroendocrinology

View full text Add to dashboard Cite

The present experiment was performed to test the hypothesis that gender differences in the capacity for brain estrogen synthesis could constitute a sexually dimorphic mechanism that limits the activational effects of testosterone (T) in females, and enhances them in males. We determined the effects of treatments with equivalent levels of either T or estradiol (E₂) on olfactory behavior and mounting in age-matched heterosexually naive gonadectomized male and female rats that were genitally ansthetized with lidocaine paste in order to minimize the contribution of sexually dimorphic somatosensory inputs to the expression of copulatory behavior. We found that T stimulated mounting to a greater extent in males than in females, but had equivalent effects on mount latency and genital investigation in the two sexes. On the other hand, E₂ stimulated equivalent levels of mounting in males and females and reduced mount latency to a similar extent in males and females. However, E₂ had a pronounced effect on the levels of genital investigation in males but not in females. Serum steroid levels and the levels of nuclear steroid receptor occupation in the brain were not different between males and females, suggesting that the behavioral differences between males and females cannot be attributed to differences in peripheral steroid metabolism or brain uptake. The results obtained corroborate previous studies suggesting that female rats normally undergo considerable male-typical behavioral masculinization during fetal development. However, such male-typical features of normal development in female rats do not extend to the regulation of preoptic aromatase activity or to the capacity of females to display olfactory behaviors in response to adult E₂ exposure, functions which are sexually dimorphic even in the rat. The present results support the view that gender differences in the capacity for brain estrogen synthesis contribute to the sexually dimorphic display of T-stimulated male-typical sexual motivation and copulatory behavior in rats.

show abstract

Intrahypothalamic Implants of Testosterone or Estradiol and Resumption of Masculine Sexual Behavior in Long-term Castrated Male Rats

Cited by 211 publications

References 1 publication

Alteration in Sex-Specific Behaviors in Male Mice Lacking the Aromatase Gene

Alteration in Sex-Specific Behaviors in Male Mice Lacking the Aromatase Gene

Evidence that Neural Aromatization of Androgen Regulates the Expression of Sexual Behaviour in Female Musk Shrews

Sex Differences in Male-Typical Copulatory Behaviors in Response to Androgen and Estrogen Treatment in Rats

Contact Info

Product

Resources

About