Levels of serum steroids, aromatase activity, and estrogen receptors in preoptic area, hypothalamus, and amygdala of B6D2F1 male house mice that differ in the display of copulatory behavior after castration.

Abstract

Most male B6D2F1 hybrid house mice continue to copulate after castration (continuers), whereas others do not (noncontinuers). Copulation in continuers appears estrogen dependent. Serum testosterone (T), 17 beta-estradiol (E2), and dihydrotestosterone (DHT), as well as aromatase activity (AA) and estrogen receptor (ER) levels in preoptic area (POA), hypothalamus (HYP), and amygdala (AM) were measured to determine if continuers and noncontinuers differ in estrogen physiology. In general, continuers and noncontinuers did not differ in serum steroid levels, AA, or ER levels. Castration reduced AA in the POA, HYP, and AM. Castration did not affect nuclear ER levels in the POA and HYP but reduced nuclear ER in AM. The data demonstrate that castrated B6D2F1 male mice continue to be under the influence of circulating nongonadal E2 that is important for copulation.

Status-appropriate singing behavior, testosterone and androgen receptor immunolabeling in male European starlings (Sturnus vulgaris)

“…For example, in a variety of vertebrates, sexual behavior occurs even in the absence of elevated T ((Day et al, 2007; Foerster et al, 2002; Fusani et al, 2007; Moore, 1983; Moore and Kranz, 1983; Park et al, 2009; Park et al, 2004; Sinchak et al, 1996; Steiger et al, 2006; Wikelski et al, 2003); reviewed in Kempenaers et al (2008)). Here, mismatches provide an opportunity to consider both T and dominance status independently.…”

“…Finally, it has been suggested that the production of sexually-motivated behaviors in the absence of elevated AR activity can be maintained by activation of estrogen receptors (Canoine et al, 2007), or that continued sexual or agonistic behavior in the absence of elevated plasma T is dependent upon local steroid production within specific brain regions (Charlier et al, 2011; Park et al, 2004; Pradhan et al, 2010; Sinchak et al, 1996; Soma et al, 2008). An increase in neurosteroid activity may compensate for a lack of plasma T in birds with undetectable T. Future work is needed to examine this possibility and to examine potential roles for other non-hormonal neuromodulators.…”

Sexual behavior in male rodents

“…One strain, the B6D2F1 hybrid, recovered the ability to copulate about 3 weeks after castration without exogenous hormones (McGill and Manning, 1976). These "continuer" males depend on E 2 ; although the source of the E 2 is not clear, it may be produced in the brain (Sinchak et al, 1996).…”

Neuroendocrinology of Male Reproductive Behavior

“…Castration in these animals, as in other genotypes, caused a profound reduction in circulating levels of T (Clemens et al, 1988;Sinchak et al, 1996) and in removal of the adrenal glands, in addition, castration of B6D2F1 male mice failed to disrupt the postcastration maintenance of mating behavior (Thompson et al, 1976). Some evidence raises the possibility that the persistence of sexual behavior in castrated B6D2F1 males depends on the activational effects of E, which continues to circulate in very low concentrations in this as well as other mouse strains even after castration (Sinchak et al, 1996). Administration of the aromatase inhibitor, ATD, to castrated B6D2F1 significantly reduced the expression of sexual behavior (Sinchak et al, 1989).…”