Sex differences in plasma concentrations of steroids during the sensitive period for brain differentiation in the zebra finch

Hutchison, J.B.; Wingfield, J. C.; Hutchison, R. E.

doi:10.1677/joe.0.1030363

Cited by 168 publications

(78 citation statements)

References 29 publications

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“…Moreover, estrogen levels were unrelated to body weight or body fat content, suggesting that these are unimportant determinants of circulating estrogens (20). Thus, we have confirmed previous reports that estrogens circulate at comparable levels in adult males and females (7,8) and are not reduced following castration of adult males (8).…”

Section: Resultssupporting

confidence: 92%

“…Because other tissues lack this enzyme, we conclude that the telencephalon is also the most likely source of estrogens that are found to circulate at high levels in blood of male songbirds (7)(8)(9)(10)(11). This idea is supported further by the observation that levels of both telencephalic aromatase and plasma estradiol are low in nonpasserine birds (17,21,23,27,28).…”

Section: Discussionmentioning

confidence: 52%

“…Subsequent studies in zebra finches and other songbirds showed that estrogens circulate at appreciable levels in both young and adult males. Presumably, this circulating estrogen is involved in the ontogeny and activation of singing behavior (7)(8)(9)(10)(11)(12). However, castration of males does not prevent the development of song (10,(13)(14)(15), does not eliminate estrogens in the circulation of developing males (10), and can increase levels of estrogens in adult males (8).…”

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confidence: 99%

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Brain is the major site of estrogen synthesis in a male songbird.

Schlinger

Arnold

1991

Proc. Natl. Acad. Sci. U.S.A.

188

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The neural system controlling song in passerine birds can undergo striking morphological and functional changes during both development and adulthood, and many of these changes are regulated by estrogenic hormones. Estrogens circulate at high levels in blood of male songbirds and persist after castration. We measured the activity of aromatase, the enzyme that converts androgens to estrogens, in various tissues from adult male and female zebra rinches. As expected, aromatase activity was present in male hypothalamus/preoptic area and pituitary and female ovary, but aromatase was unusually active in whole telencephalon of males and females. By contrast, activity was undetected in testes, adrenals, or other tissues of males. These results suggest that brain is the source of circulating estrogens in the male zebra rmch and that estrogen actions on the song system result from local rather than peripheral aromatization.

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Section: Resultssupporting

confidence: 92%

Section: Discussionmentioning

confidence: 52%

mentioning

confidence: 99%

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Brain is the major site of estrogen synthesis in a male songbird.

Schlinger

Arnold

1991

Proc. Natl. Acad. Sci. U.S.A.

188

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“…Three studies have used radioimmunoassays to investigate whether sex differences in plasma hormones exist during development. In the first (Hutchison et al, 1984), E2 and three androgens (T, androstenedione [AE] and DHT) were measured on post-hatching days 1-10. E2 concentrations increased in males from days 2-4, and then by day 10 had declined to those present on day 1.…”

Section: Descriptive Studiesmentioning

confidence: 99%

Zebra finch sexual differentiation: The aromatization hypothesis revisited

Wade

2001

Microscopy Res & Technique

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Zebra finches have emerged as an outstanding model system for the investigation of the mechanisms regulating brain and behavior. Their song system has proven especially useful, as the function of discrete anatomical regions have been identified, and striking parallels exist between the morphology of these regions and the level of their function in males and females. That is, the structures are substantially more developed in males, who sing, compared to females, who do not. These parallels extend from higher (telencephalic) centers to the brainstem motor nucleus that innervates the muscles of the vocal organ. Other dimorphic aspects of reproduction in the zebra finch, such as copulatory behaviors and sexual partner preference, however, are not associated with known sex differences in anatomy. In many species, sex differences in neural and peripheral structures and behavior are regulated by secretions from the gonads, which of course are sexually dimorphic themselves. In birds, sex differences at all of these levels (gonad, brain, and behavior) can be mediated by steroid hormones. However, it is not entirely clear that gonadal secretions normally participate at all of the levels. This paper reviews the evidence relating to the role of gonadal steroids in the sexual differentiation of reproductive behaviors and the central and peripheral structures known to regulate them in zebra finches, with a focus on estradiol, which has been most extensively studied in the masculinization of song system morphology and function.

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“…However, these welldocumented effects are difficult to reconcile with several characteristics of E-provision. In the zebra finch, neither circulating E (Adkins- Regan et al, 1990;Schlinger and Arnold, 1992; but see Hutchison et al, 1984), neural aromatase transcription (Shen et al, 1995;Saldanha et al, 1998), nor neural aromatase activity (Vockel et al, 1988(Vockel et al, , 1990Schlinger andArnold, 1991, 1992;Saldanha et al, 1998) has been found to differ between males and females. Lastly, somal aromatase expression is not dimorphic (Saldanha et al, 2000;Peterson et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Subcellular compartmentalization of aromatase is sexually dimorphic in the adult zebra finch brain

Rohmann

Schlinger

Saldanha

2006

Developmental Neurobiology

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ABSTRACT:The vertebrate brain is a source of estrogen (E) via the expression of aromatase (E-synthase). In the zebra finch (Taeniopygia guttata), despite documented dimorphisms in E-action, no differences are detectable in circulating E, or the neural levels of aromatase transcription, activity, or somal protein expression. Studies of aromatase expression at the lightand electron-microscope levels reveal greater numbers of fibers and presynaptic boutons in adult males relative to females. We assayed aromatase activity and content in synaptosomes and microsomes from the anterior [containing lMAN and Area X (males)] and posterior telencephalon (containing HVC and RA) of adult birds. In contrast to non-song birds and mammals, both cell fractions contain abundant aromatase measurable in terms of activity (enzyme assays) and content (Western blots) with minimal enrichment in microsomes. From brain homogenates of identical concentration, aromatase activity was higher in the synaptosomal relative to the microsomal fraction, in males relative to females, and in the posterior compared to anterior telencephalon. These effects were driven by high levels of synaptosomal aromatase in the male posterior telencephalon. These data suggest that males possess more aromatase per presynaptic bouton, or a greater number of aromatase-containing presynaptic boutons than females in the posterior telencephalon. Further, the present report reveals synaptic aromatization as a considerable source of E in the zebra finch brain, and supports the idea that telencephalic synapses in and around the adult male song production nuclei may be exposed to higher levels of E compared to the female brain. ' 2006 Wiley Periodicals, Inc. J Neurobiol 67: 1-9, 2007

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Sex differences in plasma concentrations of steroids during the sensitive period for brain differentiation in the zebra finch

Cited by 168 publications

References 29 publications

Brain is the major site of estrogen synthesis in a male songbird.

Brain is the major site of estrogen synthesis in a male songbird.

Zebra finch sexual differentiation: The aromatization hypothesis revisited

Subcellular compartmentalization of aromatase is sexually dimorphic in the adult zebra finch brain

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