Sexual differentiation of behavior in the zebra finch: Effect of early gonadectomy or androgen treatment

Adkins‐Regan, Elizabeth; Ascenzi, Mary

doi:10.1016/0018-506x(90)90031-r

Cited by 76 publications

(32 citation statements)

References 16 publications

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“…Sex differences in plasma steroid levels or brain aromatase have not been consistently detected in zebra finches after hatching (Hutchison et al, 1984;Schlinger and Arnold, 1992;Wade et al, 1995;Saldanha et al, 2000;Wade, 2001). Perhaps more importantly, castration or treatment with inhibitors of androgen or estrogen action or availability have typically not prevented normal masculinization of the song system (Arnold, 1975;Mathews et al, 1988;Adkins-Regan and Ascenzi, 1990;Arnold, 1990, 1991;Schlinger and Arnold, 1991;Springer and Wade, 1997;Wade et al, 1999).…”

Section: Introductionmentioning

confidence: 92%

Enhanced gene expression in the forebrain of hatchling and juvenile male zebra finches

et al. 2005

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The molecular mechanisms regulating sexual differentiation of the brain are largely unknown, although progress is being made, particularly in some mammalian systems. To uncover more of the key factors, a screen was conducted for genes involved in sexually dimorphic development of the neural song system in zebra finches. cDNA microarrays were initially used to compare gene expression in the telencephalons of hatchling and juvenile males and females. Then, real-time quantitative polymerase chain reaction (PCR) was employed to confirm sex differences, and the brain regions expressing the cDNAs of interest were localized using in situ hybridization. Several genes, including those likely to encode two ribosomal proteins (RPL17 and RPL37), SCAMP1, ZNF216, and a COBW-domain containing protein, showed enhanced expression in the telencephalon of males compared to females. In several cases, expression in the song control nuclei specifically was detected only in males. Interestingly, the sequences of some of these cDNAs shared substantial homology with regions of the chicken Z chromosome (male birds are ZZ, females ZW). Thus, we have identified genes likely to be involved in masculinization of the structure and/or function of the song circuit, some of which could be initial triggers for the sexual differentiation process.

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Section: Introductionmentioning

confidence: 92%

Enhanced gene expression in the forebrain of hatchling and juvenile male zebra finches

et al. 2005

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“…In contrast, in zebra finches (Taeniopygia guttata), early exposure to estradiol can masculinize behavior of females (song and sexual partner preference), but testosterone exposure has little effect. (43) Thus, where organization of sexually dimorphic traits by sex steroids has been shown in non-mammalian vertebrates, there exists large variation in how these hormones affect the phenotype. (42) Research on the organization of traits by steroid hormones in lower vertebrates is still in its infancy compared to mammals or birds, but so far the majority of sex-specific traits appear to be activated rather than organized.…”

Section: Sexual Differentiationmentioning

confidence: 99%

Regulation of male traits by testosterone: implications for the evolution of vertebrate life histories

Hau¹

2007

BioEssays

503

350

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The negative co-variation of life-history traits such as fecundity and lifespan across species suggests the existence of ubiquitous trade-offs. Mechanistically, trade-offs result from the need to differentially allocate limited resources to traits like reproduction versus self-maintenance, with selection favoring the evolution of optimal allocation mechanism. Here I discuss the physiological (endocrine) mechanisms that underlie optimal allocation rules and how such rules evolve. The hormone testosterone may mediate life-history trade-offs due to its pleiotropic actions in male vertebrates. Conservation in the actions of testosterone in vertebrates has prompted the 'evolutionary constraint hypothesis,' which assumes that testosterone signaling mechanisms and male traits evolve as a unit. This hypothesis implies that the actions of testosterone are similar across sexes and species, and only the levels of circulating testosterone concentrations change during evolution. In contrast, the 'evolutionary potential hypothesis' proposes that testosterone signaling mechanisms and male traits evolve independently. In the latter scenario, the linkage between hormone and traits itself can be shaped by selection, leading to variation in trade-off functions. I will review recent case studies supporting the evolutionary potential hypothesis and suggest micro-evolutionary experiments to unravel the mechanistic basis of life-history evolution.

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“…Controls (Group 1: n ϭ 3) were left intact and treated orally with 20 l saline daily for 35 days. The remainder of the birds were castrated and allowed to recover for 7 days following which low E birds (Group 2: n ϭ 3) were implanted with a blank Silastic implant (see Adkins-Regan and Ascenzi, 1990) and fed 20 g fadrozole (a potent aromatase inhibitor; Wade et al, 1994) daily for 35 days, whereas replaced E birds (Group 3: n ϭ 3) were implanted with a 5-mm Silastic implant (Adkins-Regan and Ascenzi, 1990) containing E and fed fadrozole orally. Oral treatments were administered with a micropipette containing 20 l of either saline (controls) or a 1 mg/ml solution of fadrozole in saline.…”

Section: Experiments 5: Influence Of Circulating Estradiol (E) On Arommentioning

confidence: 99%

Distribution and regulation of telencephalic aromatase expression in the zebra finch revealed with a specific antibody

et al. 2000

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In songbirds, aromatase (estrogen synthase) activity and mRNA are readily detectable in the brain. This neural aromatization presumably provides estrogen to steroid-sensitive targets via autocrine, paracrine, and synaptic mechanisms. The location of immunoreactive protein, however, has been difficult to describe completely, particularly in distal dendrites, axons, and terminals of the forebrain. Here we describe the neuroanatomical distribution of aromatase in the zebra finch by using a novel antibody raised specifically against zebra finch aromatase. The distribution of aromatase-positive somata in the zebra finch brain is in excellent agreement with previous reports. Additionally, this antibody reveals elaborate, spinous dendritic arbors, fine-beaded axons, and punctate terminals of telencephalic neurons that may synthesize estrogen. Some of these axon-like fibers extend into the high vocal center (HVC) and the robust nucleus of the archistriatum (RA) in males and females, suggesting a role for presynaptic aromatization in cellular processes within these loci. Adult males have more aromatase-positive fibers in the caudomedial neostriatum (NCM) and the preoptic area (POA) compared to females, despite the lack of detectable sex differences in the number of immunoreactive somata at these loci. Thus, the compartmentalization of aromatase in dendrites and axons may serve a sexually dimorphic function in the songbird. Finally, in adult males, aromatase expression is down-regulated by circulating estradiol in the hippocampus, but not in the NCM or POA. The distribution of aromatase suggests a role for aromatization in the regulation of pre- and postsynaptic function in steroid sensitive areas of the songbird forebrain.

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Sexual differentiation of behavior in the zebra finch: Effect of early gonadectomy or androgen treatment

Cited by 76 publications

References 16 publications

Enhanced gene expression in the forebrain of hatchling and juvenile male zebra finches

Enhanced gene expression in the forebrain of hatchling and juvenile male zebra finches

Regulation of male traits by testosterone: implications for the evolution of vertebrate life histories

Distribution and regulation of telencephalic aromatase expression in the zebra finch revealed with a specific antibody

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