Sex steroid levels in developing and adult male and female zebra finches (Poephila guttata)

The differential allocation hypothesis predicts that females invest more resources into reproduction when mating with attractive males. In oviparous animals this can include prefertilization decisions such as the production of larger eggs and the deposition of hormones, such as the steroid testosterone, into yolks. On the other hand, a compensatory hypothesis posits that females allocate more resources into the eggs when mated with males of inferior quality. In the present study, we show that free-living females of the collared flycatcher (Ficedula albicollis), a small passerine bird, do not produce larger eggs or deposit more testosterone into eggs when mating with attractive males reflected by a large forehead patch size, which is contrary to the prediction of the differential allocation hypothesis. However, we found higher yolk testosterone concentrations in eggs laid for young than older males. Because in young males genetic quality, parental experience, or willingness to invest into paternal care is likely to be low, high yolk testosterone level in their clutches may indicate that their females follow a compensatory tactic. They may elicit more paternal care from young, inexperienced males by hormonally increasing nestling begging. Laying date was also correlated with yolk testosterone level; however, when we controlled for it, male age still remained a strong determinant of testosterone allocation.

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“…Yolk testosterone was determined by RIA (Adkins-Regan et al, 1990). We homogenized 2-10 mg of yolk with 200 ll distilled water and 2000 c.p.m.…”

Section: Yolk Testosterone Assaymentioning

confidence: 99%

Female collared flycatchers adjust yolk testosterone to male age, but not to attractiveness

Michl¹,

Török²,

Péczely³

et al. 2004

Behavioral Ecology

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“…Endogenous androgens could provide an intrinsic signal regulating the maturation of NMDA-EPSCs in LMAN and RA, because testosterone levels increase over the course of song development in male zebra finches (Adkins-Regan et al 1990;Prove 1983). To confirm these hormonal changes, we measured plasma testosterone levels from a subset of the animals from which electrophysiological recordings were made (Fig.…”

Section: Androgens Hasten Nmda-epsc Maturation In Fledglings and Juvementioning

confidence: 99%

Androgens Modulate NMDA Receptor–Mediated EPSCs in the Zebra Finch Song System

White

Livingston

Mooney

1999

Journal of Neurophysiology

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Androgens potently regulate the development of learned vocalizations of songbirds. We sought to determine whether one action of androgens is to functionally modulate the development of synaptic transmission in two brain nuclei, the lateral part of the magnocellular nucleus of the anterior neostriatum (LMAN) and the robust nucleus of the archistriatum (RA), that are critical for song learning and production. We focused on N-methyl-D-aspartate-excitatory postsynaptic currents (NMDA-EPSCs), because NMDA receptor activity in LMAN is crucial to song learning, and because the LMAN synapses onto RA neurons are almost entirely mediated by NMDA receptors. Whole cell recordings from in vitro brain slice preparations revealed that the time course of NMDA-EPSCs was developmentally regulated in RA, as had been shown previously for LMAN. Specifically, in both nuclei, NMDA-EPSCs become faster over development. We found that this developmental transition can be modulated by androgens, because testosterone treatment of young animals caused NMDAEPSCs in LMAN and RA to become prematurely fast. These androgen-induced effects were limited to fledgling and juvenile periods and were spatially restricted, in that androgens did not accelerate developmental changes in NMDA-EPSCs recorded in a nonsong area, the Wulst. To determine whether androgens had additional effects on LMAN or RA neurons, we examined several other physiological and morphological parameters. In LMAN, testosterone affected ␣-amino-3-hydroxy-5-methyl-4-isoxazoleproprianate-EPSC (AMPA-EPSC) decay times and the ratio of peak synaptic glutamate to AMPA currents, as well as dendritic length and spine density but did not alter soma size or dendritic complexity. In contrast, testosterone did not affect any of these parameters in RA, which demonstrates that exogenous androgens can have selective actions on different song system neurons. These data are the first evidence for any effect of sex steroids on synaptic transmission within the song system. Our results support the idea that endogenous androgens limit sensitive periods for song learning by functionally altering synaptic transmission in song nuclei.

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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 steroid levels in developing and adult male and female zebra finches (Poephila guttata)

Cited by 229 publications

References 36 publications

Female collared flycatchers adjust yolk testosterone to male age, but not to attractiveness

Female collared flycatchers adjust yolk testosterone to male age, but not to attractiveness

Androgens Modulate NMDA Receptor–Mediated EPSCs in the Zebra Finch Song System

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

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