Act locally and think globally: Intracerebral testosterone implants induce seasonal-like growth of adult avian song control circuits

Brenowitz, Eliot A.; Lent, Karin

doi:10.1073/pnas.192308799

Cited by 83 publications

(70 citation statements)

References 68 publications

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“…Furthermore, increases in song control system nuclei volumes caused solely by exposure to a LD photoperiod are attenuated by exogenous administration of melatonin (25). Second, an intracranial T implant placed near HVC in male birds housed on a SD photoperiod is sufficient to induce growth of ipsilateral song control system nuclei (13). Third, our results show that HVC volume regresses rapidly in castrated birds even when they are kept on a LD photoperiod.…”

Section: Discussionmentioning

confidence: 57%

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Rapid seasonal-like regression of the adult avian song control system

Thompson

Bentley²,

Brenowitz

2007

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

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101

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We analyzed how rapidly avian song control nuclei regress after testosterone (T) withdrawal. Regression of neuronal attributes resulting from T withdrawal has been observed in several animal models. The time course over which regression occurs is not known, however. To address this issue, we castrated adult male white-crowned sparrows and rapidly shifted them to short-day photoperiods after being held under breeding conditions (longday photoperiod and systemic T exposure) for 3 weeks. We found that the volume of one song nucleus, HVC, regressed 22% within 12 h after T withdrawal. Changes in HVC neuron density after T withdrawal were dynamic; density increased at 12 h and then decreased by 4 days. HVC neuron number was reduced by 26% by 4 days. The volumes of Area X and the robust nucleus of the arcopallium (RA) were significantly regressed by 7 and 20 days, respectively. RA somatic area and neuronal spacing were significantly reduced by 2 days. The rapidity of HVC regression is unprecedented among vertebrate models of hormone-sensitive neural circuits. These results reveal that the rapid regression of the song control system provides a model for the important role sex steroid hormones play in mediating adult neural plasticity and in neuroprotection.birdsong ͉ neurodegeneration ͉ neuroprotection ͉ plasticity ͉ testosterone

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Section: Discussionmentioning

confidence: 57%

“…Lesions of HVC prevent the growth or induce the regression of RA and Area X in birds when they are first transferred to LDϩT or when they are maintained on LDϩT, respectively (12). T acts directly on HVC, which then acts transynaptically to stimulate growth of RA and Area X (13).…”

mentioning

confidence: 99%

Rapid seasonal-like regression of the adult avian song control system

Thompson

Bentley²,

Brenowitz

2007

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

Self Cite

101

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“…Unilateral lesions of HVC in LD photoperiod and systemic T-treated white-crowned sparrows block growth of RA and X on the ipsilateral, but not contralateral, hemisphere (Brenowitz and Lent, 2001). Small T implants unilaterally implanted near HVC in SD photoperiod-treated white-crowned sparrows increase the volumes of HVC, RA and X in the ipsilateral, but not contralateral, hemisphere, while T implants near RA have no effect (Brenowitz and Lent, 2002). Similarly, unilateral infusion of DHT and E2 near HVC in SD photoperiod exposed male white-crowned sparrows increases soma size and spontaneous firing rate in the ipsilateral, but not contralateral, RA, but DHT and E2 infused near RA have no effect (Meitzen et al, 2007a).…”

Section: Mechanisms Of Growth Photoperiod Increases Plasma T Levelmentioning

confidence: 88%

“…When small intercerebral T implants are unilaterally placed near either HVC or RA, neither nXIIts nor the syrinx increase in volume or mass, respectively (Brenowitz and Lent, 2002). Lesions of HVC prevented the growth of nXIIts (Brenowitz and Lent, 2001).…”

Section: Do Androgens Act Directly On Nxiits and The Syrinx?mentioning

confidence: 97%

Seasonal-like growth and regression of the avian song control system: Neural and behavioral plasticity in adult male Gambel’s white-crowned sparrows

Meitzen

Thompson

2008

General and Comparative Endocrinology

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Birdsong is regulated by a series of discrete brain nuclei known as the song control system. In seasonally-breeding male songbirds, seasonal changes in steroid sex hormones regulate the structure and electrophysiology of song control system neurons, resulting in dramatic changes in singing behavior. Male songbirds can be brought into the laboratory, where circulating levels of steroid hormone and photoperiod can be abruptly manipulated, providing controlled conditions under which rapid "seasonal-like" changes in behavior and morphology can be carefully studied. In this minireview, we will discuss the steroidal and cellular mechanisms underlying seasonal-like growth and regression of the song control system in adult male Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii), and its impact on song behavior. Specifically, we discuss recent advances concerning: 1) the role of androgen and estrogen receptors in inducing seasonal-like growth of the song control system; 2) how photoperiod modulates the time course of testosterone-induced growth of the song control system; 3) how bilateral intracerebral infusion of androgen and estrogen receptor antagonists near the song control nucleus HVC prevents seasonal-like increases in song stereotypy but not song rate; and 4) the steroidal and cellular mechanisms that mediate rapid regression of the song control system. Throughout this mini-review we compare data collected from white-crowned sparrows to that from other songbird species. We conclude by outlining avenues of future research.

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“…Songbirds, therefore, emerge as a powerful animal model to study the ability of projection (and inter-) neurons to specifically alter the steroidal milieu at synapses. Indeed, \trans-synaptic" steroid effects have been reported in the songbird brain (Gurney and Konishi, 1980;Brenowitz and Lent, 2002), suggesting that synaptic steroid provision may represent a powerful mode of E-provision in members of this order.…”

Section: Discussionmentioning

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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Act locally and think globally: Intracerebral testosterone implants induce seasonal-like growth of adult avian song control circuits

Cited by 83 publications

References 68 publications

Rapid seasonal-like regression of the adult avian song control system

Rapid seasonal-like regression of the adult avian song control system

Seasonal-like growth and regression of the avian song control system: Neural and behavioral plasticity in adult male Gambel’s white-crowned sparrows

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

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