title: Aromatase inhibition affects testosterone-induced masculinization of song and the neural song system in female canaries.
abstract: Songbirds have a specialized steroid-sensitive network of brain nuclei, the song system, for controlling song. Most nuclei of the song system express androgen receptors, and the sensory-motor integration nucleus High Vocal Center (HVC) alone also expresses estrogen receptors. Apart from expressing estrogen receptors in the vocal control system, songbirds are unique among birds because they have high concentrations of the estrogen-synthesizing enzyme aromatase in the neostriatum surrounding HVC. However, the role of estrogen in controlling the development of the song structure has been scarcely investigated. In this work, we show that blocking the production of estrogen during testosterone-induced song motor development in adult female canaries alters the song pattern compared to control females treated with testosterone only. These effects were correlated with inhibition of the expression of estrogen-sensitive genes, such as brain-derived nerve growth factor, in HVC. The expression of the ATP-synthase gene, an indicator of cell activity, in HVC, and the size of HVC, were not affected by the treatment. Our results provide the first example of estrogen-sensitive mechanisms controlling the structural features of adult birdsong.
authors.affiliation: Research Centre for Ornithology of the Max-Planck-Society, 82346 Andechs, Germany. lfusani@physci.ucla.edu
authors.forename: Leonida
authors.initials: L
authors.lastname: Fusani
authors.forename: Reinhold
authors.initials: R
authors.lastname: Metzdorf
authors.forename: John B
authors.initials: JB
authors.lastname: Hutchison
authors.forename: Manfred
authors.initials: M
authors.lastname: Gahr
mesh_terms: D025181:ATP Synthetase Complexes / Q000187:drug effects / Q000235:genetics; D000704:Analysis of Variance; D000818:Animals; D001141:Aromatase / Q000502:physiology; D047072:Aromatase Inhibitors; D001483:Base Sequence; D001921:Brain / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D019208:Brain-Derived Neurotrophic Factor / Q000187:drug effects / Q000235:genetics; D002171:Canaries / Q000502:physiology; D013196:Dihydrotestosterone / Q000097:blood; D004343:Drug Implants; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004958:Estradiol / Q000097:blood; D017316:Fadrozole / Q000494:pharmacology; D005260:Female; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D009132:Muscles; D009474:Neurons / Q000166:cytology / Q000201:enzymology; D012333:RNA, Messenger / Q000096:biosynthesis; D011944:Receptors, Androgen / Q000096:biosynthesis; D011960:Receptors, Estrogen / Q000096:biosynthesis; D013018:Sound Spectrography / Q000295:instrumentation; D018709:Statistics, Nonparametric; D013739:Testosterone / Q000494:pharmacology*; D014828:Vocalization, Animal / Q000187:drug effects* / Q000502:physiology
chemical_list: D047072:Aromatase Inhibitors; D019208:Brain-Derived Neurotrophic Factor; D004343:Drug Implants; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D011944:Receptors, Androgen; D011960:Receptors, Estrogen; D013196:Dihydrotestosterone; D013739:Testosterone; D004958:Estradiol; D001141:Aromatase; D025181:ATP Synthetase Complexes; D017316:Fadrozole