title: Expression of androgen receptor mRNA in zebra finch song system: developmental regulation by estrogen.
abstract: By using improved methods for in situ hybridization to detect expression of androgen receptor (AR) mRNA, the distribution of expression was mapped in the adult male zebra finch brain. In the neural song circuit, robust expression was found in area X of the lobus parolfactorius (LPO) as well as in other song regions previously reported. Expression was also found in many areas of the hypothalamus and dorsal thalamic nuclei, nucleus intercollicularis and ventricular areas of the midbrain, cerebellar Purkinje and granule cells, the hyperstriatum, medial neostriatum, medial LPO, and archistriatum. In juvenile males, AR mRNA expression was first detected in nucleus high vocal center (HVC) at posthatch day 9 (P9), in area X at P9-P11, and in the region of the robust nucleus (RA) in the medial archistriatum by P7. Estrogen treatment of hatchling females caused an increase in the expression of AR mRNA in HVC and area X by P11, whereas treatment of hatchling males with the aromatase inhibitor fadrozole decreased the expression of AR mRNA at P11. The present results indicate that masculine development of AR expression begins in area X and HVC before they are thought to be synaptically connected, suggesting that different song nuclei initiate sexual differentiation independently of transsynaptic masculinizing influences. The present results suggest that estrogen is necessary for full masculine AR expression in the song system and that the estrogenic regulation of AR contributes to subsequent differential actions of androgen in male and female song nuclei.
authors.affiliation: Department of Physiological Science and Laboratory of Neuroendocrinology of the Brain Research Institute, University of California, Los Angeles, Los Angeles, California 90095, USA.
authors.forename: Yong-Hwan
authors.initials: YH
authors.lastname: Kim
authors.forename: William R
authors.initials: WR
authors.lastname: Perlman
authors.forename: Arthur P
authors.initials: AP
authors.lastname: Arnold
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001345:Autoradiography / Q000379:methods; D001921:Brain / Q000033:anatomy & histology / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D001923:Brain Chemistry; D002452:Cell Count / Q000379:methods; D004965:Estrogen Antagonists / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology*; D017316:Fadrozole / Q000494:pharmacology; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D017403:In Situ Hybridization / Q000379:methods; D008297:Male; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism*; D012727:Sex Characteristics; D012733:Sex Differentiation; D020308:Songbirds; D014828:Vocalization, Animal
chemical_list: D004965:Estrogen Antagonists; D004967:Estrogens; D012333:RNA, Messenger; D011944:Receptors, Androgen; D017316:Fadrozole