Department of Biology, Advanced Facility for Avian Research, University of Western Ontario, London, Ontario, Canada.
PLoS One. 2012;7(7):e40060. doi: 10.1371/journal.pone.0040060. Epub 2012 Jul 6.
The song-control system is a network of discrete nuclei in the songbird brain that controls the production and learning of birdsong and exhibits some of the best-studied neuroplasticity found in the adult brain. Photoperiodic growth of the song-control system during the breeding season is driven, at least in part, by the gonadal steroid testosterone. When acting on neural tissue, however, testosterone can be metabolized into 5α-dihydrotestosterone (DHT) or 17β-estradiol (E2), which activate different hormonal signaling pathways. By treating adult starlings with both testosterone metabolites and metabolite antagonists, we attempted to isolate the effects of androgen and estrogen treatment on neuroplasticity during photostimulation in male and female European starlings (Sturnus vulgaris). Photostimulation resulted in a large HVC volume typical of the breeding season in all treatments independent of hormone treatment. E2 had additional effects on HVC growth by reducing neuron density and enhancing early survival of new neurons recruited to HVC in females but did not significantly affect HVC volume. Conversely, DHT reduced the migration of new neurons, assessed by the expression of doublecortin, to HVC. DHT also increased syrinx mass and maintained RA (robust nucleus of the arcopallium) cytoarchitecture in the presence of aromatase inhibitors. In addition, we document the first evidence of sex-specific neuroplastic responses of the song-control system to androgens and estrogens. These findings suggest that the contributions of DHT and E2 signaling in songbird neuroplasticity may be regulated by photoperiod and that future studies should account for species and sex differences in the brain.
歌曲控制系统是鸟类大脑中离散核团的网络，控制着鸟鸣的产生和学习，并表现出成年大脑中研究得最好的一些神经可塑性。繁殖季节中歌曲控制系统的光周期生长至少部分是由性腺类固醇睾丸激素驱动的。然而，当作用于神经组织时，睾丸激素可以代谢为 5α-二氢睾丸激素（DHT）或 17β-雌二醇（E2），它们激活不同的激素信号通路。通过用两种睾丸激素代谢物和代谢物拮抗剂处理成年麻雀，我们试图分离雄激素和雌激素处理对雄性和雌性欧洲麻雀（Sturnus vulgaris）光刺激期间神经可塑性的影响。光刺激导致 HVC 体积增大，这是所有治疗组在繁殖季节的典型特征，与激素治疗无关。E2 通过减少神经元密度和增强雌性 HVC 中募集的新神经元的早期存活，对 HVC 生长有额外的影响，但对 HVC 体积没有显著影响。相反，DHT 减少了新神经元向 HVC 的迁移，这可以通过双皮质蛋白的表达来评估。DHT 还增加了鸣管的质量，并在芳香酶抑制剂存在的情况下维持 RA（arcopallium 的粗壮核）细胞结构。此外，我们还记录了第一个关于雄激素和雌激素对鸣禽神经可塑性的性别特异性神经可塑性反应的证据。这些发现表明，DHT 和 E2 信号在鸣禽神经可塑性中的作用可能受到光周期的调节，未来的研究应该考虑到大脑中的物种和性别差异。
