Thompson Christopher K, Bentley George E, Brenowitz Eliot A
Graduate Program in Neurobiology and Behavior, University of Washington, Box 351525, Seattle, WA 98195-1525, USA.
Proc Natl Acad Sci U S A. 2007 Sep 25;104(39):15520-5. doi: 10.1073/pnas.0707239104. Epub 2007 Sep 17.
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 (long-day 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.
我们分析了睾酮（T）撤除后鸟类鸣叫控制核团退化的速度。在几种动物模型中都观察到了因T撤除导致的神经元属性退化。然而，退化发生的时间进程尚不清楚。为了解决这个问题，我们对成年雄性白冠雀进行阉割，并在将它们置于繁殖条件下（长日照光周期和全身性T暴露）3周后，迅速将它们转移到短日照光周期环境中。我们发现，在T撤除后12小时内，一个鸣叫核团HVC的体积缩小了22%。T撤除后HVC神经元密度的变化是动态的；密度在12小时时增加，然后在4天时下降。到4天时，HVC神经元数量减少了26%。X区和弓状皮质粗壮核（RA）的体积分别在7天和20天时显著缩小。RA的体细胞区域和神经元间距在2天时显著减小。在激素敏感神经回路的脊椎动物模型中，HVC退化的速度是前所未有的。这些结果表明，鸣叫控制系统的快速退化提供了一个模型，说明了性类固醇激素在介导成年神经可塑性和神经保护中所起的重要作用。
