Shukla Vidya, Rani Sangeeta, Malik Shalie, Kumar Vinod, Sadananda Monika
Brain Research Laboratory, Biotechnology Unit, Department of Biosciences, Mangalore University, Mangalagangothri, 574199, Karnataka, India.
Department of Zoology, University of Lucknow, Lucknow, 226007, India.
Exp Brain Res. 2020 Oct;238(10):2245-2256. doi: 10.1007/s00221-020-05888-7. Epub 2020 Jul 27.
Neural substrates, including brain areas, differential gene expression and neuroendocrine basis, of migration are known. However, very little is known about structural changes in the brain that underlie the development and cessation of migration in long-distance avian migrants. Towards this, we investigated neuromorphological changes in the higher-order associative areas in male redheaded bunting (Emberiza bruniceps), which is a Palaearctic-Indian night migrant with wintering grounds in India. Photosensitive birds (8L:16D; SD) were exposed to stimulatory long days (16L:8D; LD), with controls retained on non-stimulatory short days. LD birds depicted shifts to, and sustained night-time activity as recorded by actograms. LD birds demonstrated increased body mass, fat deposition and testicular volume in keeping with the migratory phenotype. When LD birds had exhibited 10.0 ± 2.4 cycles of Zugunruhe (intense nighttime activity in captives, akin to night migratory flight in the wild), bird brains were fixed by transcardial perfusion, and changes in the neuronal morphometry of pallial, sub-pallial and hypothalamic brain regions studied using rapid Golgi technique with modifications, as used and validated in our laboratory. There were significant differences in both area and perimeter of soma in the visual hyperpallium apicale implicated in migratory orientation and the neuroendocrine control region for timing of migration, the mediobasal hypothalamus. We attribute these neuromorphometric changes in the soma area and perimeter to the photostimulated changes associated with the development of migration and reproductive phenotypes in redheaded buntings. It is suggested that changes in the neuronal plasticity in brain control regions parallel photoperiod-induced physiological responses.
已知迁移的神经基质，包括脑区、差异基因表达和神经内分泌基础。然而，对于长距离候鸟迁移的开始和停止所依赖的大脑结构变化，我们却知之甚少。为此，我们研究了雄性赤头鹀（Emberiza bruniceps）高级联合区域的神经形态变化，赤头鹀是一种古北界 - 印度的夜行性候鸟，在印度越冬。将光敏鸟类（8小时光照：16小时黑暗；短日照）暴露于刺激性长日照（16小时光照：8小时黑暗；长日照）下，对照组保持在非刺激性短日照条件下。长日照鸟类表现出如活动记录图所示的向夜间活动的转变并持续夜间活动。长日照鸟类表现出体重增加、脂肪沉积和睾丸体积增大，符合迁徙表型。当长日照鸟类表现出10.0 ± 2.4个 Zugunruhe周期（圈养中强烈的夜间活动，类似于野外的夜间迁徙飞行）时，通过心脏灌注固定鸟类大脑，并使用在我们实验室使用和验证过的改良快速高尔基技术研究脑皮层、皮层下和下丘脑脑区的神经元形态测量变化。在与迁徙方向相关的视觉顶叶高级皮层和迁徙时间的神经内分泌控制区域——内侧基底下丘脑，其胞体的面积和周长均存在显著差异。我们将胞体面积和周长的这些神经形态测量变化归因于与赤头鹀迁徙和生殖表型发展相关的光刺激变化。有人提出，大脑控制区域神经元可塑性的变化与光周期诱导的生理反应平行。
