雌性斑胸草雀发育和成体期发声核团LMAN中神经元数量的高水平维持(英文)

Neuronal number in song nucleus LMAN remains high in female zebra finches throughout development and in adulthood

鸟类的发声和发声学习涉及处于脑中不同水平的相互联系的一些发声核团。在很多鸟类中, 仅雄性鸣啭, 例如在斑胸草雀(Taeniogygia guttata) 中, 雌雄个体间存在显著的性差异, 雌性发声系统和发声核团中的神经元数量显著少于雄性。推测这种性差异也可能存在于弓状皮质前部大细胞外侧核(LMAN), 但有关这方面的报道还很少。为探讨雌雄鸣禽脑中神经元数量发育的规律, 我们应用半薄切片对斑胸草雀发育不同阶段的神经元数量和密度的变化进行了数量分析。结果表明, 在全部实验组中, 发育10 d和成体雌性LMAN中神经元的密度和神经元数量均无明显变化, 神经元的数量维持在一个较高水平。在雄鸟中, 我们发现在发育早期神经元的数量有极为显著的减少, 这与已有的报道, 即应用非类固醇技术获得的结果相似。LMAN中神经元数量的减少(57%) 一直持续到成体。因此, 成年雌鸟LMAN中的全部神经元数量是雄鸟的4 倍(P<0 001)。推测雌鸟脑中存在较多的神经元数量可能与其在发育和成体期间需维持适当的神经网络有关, 这种神经构筑对于动物种间识别等功能可能具有特殊意义。

Song learning and production in birds involve a discrete set of interconnected song nuclei in the avian brain. In species where only males sing, such as the zebra finch Taeniogygia guttata, large sex differences are present in song system nuclei and the number of neurons is much smaller in females compared to males. Whereas it is assumed that this also applies to the lateral magnocellular nucleus of the anterior nidopallium (LMAN), a detailed analysis is still lacking. To close this gap and to learn more about the development of neuronal numbers in both sexes, we have quantified neuronal density and number on semithin sections in small time intervals using the disector-technique. In females, neither neuronal density nor number increased or decreased significantly between 10 days and adulthood at any time interval sampled, so that neuronal density and number remained high in adult females. In males, we found a strong decrease in neuron number very early in development as known from literature using non-stereological techniques, and an additional decrease in neuron number (57%) that lasts up to adulthood. Therefore, the total number of neurons in LMAN in adult birds was about 4 times higher in females than in males (P<0.001). The larger neuronal number in females may reflect the ability of keeping up a neuronal network that can be used throughout development and in adulthood, probably for tasks that may be related particularly to species-specific recognition tasks as it has been shown for this brain region in other passerine female birds.