Singh Tryambak D, Heinrich Julie E, Wissman Anne M, Brenowitz Eliot A, Nordeen E J, Nordeen K W
Department of Brain and Cognitive Sciences, University of Rochester, Rochester, New York 14627, USA.
J Neurobiol. 2003 Mar;54(4):593-603. doi: 10.1002/neu.10178.
Developmental changes in the composition and function of N-methyl-D-aspartate receptors (NMDARs) are believed to regulate neural plasticity. For example, in songbirds, vocal learning entails NMDAR activation, and the sensitive period for such learning in zebra finches (ZFs) parallels developmental changes in NMDAR density and phenotype within several song-related brain regions. In contrast to ZFs, canaries exhibit vocal plasticity recurrently throughout adulthood, prompted by seasonal changes in day length and testosterone (T) levels. We used in situ hybridization to determine if such changes in photoperiod affect NMDAR subunit expression in adult canaries. Birds were sacrificed while on short days (SD) when T levels were low, or on long days (LD) when T levels were high. Transcript levels for the constitutive NMDAR subunit (NR1) and two modulatory subunits (NR2A, NR2B) were measured in four song control nuclei: lMAN, Area X, HVc, and RA. NR1 and NR2A mRNA levels were comparable in SD and LD groups in all four song regions studied. However, NR2B mRNA levels within lMAN and RA were significantly higher in SD than in LD birds. Photoperiod did not affect NR2B transcript levels in Area X, HVc, or a nonsong region just lateral to lMAN. Our data support the hypothesis that changes in NMDAR subunit expression may contribute to the neural and behavioral reorganization that accompanies seasonal song remodeling in adulthood.
N-甲基-D-天冬氨酸受体（NMDARs）的组成和功能的发育变化被认为可调节神经可塑性。例如，在鸣禽中，发声学习需要NMDAR激活，而斑胸草雀（ZFs）这种学习的敏感期与几个与鸣叫相关的脑区中NMDAR密度和表型的发育变化平行。与斑胸草雀不同，成年金丝雀在整个成年期都会反复表现出发声可塑性，这是由日照长度和睾酮（T）水平的季节性变化所引发的。我们使用原位杂交技术来确定这种光周期变化是否会影响成年金丝雀中NMDAR亚基的表达。当T水平较低时，在短日照（SD）条件下处死鸟类；当T水平较高时，在长日照（LD）条件下处死鸟类。在四个鸣叫控制核团：外侧巨细胞核（lMAN）、X区、HVC核和古纹状体粗核（RA）中测量组成型NMDAR亚基（NR1）和两个调节亚基（NR2A、NR2B）的转录水平。在所研究的所有四个鸣叫区域中，SD组和LD组的NR1和NR2A mRNA水平相当。然而，SD组的lMAN和RA内的NR2B mRNA水平显著高于LD组的鸟类。光周期并未影响X区、HVC核或lMAN外侧的一个非鸣叫区域中的NR2B转录水平。我们的数据支持这样的假设，即NMDAR亚基表达的变化可能有助于成年期季节性鸣叫重塑所伴随的神经和行为重组。
