Transiently increased colocalization of vesicular glutamate transporters 1 and 2 at single axon terminals during postnatal development of mouse neocortex: a quantitative analysis with correlation coefficient
Transiently increased colocalization of vesicular glutamate transporters 1 and 2 at single axon terminals during postnatal development of mouse neocortex: a quantitative analysis with correlation coefficient
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DOI：
10.1111/j.1460-9568.2007.05868.x
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发表时间：
2007-12-01
影响因子：
3.4
通讯作者：
Kaneko, Takeshi
中科院分区：
文献类型：
--
作者：
Nakamura, Kouichi;Watakabe, Akiya;Kaneko, Takeshi
囊泡谷氨酸转运体1（VGLUT 1）和VGLUT 2在新皮质中呈互补分布，VGLUT 1主要表达于新皮质神经元的轴突终末，而VGLUT 2主要表达于丘脑皮质轴突终末。然而，我们最近报道了VGLUT 1和VGLUT 2在出生后发育中的新皮层轴突终末的一个子集中的频繁共定位。在这里，我们量化的频率VGLUT 1和VGLUT 2免疫反应性在单个轴突终末之间的共定位使用的相关系数（CC）作为一个指标，以确定共定位的时间过程和空间范围在小鼠新皮层出生后的发展。初级躯体感觉（S1）区的共定位比初级视觉（V1）区和运动区更频繁;在S1区皮质层中，出生后第7天（P）和成年期的IV层桶中的共定位最明显。IV层CC在S1区P7处有一个峰，在V1区P10处有一个峰，但后者的峰比前者小得多。这些结果表明，丘脑皮质轴突终末不仅含有VGLUT 2，但也VGLUT 1，特别是在P7-10。双荧光原位杂交证实VGLUT 1和VGLUT 2 mRNA的共表达在P7的丘脑体感觉核，后来在丘脑背外侧膝状体核。由于VGLUT 1经常用于成年大脑中显示突触可塑性的轴突末梢，因此本研究结果表明，VGLUT 1在出生后需要可塑性时短暂地用于丘脑皮质轴突。
Vesicular glutamate transporter 1 (VGLUT1) and VGLUT2 show complementary distribution in neocortex; VGLUT1 is expressed mainly in axon terminals of neocortical neurons, whereas VGLUT2 is located chiefly in thalamocortical axon terminals. However, we recently reported a frequent colocalization of VGLUT1 and VGLUT2 at a subset of axon terminals in postnatal developing neocortex. We here quantified the frequency of colocalization between VGLUT1 and VGLUT2 immunoreactivities at single axon terminals by using the correlation coefficient (CC) as an indicator in order to determine the time course and spatial extent of the colocalization during postnatal development of mouse neocortex. The colocalization was more frequent in the primary somatosensory (S1) area than in both the primary visual (V1) and the motor areas; of area S1 cortical layers, colocalization was most evident in layer IV barrels at postnatal day (P) 7 and in adulthood. CC in layer IV showed a peak at P7 in area S1, and at P10 in area V1 though the latter peak was much smaller than the former. These results suggest that thalamocortical axon terminals contained not only VGLUT2 but also VGLUT1, especially at P7-10. Double fluorescence in situ hybridization confirmed coexpression of VGLUT1 and VGLUT2 mRNAs at P7 in the somatosensory thalamic nuclei and later in the thalamic dorsal lateral geniculate nucleus. As VGLUT1 is often used in axon terminals that show synaptic plasticity in adult brain, the present findings suggest that VGLUT1 is used in thalamocortical axons transiently during the postnatal period when plasticity is required.