Monosynaptic pathway from rat vibrissa motor cortex to facial motor neurons revealed by lentivirus-based axonal tracing
Monosynaptic pathway from rat vibrissa motor cortex to facial motor neurons revealed by lentivirus-based axonal tracing
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DOI：
10.1523/jneurosci.2235-05.2005
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发表时间：
2005-09-07
影响因子：
5.3
通讯作者：
Osten, P
中科院分区：
文献类型：
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作者：
Grinevich, V;Brecht, M;Osten, P
哺乳动物的运动皮质通常通过寡突触通路间接地支配运动神经元。然而，在人类，猿，和一些猴子物种熟练的手指运动的进化与出现丰富的单突触皮质投射到脊髓运动神经元支配远端肢体肌肉。大鼠执行熟练的动作与他们的胡须，我们研究的可能性，大鼠触须运动皮层（VMC）项目单突触到面部运动神经元控制的胡须运动。首先，单次注射慢病毒VMC网站确定皮质内微刺激被用来标记一个不同的亚群的VMC轴突或突触前终端的表达增强的绿色荧光蛋白（GFP）或GFP标记的突触素，分别。注射4周后，GFP和突触素GFP标记的轴突和推定的突触前末梢中检测到的面核（FN）的外侧部分，在接近运动神经元的形态学鉴定和轴突回标记的须滤泡。VMC预测检测双边，与三倍大的标记密度在对侧FN。接下来，使用多次VMC注射来标记大部分VMC轴突，导致总体上更密集但仍然横向受限的FN标记。GFP标记的VM Caxon的超微结构分析证实了FN运动神经元的树突和胞体上的突触接触的存在。这些发现提供了大鼠单突触VMC-到-FN通路的解剖学证明，并表明基于慢病毒的GFP和GFP标记的突触前蛋白的表达可用作高分辨率神经解剖学追踪方法。
The mammalian motor cortex typically innervates motor neurons indirectly via oligosynaptic pathways. However, evolution of skilled digit movements in humans, apes, and some monkey species is associated with the emergence of abundant monosynaptic cortical projections onto spinal motor neurons innervating distal limb muscles. Rats perform skilled movements with their whiskers, and we examined the possibility that the rat vibrissa motor cortex (VMC) projects monosynaptically onto facial motor neurons controlling the whisker movements. First, single injections of lentiviruses to VMC sites identified by intracortical microstimulations were used to label a distinct subpopulation of VMC axons or presynaptic terminals by expression of enhanced green fluorescent protein (GFP) or GFP-tagged synaptophysin, respectively. Four weeks after the injections, GFP and synaptophysin-GFP labeling of axons and putative presynaptic terminals was detected in the lateral portion of the facial nucleus (FN), in close proximity to motor neurons identified morphologically and by axonal back-labeling from the whisker follicles. The VMC projections were detected bilaterally, with threefold larger density of labeling in the contralateral FN. Next, multiple VMC injections were used to label a large portion of VMC axons, resulting in overall denser but still laterally restricted FN labeling. Ultrastructural analysis of the GFP-labeled VM Caxons confirmed the existence of synaptic contacts onto dendrites and somata of FN motor neurons. These findings provide anatomical demonstration of monosynaptic VMC-to-FN pathway in the rat and show that lentivirus-based expression of GFP and GFP-tagged presynaptic proteins can be used as a high-resolution neuroanatomical tracing method.