Glutamatergic Reinnervation and Assembly of Glutamatergic Synapses in Adult Rat Skeletal Muscle Occurs at Cholinergic Endplates
Glutamatergic Reinnervation and Assembly of Glutamatergic Synapses in Adult Rat Skeletal Muscle Occurs at Cholinergic Endplates
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DOI：
10.1097/nen.0b013e3181b7bfc8
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发表时间：
2009-10-01
影响因子：
3.2
通讯作者：
Pizzi, Marina
中科院分区：
文献类型：
--
作者：
Francolini, Maura;Brunelli, Giorgio;Pizzi, Marina
成年大鼠腹肌失神经后，神经肌肉接头突触后装置(NMJ)仍保持其原有的构筑和乙酰胆碱受体(AChRs)的聚集状态。当脊髓的下行纤维通过神经移植手术转移到这块肌肉时，脊髓上的谷氨酸能神经元可以神经支配肌肉纤维并恢复运动功能；新形成的NMJ从胆碱能切换到谷氨酸能型突触。我们在这里展示了再生神经末梢在胆碱能终板占据的区域与纤维接触。这些NMJ在形态上与对照组没有区别，但它们在AChRs的亚单位组成上有所不同。此外，通过免疫荧光和免疫电子显微镜观察，新的NMJ表达谷氨酸能突触标志。Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic酸(AMPA)受体亚单位GluR_1与AChRs部分共存，囊泡谷氨酸转运体2定位于突触前室。免疫共沉淀分析表明，AMPA受体亚基GluR1和GluR2与位于NMJ的AChR锚定蛋白Rapsyn发生免疫共沉淀。综上所述，这些结果表明胆碱能终板可以被新的谷氨酸能投射靶向，AMPA受体的聚集发生在那里。
After denervation of adult rat abdominal muscles, the postsynaptic apparatus of neuromuscular junctions (NMJs) retains its original architecture and clustering of acetylcholine receptors (AChRs). When descending fibers of the spinal cord are surgically diverted to this muscle by a nerve grafting procedure, supraspinal glutamatergic neurons can innervate muscle fibers and restore motor function; the newly formed NMJs switch from a cholinergic to a glutamatergic-type synapse. We show here that regenerating nerve endings contact the fibers in an area occupied by cholinergic endplates. These NMJs are morphologically indistinguishable From those in controls, but they differ in the subunit composition of AChRs. Moreover, by immunofluorescence and immunoelectron microscopy, new NMJs express glutamatergic synapse markers. The alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit GluR1 partially colocalizes with AChRs, and vesicular glutamate transporter 2 is localized in the presynaptic compartment. Immunoprecipitation analysis of membranes from reinnervated muscle showed that AMPA receptor subunits GluR1 and GluR2 coimmunoprecipitate with rapsyn, the AChR-anchoring protein at the NMJ. Taken together, these results indicate that cholinergic endplates can be targeted by new glutamatergic projections and that the clustering of AMPA receptors occurs there.