Midorikawa Mitsuharu, Miyata Mariko
Division of Neurophysiology, Department of Physiology, School of Medicine, Tokyo Women's Medical University, Tokyo 162-8666, Japan
Proc Natl Acad Sci U S A. 2021 Mar 16;118(11). doi: 10.1073/pnas.2022423118.
For neuronal circuits in the brain to mature, necessary synapses must be maintained and redundant synapses eliminated through experience-dependent mechanisms. However, the functional differentiation of these synapse types during the refinement process remains elusive. Here, we addressed this issue by distinct labeling and direct recordings of presynaptic terminals fated for survival and for elimination in the somatosensory thalamus. At surviving terminals, the number of total releasable vesicles was first enlarged, and then calcium channels and fast-releasing synaptic vesicles were tightly coupled in an experience-dependent manner. By contrast, transmitter release mechanisms did not mature at terminals fated for elimination, irrespective of sensory experience. Nonetheless, terminals fated for survival and for elimination both exhibited developmental shortening of action potential waveforms that was experience independent. Thus, we dissected experience-dependent and -independent developmental maturation processes of surviving and eliminated presynaptic terminals during neuronal circuit refinement.
为使大脑中的神经回路成熟,必须通过依赖经验的机制维持必要的突触并消除多余的突触。然而,在精细化过程中这些突触类型的功能分化仍不清楚。在这里,我们通过对体感丘脑(somatosensory thalamus)中注定存活和注定消除的突触前终末进行不同标记和直接记录来解决这个问题。在存活的终末,可释放囊泡的总数首先增加,然后钙通道和快速释放的突触囊泡以依赖经验的方式紧密偶联。相比之下,无论感觉经验如何,注定消除的终末的递质释放机制都不会成熟。尽管如此,注定存活和注定消除的终末都表现出动作电位波形的发育性缩短,这与经验无关。因此,我们剖析了神经回路精细化过程中存活和消除的突触前终末的依赖经验和不依赖经验的发育成熟过程。
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