Long-term depression-associated signaling is required for an in vitro model of NMDA receptor-dependent synapse pruning.
Long-term depression-associated signaling is required for an in vitro model of NMDA receptor-dependent synapse pruning.
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DOI：
10.1016/j.nlm.2016.10.013
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发表时间：
2017-02
影响因子：
2.7
通讯作者：
Dudek SM
中科院分区：
文献类型：
--
作者：
Henson MA;Tucker CJ;Zhao M;Dudek SM
突触接触的活动依赖性修剪在塑造神经元回路以响应出生后大脑发育过程中的环境方面发挥着关键作用。尽管有令人信服的证据表明树突棘的收缩与突触长期抑制（LTD）同时发生，并且LTD伴随着突触损失，但NMDA受体（NMDAR）依赖性LTD是否是突触修剪过程中的必要步骤仍不清楚。通过重复应用 NMDA 在离解的大鼠神经元培养物中诱导 LTD，我们发现，通过突触前和突触后结构的荧光标记共定位测量的突触密度下降，无论使用的突触前标记、治疗后恢复时间和突触的树突位置如何。与之前的研究一致，我们发现突触丢失可能会在没有明显的净刺丢失或细胞死亡的情况下发生。此外，突触丢失不太可能需要与小胶质细胞直接接触，因为这些细胞的数量在我们的培养物中很少。 NMDA 对荧光共定位的影响被磷酸酶和半胱天冬酶抑制剂阻止，这支持了突触丢失需要 NMDAR-LTD 的模型。此外，基因转录和蛋白质翻译似乎也是假定突触丢失所必需的。这些数据支持 NMDAR 依赖性 LTD 是突触修剪的必要步骤这一观点，并有助于我们理解这一发育过程的基本机制。
Activity-dependent pruning of synaptic contacts plays a critical role in shaping neuronal circuitry in response to the environment during postnatal brain development. Although there is compelling evidence that shrinkage of dendritic spines coincides with synaptic long-term depression (LTD), and that LTD is accompanied by synapse loss, whether NMDA receptor (NMDAR)-dependent LTD is a required step in the progression toward synapse pruning is still unknown. Using repeated applications of NMDA to induce LTD in dissociated rat neuronal cultures, we found that synapse density, as measured by colocalization of fluorescent markers for pre- and postsynaptic structures, was decreased irrespective of the presynaptic marker used, post-treatment recovery time, and the dendritic location of synapses. Consistent with previous studies, we found that synapse loss could occur without apparent net spine loss or cell death. Furthermore, synapse loss was unlikely to require direct contact with microglia, as the number of these cells was minimal in our culture preparations. Supporting a model by which NMDAR-LTD is required for synapse loss, the effect of NMDA on fluorescence colocalization was prevented by phosphatase and caspase inhibitors. In addition, gene transcription and protein translation also appeared to be required for loss of putative synapses. These data support the idea that NMDAR-dependent LTD is a required step in synapse pruning and contribute to our understanding of the basic mechanisms of this developmental process.