Orexin-A differentially modulates inhibitory and excitatory synaptic transmission in rat inner retina
Orexin-A differentially modulates inhibitory and excitatory synaptic transmission in rat inner retina
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Orexin-A 差异调节大鼠内视网膜的抑制性和兴奋性突触传递
DOI：
10.1016/j.neuropharm.2021.108492
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发表时间：
2021-02-24
影响因子：
4.7
通讯作者：
Zhong, Yong-Mei
中科院分区：
文献类型：
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作者：
Ruan, Hang-ze;Wang, Li-Qing;Zhong, Yong-Mei
本工作通过检测神经肽对大鼠视网膜神经节细胞(GCs)微小兴奋性突触后电流(MEPSCs)和微小抑制性突触后电流(MIPSCs)的影响，研究了增食欲素A对双极细胞和无长突细胞释放谷氨酸和GABA的调节作用。应用RNAScope原位杂交结合免疫组织化学方法，双极细胞终末表达增食欲素受体-1(OX1R)，无长突细胞终末表达增食欲素受体-2(OX2R)。通过大鼠视网膜脑片全细胞膜片钳记录，我们证明了Oresin-A通过OX1R缩短了mEPSCs的事件间期。然而，它通过OX2R延长由GABAA受体介导的mIPSCs的事件间隔。此外，PI-PLC抑制剂或PKC抑制剂的应用可取消食欲素-A引起的mEPSC事件间期缩短。反之，食欲素-A引起的GABA能mIPSC间期延长可被8-溴-cAMP或腺苷环化酶激动剂模拟，但可被PKA拮抗剂消除。最后，应用L钙通道阻断剂尼莫地平可延长mEPSC和mIPSC的间期，而联合应用增食欲素-A不再改变mEPSC和mIPSC。我们认为食欲素-A通过激活双极细胞的L钙通道增加突触前谷氨酸的释放，这一过程是由OX1R/PI-PLC/PKC信号通路介导的。然而，食欲素-A通过抑制无长突细胞上的L型钙通道来减少突触前GABA在GC上的释放，这一过程是由OX2R/cAMP-PKA信号通路介导的。
In this work, modulation by orexin-A of the release of glutamate and GABA from bipolar and amacrine cells respectively was studied by examining the effects of the neuropeptide on miniature excitatory postsynaptic currents (mEPSCs) and miniature inhibitory postsynaptic currents (mIPSCs) of rat retinal ganglion cells (GCs). Using RNAscope in situ hybridization in combination with immunohistochemistry, we showed positive signals for orexin receptor-1 (OX1R) mRNA in the bipolar cell terminals and those for orexin receptor-2 (OX2R) mRNA in the amacrine cell terminals. With whole-cell patch-clamp recordings in rat retinal slices, we demonstrated that application of orexin-A reduced the interevent interval of mEPSCs of GCs through OX1R. However, it increased the interevent interval of mIPSCs, mediated by GABAA receptors, through OX2R. Furthermore, orexin-A-induced reduction of mEPSC interevent interval was abolished by the application of PI-PLC inhibitors or PKC inhibitors. In contrast, orexin-A-induced increase of GABAergic mIPSC interevent interval was mimicked by 8-Br-cAMP or an adenylyl cyclase activator, but was eliminated by PKA antagonists. Finally, application of nimodipine, an L type Ca2+ channel blocker, increased both mEPSC and mIPSC interevent interval, and co-application of orexin-A no longer changed the mEPSCs and mIPSCs. We conclude that orexin-A increases presynaptic glutamate release onto GCs by activating L-type Ca2+ channels in bipolar cells, a process that is mediated by an OX1R/PI-PLC/PKC signaling pathway. However, orexin-A decreases presynaptic GABA release onto GCs by inhibiting L-type Ca2+ channels in amacrine cells, a process that is mediated by an OX2R/cAMP-PKA signaling pathway.