食欲素B增强外膝体纤维投射至视皮层第6b层锥体细胞的突触传递

Orexin B Enhances the Synaptic Transmission from LGN to Orexin-sensitive Neurons in L6b of Visual Cortex

[目的]探究食欲素B(Orexin B)调控外膝体(LGN)纤维投射至视皮层(visual cortex,VC)第6层b亚层(L6b)中的食欲素B敏感神经元(Orexin敏感神经元)的突触传递作用.[方法]选用P25~P30的C57小鼠,脑立体定位注射CTB555或者ChR2-EGFP,分别标记VC中L6b反馈投射到LGN的神经细胞和源自LGN前馈投射至L6b的神经纤维.膜片钳的方法记录CTB555标记的L6b中的神经细胞的突触后电流(EPSC),电刺激皮层白质或蓝光刺激ChR2-EGFP(Channelrhodopsin 2-Enhanced Green Fluorescent Protein)标记的LGN投射到VC的神经纤维.[结果]从L6b反馈投射至LGN的神经细胞中,92.5%为锥体神经元,且这些锥体神经细胞中有63.3%的细胞对Orexin B受体激动剂敏感.电刺激或光刺激LGN前馈投射至L6b的神经纤维,Orexin B增强L6b中Orexin敏感细胞的突触后NMDAR电流[电刺激:(125.1±3.7)%,光刺激:(123.8±3.8)%,在OX2R阻断剂的存在下,Orexin B对突触后电流振幅的效应消失,具有明显统计学意义,P<0.05],因此,OrexinB增强LGN——Orexin敏感神经细胞之间的突触传递.[结论]Orexin B增强外膝体(LGN)纤维投射至视皮层L6b中的锥体细胞之间的突触传递.

【Objective】To unmask the effect of Orexin B on the synaptic transmission between feed-forward projection from the lateral geniculate nucleus(LGN)to orexin-sensitive neurons in layer 6b(L6b)of visual cortex(VC)【.Methods】C57 mice at P25-P30 were used for micro-injection of CTB555 and ChR2-EGFP into LGN to label the neurons feedback projection to LGN from L6b and the feed-forward projection from LGN to the neurons in L6b of VC respectively.The EPSC in L6b cells was intracellularly recorded from the neurons labeled by CTB555.【Results】The neurons feedback projection to LGN in L6b are mainly pyramidal neurons,and the most of these cells are activated by orexin B,called orexin-sensitive neurons.Orexin B enhanced the NMDAR-mediated postsynaptic current in orexin-sensitive neurons in L6b by electrical or optical stimulation on the LGN projection to VC[electrical stimulation:(125.1±3.7)%,optical stimulation:(123.8±3.8)%.In the case of OX2R′s blocker,the effect of Orexin B on EPSC amplitude disappeared with significant statistical significance,P<0.05],thus,strengthning the synaptic transmission between LGN and orexin-sensitive neurons in L6b.【Conclusions】Orexin B enhances the synaptic transmission between LGN to pyramidal neurons in L6b of VC.