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5-HT2C受体亚型参与易化大鼠内嗅区-海马通路的突触传递：平面微电极阵列记录技术研究

许燕, 金建慧, 王燕, 王蕊蕊, 李震, 陈军

首都医科大学疼痛生物医学研究所，北京 100069；第四军医大学唐都医院疼痛生物医学研究所暨功能性脑疾病研究所，西安 710038

摘要

本实验旨在运用64通道(8 × 8)平面微电极阵列记录技术(MED-64系统)探讨5-HT2C受体在调节内嗅区-海马突触传递和突触联系中的作用。将急性分离的大鼠海马脑片置于MED-64系统的电极平皿中，持续灌流通入95% O2 和5% CO2混合气的人工脑脊液，孵育2 h后进行多电极阵列同步记录。选一个电极进行电刺激(刺激强度30~199 µA，正负双波脉冲，单波宽0.1 ms，频率0.1 Hz)，其余63个电极作为记录电极。最佳有效刺激部位恰好位于前穿质通路(perforant path, PP)上，电刺激结果可以分别在海马CA1区和齿状回(dentate gyrus, DG)记录到兴奋性突触后场电位(field excitatory post-synaptic potential, fEPSP)。我们以往研究结果已显示内嗅区-CA1和内嗅区-DG直接突触联系是由谷氨酸非NMDA受体所介导的兴奋通路。在稳定地诱导出网络fEPSP后，分别给予5-HT2C受体激动剂DOI和选择性拮抗剂SB242084，观察与计算fEPSP的反应幅值与斜率变化。同时利用双线性内插法计算出64个点的电流源(current source)与电流井(current sink)，并将其转换为二维电流源密度(two-dimensional current source density, 2D-CSD)分布图。结果显示，结合fEPSP波的极相与2D-CSD成像，可见电刺激PP纤维在CA1区(腔隙分子层、锥体细胞层)和上部DG的分子层均发生突触兴奋引起的去极化，fEPSP为负向波，在空间上形成2D-CSD成像的电流井(蓝色区域)。同时，可在DG的颗粒细胞层和门部检测出正向波，形成2D-CSD成像的电流源(黄色区域)，这反映了颗粒细胞在树突部位发生去极化后很快沿门向CA3传播电信号。在此基础上，给予5-HT2C受体激动剂DOI后，海马内有效突触联系(>基线20%的fEPSP)的空间网络范围显著扩大，突触传递效能显著增强。而相对应的是，给予5-HT2C受体的选择性拮抗剂SB242084，则海马内有效突触联系空间网络范围显著缩小，突触反应强度减弱。以上结果提示，内源性5-HT作用于5-HT2C受体可易化内嗅区-海马突触传递效能，扩大有效突触联系，引起突触反应的兴奋作用。

关键词： 5-TH2C受体; 内嗅区-海马通路; 突触传递; 平面微电极阵列记录技术; 大鼠

分类号：R338.8

[Facilitation of synaptic transmission and connections of entorhinal-hippocampal pathway by 5-HT2C receptor subtype: multi-electrode array recordings.] [Article in Chinese]

Xu Yan, JIN Jian-Hui, WANG Yan, WANG Rui-Rui, LI Zhen, CHEN Jun

Institute for Biomedical Sciences of Pain, Capital Medical University, Beijing 100069, China； Institute for Biomedical Sciences of Pain and Institute for Functional Brain Disorders, Tangdu Hospital, The Fourth Military Medical University, Xi’an 710038, China

Abstract

Using 64-channels (8 × 8) multi-electrode array technique (MED-64 system), the modulatory actions of 5-hydroxytryptamine (5-HT) 2C receptor subtype on the entorhinal (EC)-hippocampal synaptic transmission and connections were studied. One of freshly dissociated acute hippocampal slices of rats which was placed on the MED-64 probe, was subject to constant perfusion with oxygenated artificial cerebrospinal fluid (ACSF, 95% O2 and 5% CO2). Two hours after ACSF incubation, simultaneous multi-site electrophysiological recordings were performed. One electrode was selected to be used for perforant path (PP) stimulation, and the remaining 63 electrodes were used for recordings of network field excitatory postsynaptic potentials (fEPSPs) within both CA1 and dentate gyrus (DG) that have been previously proved to be mediated by glutamate non-NMDA receptors. After stability of network fEPSPs was achieved, (±)-1(2, 5-Dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI, an agonist of 5-HT2C receptor subtype), or SB242084 (6-Chloro-2,3-dihydro-5-methyl-N-[6-[(2-methyl-3-pyridinyl)oxy]-3-pyridinyl]-1H-indole-1-carboxyamide dihydrochloride hydrate) (a selective antagonist of 5-HT2C receptor subtype) was applied for 10 min perfusion, respectively. Two-dimensional current source density (2D-CSD) analysis was also transformed by bilinear interpolation at each point of the 64 electrodes for spatial imaging of the fEPSP network responses. Based upon the polarities of fEPSP and 2D-CSD imaging, it was clearly shown that synaptic activations were evoked to occur within the molecular layer of DG and pyramidal cell layer of CA1 by the PP stimulation in which negative-going field potentials and current sink (blue) could be recorded. While, positive-going field potentials and current source (yellow) were mainly localized within the granule cell layer and hilus of DG and alveus of CA1, reflecting spread of electrical signals derived from depolarized region toward CA3 area or subiculum and fimbria along the axons. Perfusion of the hippocampal slices with DOI resulted in a significant enlargement of synaptic connection size at network level and enhancement of synaptic efficacy. However, on the contrary, perfusion with SB242084 produced reversal effect with either reduction in synaptic network size or decreased magnitude of fEPSPs (amplitude and slope) in the CA1 and DG. These results suggest that endogenous 5-HT causes facilitation of EC-CA1 and EC-DG synaptic transmission and connections via acting on 5-HT2C receptor subtype, leading to gain in synaptic transmission and enlargement of synaptic connections.

Key words: 5-HT2C receptor subtype; hippocampus; synaptic transmission; planar multi-electrode array; rat

收稿日期：2012-03-02　　录用日期：2012-05-02

通讯作者：陈军　　E-mail: junchen@fmmu.edu.cn

引用本文：

许燕, 金建慧, 王燕, 王蕊蕊, 李震, 陈军. 5-HT2C受体亚型参与易化大鼠内嗅区-海马通路的突触传递：平面微电极阵列记录技术研究[J]. 生理学报 2012; 64 (3): 259-268.

Xu Yan, JIN Jian-Hui, WANG Yan, WANG Rui-Rui, LI Zhen, CHEN Jun. [Facilitation of synaptic transmission and connections of entorhinal-hippocampal pathway by 5-HT2C receptor subtype: multi-electrode array recordings.] [Article in Chinese]. Acta Physiol Sin 2012; 64 (3): 259-268 (in Chinese with English abstract).