N-methyl-D-aspartate receptors at parallel fiber synapses in the dorsal cochlear nucleus.
N-methyl-D-aspartate receptors at parallel fiber synapses in the dorsal cochlear nucleus.
复制标题
耳蜗背核平行纤维突触处的 N-甲基-D-天冬氨酸受体。
DOI：
10.1152/jn.1996.76.3.1639
复制
发表时间：
1996
影响因子：
2.5
通讯作者：
Molitor,SC
中科院分区：
文献类型：
--
作者：
Manis,PB;Molitor,SC
1. N-甲基-D-天冬氨酸（NMDA）结合和NMDA受体免疫定位实验表明，这些受体在耳蜗背核（DCN）的外两层的表达增强。受体的分布与颗粒细胞-平行纤维系统产生的突触的分布一致。为了确定NMDA受体在平行纤维突触的功能分布和贡献，在豚鼠和大鼠耳蜗背核的体外脑片制备中研究了对平行纤维刺激的突触反应。2.豚鼠对平行纤维刺激的场电位反应包括三个突触后成分。短潜伏期成分（P3（2）和N2（2））被一般兴奋性受体拮抗剂阻断，包括非NMDA受体阻断剂6，7-二硝基喹喔啉-2，3-二酮（DNQX）和6-氰基-7-硝基喹喔啉-2，3-二酮（CNQX），但对NMDA受体拮抗剂不敏感。3.当用低镁溶液洗涤切片以消除通过NMDA受体的电流的镁阻断时，显示较慢的组分（P4（2））。该缓慢组分可被D-或DL-2-氨基-5-膦酰基戊酸（D-APV，DL-APV）和3-[（+/-）-2-羧基哌嗪-4-基]丙基-1-膦酸酯还原，但不被DNQX或CNQX阻断。消除NMDA受体的电压依赖性也导致在一些切片中的复杂的振荡响应。这种反应表现出与慢电位相同的药理学敏感性。对NMDA受体拮抗剂的药理学敏感性表明，慢成分（P4（2））和相关的振荡反应是通过激活NMDA受体介导的。4.对平行纤维诱发场电位进行电流源密度分析，以确定快、慢突触电流的相对空间分布。这两个突触组件都与一个表面的电流汇和一个更深的电流源，位于表面的250 μ M的核。在五个切片中的三个切片中，慢（APV敏感）电流相对于快（DNQX敏感）电流在深度上略有偏移，最大电流吸收和电流源距离DCN表面约16微米。这些数据表明，要么NMDA受体不存在于所有的突触，产生快速非NMDA电流或突触后细胞具有不同的树突状分布有不同的密度的NMDA受体。5.研究了第1层和第2层中表现出NMDA受体介导的突触电位的细胞类型。在豚鼠脑片上用尖电极进行细胞内记录表明，在低镁环境中消除NMDA受体的电压依赖性，在简单和复杂的尖峰细胞中都显示出缓慢的兴奋性突触后电位（EPSP）。APV可降低两种细胞EPSP的晚期。这些结果可能与突触后细胞上的NMDA受体或兴奋性中间神经元上的NMDA受体有关。试图证明一个适当的电压依赖性的平行纤维突触反应在正常镁介质下电流钳混淆的内在电压依赖性的电导的细胞。6.为了确定是否NMDA受体存在于突触后细胞上，在细胞内记录期间检查DCN细胞对NMDA应用的直接敏感性。简单峰电位和复杂峰电位细胞对NMDA都有去极化反应。对NMDA的反应持续时，非...
1. N-methyl-D-aspartate (NMDA) binding and NMDA-receptors immunolocalization experiments have revealed an enhanced expression of these receptors in the outer two layers of the dorsal cochlear nucleus (DCN). The distribution of the receptors is congruent with the distribution of synapses produced by the granule cell-parallel fiber system. To determine the functional distribution and contribution of NMDA receptors at parallel fiber synapses, synaptic responses to parallel fiber stimulation were studied in in vitro brain slice preparations of the guinea pig and rat dorsal cochlear nucleus. 2. The field potential response to parallel fiber stimulation in guinea pigs includes three postsynaptic components. The short latency components (the P3(2) and N2(2)) are blocked by general excitatory receptor antagonists, including the non-NMDA-receptor blockers 6,7-dinitroquinoxaline-2,3-dione (DNQX) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), but are insensitive to NMDA-receptor antagonists. 3. A slower component (P4(2)) is revealed when the slices are washed with a low magnesium solution to eliminate the magnesium block of currents through NMDA receptors. This slow component is reduced by D- or DL-2-amino-5-phosphonovaleric acid (D-APV, DL-APV) and 3-[(+/-)-2-carboxypiperazine-4-yl] propyl-1-phosphonate, but is not blocked by DNQX or CNQX. Eliminating the voltage dependence of the NMDA receptors also results in a complex oscillatory response in some slices. This response exhibits the same pharmacological sensitivity as the slow potential. The pharmacologic sensitivity to NMDA-receptor antagonists suggest that the slow component (P4(2)) and the associated oscillatory response are mediated through activation of NMDA receptors. 4. Current source-density analysis of the parallel fiber-evoked field potentials was carried out to determine the relative spatial distributions of the fast and slow synaptic currents. Both synaptic components were associated with a superficial current sink and a deeper current source, localized within the superficial 250 microM of the nucleus. The slow (APV-sensitive) current was slightly shifted in depth relative to the fast (DNQX-sensitive) current in three of five slices with the maximum current sink and source occurring approximately 16 microns further from the surface of the DCN. These data suggest that either the NMDA receptors are not present at all of the synapses that generate the fast non-NMDA currents or that postsynaptic cells with different dendritic distributions have different densities of NMDA receptors. 5. The types of cells in layers 1 and 2 exhibiting NMDA-receptor-mediated synaptic potentials were investigated. Intracellular recordings with sharp electrodes in guinea pig slices showed that eliminating the voltage dependence of the NMDA receptors in low magnesium revealed a slow excitatory postsynaptic potential (EPSP) in both simple and complex spiking cells. The late phase of the EPSP could be reduced by APV in both cell types. These results could be explained by NMDA receptors on the postsynaptic cells or by NMDA receptors on excitatory interneurons. Attempts to demonstrate an appropriate voltage dependence of the parallel fiber synaptic response in normal magnesium medium under current clamp were confounded by the intrinsic voltage-dependent conductances of the cells. 6. To determine whether NMDA receptors were present on postsynaptic cells, the direct sensitivity of DCN cells to NMDA application was examined during intracellular recording. Both simple spiking and complex spiking cells responded to NMDA with depolarization. The response to NMDA persisted when non …