Developmental changes in membrane properties and postsynaptic currents of granule cells in rat dentate gyrus
Developmental changes in membrane properties and postsynaptic currents of granule cells in rat dentate gyrus
复制标题
DOI：
10.1152/jn.1996.76.2.1074
复制
发表时间：
1996-08-01
影响因子：
2.5
通讯作者：
Trommer, BL
中科院分区：
文献类型：
--
作者：
Liu, YB;Lio, PA;Trommer, BL
1. 全细胞膜片钳记录用于研究幼年大鼠（出生后第 8-32 天）海马切片中的齿状回颗粒细胞。使用电流钳记录测量膜特性，并与充满生物胞素的神经元亚群的形态相关。通过在电压钳记录中使用特定受体拮抗剂来表征由内侧穿通路径刺激诱导的突触后电流（PSC）的成分。2．将位于海马头侧三分之一颗粒层上叶中部的颗粒细胞根据其输入阻力（IR）分为三组。低 IR（206 +/- 182 M Omega，平均值 +/- SD）的神经元具有超极化的静息膜电位（-82 +/- 7 mV）和高振幅动作电位（108 +/- 23 mV）。具有高 IR (1,259 +/- 204 M Omega) 的神经元具有更多的去极化静息膜电位 (-54 +/- 6 mV) 和较低幅度的动作电位 (71 +/- 10 mV)。具有中等 IR (619 +/- 166 M Omega) 的神经元也具有中等静息膜电位 (-63 +/- 7 mV) 和动作电位幅度 (86 +/- 14 mV)。随着出生后年龄的增长，低IR神经元变得越来越普遍，但在整个研究期间都可以发现每组的神经元。3。低红外神经元的形态学研究揭示了广泛的树突状树枝化，它穿过整个分子层，是成熟颗粒细胞的特征。高IR细胞具有较小的体细胞和短而简单的树突状树枝状结构，不完全穿透分子层，被归类为不成熟细胞。 Intermediate-IR细胞具有中等成熟度的形态特征。4．在 -80 mV 处诱发的 PSC 初始阶段是快速内向电流，在所有成熟神经元中保持在 -80 mV 时，其峰值潜伏期、起始潜伏期和 10-90% 上升时间相当。该电流对 6-氰基-7-硝基喹喔啉-2,3-二酮敏感。5． PSC 在 -80 mV 时的衰减阶段随神经元成熟度的变化而变化。成熟神经元具有单指数衰减（tau=8.9+/-3.6）。中间和未成熟的神经元具有显着的后期内向电流，导致较慢的衰减。对于未成熟神经元，衰减阶段的内向电流可以与初始的快速内向峰值分开。中间和未成熟神经元的后期内向电流对荷包牡丹碱敏感。6．通过使用细胞外和贴片溶液的均匀离子条件，药理学分离的α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）、N-甲基-D-天冬氨酸（NMDA）和γ-氨基丁酸-A（GABA（A））电流的电流-电压关系和反转电位在所有细胞成熟度中具有可比性。峰值 GABA(A)/NMDA/AMPA 电流的计算比率随着成熟而显着降低，如下：未成熟细胞为 9.4+/-2.9/1.4 +/-0.5/1.0，中间细胞为 7.2+/-2.5/1.5+/-0.7/1.0，成熟细胞为 2.0+/-1.2/0.9+/-0.4/1.0。7． GABA 电流由中间神经元的多突触激活和通过颗粒细胞的单突触输入直接激活中间神经元介导。单突触和多突触 GABA 对总 GABA 的比例贡献在所有细胞成熟度中是可比的；单突触和多突触成分的峰值 GABA 电流潜伏期随着细胞成熟度的增加而降低。8．我们得出的结论是，所有成熟神经元中内侧穿通通路激活在颗粒细胞中诱发的 PSC 由谷氨酸能和 GABA 能成分组成。 PSCs 在未成熟的颗粒细胞中以 GABA 能神经传递为主，谷氨酸能神经传递的贡献随着神经元的成熟而增加。与成熟颗粒细胞相比，未成熟颗粒细胞中 GABA(A) 峰值与谷氨酸电流的比率更大，并且它们各自峰值之间的时间间隔更长，从而产生独特的 PSC 形状。
1. Whole cell patch-clamp recordings were used to study dentate gyrus granule cells in hippocampal slices from juvenile rats (postnatal days 8-32). Membrane properties were measured with the use of current-clamp recordings and were correlated with the morphology of a subgroup of neurons filled with biocytin. The components of the postsynaptic currents (PSCs) induced by medial perforant path stimulation were characterized with the use of specific receptor antagonists in voltage-clamp recordings.2. Granule cells located in the middle third of the superior blade of stratum granulosum from the rostral third of hippocampus were divided into three groups according to their input resistance (IR). Neurons with low IR (206 +/- 182 M Omega, mean +/- SD) had hyperpolarized resting membrane potentials (-82 +/- 7 mV) and high-amplitude action potentials (108 +/- 23 mV). Neurons with high IR (1,259 +/- 204 M Omega) had more depolarized resting membrane potentials (-54 +/- 6 mV) and lower-amplitude action potentials (71 +/- 10 mV). Neurons with intermediate IR (619 +/- 166 M Omega) also had intermediate resting membrane potentials (-63 +/- 7 mV) and action potential amplitudes (86 +/- 14 mV). Low-IR neurons became increasingly prevalent with advancing postnatal age, but neurons from each group could be found throughout the entire period under study.3. Morphological studies of low-IR neurons revealed an extensive dendritic arborization that traversed the entire molecular layer and was characteristic of mature granule cells. High-IR cells had smaller somata and short, simple dendritic arborization that incompletely penetrated the molecular layer and were classified as immature. Intermediate-IR cells had morphological features of intermediate maturity.4. The initial phase of the PSC evoked at -80 mV was a fast inward current that was comparable with respect to latency to peak, latency to onset, and 10-90% rise time in neurons of all maturities held at -80 mV. This current was 6-cyano-7-nitroquinoxaline-2,3-dione sensitive.5. The decay phases of PSCs at -80 mV varied with neuronal maturity. Mature neurons had monoexponential decays (tau=8.9+/-3.6). Intermediate and immature neurons had prominent later inward currents that resulted in slower decays. In the case of the immature neurons, the inward current during the decay phase could be separated from the initial fast inward peak. The later inward currents in intermediate and immature neurons were bicuculline sensitive.6. With the use of uniform ionic conditions of the extracellular and patch solutions, current-voltage relations and reversal potentials for pharmacologically isolated alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), N-methyl-D-aspartate (NMDA), and gamma-aminobutyric acid-A (GABA(A)) currents were comparable across all cell maturities. Calculated ratios for peak GABA(A)/NMDA/AMPA currents decreased significantly with maturation as follows: 9.4+/-2.9/1.4 +/-0.5/1.0 for immature cells, 7.2+/-2.5/1.5+/-0.7/1.0 for intermediate cells, and 2.0+/- 1.2/0.9+/-0.4/1.0 for mature cells.7. GABA current was mediated both by polysynaptic activation of interneurons and by direct activation of interneurons with monosynaptic input onto granule cells. The proportional contributions of mono- and polysynaptic GABA to total GABA were comparable across all cell maturities; latency to peak GABA current decreased with increasing cell maturity for both mono- and polysynaptic components.8. We conclude that PSCs evoked in granule cells by medial perforant path activation in neurons of all maturities consist of both glutamatergic and GABAergic components. PSCs are dominated by GABAergic neurotransmission in immature granule cells, and the contribution of glutamatergic neurotransmission increases with neuronal maturation. The greater ratio of peak GABA(A) to glutamate currents and the longer time interval between their respective peaks combine to produce a distinctive PSC shape in the immature compared with mature granule cells.