Shift from depolarizing to hyperpolarizing glycine action in rat auditory neurones is due to age-dependent Cl- regulation
Shift from depolarizing to hyperpolarizing glycine action in rat auditory neurones is due to age-dependent Cl- regulation
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DOI：
10.1111/j.1469-7793.1999.00121.x
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发表时间：
1999-10-01
影响因子：
5.5
通讯作者：
Friauf, E
中科院分区：
文献类型：
--
作者：
Ehrlich, I;Löhrke, S;Friauf, E
1.抑制性神经递质甘氨酸可引起未成熟神经元的去极化反应。研究了大鼠外侧上级橄榄核（lateral superior olive，LSO）神经元在发育过程中甘氨酸反应的变化及其离子机制.从脑切片中目视识别的LSO神经元进行全细胞和短杆菌肽穿孔斑记录，并向索马施加甘氨酸压力3-100 ms。甘氨酸诱发的电流被士的宁可逆地阻断。在穿孔斑片记录中，P8-11神经元大多数为单相反应，但也有30%的神经元出现双相反应.在全细胞记录从P2-11神经元，甘氨酸诱发电流（E-Gly）的逆转电位确定的跨膜Cl-梯度，并密切对应于能斯特电位的Cl-，无论年龄。这表明Cl-是渗透甘氨酸受体的主要离子，但也与HCO 3-的相对低渗透性（10-20%）一致。Cl-梯度也决定了甘氨酸诱发的膜电位变化的极性和幅度.在短杆菌肽穿孔膜片记录中不干扰天然细胞内[Cl-]的情况下，我们发现E-Gly的高度显著的年龄依赖性变化，从-46.8 +/- 1.8 mV（P1-4，n = 28）到-67.6 +/- 3.3 mV（P5-8，n = 10）到-82.2 +/- 4.1 mV（P9-11，n = 18）。大多数P1-4神经元被甘氨酸去极化（约80%），并诱发棘波（约30%）。相反，P9-11神经元呈超极化.在穿孔斑片记录中，E-Gly受电压方案和甘氨酸应用间隔的影响，它可以在正和负方向上移动。对于给定的应用间隔，这些变化总是在P1-4比P8-11神经元更大，这表明年轻神经元的Cl-调节机制不太有效。阳离子-Cl-协同转运体阻断剂呋塞米（frusemide）可逆性地使P2-4神经元的E-Gly负向移动，而在P8-10神经元的E-Gly正向移动，分别表明阻断了Cl-净内向和净外向转运体.两者合计，年龄依赖性的变化，积极氯调节可能会导致发展的转变，从去极化到超极化甘氨酸反应。在新生LSO神经元中产生高细胞内[Cl-]，其在成熟过程中减少。
1. The inhibitory neurotransmitter glycine can elicit depolarizing responses in immature neurones. We investigated the changes in glycine responses and their ionic mechanism in developing neurones of the rat lateral superior olive (LSO), an auditory brainstem nucleus involved in sound localization.2. Whole-cell and gramicidin perforated-patch recordings were performed from visually identified LSO neurones in brain slices and glycine was pressure applied for 3-100 ms to the soma. Glycine-evoked currents were reversibly blocked by strychnine. They were mostly monophasic, but biphasic responses occurred in similar to 30% of P8-11 neurones in perforated patch recordings.3. In whole-cell recordings from P2-11 neurones, the reversal potential of glycine-evoked currents (E-Gly) was determined by the transmembranous Cl- gradient and corresponded closely to the Nernst potential for Cl-, regardless of age. This indicates that Cl- is the principle ion permeating glycine receptors, but is also consistent with a low relative (10-20%) permeability for HCO3-. The Cl- gradient also determined the polarity and amplitude of glycine-evoked membrane potential changes.4. Leaving the native intracellular [Cl-] undisturbed with gramicidin perforated-patch recordings, we found a highly significant, age-dependent change of E-Gly from -46.8 +/- 1.8 mV (P1-4, n = 28) to -67.6 +/- 3.3 mV (P5-8, n = 10) to -82.2 +/- 4.1 mV (P9-11, n = 18). The majority of P1-4 neurones were depolarized by glycine (similar to 80 %) and spikes were evoked in similar to 30 %. In contrast, P9-11 neurones were hyperpolarized.5. In perforated-patch recordings, E-Gly was influenced by the voltage protocol and the glycine application interval; it could be shifted in the positive and negative direction. For a given application interval, these shifts were always larger in P1-4 than in P8-11 neurones, pointing to less effective Cl- regulation mechanisms in younger neurones.6. Furosemide (frusemide), a blocker of cation-Cl- cotransporters, reversibly shifted E-Gly in the negative direction in P2-4 neurones, yet in the positive direction in P8-10 neurones, suggesting the blockade of net inward and net outward Cl- transporters, respectively.7. Taken together, age-dependent changes in active Cl- regulation are likely to cause the developmental shift from depolarizing to hyperpolarizing glycine responses. A high intracellular [Cl-] is generated in neonatal LSO neurones which decreases during maturation.