Properties of the GABAA receptor of rat posterior pituitary nerve terminals.
Properties of the GABAA receptor of rat posterior pituitary nerve terminals.
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大鼠垂体后神经末梢 GABAA 受体的特性。
DOI：
10.1152/jn.1995.73.3.1135
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Jackson,MB
中科院分区：
文献类型：
--
作者：
Zhang,SJ;Jackson,MB
1.我们使用薄片膜片钳技术研究了垂体后神经末梢轴突肿胀中的γ-氨基丁酸（GABA）受体。 2.神经末梢GABAA受体的激活引起1.5nS的平均电导变化。标准化面积得到的平均电导密度为 0.38 mS/cm2。 3. 虽然在 91% 的测试神经末梢中可以看到 GABAA 受体介导的反应，但无法检测到 GABAB 受体介导的反应。 GABAB 受体激动剂巴氯芬对保持电流或电压激活的 K+ 和 Ca2+ 通道没有影响。垂体后叶的神经末梢不太可能含有 GABAB 受体。 4.由神经末梢GABAA受体门控的通道仅表现出单一的开放电导水平。仅观察到完全打开和完全关闭状态。在垂体后神经末梢的 GABA 门控通道中没有看到其他 GABAA 受体通道典型的亚电导状态。 5.开放时间和闭合时间分布都是双指数的，表明通道至少有两个开放构象和两个闭合构象。在较高的 GABA 浓度下，长持续时间的开口占主导地位，这表明长持续时间的开口与短持续时间的开口的区别在于占据了更多的激动剂结合位点。 6. 持续应用GABA可通过简单的指数动力学使受体脱敏。 GABA 和蝇蕈醇的脱敏时间常数约为 9 秒。 7. 浓度为 100 µM 的锌离子仅使 GABA 反应降低 22%。这种对锌的弱敏感性，加上之前观察到的苯二氮卓敏感性，表明神经末梢 GABAA 受体拥有一个 γ 亚基。 8. 在移液管溶液中没有 Mg-ATP 的情况下，GABAA 受体介导的反应在整个终端记录中持续存在。因此，与许多其他 GABAA 受体相反，该受体在没有 ATP 的情况下没有表现出衰退。 9.垂体后神经末梢的GABAA受体通道与其他制剂的GABAA受体有许多共同的特性。这里描述的神经末梢受体和其他地方描述的细胞体受体之间的许多细微差别可能反映了神经末梢独特的受体蛋白亚基的存在。
1. We investigated gamma-aminobutyric acid (GABA) receptors using thin slice patch-clamp techniques in the swellings along axons of posterior pituitary nerve terminals. 2. Activation of the nerve terminal GABAA receptor induced a mean conductance change of 1.5 nS. Normalizing to area gave a mean conductance density of 0.38 mS/cm2. 3. Whereas GABAA receptor-mediated responses could be seen in 91% of the nerve terminals tested, GABAB receptor-mediated responses could not be detected. The GABAB receptor agonist baclofen had no effect on holding current or on voltage-activated K+ and Ca2+ channels. It is unlikely that nerve terminals of the posterior pituitary contain GABAB receptors. 4. The channel gated by the nerve terminal GABAA receptor exhibited only a single open conductance level. Only fully open and fully closed states were observed. Subconductance states typical of other GABAA receptor channels were not seen in the GABA-gated channels of posterior pituitary nerve terminals. 5. Both open time and closed time distributions were biexponential, indicating at least two open and two closed conformations of the channel. At a higher GABA concentration, long-duration openings predominated, suggesting that long-duration openings were distinguished from short-duration openings by the occupation of a greater number of agonist binding sites. 6. Sustained application of GABA desensitized the receptor with simple exponential kinetics. The time constant for desensitization was approximately 9 s for both GABA and muscimol. 7. Zinc ions at concentrations of 100 microM reduced GABA responses by only 22%. This weak sensitivity to zinc, together with a previous observation of benzodiazepine sensitivity, suggested that the nerve terminal GABAA receptor possesses a gamma-subunit. 8. Responses mediated by the GABAA receptor persist in whole terminal recordings without Mg-ATP in the pipette solution. Thus, in contrast to many other GABAA receptors, this receptor showed no rundown in the absence of ATP. 9. The GABAA receptor channel of posterior pituitary nerve terminals has many properties in common with GABAA receptors of other preparations. A number of subtle differences between the nerve terminal receptor described here and cell body receptors described elsewhere may reflect the presence of receptor protein subunits unique to nerve terminals.