NOISE AND SINGLE CHANNELS ACTIVATED BY EXCITATORY AMINO-ACIDS IN RAT CEREBELLAR GRANULE NEURONS
NOISE AND SINGLE CHANNELS ACTIVATED BY EXCITATORY AMINO-ACIDS IN RAT CEREBELLAR GRANULE NEURONS
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DOI：
10.1113/jphysiol.1988.sp017117
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发表时间：
1988-06-01
影响因子：
5.5
通讯作者：
OGDEN, DC
中科院分区：
文献类型：
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作者：
CULLCANDY, SG;HOWE, JR;OGDEN, DC
1. 用膜片钳方法研究了外植体培养物中维持的大鼠小脑颗粒细胞中的谷氨酸受体离子通道。这些通道的特性是通过全细胞电流的噪声分析以及从外侧膜片中记录的噪声和单通道电流来确定的。 2.谷氨酸(10-20μM)引起两种类型的反应。一些颗粒细胞给出小的内向电流，伴随着电流噪声的明显增加（“大噪声”响应），而其他细胞给出更大的内向电流和小噪声增加（“小噪声”响应）。 3.估计来自四个“大噪声”细胞的谷氨酸的平均单通道电导(γ)为46.6 pS。平均 .gamma。对于其他七个“大噪声”单元，估计值为 8.4 pS。结果表明，在后者的细胞中，谷氨酸激活了大电导通道（.simeq. 50 pS）和小电导通道（.simeq. 140 fS）。 4.应用天冬氨酸（10-30μM）或N-甲基-D-天冬氨酸（NMDA，10-30μM）产生较小的内向电流和较大的噪声增加；伽马噪声 = 48.5 pS（天冬氨酸）和 46.7 pS（NMDA）。 5. 在由外向外的贴片中，谷氨酸、天冬氨酸和 NMDA 会引起大的单通道电流。对于最大幅值开口获得的平均电导值为：γ（谷氨酸）= 49.5 pS，γ（天冬氨酸）= 51.5 pS，以及γ（NMDA）= 53.0 pS。对于每种激动剂，这些 50 pS 开口构成了每个贴片中完全解析电流的 75-85%。 40 和 30 pS 电导水平的开口分别占总数的 10-15% 和 3-7%，并且这些水平和 50 pS 水平之间明显直接过渡的存在表明它们是相同多电导通道的子水平。 6.根据使君子酸盐(10-30μM)引起的噪声估计平均通道电导为22.9pS。在四个补丁中检查单通道电流。在两种情况下，使君子主要诱发两个振幅γ的小电流。 = 8.4 pS 和 16.5 pS；还存在约 50 个 pS 开口。在另外两个补丁中，大多数空缺都是 50 pS 事件。 7.颗粒细胞向红藻氨酸提供内向电流(10-30μM)，并且根据红藻氨酸噪声估计3.1pS的平均电导。在天冬氨酸或 NMDA 主要产生 50 pS 开口的斑块中，红藻氨酸引起的单通道电流中超过 74% 的幅度较小，平均电导为 γ。 = 8.1 和 15.1 pS。 Kainate 还激活 50 pS 通道并产生一些 30 和 40 pS 开口。 8.根据谷氨酸(10-20μM)引起的“小噪声”全细胞电流估计140fS的平均单通道电导。在“小噪声”细胞的向外斑块中谷氨酸产生的噪声光谱与红藻氨酸在斑块中产生的噪声光谱相似。 9. 我们的结果表明颗粒细胞具有至少三种类型的谷氨酸受体通道。一种类型的最大电导约为 50 pS；它显示出多个开放水平，并且似乎被天冬氨酸和 NMDA 选择性激活。红藻氨酸和使君子酸盐大量产生电导率为 8 和 15 pS 的开口，并且它们似乎不太可能是 50 pS 通道的子水平。大多数颗粒细胞中电导估计为 140 fS 的通道似乎以高密度存在。这些通道可被谷氨酸和红藻氨酸激活，但不会被天冬氨酸或 NMDA 激活到任何显着程度。
1. Glutamate-receptor ion channels in rat cerebellar granule cells maintained in explant cultures have been investigated with patch-clamp methods. Properties of these channels were determined from noise analysis of whole-cell currents and from noise and single-channel currents recorded in outside-out membrane patches. 2. Glutamate (10-20 .mu.M) evoked two types of response. Some granule cells gave small inward currents accompanied by clear increases in current noise (''large noise'' responses), whereas other cells gave larger inward currents and small noise increases (''small noise'' responses). 3. A mean single-channel conductance (.gamma.) of 46.6 pS was estimated for glutamate from four ''large noise'' cells. A mean .gamma. value of 8.4 pS was estimated for seven other ''large noise'' cells. The results suggest that in these latter cells glutamate activated both large (.simeq. 50 pS) and small conductance (.simeq. 140 fS) channels. 4. Applications of aspartate (10-30 .mu.M) or N-methyl-D-aspartate (NMDA, 10-30 .mu.M) produced small inward currents and large increases in noise; .gamma.noise = 48.5 pS (aspartate) and 46.7 pS (NMDA). 5. Large single-channel currents were evoked by glutamate, aspartate and NMDA in outside-out patches. The mean conductance values obtained for the largest amplitude openings were: .gamma.(glutamate) = 49.5 pS, .gamma.(aspartate) = 51.5 pS, and .gamma.(NMDA) = 53.0 pS. For each agonist, these 50 pS openings comprised 75-85% of the completely resolved currents in each patch. Openings to 40 and 30 pS conductance levels accounted for 10-15% and 3-7% of the total, and the presence of apparently direct transitions between these levels and the 50 pS level suggests they are sublevels of the same multi-conductance channels. 6. A mean channel conductance of 22.9 pS was estimated from noise evoked by quisqualate (10-30 .mu.M). Single-channel currents were examined in four patches. In two, quisqualate evoked predominantly small currents for two amplitudes, .gamma. = 8.4 pS and 16.5 pS; some 50 pS openings were also present. In the other two patches, most openings were 50 pS events. 7. Granule cells gave inward currents to kainate (10-30 .mu.M), and a mean conductance of 3.1 pS was estimated from kainate noise. In patches in which aspartate or NMDA produced mainly 50 pS openings, more than 74% of the single channel currents evoked by kainate were of smaller amplitude, with mean conductances of .gamma. = 8.1 and 15.1 pS. Kainate also activated 50 pS channels and produced some 30 and 40 pS openings. 8. A mean single-channel conductance of 140 fS was estimated from ''small noise'' whole-cell currents evoked by glutamate (10-20 .mu.M). Spectra of noise produced by glutamate in outside-out patches from ''small noise'' cells were similar to spectra of noise produced in patches by kainate. 9. Our results indicate that granule cells possess at least three types of glutamate-receptor channels. One type has a maximum conductance of approximately 50 pS; it displays multiple open levels and appears to be activated selectively by aspartate and NMDA. Openings with conductances of 8 and 15 pS are produced by kainate and quisqualate in large numbers and it appears unlikely they are sublevels of the 50 pS channels. Channels with an estimated conductance of 140 fS appear to be present at high density in most granule cells. These channels are activated by glutamate and kainate, but not by aspartate or NMDA to any significant extent.