CHARACTERIZATION OF PROTON CURRENTS IN NEURONS OF THE SNAIL, LYMNAEA-STAGNALIS
CHARACTERIZATION OF PROTON CURRENTS IN NEURONS OF THE SNAIL, LYMNAEA-STAGNALIS
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DOI：
10.1113/jphysiol.1989.sp017642
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发表时间：
1989-06-01
影响因子：
5.5
通讯作者：
SUEN, Y
中科院分区：
文献类型：
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作者：
BYERLY, L;SUEN, Y
采用内灌流电压钳和内面向外膜片钳技术研究了蜗牛神经元胞体的电压依赖性H+电流。在全细胞中，在步进到+40 mV后60 ms测量电压激活的外向H+电流，内部pH（pHi）为5.9，没有内部K +（[K +] i = 0），并且在pHi = 7.3和[K +] i = 74 mM下步进到+40 mV后60 ms测量延迟K+电流。平均H+和K+电流密度为14.6 ± 1.5。7.8和38.2. ±-。14.0 nA/nF，给出H+与K+电流的平均比率为0.4 ± 0.5。0.2.在不同的细胞中发现的两种外向电流的密度之间没有很强的相关性。由内而外的补丁的研究表明，H+和K+电流分布在膜上有很大的不同。虽然85%的所有补丁的K+电流，只有五个研究的38补丁H+电流。在这五个贴片中，在+30 mV下测得的H+电流范围为10.7至21.0 pA，并且在+30 mV下H+和K+电流的比率为0.83。0.38.所有38个贴片的平均H+和K+电流为1.9 ± 1.0。4.9和10.5.+-。7.9 PA，分别。电流分布模式表明，H+电流不流经延迟的K+电流通道，即使这两个电流具有相似的电压依赖性和时间过程。发现各种细胞外二价阳离子阻断H+电流的相对能力为Cu2+·simeq。Zn 2 +> Ni 2 +> Cd 2 +> Co 2 +> Mn 2 +> Mg 2 += Ca 2 += Ba 2+。由于100 μ M-Zn2+对H+电流的阻断大于其对Ca2+电流的阻断，因此其可用于减少H+电流对Ca2+电流测量的污染。H+电流的大小比延迟K+电流的大小具有更强的温度敏感性。H+电流大小的Q10为2.1 ±。0.4，而K+电流幅度为1.4。0.04.这表明H+电流的传导可能涉及比K+电流更高的活化能。在贴片中测量的H+电流的平滑时间过程表明，酉H+电流的大小是非常小的。虽然H+电流在-30 mV和+10 mV之间激活，但记录的电流变化显示在该电压范围内没有显著增加。+10 mV时的单位电流估计小于0.004 pA。
Internal perfusion voltage-clamp and inside-out patch-clamp techniques were used to study the voltage-dependent H+ currents in snail neuron cell bodies. In whole cells the voltage-activated outward H+ current was measured 60 ms after stepping to +40 mV with an internal pH (pHi) of 5.9 and no internal K+ ([K+]i = 0), and the delayed K+ current was measured 60 ms after stepping to +40 mV with pHi = 7.3 and [K+]i = 74 mM. The mean H+ and K+ current densities were 14.6 .+-. 7.8 and 38.2 .+-. 14.0 nA/nF, respectively, giving a mean ratio of the H+ to K+ current of 0.4 .+-. 0.2. There is not a strong correlation between the densities of the two kinds of outward currents found in different cells. Inside-out patch studies reveal that the H+ and K+ currents are distributed quite differently in the membrane. While 85% of all patches had K+ current, only five out of thirty-eight patches studied had H+ currents. In those five patches the H+ currents measured at +30 mV ranged from 10.7 to 21.0 pA, and the ratio of the H+ and K+ currents at +30 mV was 0.83 .+-. 0.38. The mean H+ and K+ currents for all thirty-eight patches were 1.9 .+-. 4.9 and 10.5 .+-. 7.9 pA, respectively. The current distribution patterns demonstrate that the H+ current does not flow through the delayed K+ current channels even though the two currents have similar voltage dependence and time course. The relative ability of various extracellular divalent cations to block the H+ current was found to be Cu2+ .simeq. Zn2+ > Ni2+ > Cd2+ > Co2+ > Mn2+ > Mg2+ = Ca2+ = Ba2+. Since 100 .mu.M-Zn2+ blocks the H+ current more than it blocks the Ca2+ current, it can be used to reduce the contamination of Ca2+ current measurements by the H+ current. The magnitude of the H+ current has a stronger temperature sensitivity than does the magnitude of the delayed K+ current. The Q10 of the H+ current magnitude is 2.1 .+-. 0.4, while the K+ current magnitude is 1.4 .+-. 0.04. This suggests a higher activation energy may be involved in the conduction of the H+ current than for K+ current. The smooth time course of the H+ current measured in patches indicates that the size of the unitary H+ current is very small. Although the H+ current activates between -30 and +10 mV, the variance of the currents recorded shows no significant increase in this voltage range. The unitary current at +10 mV is estimated to be less than 0.004 pA.