MEMBRANE CURRENTS OF INTERNALLY PERFUSED NEURONS OF THE SNAIL, LYMNAEA-STAGNALIS, AT LOW INTRACELLULAR PH
MEMBRANE CURRENTS OF INTERNALLY PERFUSED NEURONS OF THE SNAIL, LYMNAEA-STAGNALIS, AT LOW INTRACELLULAR PH
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DOI：
10.1113/jphysiol.1986.sp016165
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发表时间：
1986-07-01
影响因子：
5.5
通讯作者：
MOODY, WJ
中科院分区：
文献类型：
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作者：
BYERLY, L;MOODY, WJ
1.采用内灌流和离子敏感微电极技术，研究了低pH值对钉螺神经元体细胞膜电流的影响。2.用pH敏感微电极记录灌流液pH在7.3~6.3之间的变化，结果表明，只有在较高的缓冲浓度(100 MM)下才能有效地改变pH。与K+等无缓冲离子相比，H+交换进入细胞质的速度较慢。3.当phi降至5.9时，在-30 mV的正电压下可记录到较大的外向H+电流。这些电流的时程和幅度不影响快速瞬变K+电流(A-电流)峰值的测量，但严重干扰了钙电流和延迟K+电流的测量。4.低pH值阻断A-电流。滴定曲线与两个H离子结合在一个pK值为6.05的位点上阻断该通道相一致。5.低pH值可阻断延迟外向电流的缓慢失活，但对其峰值无明显影响。然而，当对低phi时H+电流的增加进行校正时，发现内部H+的作用是延迟K+电流的阻断，而对失活没有一致的影响。6.低pH时钙电流也降低，但我们不能确定这是Phi的直接作用，还是内源性[Ca~(2+)]升高的继发性作用。如果不对H+电流进行校正，钙电流的阻断似乎比实际情况更大和更可逆。7.我们的结论是，在某些条件下，如低phi，H+电流在蜗牛神经元的总外向电流中占有相当大的比例，也可能存在于其他多种细胞中。为了准确地研究K+和Ca~(2+)电流的性质，必须在这种条件下考虑H~+电流。
1. The effects of low intracellular pH (pHi) on the membrane currents of snail neurone somata were studied using the internal perfusion and ion-sensitive microelectrode techniques. 2. Recordings with pH-sensitive micro-electrodes made while the pH of the perfusion solution was changed between 7.3 and 6.3 indicated that only with high buffer concentrations (100 mM) could pHi be changed effectively. H+ was slower to exchange into the cytoplasm than an unbuffered ion such as K+. 3. When pHi was decreased to 5.9, large outward H+ currents could be recorded at voltages positive to -30 mV. The time course and amplitude of these currents were such that they did not affect the measurement of the peak amplitude of the fast transient K+ current (A-current), but severly contaminated both Ca2+ and delayed K+ current measurements. 4. Low pHi blocked the A-current. The titration curve was consistent with the binding of two H ions to a site with a pK of 6.05 to block the channel. 5. Low pHi appeared to block the slow inactivation of the delayed outward current without greatly changing its peak amplitude. However, when correction was made for the increase of H+ current at low pHi, the effect of internal H+ was found to be a block of the delayed K+ current with no consistent effect on inactivation. 6. The Ca2+ current was also decreased at low pHi, but we were unable to determine whether this was a direct effect of pHi or secondary to a rise in internal free [Ca2+]. If no correction was made for H+ currents, the block of the Ca2+ current appeared greater and more reversible than it actually was. 7. We conclude that under certain conditions, such as low pHi, the H+ current is a significant fraction of the total outward current in snail neurones, and may also be in a variety of other cells. The H+ currents must be accounted for under such conditions in order to study accurately the properties of K+ and Ca2+ currents.