Treistman S N, Wilson A
Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts 01545.
J Neurosci. 1987 Oct;7(10):3207-14. doi: 10.1523/JNEUROSCI.07-10-03207.1987.
The effects of ethanol (EtOH) on the early potassium current, IA, were examined in 3 identified neurons of Aplysia using voltage-clamp techniques. The primary effect of EtOH on this current was a pronounced increase in the time constant of decay. However, this effect was cell specific, being evident in cells MCC and R15 but not in cell B1. Other parameters of IA were not greatly affected in any of the cells, in comparison with the effects on decay time constant. Baseline parameters of IA were measured in each of the cells to determine whether subpopulations of IA channel might exist, and be differentially sensitive to EtOH. While differences did appear among cells, they were not consistent with an explanation of EtOH's actions based upon distribution of channel subtypes. The effect of EtOH on IA decay was dependent upon the voltage-clamp protocol used. When inactivation of IA developed at -20 mV, the slower development of inactivation noted above occurred. When inactivation without channel opening was produced by means of a prepulse to -40 mV, EtOH speeded up the development of inactivation. A number of possible explanations for these findings are discussed. Most of the effects of EtOH occurred within 1 min of application of the drug, suggesting relatively rapid access to the site of action. Effects continued to develop over succeeding minutes. This slower-developing effect may reflect either a delayed access to channels due to slower diffusion into or lateral movement within the lipid phase of the membrane, or it may indicate that channels are accessible to the EtOH molecule only when in certain states.
运用电压钳技术，在海兔的3个已鉴定神经元中研究了乙醇（EtOH）对早期钾电流IA的影响。EtOH对该电流的主要作用是使衰减时间常数显著增加。然而，这种作用具有细胞特异性，在MCC和R15细胞中明显，但在B1细胞中不明显。与对衰减时间常数的影响相比，IA的其他参数在任何细胞中均未受到很大影响。测量每个细胞中IA的基线参数，以确定是否可能存在IA通道亚群，以及它们对EtOH的敏感性是否存在差异。虽然细胞之间确实存在差异，但这些差异并不符合基于通道亚型分布对EtOH作用的解释。EtOH对IA衰减的影响取决于所使用的电压钳方案。当IA在-20 mV时发生失活，会出现上述较慢的失活发展情况。当通过预脉冲至-40 mV产生无通道开放的失活时，EtOH加速了失活的发展。讨论了对这些发现的一些可能解释。EtOH的大多数作用在药物应用后1分钟内出现，表明其相对较快地到达作用部位。在随后的几分钟内作用持续发展。这种较慢发展的作用可能反映了由于向膜脂相的扩散较慢或在膜脂相内横向移动而导致对通道的延迟作用，或者可能表明通道仅在某些状态下才对EtOH分子可及。
