EFFECTS OF ETHANOL ON RECEPTOR ION-CHANNEL BEHAVIOR

已有研究表明，乙醇降低了表观解离。 肌型烟碱能离子通道激活常数 受体。此外，众所周知，乙醇会加速 受体的脱敏，这可能倾向于抵消 乙醇在某些情况下具有增敏作用。这个 乙醇诱导的乙酰胆碱亲和力增加已在 乙酰胆碱与受体和乙酰胆碱结合的研究 放射性离子的活化通量。这一发现已经被复制到 其他受体包括GABA受体和神经元性乙酰胆碱 受体。这一现象现在将在 膜片钳培养细胞膜上的单一受体离子通道。 需要回答的问题是，乙醇是否会导致 离子通量是由于通道开通率的增加或 渠道关闭速度的降低。我们希望确定是否有 是在以下情况下通道打开的概率的增加 或者，如果通道只是在打开后保持更长的开放时间。 类似地，我们将研究乙醇对乙醇提取过程的影响 不同浓度激动剂脉冲作用的脱敏作用 到隔离的膜贴片，在那里受体的数量可以 通过电生理学方法量化，并计算出 脱敏反应是可以估计的。这种脱敏作用 也可以通过量化与单个通道的行为相关 受体引起的通道关闭时间分布 失活，因为它随着脱敏过程的变化而变化。这些 将用小鼠肌肉型乙酰胆碱进行研究 大鼠神经元性乙酰胆碱受体在BC3H-L细胞上的受体 PC-12细胞和培养的小鼠脊髓神经元上的GABA受体。 对乙醇分子效应的精确理解 受体水平将有助于最终分析该部位是否 作用的关键是在脂质界面或受体蛋白。

It has been demonstrated that ethanol reduces the apparent dissociation constant for activation of the ion channel of the muscle-type nicotinic receptor. In addition it is known that ethanol accelerates the desensitization of the receptor which may tend to counteract the sensitizing effect of ethanol under some circumstances. The ethanol-induced increase in acetylcholine affinity has been verified in studies of acetylcholine binding to the receptor and acetylcholine activated flux of radioactive ions. This finding has been replicated for other receptors including the GABA receptor and a neuronal acetylcholine receptor. The phenomenon will now be investigated at the level of the single receptor ion channel in patch-clamped membranes of cultured cells. The question to be answered is whether the ethanol-induced increase in ion flux is due to an increase in the rate of channel opening or a decrease in the rate of channel closing. We wish to determine if there is an increase in the probability of channel opening in the presence of ethanol or if the channels merely stay open longer after opening. Similarly, we will study the effects of ethanol on the process of desensitization by applying pulses of agonist at different concentrations to isolated membrane patches where the number of receptors can be quantified by electrophysiological methods and the decay constant of the response due to desensitization can be estimated. This desensitization can also be related to the behavior of the single channel by quantifying the distribution of channel closed times which is caused by receptor inactivation as it changes with the desensitization process. These studies will be carried out with the mouse muscle-type acetylcholine receptor on BC3H-l cells, the rat neuronal acetylcholine receptor on PC-12 cells and the GABA receptor on cultured mouse spinal cord neurons. A precise understanding of the molecular effects of ethanol at the single receptor level will be useful in the final analysis of whether the site of action is at the lipid interface or the receptor protein.