Ethanol-Neurotransmitter Interactions in Brain Neurons

描述(由申请者提供)：本项目的总体具体目标是了解乙醇在调节奖赏的大脑通路上的作用。腹侧被盖区的多巴胺能神经元(DA-VTA神经元)在乙醇的增强作用中起重要作用，乙醇可增加这些神经元的放电频率。我们发现5-羟色胺能增强乙醇对DA-VTA神经元的兴奋作用。我们随后的研究对DA-VTA神经元膜上的离子电流进行了研究，以阐明这种增强的离子机制。在之前的项目期间，我们重点研究了可能支持5-羟色胺增强的两种膜电流，钙依赖型钾电流SK和混合阳离子电流LH。SK可以通过阿帕明等药物或通过耗尽细胞内钙来减少。我们发现，5-羟色胺降低iH，并产生类似于阿帕明产生的变化的尖峰后超极化。在我们的初步研究中，我们发现这两种电流的同时减少会对乙醇激发产生深远的增强作用。我们开发了一个模型来解释这一观察结果。在拟议的研究中，五个特定的目标将寻求探索乙醇兴奋和5-羟色胺增强这种兴奋之间的关系。具体目标#1将建立在SK和Ih被阻断期间极低浓度乙醇的浓度-反应曲线。具体目标#2将确定乙醇刺激的5-羟色胺增强是否是由SK和Ih同时减少所介导的。具体目标#3和#4将确定阻断SK和Ih如何改变DA-VTA神经元的特异膜属性，以及如何通过SK和Ih阻断改变乙醇对特异膜属性的影响。具体目标#5将使用细胞内游离钙的成像来确定长期服用5-羟色胺是否会耗尽细胞内的钙储存。这些研究直接建立在我们有趣的通过阻断SK和IH增强乙醇的初步观察的基础上，并将提供关于DA-VTA神经元中神经递质对离子电流的影响如何调节对乙醇兴奋的敏感性的重要信息。最终，这个项目产生的信息可能有助于开发改善酒精中毒的药物疗法。

DESCRIPTION (provided by applicant): The overall specific aims of this project are to understand the action of ethanol on brain pathways that mediate reward. The dopaminergic neurons of the ventral tegmental area (DA-VTA neurons) are important for the mediation of the reinforcing properties of ethanol, and the firing rate of these neurons is increased by ethanol. We have shown that serotonin potentiates ethanol excitation of DA-VTA neurons. Our subsequent studies have investigated ionic currents in the membrane of DA-VTA neurons to elucidate the ionic mechanism of this potentiation. In the previous project period, we focused on two membrane currents that may underlie the serotonin potentiation, the calcium-dependent potassium current SK, and the mixed cationic current lh. SK can be reduced by drugs like apamin or by depletion of intracellular calcium. We found that serotonin reduces Ih, and produces changes in the spike afterhyperpolarization similar to those produced by apamin. In our preliminary studies, we found that concurrent reduction of both of these currents produces profound potentiation of ethanol excitation. We have developed a model to explain this observation. In the proposed studies, five specific aims will seek to explore the relationship between ethanol excitation and potentiation of that excitation by serotonin. Specific Aim #1 will establish the concentration-response curve for very low concentrations of ethanol during blockade of SK and Ih. Specific Aim #2 will ascertain whether serotonin potentiation of ethanol excitation is mediated by concurrent reduction of SK and Ih. Specific Aims #3 and #4 will determine how blockade of SK and Ih alter specific membrane properties of DA-VTA neurons, and how ethanol effects on specific membrane properties are altered by SK and Ih blockade. Specific Aim #5 will use imaging of intracellular free calcium to determine whether prolonged administration of serotonin depletes intracellular stores of calcium. These studies directly build on our interesting initial observations of ethanol potentiation by blockade of SK and Ih, and will provide important information on how sensitivity to ethanol excitation may be modulated by neurotransmitter effects on ionic currents in DA-VTA neurons. Ultimately, information generated by this project may help in the development of pharmacotherapies for the amelioration of alcoholism.