Alcohol and GABAergic Transmission in the Developing Neocortex

描述(申请人提供)：胎儿酒精综合征(FAS)仍然是导致出生缺陷的主要原因之一。虽然怀孕期间不饮酒是可以预防的，但据估计，在美国，每1000名活产中就有0.2到1.0人患有Fas。目前还没有可预防的治疗方法。在发育过程中，酒精暴露会影响中枢神经系统，从微小的结构和功能变化到广泛的神经元死亡，这是一个很好的特征。乙醇(Etoh)暴露后，其如何导致广泛的神经元变性的机制尚未得到很好的描述。据推测，乙醇诱导的细胞死亡是由于发育中的新皮质中神经元活动受到过度抑制所致。Etoh被认为通过在突触后增强GABA受体而起到苯二氮卓类的作用。然而，我们实验室以前的工作表明，乙醇通过增加GABA的释放来增加神经元的兴奋性。我假设乙醇增加了GABA的释放，导致皮层神经元的兴奋，皮质层经历了乙醇暴露导致的细胞死亡(II层和IV层)，但不是在没有这种作用的层(即III层)。在具体目标1中，我将使用全细胞和穿孔贴片电生理技术的组合来确定无水乙醇是否对新生儿躯体感觉皮质INV层的GABA能传递产生不同的影响。在特定的目标#2中，我将使用松散的细胞附着电生理和钙成像技术相结合的方法来确定GABAAR的激活是否导致相同神经元层的兴奋。如果我确定靶细胞的兴奋性增加，我将确定乙醇是否通过增加依赖动作电位的GABA释放来增加兴奋性。从长远来看，这些研究可能成为开发针对Fas的新的治疗干预措施的基础，该干预措施针对GABAARs在未成熟神经元中的兴奋作用。 总结：在美国，胎儿接触酒精是导致智力残疾的常见原因。酒精损害发育中的大脑的机制还没有得到充分的描述。这里提出的研究将增加我们对酒精如何影响神经递质GABA活动的理解，从长远来看，可能会形成针对这一问题的发育治疗的基础。

DESCRIPTION (provided by applicant): Fetal alcohol syndrome (FAS) continues to be one of the leading causes of birth defects. Although it is preventable by abstaining from alcohol consumption while pregnant, the estimated incidence for FAS in the United States is 0.2 to 1.0 per 1000 live births. Currently there are no preventable treatments for FAS. It is well characterized that ethanol exposure during development affects the central nervous system ranging from subtle structural and functional alterations to widespread neuronal death. Following ethanol (EtOH) exposure, the mechanism as to how it causes widespread neuronal degeneration is not well characterized. It has been postulated that EtOH-induced cell death results from excessive inhibition of neuronal activity in the developing neocortex. EtOH has been thought to act like a benzodiazepine by enhancing GABAARs postsynaptically. However, previous work from our laboratory suggests that EtOH increases neuronal excitability, by increasing GABA release. I hypothesize that EtOH increases GABA release leading to excitation of neurons in cortical layers that undergo apoptotic cell death in response to EtOH exposure (layers II and IV) but not in layers that do not (i.e. layer III). In specific aim #1, I will use a combination of whole-cell and perforated patch-electrophysiological techniques to determine if EtOH is differentially affecting GABAergic transmission in layers INV of the neonatal somatosensory cortex. In specific aim #2, I will determine if activation of the GABAAR results in excitation in the same neuronal layers by using a combination of loose cell-attached electrophysiological and Ca2+ imaging techniques. If I determine that there is an increase in excitability of the target cell, I will then determine if EtOH increases excitability by increasing action potential-dependent GABA release. In the long-term, these studies might form the basis for the development of novel therapeutic interventions against FAS that target the excitatory actions of GABAARs in immature neurons. Lay summary: Fetal alcohol exposure is a common cause of mental disabilities in the U.S. The mechanism by which alcohol damages the developing brain are poorly characterized. The studies proposed here will increase our understanding of how alcohol affects the actions of the neurotransmitter GABA and in the long term might form the basis for the developmental treatments against this problem.