Molecular Mechanisms of Alcohol Actions in the Adolescent Brain

描述(由申请人提供)：与成年人相比，饮酒的青少年患记忆力和认知缺陷的风险更大。青少年酗酒引起的这种认知和记忆障碍严重影响心理社会功能，并可持续到成年。记忆缺陷持续存在的分子机制尚不清楚，但可能涉及乙醇诱导的涉及记忆形成的突触的变化。我们的发现显示，在青少年时期长期接触乙醇的动物的CA1海马突触中，突触反应的长期增强(LTP)得到了新的增强。在老年动物中，类似的乙醇暴露不会对海马LTP产生同样的影响。海马LTP是突触可塑性的一种形式，导致兴奋性突触传递的持续增强，被认为是记忆的底物。重要的是，LTP是由细胞内钙离子的内流触发的，并启动下游的信号转导和基因表达。在对照条件下，CA1突触的LTP是由突触后NMDA型谷氨酸受体亚型的钙离子内流启动的；而我们的发现表明，NMDA型受体不参与青少年时期接触乙醇的大鼠脑片LTP反应的增强。该提案将侧重于确定导致青少年酒精暴露所产生的独特LTP反应的钙信号级联。这些实验将结合细胞(细胞外电生理学和细胞内电流钳记录)和生化工具(蛋白质印迹分析)从长期间歇乙醇暴露的青春期大鼠和年龄匹配的乙醇-NA对照组的青春期大鼠的海马CA1切片中进行。我们将检验以下假设：青少年酒精暴露：(1)上调海马区Sigma-1受体的表达和/或功能，Sigma-1受体是神经活性类固醇和细胞内钙动态调节的内源性靶点；(2)促进突触后L型电压依赖性钙通道的激活；(3)激活与L型钙通道激活相关的关键信号蛋白，包括MAPK/ERK1/2、CREB、BDNF和TrkB-受体。这些实验将为青少年发育期酒精暴露引起LTP激活通路中年龄相关开关的分子机制提供关键的见解。

DESCRIPTION (provided by applicant): Adolescents who use alcohol have a greater risk for developing memory and cognitive deficits compared to adults. Such cognitive and memory disturbances elicited by adolescent alcohol abuse significantly impact psychosocial functioning and can persist long into adulthood. The molecular mechanisms responsible for the persistence of memory deficits are unknown, but likely involve ethanol-induced changes at synapses involved in memory formation. Our findings show a novel enhancement of long-term potentiation (LTP) of synaptic responses in CA1 hippocampal synapses in animals that have been chronically exposed to ethanol as early adolescents. Similar ethanol exposure in older animals does not produce the same effects on hippocampal LTP. Hippocampal LTP is a form of synaptic plasticity that results in the persistent enhancement of excitatory synaptic transmission and is considered a substrate for memory. Importantly, LTP is triggered by an influx of intracellular Ca2+ and initiates downstream actions on signaling cascades and gene expression. Under control conditions LTP at CA1 synapses is initiated by Ca2+ influx via postsynaptic NMDA- subtype of glutamate receptors; whereas our findings show that NMDA-receptors are not involved in the enhanced LTP response in slices from rats exposed to ethanol as early-adolescents. The proposal will focus on identifying the Ca2+ signaling cascades that contribute to the unique LTP response produced by adolescent ethanol exposure. The experiments will incorporate cellular (extracellular electrophysiology and intracellular current-clamp recordings) and biochemical tools (Western blot protein analysis) in hippocampal CA1 slices from adolescent rats exposed to chronic intermittent ethanol and age-matched ethanol-na¿ve controls. We will test the hypotheses that ethanol exposure in adolescents (1) upregulates the expression and/or function of sigma-1-receptors in hippocampus, which are endogenous targets of neuroactive steroids and regulators of intracellular Ca2+ dynamics; (2) facilitates the activation of postsynaptic L-type voltagegated calcium channels; (3) activates critical signaling proteins, including the MAPK/ERK1/2, CREB, BDNF and TrKB-receptors that are linked to L-type Ca2+ channel activation. These experiments will provide critical insights into the molecular mechanisms responsible for the age-dependent switch in the LTP-activated pathways elicited by ethanol exposure during the adolescent period of development.