Molecular Mechanisms of Alcohol Actions in the Adolescent Brain

描述（由申请人提供）：与成年人相比，使用酒精的青少年有更大的记忆和认知缺陷风险。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，并可能持续到成年。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记忆形成突触的变化。我们的研究结果表明，在动物的CA 1海马突触的突触反应的长时程增强（LTP）的一种新的增强已长期暴露于乙醇作为早期青少年。在老年动物中，类似的乙醇暴露不会对海马LTP产生相同的影响。海马LTP是突触可塑性的一种形式，其导致兴奋性突触传递的持续增强，并且被认为是记忆的底物。重要的是，LTP是由细胞内Ca 2+的流入触发的，并启动对信号级联和基因表达的下游作用。在控制条件下，CA 1突触的LTP是通过突触后NMDA-谷氨酸受体亚型的Ca 2+内流启动的;而我们的研究结果表明，NMDA受体不参与从大鼠暴露于乙醇作为早期青少年的切片中增强的LTP反应。该提案将集中于确定Ca 2+信号级联，有助于青少年乙醇暴露产生的独特的LTP反应。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（蛋白质印迹蛋白分析）在海马CA 1切片从青少年大鼠暴露于慢性间歇性乙醇和年龄匹配的乙醇初治对照。我们将检验以下假设：青少年的乙醇暴露（1）上调海马中σ-1受体的表达和/或功能，σ-1受体是神经活性类固醇的内源性靶点和细胞内Ca 2+动力学的调节剂;（2）促进突触后L型电压门控钙通道的激活;（3）激活关键信号蛋白，包括与L型Ca 2+通道激活相关的MAPK/ERK 1/2、CREB、BDNF和TrKB受体。这些实验将提供关键的见解，负责的年龄依赖性开关的LTP激活的途径引起的乙醇暴露在青春期的发展过程中的分子机制。

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.