TRANSIENT EXPRESSION OF CHOLINERGIC MARKERS IN THE PVCN

描述（由申请人提供）：大脑中的通路和突触连接是由一系列精心策划的神经化学事件建立的。虽然中枢听觉系统的突触在听觉开始后被经验修改，但突触连接是在第八神经对外部环境做出反应之前建立的。有新的文献表明，一些在成人大脑神经传递中起次要作用的酶和蛋白质在发育过程中对轴突的引导和突触的建立起重要作用。乙酰胆碱（ACh）、乙酰胆碱酯酶（AChE）和a7烟碱乙酰胆碱受体（nAChR）是调节突触事件的神经化学物质，包括靶神经元成熟突触形成所必需的基因表达。在我们的实验室中，我们发现了一条通往啮齿动物章鱼后腹侧耳蜗核（PVCN）细胞区域的通道，该通道短暂表达AChE和a？nAChR在出生后第二周。超微结构研究表明，在出生后第3天，突触连接很少存在，而P5则大量存在。胆碱能标记物表达的时间序列以及其他实验室的电生理数据表明，乙酰胆碱和相关酶和蛋白质对突触的成熟至关重要。其功能之一可能是调节谷氨酸受体基因的表达。专门影响胆碱能受体的毒素，如尼古丁，以生理上相关的浓度集中在胎儿和出生后的大脑中。虽然这不会导致耳聋，但它可能会导致长期的语言缺陷。本研究旨在阐明啮齿动物PVCN突触成熟和NMDA受体基因表达调控的胆碱能分子机制。总的假设是，ACh的弥漫性释放通过聚集在PVCN章鱼细胞突触后的a7个烟碱乙酰胆碱受体调节细胞内钙，从而调节NMDA谷氨酸受体的表达。具体假设为：(1)乙酰胆碱释放为非囊泡性；(2) nachr在章鱼细胞突触后聚集；章鱼细胞上的ACh (3) a7 nAChRs在听力发生前调节细胞内钙，而在听力发生后不调节；(4)烟碱会上调NMDA受体基因的表达，而不会上调AMPA受体基因的表达；(5)乙酰胆碱通过a7个nAChRs调控NMDA谷氨酸受体的表达。

DESCRIPTION (provided by applicant): The pathways and synaptic connections in the brain are established by a finely orchestrated series of neurochemical events. Although central auditory system synapses are modified by experience after the onset of hearing, synaptic connectivity is established before the eighth nerve is responsive to the external environment. There is an emerging literature indicating that some enzymes and proteins with minor roles in neurotransmission in the adult brain have major roles in guiding axons and establishing synapses during development. Acetylcholine (ACh), acetylcholinesterase (AChE) and the a7 nicotinic acetylcholine receptor (nAChR) are among the neurochemicals that regulate synaptic events, including the expression of genes obligatory for mature synapse formation in target neurons. In our laboratory, we have discovered a pathway projecting to the rodent octopus cell region of the posterior ventral cochlear nucleus (PVCN) that transiently expresses AChE and the a? nAChR during the second postnatal week. Ultrastructural studies indicate that few synaptic junctions are present by postnatal day 3, and are abundant by P5. The temporal sequence of the expression of the cholinergic markers, together with electrophysiological data from other laboratories, suggests that ACh and related enzymes and proteins are essential for the maturation of synapses. One of their functions may be to modulate glutamatergic receptor gene expression. Toxins that specifically affect cholinergic receptors, such as nicotine, concentrate in the fetal and postnatal brain in physiologically relevant concentrations. While this would not cause deafness, it could contribute to long-term language deficits. The goal of the proposed studies is to elucidate the cholinergic molecular mechanisms related to the maturation of synapses and regulation of NMDA receptor gene expression in the rodent PVCN. The overall hypothesis is that the diffuse release of ACh regulates NMDA glutamate receptor expression by regulating intracellular calcium through a7 nicotinic acetylcholine receptors clustered on postsynaptic sites of PVCN octopus cells. The specific hypotheses are: (1) ACh release is nonvesicular; (2) nAChRs are clustered postsynaptically on octopus cells; ACh (3) a7 nAChRs on octopus cells regulate intracellular calcium before, but not after, the onset of hearing; (4) nicotine administration will upregulate NMDA, but not AMPA, receptor gene expression; and (5) ACh, through a7 nAChRs, regulates NMDA glutamate receptor expression.