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。虽然在听觉开始后，中枢听觉系统的突触会被经验改变，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。有一个新兴的文献表明，一些酶和蛋白质在成人大脑中的神经传递中起次要作用，但在发育过程中在引导轴突和建立突触中起重要作用。乙酰胆碱（ACh）、乙酰胆碱酯酶（AChE）和α 7烟碱乙酰胆碱受体（nAChR）是调节突触事件的神经化学物质，包括靶神经元中成熟突触形成所必需的基因的表达。在我们的实验室中，我们已经发现了一个途径投射到啮齿动物的章鱼细胞区域的后腹侧耳蜗核（PVCN），瞬时表达乙酰胆碱酯酶和a？nAChR在产后第二周。超微结构研究表明，很少突触连接是目前出生后第3天，并丰富的P5。胆碱能标记物表达的时间顺序，以及来自其他实验室的电生理数据表明，乙酰胆碱和相关的酶和蛋白质是突触成熟所必需的。其功能之一可能是调节多巴胺能受体基因的表达。专门影响胆碱能受体的毒素，如尼古丁，以生理相关浓度集中在胎儿和出生后的大脑中。虽然这不会导致耳聋，但可能会导致长期的语言缺陷。本研究的目的是阐明啮齿动物PVCN中与突触成熟和NMDA受体基因表达调控相关的胆碱能分子机制。总的假设是ACh的扩散释放通过聚集在PVCN章鱼细胞突触后位点上的α 7烟碱乙酰胆碱受体调节细胞内钙来调节NMDA谷氨酸受体的表达。具体假设如下：（1）ACh的释放是非囊泡性的;（2）nAChR聚集在章鱼细胞的突触后;（3）章鱼细胞上的α 7 nAChR在听力开始之前而不是之后调节细胞内钙;（4）尼古丁给药将上调NMDA受体基因表达，但不上调AMPA受体基因表达;（5）ACh通过α 7 nAChR调节NMDA谷氨酸受体表达。

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.