NEURONAL NICOTINC ACETYLCHOLINE RECEPTORS

这项研究的长期目标是了解 神经支配调节烟碱的数量和分布 乙酰胆碱受体（AChRs）。 我们的方法是 一个简单而易处理的系统，青蛙心脏神经节， 副交感神经元可通过免疫细胞化学分析， 放射自显影和生物化学，以及神经支配的影响 在成人去神经支配和再神经支配期间， 青蛙（蛙）以及在胚胎（非洲爪蟾）最初的神经支配。 在过去的奖励期间，我们发现去神经支配并没有增加 心脏神经节细胞表面AChR的数量，通过 125 I-神经元银环蛇毒素（一种阻断AChR的蛇毒素）的结合 功能 去神经支配确实增加了心神经节的敏感性 细胞通过微量移液管施加乙酰胆碱（ACh）;这种效果 似乎是由于水解的有效性降低， 酶乙酰胆碱酯酶（AChE），而不是数量的变化， 细胞表面的功能性乙酰胆碱受体。 我们有三个具体目标。 首先，我们将研究 去神经支配和再神经支配对神经分布的影响 尖音蛙（Rana pipiens）AChRs和AChR簇。 第二个目标，我们 将决定去神经超敏性是否可以解释为 细胞外空间中乙酰胆碱酯酶分子数量的减少 周围神经节细胞和/或其动力学性质的变化。 我们还将研究乙酰胆碱敏感性的降低是否 在神经再支配的第一阶段是由于乙酰胆碱酯酶的变化， AChR，或两者。 在第三个目标中，我们将研究乙酰胆碱受体是否 在非洲爪蟾的心脏神经节细胞上表达， 在细胞与节前轴突接触期间或之后。 我们将 确定AChR是否出现在从未受神经支配的神经元上 如果是这样，神经支配是否会增强AChR 表情 这些研究应该增加我们对神经元烟碱 AChRs和ACh敏感性受神经支配调节。

The long-range objective of this research is to understand how innervation regulates the number and distribution of nicotinic acetylcholine receptors (AChRs) on neurons. Our approach has been to use a simple and tractable system, the frog cardiac ganglion, where AChRs on parasympathetic neurons can be analyzed by immunocytochemistry, autoradiography, and biochemistry, and where the influence of innervation upon AChRs can be monitored during denervation and reinnervation in adult frogs (Rana) as well during initial innervation in embryos (Xenopus). In the past award period we found that denervation does not increase the number of AChRs on the surface of cardiac ganglion cells, measured by the binding of 125I-neuronal bungarotoxin, a snake toxin that blocks AChR function. Denervation does increase the sensitivity of cardiac ganglion cells to acetylcholine (ACh) applied via a micropipet; this effect appears to be due to a reduction in the effectiveness of the hydrolytic enzyme acetylcholinesterase (AChE) and not to a change in the number of functional AChRs on the cell surface. We have three specific aims. In the first, we will examine the consequences of denervation and reinnervation upon the distribution of AChRs and AChR clusters in adult Rana pipiens. In the second aim, we will determine whether denervation supersensitivity can be explained by a reduction in the number of AChE molecules in the extracellular space surrounding ganglion cells and/or a change in their kinetic properties. We will also examine whether the reduction in ACh sensitivity that occurs during the first stages of reinnervation is due to a change in AChE, in AChRs, or in both. In the third aim we will examine whether AChRs are expressed on developing cardiac ganglion cells in Xenopus laevis before, during, or after cells are contacted by preganglionic axons. We will determine whether AChRs appear on neurons that have never been innervated by preganglionic axons, and, if so, whether innervation enhances AChR expression. These studies should increase our understanding of how neuronal nicotinic AChRs and ACh sensitivity are regulated by innervation.