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 神经元上的乙酰胆碱受体(AChRs)。我们的方法一直是使用 一个简单易处理的系统，青蛙心脏神经节，AChRs在那里 副交感神经元可以通过免疫细胞化学进行分析， 放射自显影，生物化学，以及神经支配的影响 在成人去神经和再神经支配过程中可以监测AChRs 蛙类(Rana)以及胚胎的初始神经支配(非洲爪哇)。 在过去的获奖期，我们发现去神经并不会增加 心脏神经节细胞表面AChRs的数量 阻断AChR的蛇毒125I-神经元银环蛇毒素的结合 功能。去神经确实增加了心脏神经节的敏感性 细胞对乙酰胆碱(ACh)通过微管施加；这一效应 似乎是由于水解物的有效性降低 酶的乙酰胆碱酯酶(AChE)和不改变的数量 细胞表面的功能性AChRs。 我们有三个具体目标。首先，我们将研究 去神经和再神经支配对脑电分布的影响 尖吻林蛙成体的AChRs和AChR簇。在第二个目标中，我们 将决定去神经超敏是否可以用 细胞外间隙中AChE分子数量的减少 周围的神经节细胞和/或其动力学特性的改变。 我们还将检查ACh敏感度的降低是否 在神经再支配的第一个阶段是由于疼痛的变化，在 AChRs，或两者都有。在第三个目标中，我们将检查AChRs是否 在非洲爪哇发育中的心脏神经节细胞上表达， 在神经节前轴突接触细胞期间或之后。我们会 确定AChRs是否出现在从未被神经支配的神经元上 通过节前轴突，如果是这样，神经支配是否增强AChR 表情。 这些研究应该会增加我们对神经元尼古丁如何 AChRs和ACh敏感性受神经支配的调节。

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.