FUNCTIONAL PROPERTIES OF NEURONAL NICOTINIC RECEPTORS

中枢神经系统的烟碱型乙酰胆碱受体(NAChRs) 与文献中发现的尼古丁受体相比，人们对尼古丁受体了解较少 肌肉和电子组织。与肌肉受体不同的是，受体 在中枢神经系统中，从遗传和药理上来说是相当的 异质的。各种神经元nAChR亚基已经被分离出来，并且 这些亚基的某些组合在以下情况下会产生功能性nAChR 在青蛙卵母细胞中表达。药理学研究提供了证据 功能性nAChR亚型也存在于原位。这样做的目的是 建议表征功能性神经元nAChR亚型在 并在药理学基础上区分受体亚型 和电生理特性。 用来检测原位受体的方法有两种。第一, 细胞内电生理记录将在选定的 雏鸡和大鼠脑的细胞核。被选中的原子核很可能有 基于结果的不同功能烟碱受体亚型 烟碱的放射自显影和原位杂交研究 感受器。第二种方法涉及培养选定的中央 鸡和大鼠神经元的膜片钳电生理研究 记录这些细胞表达的尼古丁受体的特征。 这些原位nAChRs的性质将直接与那些 一些基因定义的nAChR亚型将被表达 在青蛙卵母细胞或细胞系中。鸡、大鼠和人脑的亚基 将由膜片钳电生理学检查。 在这些实验中使用的一个重要的药理学工具是 蛇毒毒素家族被称为卡帕-神经毒素(K-毒素)。 最具特性的K-毒素，卡帕-银环蛇毒素，表现出很大的不同 不同神经元nAChR亚型的亲和力。因此，这是一个有用的探测器 用于在原位确定功能受体。三种额外的K毒素 在这个实验室中提纯的物质也将被检测为潜在的选择性 神经元nAChR拮抗剂。来自卵母细胞实验的证据表明 蛇毒成分识别某些受体亚型，具有更高的 亲和力强于卡帕-银环蛇毒素。几种不同组分的药效试验 因此，毒液也将在这些实验中进行检测。 人类的几种疾病状态涉及神经元胆碱能的改变 功能。观察到胆碱能传递明显减少。 患有阿尔茨海默病和亨廷顿病的患者。在……里面 此外，香烟烟雾中的主要成瘾成分是尼古丁， 通过中枢尼古丁受体产生刺激作用。通过 这些实验表征了中枢尼古丁受体亚型 在这项研究中提出的建议可能会提供更好的理解 疾病。

Nicotinic acetylcholine receptors (nAChRs) in the central nervous system are poorly understood in comparison with the nicotinic receptor found in muscle and electric tissue. In contrast to the muscle receptor, receptors in the central nervous system are genetically and pharmacologically quite heterogeneous. Various neuronal nAChR subunits have been isolated, and certain combinations of these subunits produce functional nAChR when expressed in frog oocytes. Pharmacological studies provide evidence that subtypes of functional nAChR exist in situ as well. The goal of this proposal is to characterize functional neuronal nAChR subtypes expressed in situ and to distinguish receptor subtypes on the basis of pharmacological and electrophysiological properties. The approach taken to examine in situ receptors is two-fold. First, intracellular electrophysiological recordings will be made in selected nuclei of chick and rat brain. The chosen nuclei are likely to have different subtypes of functional nicotinic receptors based on the results of autoradiographic and in situ hybridization studies of nicotinic receptors. The second approach involves culturing of selected central neurons from chick and rat, and using patch clamp electrophysiological recording to characterize nicotinic receptors expressed by these cells. The properties of these in situ nAChRs will be directly compared with those of a number of genetically defined nAChR subtypes which will be expressed in frog oocytes or cell lines. Subunits from chick, rat and human brain will be examined by patch clamp electrophysiology. An important pharmacological tool to be used in these experiments is the family of snake venom toxins known as the kappa-neurotoxins (K-Toxins). The best characterized K-Toxin, kappa-bungarotoxin, shows widely different affinities for various neuronal nAChR subtypes. It is thus a useful probe for defining functional receptors in situ. Three additional K-Toxins purified in this laboratory will also be examined as potential selective neuronal nAChR antagonists. Evidence from oocyte experiments implies that a snake venom component recognizes certain receptor subtypes with higher affinity than does kappa-bungarotoxin. The effects of several fractions of venom will therefore also be examined in these experiments. Several human disease states involve alterations in neuronal cholinergic function. A marked decrease in cholinergic transmission has been observed in patient's suffering Alzheimer's disease and Huntington's disease. In addition, the major addictive component in cigarette smoke is nicotine, which produces its stimulatory effect via central nicotinic receptors. By characterizing central nicotinic receptor subtypes, the experiments proposed in this study may provide a better understanding of these diseases.