CHARACTERIZATION OF OPIOID AND PEPTIDE RECEPTORS IN BRAIN AND PERIPHERAL TISSUES

我们已经使用定量配体结合研究来表征复合物， 大脑中激素和神经递质的异源受体， 其他组织。 我们已经评估了这一假设，即同型半胱氨酸（HCA）是一种 天然存在的N-甲基-D-天冬氨酸（NMDA）神经递质 谷氨酸受体的类型。NMDA受体是变构偶联的 - 离子通道，药物MK-801以高亲和力与其结合， 的特异性我们检测了[3 H]-MK-801与脑细胞膜的结合 将其彻底洗涤以除去内源性氨基酸和其它 小分子配体L-谷氨酸或L-同型半胱氨酸的补充导致 [3 H]-MK-801结合的平行剂量反应曲线。该效应 通过低浓度的甘氨酸（一种已知的变构调节剂）增强 这个系统。其他20多种氨基酸无效， 证明了L-HCA的特异性。中等程度的 证明了立体选择性。HCA似乎是选择性的， NMDA受体，而对红藻氨酸或使君子酸无效 受体。连同数据（例如，电生理学） 实验室，这些研究支持的假设，L-HCA可能是 兴奋性氨基酸受体的内源性神经递质。 研究了几种一价和二价阳离子对 已经检测了“sigma”和苯环己哌啶（PCP）受体的配体， 详细这两种类型的受体显示出不同的敏感性 离子。 大鼠和豚鼠脑细胞膜上的σ和PCP受体， 使用定量配体结合研究进行表征， 交叉位移研究，剂量响应面和广泛的计算机 建模我们证明，西格玛和PCP网站是不同的， PCP位点对两种大鼠都可以分解为高亲和力和低亲和力形式 和豚鼠，而σ受体可以分为两种形式， 豚鼠

We have used quantitative ligand binding studies to characterize complex, heterogenous receptors for hormones and neurotransmitters in brain and other tissues. We have evaluated the hypothesis, that homocysteic acid (HCA) is a naturally occurring neurotransmitter for the N-methyl-D-Aspartate (NMDA) type of the glutamate receptor. The NMDA receptor is allosterically coupled to an ion channel, to which the drug MK-801 binds with high affinity and specificity. We examined the binding of [3H]-MK-801 to brain membranes which were thoroughly washed to remove endogenous amino acids and other small ligands. Repletion of L-glutamate, or L-homocysteic acid, resulted in parallel dose response curves for [3H]-MK-801 binding. This effect was potentiated by low concentrations of glycine, a known allosteric modulator of this system. More than 20 other amino acids were ineffective, demonstrating the specificity of L-HCA. A moderate degree of stereoselectivity was demonstrated. HCA appears to be selective for the NMDA receptor, and not effective at the kainic acid or quisqualate receptors. Together with data (e.g., electrophysiological) from other laboratories, these studies support the hypothesis that L-HCA may be an endogenous neurotransmitter at excitatory amino acid receptors. The effects of several monovalent and divalent cations on the binding of ligands to the "sigma" and phencyclidine (PCP) receptors have been examined in detail. These two types of receptors show differential sensitivity to ions. The sigma and PCP receptors of membranes from rat and guinea pig brain have been characterized using quantitative ligand binding studies with self-and cross displacement studies, dose response surfaces and extensive computer modelling. We demonstrate that sigma and PCP sites are distinct, and that the PCP sites can be resolved into high and low affinity forms for both rat and guinea pig, while the sigma receptor can be resolved into two forms in the guinea pig.