Sugamori K S, Sunahara R K, Guan H C, Bulloch A G, Tensen C P, Seeman P, Niznik H B, Van Tol H H
Department of Pharmacology, University of Toronto, Ontario, Canada.
Proc Natl Acad Sci U S A. 1993 Jan 1;90(1):11-5. doi: 10.1073/pnas.90.1.11.
Serotonin (5-HT) is a major neurotransmitter that influences various behaviors, neuronal plasticity, learning, and memory in molluscs. Although the physiology of 5-HT transmission in molluscs is well studied, little is known about the pharmacology and diversity of the 5-HT receptor system. Based on the high homology of genes coding for guanine nucleotide-binding protein (G protein)-coupled receptors, we have cloned a gene for the Lymnaea stagnalis 5-HT (5HTlym) receptor. The putative receptor protein, 509 amino acids long, has highest homology with the Drosophila 5-HT receptors and mammalian 5HT1 receptors. As revealed by RNA blot-hybridization analysis, two mRNA species of 2.3 and 3.2 kb are detected in the central nervous system of Lymnaea. Transient expression of 5HTlym in COS-7 cells showed saturable [3H]lysergic acid diethylamide binding with an estimated dissociation constant of 0.9 nM. The 5HTlym receptor exhibited a mixed 5HT-like pharmacology that cannot be precisely categorized with existing mammalian classification nomenclature. However, the 5HTlym receptor does display some characteristics that have been attributed to the putative mammalian vascular 5HT1-like receptor.
血清素（5-羟色胺，5-HT）是一种主要的神经递质，它影响着软体动物的各种行为、神经元可塑性、学习和记忆。尽管对软体动物中5-HT传递的生理学已有深入研究，但对5-HT受体系统的药理学和多样性却知之甚少。基于编码鸟嘌呤核苷酸结合蛋白（G蛋白）偶联受体的基因具有高度同源性，我们克隆了椎实螺5-HT（5HTlym）受体的一个基因。推测的受体蛋白长度为509个氨基酸，与果蝇5-HT受体和哺乳动物5HT1受体具有最高的同源性。RNA印迹杂交分析显示，在椎实螺的中枢神经系统中检测到两种mRNA，大小分别为2.3 kb和3.2 kb。5HTlym在COS-7细胞中的瞬时表达显示出可饱和的[3H]麦角酰二乙胺结合，估计解离常数为0.9 nM。5HTlym受体表现出一种混合的5-HT样药理学特性，无法用现有的哺乳动物分类命名法精确分类。然而，5HTlym受体确实表现出一些已归因于推测的哺乳动物血管5HT1样受体的特征。
