Kuriyama K, Hirouchi M
Department of Pharmacology, Kyoto Prefectural University of Medicine, Japan.
Nihon Yakurigaku Zasshi. 1989 Jul;94(1):7-15. doi: 10.1254/fpj.94.7.
The gamma-aminobutyric acid (GABA) receptor has been classified into two receptor subtypes (GABAA and GABAB receptors) based on their pharmacological properties. The GABAA receptor in the central nervous system (CNS) has been found to be coupled structurally as well as functionally with the benzodiazepine receptor and Cl- channel. Purified GABAA receptor from bovine brain consisted of both alpha and beta subunits. The complementary DNAs encoding the GABAA receptor alpha and beta subunits have been cloned; and from their elucidated nucleotide sequences, the amino acid sequences of the subunits were deduced. The structure of both subunits, having four putative membrane domains, has been found to be similar to other ligand-gated receptors such as the nicotinic acetylcholine receptor alpha subunit and glycine receptor 48K subunit. Therefore, it has been suggested that these ligand-gated receptors comprise a superfamily. In addition, the presence of similarities in the nucleotide and deduced amino acid sequences of human brain GABAA receptor with those of bovine brain has been noted. On the other hand, the GABAB receptor, which is insensitive to bicuculline but sensitive to baclofen, has been found to be pharmacologically distinct from the GABAA receptor. The GABAB receptor in the brain has been found to be coupled with GTP-binding protein and generates the inhibitory transmission coupled with various intracellular effector systems such as adenylate cyclase and phosphoinositides turnover. The exact structure and function of the GABAB receptor in the CNS, however, remain to be clarified in future studies.
γ-氨基丁酸（GABA）受体已根据其药理学特性分为两种受体亚型（GABAA和GABAB受体）。已发现中枢神经系统（CNS）中的GABAA受体在结构和功能上均与苯二氮䓬受体和氯离子通道偶联。从牛脑中纯化的GABAA受体由α和β亚基组成。编码GABAA受体α和β亚基的互补DNA已被克隆；从其阐明的核苷酸序列中推导了亚基的氨基酸序列。已发现这两种亚基的结构都有四个假定的膜结构域，与其他配体门控受体如烟碱型乙酰胆碱受体α亚基和甘氨酸受体48K亚基相似。因此，有人提出这些配体门控受体构成一个超家族。此外，还注意到人类脑GABAA受体的核苷酸和推导氨基酸序列与牛脑的相似。另一方面，已发现对荷包牡丹碱不敏感但对巴氯芬敏感的GABAB受体在药理学上与GABAA受体不同。已发现脑中的GABAB受体与GTP结合蛋白偶联，并产生与各种细胞内效应系统如腺苷酸环化酶和磷酸肌醇周转偶联的抑制性传递。然而，CNS中GABAB受体的确切结构和功能仍有待未来研究阐明。
