Zhainazarov A B, Wachowiak M, Boettcher A, Elenes S, Ache B W
Whitney Laboratory, University of Florida, St. Augustine 32086, USA.
J Neurophysiol. 1997 May;77(5):2235-51. doi: 10.1152/jn.1997.77.5.2235.
This study reports an ionotropic GABA (gamma-aminobutyric acid) receptor in projection neurons acutely dissociated from the olfactory lobe of the brain of the spiny lobster and analyzed by whole cell and cell-free patch-clamp recording. GABA evokes a macroscopic current in the cells that is linear from -100 to + 100 mV, reverses at the imposed chloride equilibrium potential, has a permeability sequence of Cl- > acetate > bicarbonate > phosphate > propionate and SCN- > Br- > I- > Cl- > F-, and is reversibly blocked by the Cl channel blocker picrotoxin but not tert-butylbicyclophosphorothionate (TBPS). The current is bicuculline insensitive and activated by muscimol, isoguvacine, cis-4-aminocrotonic acid (CACA), and trans-aminocrotonic acid (TACA), as well as by the GABA(C)-receptor antagonists 4,5,6,7-tetrahydroisoxazolo [5,4,-c]pyridin-3-ol (THIP), 3-amino-1-propanesulfonic acid (3-APS), and imidazole-4-acetic acid (I-4AA), but not the GABA(B)-receptor agonists baclofen and 3-aminopropylphosphonic acid (3-APA). Agonist potency for the receptor is TACA > muscimol > GABA > I-4AA > isoguvacine > 3-APS > CACA > THIP. Unitary chloride currents in cell-free, outside-out patches from the cells share enough of these pharmacological properties to indicate that the channel underlies the macroscopic current. The receptor mediates an inhibitory current in the cells in vivo. The receptor is similar, if not identical, to one from neurons cultured from the thoracic ganglia of the clawed lobster. The more extensive pharmacological characterization of the receptor reported here indicates that this lobster CNS receptor is pharmacologically distinct from previously characterized ionotropic GABA receptors.
本研究报告了一种离子型γ-氨基丁酸（GABA）受体，该受体存在于从多刺龙虾大脑嗅叶急性解离的投射神经元中，并通过全细胞和无细胞膜片钳记录进行分析。GABA在细胞中诱发一种宏观电流，该电流在-100至+100 mV范围内呈线性，在施加的氯离子平衡电位处反转，其通透性顺序为Cl->醋酸根>碳酸氢根>磷酸根>丙酸根，且SCN->Br->I->Cl->F-，并且可被氯离子通道阻滞剂印防己毒素可逆性阻断，但不能被叔丁基双环磷硫代酸酯（TBPS）阻断。该电流对荷包牡丹碱不敏感，可被蝇蕈醇、异鹅膏蕈氨酸、顺式-4-氨基巴豆酸（CACA）、反式-氨基巴豆酸（TACA）以及GABA(C)受体拮抗剂4,5,6,7-四氢异恶唑并[5,4,-c]吡啶-3-醇（THIP）、3-氨基-1-丙烷磺酸（3-APS）和咪唑-4-乙酸（I-4AA）激活，但不能被GABA(B)受体激动剂巴氯芬和3-氨基丙基膦酸（3-APA）激活。该受体的激动剂效力顺序为TACA>蝇蕈醇>GABA>I-4AA>异鹅膏蕈氨酸>3-APS>CACA>THIP。来自这些细胞的无细胞、外翻膜片中的单位氯离子电流具有足够多的这些药理学特性，表明该通道是宏观电流的基础。该受体在体内介导细胞中的抑制性电流。该受体与从螯龙虾胸神经节培养的神经元中的受体相似，即便不完全相同。此处报道的对该受体更广泛的药理学特征表明，这种龙虾中枢神经系统受体在药理学上与先前表征的离子型GABA受体不同。
