Glutamate receptor-channels induced by brain messenger RNA in Xenopus oocytes

用脑皮层、纹状体和海马提取的mRNA注射大鼠脑和牛脑后，观察其在非洲爪蟾卵母细胞膜上诱导谷氨酸受体通道的电生理变化。(1)卵母细胞静息膜电位范围为-50 ~ -60 mV。谷氨酸及其类似物n -甲基- d -天冬氨酸、半胱甘肽和盐酸盐浓度为10^<-6>M时，膜电位发生变化。大多数情况下观察到去极化反应，但有时也会出现超极化反应。(2)从大脑皮层、纹状体和海马提取的mrna，以及大鼠脑和牛脑提取的mrna对受体通道的诱导均无差异。(3) Kainate总是以剂量依赖的方式使膜去极化，阈值浓度低至10^<-8>M。卵母细胞对盐酸盐的反应分为三种不同的类型：1型，快速去极化，长时间不复极化；第2型，峰状去极化后呈高原状缓慢去极化；3型，尖峰状去极化。(4)兴奋性氨基酸拮抗剂D-己二酸、2-氨基-4-磷酸丁酸、谷氨酸二乙基酯和-D-谷氨酰甘氨酸对海碱盐的三种反应均无抑制作用。(5)对盐酸盐无致敏反应。

The glutamate receptor-channels induced in the membrane of Xenopus laevis oocyte injected with mRNA extracted from cerebral cortex, striatum and hippocampus in the rat brain and the bovine brain were investigated electrophysiologically.(1) The oocyte resting membrane potential ranged from -50 to -60 mV. The changes in the membrane potentials were induced in 10^<-6>M concentration of glutamate and its analogues, N-methyl-D-aspartate, quisqualate and kainate. The depolarizing responses were mostly observed, but some-times the hyperpolarizing responses occurred.(2) The differences in the induction of receptor-channels were not found between mRNAs extracted from cerebral cortex, striatum and hippocampus, and between the rat brain and the bovine brain.(3) Kainate always depolarized the membranes, in a dose-dependent manner, with threshold concentration as low as 10^<-8>M. The oocyte responses to kainate were separated into the three distinct types: Type 1, the fast depolarization without repolarization for a long period; Type 2, the spike-like depolarization followed by slow depolarization in the shape of plateau; Type 3, the spike-like depolarization.(4) The antagonists to the excitatory amino acid, D- -adipate,2-amino-4-phosphonobutyric acid, glutamate diethylester and -D-glutamylglycine did not inhibit the three types of responses to kainate.(5) The responses to kainate were not sensitized.