【摘要】 应用全细胞膜片钳记录技术,在大鼠新鲜分离背根神经节（dorsal root ganglion,DRG）神经元上,观察预加咖啡因对GABA-激活电流(I_GABA)的调制作用。实验中,大部分受检细胞（97.4%,113/116）对外加GABA敏感。1～1000μmol/L GABA引起一剂量依赖性、有明显去敏感作用的内向电流。在受检的108个DRG细胞中,约有半数（53.7%,58/108）对胞外加咖啡因（0.1～100μmol/L）敏感,产生一幅值很小的内向电流。预加咖啡因（0.1～100μmol/L）30s后再加GABA能明显抑制GABA（100μmol/L）激活电流的幅值。预加咖啡因后GABA量效曲线明显下移;GABA-激活电流的最大值较之对照下降约57%;而K_d值（30μmol/L）几乎不变,表示此种抑制为非竞争性的。预加安定（diazepam,1μmol/L）对GABA（100μmol/L）激活电流有增强作用,而预加咖啡因（10μmol/L）有拮抗安定增强I_GABA的作用。胞内透析H-8后,几乎可以完全消除咖啡因对I_GABA的抑制作用。已知GABA作用于初级感觉神经元能引起初级传入去极化,因而实验结果提示,咖啡因有可能在初级传入末梢产生对抗突触前抑制的效应。更多还原

【Abstract】 By means of whole-cell patch clamp technique, the modulatory effect of caffeine on GABA-activated currents (I_GABA) wasinvestigated in acutely isolated rat dorsal root ganglion （DRG） neurons. The majority of the neurons examined （113/116） were sensitiveto GABA （1～1000μmol/L）. GABA activated a concentration-dependent inward current, which manifested obvious desensitization. In 58out of 108 neurons, caffeine induced a small inward current, while in others no detectable current was observed. After the neurons weretreated with caffeine （0.1～100μmol/L） prior to the application of GABA （100 μmol/L） for 30 s, GABA-activated inward currents wereobviously inhibited. Caffeine shifted the GABA dose-response curve downward and decreased the maximum response to 57% withoutchanging K_d value. These results indicate that the inhibitory effect is non-competitive. The pretreatment with caffeine （10μmol/L） inhibitedI_GABA which was potentiated by diazepam （1μmol/L）. Intracellular application of H-8 almost completely abolished the inhibitory effectof caffeine on I_GABA. Because GABA can induce primary afferent depolarization （PAD）, our results suggest that caffeine may be able toantagonize the effect of presynaptic inhibition of GABA in primary afferent.更多还原