Akaike Norio, Murakami Nobuya, Katsurabayashi Shutaro, Jin Young-Ho, Imazawa Takayoshi
Cellular and System Physiology, Department of Phychosomatic Medicine, Faculty of Medicine, Graduate School of Medical Sciences, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812-8582, Japan.
Neurosci Res. 2002 Mar;42(3):187-95. doi: 10.1016/s0168-0102(01)00320-0.
Evoked inhibitory postsynaptic currents (eIPSCs) generated from a single GABAergic bouton were recorded and the functional properties were investigated. Native single boutons attached to mechanically dissociated rat hippocampal CA1 neurons, namely "synaptic bouton" preparation, were visualized with FM 1-43 dye and selectively stimulated by a glass pipette directed to a single bouton by focal stimulation. The GABAergic eIPSCs were elicited in like all-or-none fashion regarding both stimulus strength and pipette location, thus indicating that the eIPSCs result from the activation of a single bouton. The GABA release from the boutons was action potential dependent since eIPSCs were blocked in the presence of either voltage-dependent Na(+) or Ca(2+)channel blocker. Even in the presence of tetrodotoxin (TTX), eIPSCs could be elicited by additional application of a voltage-dependent K(+) channel blocker, 4-AP. The GABA release depended on external Ca(2+) concentration. Amplitude histogram of eIPSCs did not follow Poisson distribution or show discrete peaks. As a result, this new experimental approach using both focal stimulation and a synaptic bouton preparation allows for a detailed study of the native synaptic machinery in nerve terminals measuring smaller than 1 microm in size in the CNS.
记录了从单个GABA能终扣产生的诱发抑制性突触后电流（eIPSCs），并对其功能特性进行了研究。用FM 1-43染料可视化附着在机械解离的大鼠海马CA1神经元上的天然单个终扣，即“突触终扣”标本，并通过聚焦刺激用玻璃微管将其定向到单个终扣进行选择性刺激。GABA能eIPSCs在刺激强度和微管位置方面均以全或无的方式诱发，因此表明eIPSCs是由单个终扣的激活产生的。终扣释放GABA依赖于动作电位，因为在存在电压依赖性Na(+)或Ca(2+)通道阻滞剂的情况下，eIPSCs被阻断。即使在存在河豚毒素（TTX）的情况下，额外施加电压依赖性K(+)通道阻滞剂4-AP也能诱发eIPSCs。GABA释放依赖于细胞外Ca(2+)浓度。eIPSCs的幅度直方图不遵循泊松分布，也没有显示离散的峰值。因此，这种同时使用聚焦刺激和突触终扣标本的新实验方法，能够对中枢神经系统中尺寸小于1微米的神经末梢中的天然突触机制进行详细研究。
