Xia Yang, Zhao Yuan, Yang Mingpo, Zeng Shaoqun, Shu Yousheng
Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, P. R. China.
Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics-Huazhong University of Science and Technology, Wuhan, P. R. China.
PLoS One. 2014 Jun 27;9(6):e100968. doi: 10.1371/journal.pone.0100968. eCollection 2014.
GABAA receptors distributed in somatodendritic compartments play critical roles in regulating neuronal activities, including spike timing and firing pattern; however, the properties and functions of GABAA receptors at the axon are still poorly understood. By recording from the cut end (bleb) of the main axon trunk of layer -5 pyramidal neurons in prefrontal cortical slices, we found that currents evoked by GABA iontophoresis could be blocked by picrotoxin, indicating the expression of GABAA receptors in axons. Stationary noise analysis revealed that single-channel properties of axonal GABAA receptors were similar to those of somatic receptors. Perforated patch recording with gramicidin revealed that the reversal potential of the GABA response was more negative than the resting membrane potential at the axon trunk, suggesting that GABA may hyperpolarize the axonal membrane potential. Further experiments demonstrated that the activation of axonal GABAA receptors regulated the amplitude and duration of action potentials (APs) and decreased the AP-induced Ca2+ transients at the axon. Together, our results indicate that the waveform of axonal APs and the downstream Ca2+ signals are modulated by axonal GABAA receptors.
分布于树突体部分的GABAA受体在调节神经元活动（包括放电时间和放电模式）中发挥关键作用；然而，轴突上GABAA受体的特性和功能仍知之甚少。通过记录前额叶皮层切片中5层锥体神经元主轴突干的切断端（泡），我们发现GABA离子电渗法诱发的电流可被印防己毒素阻断，这表明轴突中存在GABAA受体的表达。静态噪声分析显示，轴突GABAA受体的单通道特性与体细胞受体相似。用短杆菌肽进行的穿孔膜片钳记录显示，轴突干处GABA反应的反转电位比静息膜电位更负，这表明GABA可能使轴突膜电位超极化。进一步的实验表明，轴突GABAA受体的激活调节动作电位（AP）的幅度和持续时间，并减少轴突处AP诱导的Ca2+瞬变。总之，我们的结果表明，轴突AP的波形和下游Ca2+信号受轴突GABAA受体的调节。
