Keio University School of Medicine, Department of Pharmacology, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
J Biomed Opt. 2010 Mar-Apr;15(2):020503. doi: 10.1117/1.3365135.
The electrical properties of axons critically influence the nature of communication between neurons. However, due to their small size, direct measurement of membrane potential dynamics in intact and complex mammalian axons has been a challenge. Furthermore, quantitative optical measurements of axonal membrane potential dynamics have not been available. To characterize the basic principles of somatic voltage signal propagation in intact axonal arbors, second-harmonic-generation (SHG) imaging is applied to cultured mouse hippocampal neurons. When FM4-64 is applied extracellularly to dissociated neurons, whole axonal arbors are visualized by SHG imaging. Upon action potential generation by somatic current injection, nonattenuating action potentials are recorded in intact axonal arbors. Interestingly, however, both current- and voltage-clamp recordings suggest that nonregenerative subthreshold somatic voltage changes at the soma are poorly conveyed to these axonal sites. These results reveal the nature of membrane potential dynamics of cultured hippocampal neurons, and further show the possibility of SHG imaging in physiological investigations of axons.
轴突的电学性质对神经元之间的通讯性质有重要影响。然而，由于其尺寸小，对完整和复杂的哺乳动物轴突中的膜电位动力学进行直接测量一直是一个挑战。此外，轴突膜电位动力学的定量光学测量尚不可用。为了表征完整轴突树突中体电压信号传播的基本原理，应用二次谐波产生（SHG）成像来研究培养的小鼠海马神经元。当将 FM4-64 施加到分离的神经元的细胞外时，通过 SHG 成像可以可视化整个轴突树突。通过在体电流注射产生动作电位时，在完整的轴突树突中记录到非衰减的动作电位。然而，有趣的是，电流和电压钳记录都表明，体上的非再生亚阈值电压变化不能很好地传递到这些轴突部位。这些结果揭示了培养的海马神经元的膜电位动力学的性质，并进一步表明了 SHG 成像在轴突的生理研究中的可能性。
