Zhou F M, Hablitz J J
Neurobiology Research Center, University of Alabama at Birmingham 35294, USA.
J Neurosci. 1996 Feb 1;16(3):1131-9. doi: 10.1523/JNEUROSCI.16-03-01131.1996.
Using whole-cell patch-clamp techniques in brain slices, we studied the postnatal development of electrophysiological properties of rat neocortical layer I neurons during the first three weeks of postnatal life. Neurons, including Cajal-Retzius cells, were visualized under Nomarski optics before recording. In the first postnatal week, all layer I neurons, including Cajal-Retzius cells, had low resting membrane potentials (-40 to -55 mV), high input resistances (1-5 G omega), and long membrane time constants (80-130 msec). Action potentials (APs) of layer I neurons early in postnatal development were lower in amplitude and longer in duration. The threshold for APs also was more depolarized than in older neurons. A medium after-hyperpolarization already was present at postnatal day 0 (PN0), but fast afterhyperpolarizations were not seen until PN10. At all postnatal ages, layer I neurons were capable of repetitive firing, displayed little or no frequency adaptation, and did not display slow afterhyperpolarizations. Early in development, layer I neurons had a prominent hyperpolarization-activation depolarizing sag that decreased with age. These results suggest that the membrane properties of rat neocortical layer I neurons mature rapidly during the first two postnatal weeks. Cajal-Retzius cells had electrical properties similar to other layer I neurons and did not show an earlier maturation of membrane properties.
利用脑片全细胞膜片钳技术，我们研究了出生后前三周大鼠新皮层I层神经元电生理特性的产后发育情况。在记录前，通过诺马斯基光学显微镜观察包括Cajal-Retzius细胞在内的神经元。在出生后的第一周，所有I层神经元，包括Cajal-Retzius细胞，静息膜电位较低（-40至-55 mV），输入电阻较高（1-5 GΩ），膜时间常数较长（80-130毫秒）。出生后早期I层神经元的动作电位（APs）幅度较低，持续时间较长。APs的阈值也比成熟神经元更去极化。在出生后第0天（PN0）就已经存在中等程度的超极化后电位，但直到PN10才出现快速超极化后电位。在所有出生后年龄段，I层神经元都能够重复放电，几乎没有或没有频率适应性，并且不表现出缓慢的超极化后电位。在发育早期，I层神经元有一个明显的超极化激活去极化凹陷，随着年龄增长而减小。这些结果表明，大鼠新皮层I层神经元的膜特性在出生后的前两周迅速成熟。Cajal-Retzius细胞具有与其他I层神经元相似的电特性，并且没有表现出膜特性的提前成熟。
