DEVELOPMENTAL-CHANGES IN NA+ CONDUCTANCES IN RAT NEOCORTICAL NEURONS - APPEARANCE OF A SLOWLY INACTIVATING COMPONENT
DEVELOPMENTAL-CHANGES IN NA+ CONDUCTANCES IN RAT NEOCORTICAL NEURONS - APPEARANCE OF A SLOWLY INACTIVATING COMPONENT
复制标题
DOI：
10.1152/jn.1988.59.3.778
复制
发表时间：
1988-03-01
影响因子：
2.5
通讯作者：
PRINCE, DA
中科院分区：
文献类型：
--
作者：
HUGUENARD, JR;HAMILL, OP;PRINCE, DA
1. 大鼠感觉运动区新皮质神经元的Na+电导已被表征。从胚胎第16天（E16）到出生后第50天（P50）的发育阶段，通过急性解离获得神经元，以量化Na+电导动力学特性的任何发育变化。2. 根据形态学将神经元分为两类，以确定Na+电导是否存在细胞类型特异性差异，从而导致体外电流钳记录的不同动作电位形态。3. 分离后，使用膜片钳技术的全细胞变体对神经元进行电压钳夹。两种细胞类型，锥体和非锥体，在发育期间都表现出Na+电流密度的大幅增加（E16-P50）。胚胎动物神经元的归一化电导接近10 pS/micron2，在出生后2周内增加了6- 10倍。锥体神经元的最终电导高于非锥体神经元。4. 我们发现锥体和非锥体两种细胞类型在激活的电压依赖性、失活动力学、稳态失活的电压依赖性和失活后的恢复方面没有差异。5. 未成熟神经元内Na+电流的时间过程符合经典霍奇金-赫胥黎动力学。然而，在更成熟的神经元中，失活的动力学变得更加复杂，以至于需要两个衰变成分才能获得良好的拟合。慢衰组分的时间过程比快衰组分慢5 ~ 10倍。6. 采用了几种方法来降低成熟神经元中Na+电导的大小，以确保梯度的、电压依赖的内向电流。这些包括细胞外[Na+]降低，河豚毒素浓度低于最大值，保持电位降低。在这两种条件下，我们都能够验证Na+电流失活的观察结果，即Na+电流失活发生在两个指数上。7. 单通道Na+电流从细胞附着的贴片中获得。活性Na+通道的膜密度随着发育而增加，成熟神经元的总体平均表现为两个失活过程。缓慢的失活过程是由与短潜伏期打开相同振幅的长潜伏期单通道打开造成的。8. 我们得出结论，Na+通道在细胞类型之间没有动力学差异。因此，动作电位的差异不能用Na+电流动力学的差异来解释，但可能部分地由不同的密度来解释。（摘要删节为400字）
1. Na+ conductances have been characterized in rat neocortical neurons from the sensorimotor area. Neurons were obtained by acute dissociation from animals at developmental stages from embryonic day 16 (E16) to postnatal day 50 (P50) to quantify any developmental changes in the kinetic properties of the Na+ conductance. 2. Neurons were divided into two classes, based on morphology, to determine whether there are any cell-type specific differences in Na+ conductances that contribute to the different action potential morphologies seen in current-clamp recordings in vitro. 3. Upon isolation, neurons were voltage clamped using the whole-cell variation of the patch-clamp technology. Both cell types, pyramidal and nonpyramidal, demonstrate large increases in Na+ current density during this developmental period (E16-P50). Normalized conductances were near 10 pS/micron2 in neurons from embryonic animals, and increased 6- to 10-fold during the first 2 wk postnatal. The final conductance reached in pyramidal neurons was higher than in non-pyramidal neurons. 4. We found no differences between the two cell types, pyramidal and nonpyramidal, in the voltage dependence of activation, inactivation kinetics, voltage dependence of steady-state inactivation, and recovery from inactivation. 5. The time course of Na+ current in immature neurons were fit with classical Hodgkin-Huxley kinetics. However, in more mature neurons the kinetics of inactivation became more complicated such that two decay components were required to obtain good fit. The slowly decaying component had a time course 5 to 10 times slower than the fast component. 6. Several procedures were used to reduce the magnitude of Na+ conductance in mature neurons to ensure graded, voltage-dependent inward currents. These included reduced extracellular [Na+], submaximal tetrodotoxin concentrations, and reduced holding potential. Under each of these conditions we were able to verify the observation that Na+ current inactivation occurs with two exponentials. 7. Single-channel Na+ currents were obtained from cell-attached patches. The membrane density of active Na+ channels increases with development, and ensemble averages from mature neurons demonstrated two inactivation processes. The slow inactivation process was accounted for by long-latency single-channel openings of the same amplitude as the short-latency openings. 8. We conclude that there are no kinetic differences in the Na+ channels between cell types. Differences in action potentials are then not explained by differences in Na+ current kinetics, but might be partially explained by the different densities.(ABSTRACT TRUNCATED AT 400 WORDS)