Amitai Y
Center for Brain Research, Unit of Physiology, Faculty of Health Sciences, Ben-Gurion University, Beer-Sheva, Israel.
Neuroscience. 1994 Nov;63(1):151-61. doi: 10.1016/0306-4522(94)90013-2.
Membrane potential oscillations were studied in slices of rat somatosensory cortex maintained in vitro, using intracellular recordings from cells in layers 2/3 and 5. The cells were classified according to their firing patterns during long (0.8-1 s) depolarizing current steps. Subthreshold voltage oscillations were revealed by depolarizing the membrane to voltages around threshold for action potentials; however, these were obvious mainly in cells showing marked spike adaptation. When neurons of all firing patterns were stimulated to fire at 40-60 Hz for tens of seconds, spikes abruptly indicated. Hyperpolarizing the cells by 5-10 mV precipitated pronounced oscillations in 24 out of 35 cells. These oscillations existed in a narrow voltage range, and their frequency varied between 7 and 40 Hz, in a voltage-dependent manner. Spiking frequency was faster than the oscillation frequency for the same membrane potential in a given cell. The Na+ channel blocker tetrodotoxin abolished both the spikes and the oscillations, and blockade of K+ channels by tetraethylammonium converted the oscillations into prolonged and irregular plateaus. Blocking Ca2+ conductance with Co2+ reduced the oscillations amplitude and frequency in two out of three cells. The oscillations that followed spike inactivation varied in amplitude, frequency and persistence among different cells. Layer 5 nonadapting cells possessed the most periodic oscillations, as judged by autocorrelation analysis. Oscillations were also most persistent in this group, maintaining a stable steady-state. In other cell types, the oscillations were less regular and decayed with time. There was no difference among cell groups in the maximal peak to peak amplitude of the oscillations, or their frequency range. It is suggested that the oscillations are generated by ionic conductances that operate within the voltage range just above and below spike threshold, and thus can shape the cells' firing pattern. The prominence of the oscillations in a specific subset of layer 5 cells may indicate the mechanism that underlies the rhythmic firing pattern of those cells.
利用细胞内记录技术，对体外培养的大鼠体感皮层切片中2/3层和5层的细胞进行了膜电位振荡研究。根据细胞在长时（0.8 - 1秒）去极化电流刺激下的放电模式对细胞进行分类。通过将膜电位去极化至动作电位阈值附近来揭示阈下电压振荡；然而，这些振荡主要在表现出明显峰适应的细胞中较为明显。当所有放电模式的神经元被刺激以40 - 60赫兹的频率放电数十秒时，会突然出现动作电位。将细胞超极化5 - 10毫伏会使35个细胞中的24个出现明显振荡。这些振荡存在于一个狭窄的电压范围内，其频率在7至40赫兹之间以电压依赖的方式变化。在给定细胞中，相同膜电位下的动作电位发放频率比振荡频率快。钠离子通道阻滞剂河豚毒素消除了动作电位和振荡，而四乙铵对钾离子通道的阻断将振荡转变为延长的不规则平台。用钴离子阻断钙离子电导使三个细胞中的两个细胞的振荡幅度和频率降低。峰电位失活后的振荡在不同细胞之间，其幅度、频率和持续性各不相同。通过自相关分析判断，5层非适应性细胞具有最具周期性的振荡。该组中的振荡也是最持久的，保持稳定的稳态。在其他细胞类型中，振荡不太规则且随时间衰减。不同细胞组之间在振荡的最大峰峰值幅度或其频率范围上没有差异。研究表明，这些振荡是由在峰电位阈值上下的电压范围内起作用的离子电导产生的，因此可以塑造细胞的放电模式。5层特定子集细胞中振荡的突出可能表明了这些细胞节律性放电模式的潜在机制。
