Solessio Eduardo, Vigh Jozsef, Cuenca Nicolas, Rapp Kevin, Lasater Eric M
Department of Ophthalmology and Visual Sciences, John Moran Eye Center, University of Utah, Salt Lake City 8413, USA.
J Physiol. 2002 Nov 1;544(3):831-47. doi: 10.1113/jphysiol.2002.021899.
In the retina, amacrine cells modulate the transfer of information from bipolar to ganglion cells. The nature of the modulation depends on the synaptic input and the membrane properties of the cells. In the retina of white bass, we identified a class of bistratified, wide-field amacrine cell characterized by immunopositive labelling for GABA and calmodulin. In isolation, the cells presented resting membrane potentials averaging -69 mV although some cells settled at more depolarized values (-30 mV). Injection of depolarizing current pulses induced oscillatory membrane responses. When elicited from depolarized cells, the oscillations were short-lived (< 40 ms). For the most part, the oscillatory potentials of hyperpolarized cells remained unattenuated throughout the depolarizing pulse. The frequency of the oscillations increased logarithmically with mean membrane potential, ranging from 74 to 140 Hz. Cells exhibiting depolarized membrane potentials oscillated at twice that rate. When the membrane potential of these cells was hyperpolarized to -70 mV, the oscillations became unattenuated and slowed. We found the cells expressed voltage-gated sodium, potassium and calcium currents and calcium-dependent potassium currents. We demonstrate that the oscillatory potentials arose as a result of the interplay between calcium and potassium currents. The cells responded to local application of GABA and glycine, both of which modulate the oscillatory potentials. Glutamate and its analogues depolarized the cell and induced oscillatory potentials. Our results indicate that oscillatory responses of a type of wide-field amacrine cell are an intrinsic feature of the cell and not due to circuit properties.
在视网膜中，无长突细胞调节信息从双极细胞向神经节细胞的传递。这种调节的性质取决于突触输入和细胞的膜特性。在白鲈的视网膜中，我们鉴定出一类双分层、广域无长突细胞，其特征是对γ-氨基丁酸（GABA）和钙调蛋白呈免疫阳性标记。单独分离时，这些细胞呈现的静息膜电位平均为-69 mV，不过有些细胞稳定在更正极的电位值（-30 mV）。注入去极化电流脉冲会诱发振荡性膜反应。当从去极化细胞诱发时，振荡持续时间较短（<40毫秒）。在大多数情况下，超极化细胞的振荡电位在整个去极化脉冲期间保持不衰减。振荡频率随平均膜电位呈对数增加，范围从74至140赫兹。膜电位呈去极化的细胞振荡频率是前者的两倍。当这些细胞的膜电位超极化至-70 mV时，振荡变得不衰减且变慢。我们发现这些细胞表达电压门控钠电流、钾电流和钙电流以及钙依赖性钾电流。我们证明振荡电位是钙电流和钾电流相互作用的结果。这些细胞对局部施加的GABA和甘氨酸有反应，二者均调节振荡电位。谷氨酸及其类似物使细胞去极化并诱发振荡电位。我们的结果表明，一类广域无长突细胞的振荡反应是该细胞的固有特征，而非由回路特性所致。
