Ionic basis of learning-correlated excitability changes in Hermissenda type A photoreceptors.
Ionic basis of learning-correlated excitability changes in Hermissenda type A photoreceptors.
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Hermissenda A 型光感受器学习相关兴奋性变化的离子基础。
DOI：
10.1152/jn.1997.77.4.1861
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Han,Y
中科院分区：
文献类型：
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作者：
Farley,J;Han,Y
法利，约瑟夫和韩云如。学习相关的兴奋性变化的离子基础在Hermissendatype A光感受器。神经生理学杂志。77：1861-1888，1997。光和旋转（条件反射）的重复配对导致Hermissendatype B和A光感受器的兴奋性持续变化，这与趋光行为的配对特异性降低相关。虽然相当多的注意力已经致力于表征条件反射产生的神经生理学变化，发生在B型细胞，较少的信息是关于A型细胞中产生的变化。在这里，我们记录了从确定的，突触隔离的外侧和内侧A型光感受器的条件，随机对照，或未经训练的动物在保留日后的条件。来自条件动物的A型光感受器对光的反应与受体电位显著小于随机对照或未经训练的动物的受体电位，两者没有差异。趋光性抑制和A型细胞光反应幅度呈负相关的个别条件动物。表现出强烈趋光抑制的动物也表现出小的光反应。与训练相关的光反应差异的表达是一种钙依赖性现象：将细胞外钙降低至<1 μM可增强A细胞的发生器电位，而与条件反射史无关，并大大降低了可归因于训练的发生器电位振幅差异。电压钳研究表明，条件反射导致电压依赖性、持续性外向钾电流的振幅增加2 - 3倍对于单个条件动物，ID值大小与趋光性抑制正相关：表现出强烈趋光性抑制的动物的A型细胞表达大的ID值。1）残余A电流（IA）;2）缓慢的、四乙基铵敏感的钙激活K+电流（IK-Ca）;和3）延迟整流型、电压依赖性K+电流（IK，v）。对这些电流的分析未能揭示与训练相关的IAorIK-Ca的显著变化。但是，在外侧和内侧细胞中，IK，v均增强了60-150%，因此有助于条件相关的增加。
Farley, Joseph and Yunru Han.Ionic basis of learning-correlated excitability changes inHermissendatype A photoreceptors.J. Neurophysiol.77: 1861–1888, 1997. Repeated pairings of light and rotation (conditioning) result in persistent changes in excitability ofHermissendatype B and A photoreceptors, which are correlated with pairing-specific reductions in phototactic behavior. Although considerable attention has been devoted to characterization of conditioning-produced neurophysiological changes that occur in type B cells, less information is available concerning the changes produced in type A cells. Here we recorded from identified, synaptically isolated lateral and medial type A photoreceptors from conditioned, random-control, or untrained animals on retention days following conditioning. Type A photoreceptors from conditioned animals responded to light with a receptor potential that was significantly smaller than those of random-control or untrained animals, which did not differ. The phototactic suppression and type A cell light response magnitudes were negatively correlated for individual conditioned animals. Animals exhibiting strong phototactic suppression also showed small light responses. Expression of the training-associated light response difference was a calcium-dependent phenomenon: reducing extracellular calcium to <1 μM enhanced the generator potential of A cells, regardless of conditioning history, and greatly reduced the differences in generator potential amplitude attributable to training. Voltage-clamp studies revealed that conditioning resulted in a two- to threefold increase in the amplitude of a voltage-dependent, sustained outward K+current (IDelayed).IDelayedmagnitudes were positively correlated with phototactic suppression for individual conditioned animals: type A cells of animals exhibiting strong phototactic suppression expressed large values ofIDelayed.IDelayedis a composite current, consisting of at least three separable components:1) residual A current (IA);2) slow, tetraethylammonium-sensitive calcium-activated K+current (IK-Ca); and3) a delayed-rectifier-type, voltage-dependent K+current (IK,v). Analysis of these currents failed to reveal significant training-associated changes inIAorIK-Ca. ButIK,vwas enhanced by ∼60–150% in both lateral and medial cells and thus contributes to the conditioning-associated increase inIDelayed.