鲤科鱼视网膜光感受器电位的明适应特性

本实验室以前曾报道,视网膜电图 b 波的敏感度在明适应过程中的变化因背景光强而异:在较弱背景光时随时间逐渐降低,当背景光强达到一定水平后,则在明适应过程中出现一定程度的回复。本工作应用分离、灌流的鲤科鱼视网膜,详细地考察了用谷氨酸分离的感受器电位(PⅡ)的明适应特性。在较弱背景光下,PⅡ敏感度除初始时降低外,不随时间作进一步变化。当背景光强达到一定水平后,与 b 波相似,PⅡ敏感度也随时间而回复。对 PⅡ光谱敏感性和不同波长辨增阈的测定表明,PⅡ的这两型变化交替的光强恰为视杆系统与视锥系统活动交替的光强;当背景光完全压抑视杆系统的活动后(仅接收视杆输入的水平细胞的胞内记录的反应完全被压抑),PⅡ即呈现回复型变化。这些结果提示,b 波的回复型变化部分地反映了视锥细胞的明适应特性。

IIGHT ADAPTATION PROPERTIES OF RECEPTOR POTENTIALS OF CYPRINID RETINA

It was previously reported that changes in sensitivities of electroretinographic b-wave in the course of light adaptation depended on the intensity of background lights. B-wave sensitivity decreased with time by dimmer background lights, while it recovered during illumination with background lights of higher intensities. In this work we examined light adaptation properties of glutamate-isolated receptor potentials (P III components), using isolated and superfused cyprinid retinas. During dimmer background illumination, P III components were unchanged. When background lights were increased above certain levels, P III components showed partial recovery with time in the light. A detailed analysis of spectral sensitivities of P III components and their increment thresholds for several wavelengths indicated that the recovery of P III sensitivity appeared with background lights at which rod function was taken over by cone function. The results suggest that the recovery of b-wave sensitivity during brighter background illumination is partially a reflection of the adaptation property of cone photoreceptors.