鲤科鱼视网膜光感受器电位的明适应特性

IIGHT ADAPTATION PROPERTIES OF RECEPTOR POTENTIALS OF CYPRINID RETINA

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。

It was previously reported that changes in sensitivities of electroretinographiob-wave in the course of light adaptation depended on the intensity of backgroundlights.B-wave sensitivity decreased with time by dimmer background lights,whileit recovered during illumination with background lights of higher intensities.Unthis work we examined light adaptation properties of glutamate-isolated receptorpotentials(PⅢ components),using isolated and surperfused cyprinid retinas.During dimmer background illumination,PⅢ components were unchanged.Whenbackground lights were increased above certain levels,PⅢ components showedpartial recovery with time in the light.A detailed analysis of spectral sensitivitiesof PⅢ components and their increment thresholds for several wavelengths indicat-ed that the recovery of PⅢ sensitivity appeared with background lights at whichrod function was taken over by cone function.The results suggest that the recoveryof b-wave sensitivity during brighter background illumination is partially a reflec-tion of the adaptation property of cone photoreceptors.