Neuroethological study of the wavelength-discriminat ion in the extraocular phtoreceptor.

人们普遍认为，松果体是低等脊椎动物的光敏器官。松果体器官中含有光感受器细胞，光感受器获得的光信息通过松果体器官中的二级神经元——神经节细胞传递到中枢神经系统。已经鉴定出两种类型的神经节细胞，即无色型和彩色型神经节细胞。消色差型神经节细胞在黑暗中自发活动，受到可见光的抑制。色型松果体神经节细胞的脉冲放电受到紫外光的抑制，而受到中长波长光的激发。色度响应使松果体复合体能够检测环境光中紫外线与可见光的比例，从而独立于眼睛实现松果体复合体的波长识别。然而，色型神经节细胞的功能尚不清楚。研究了紫外光和绿光对沙七鳃鳗游动行为的影响。首先从电生理学的角度证明了在沙七鳃鳗的松果体中存在彩色神经节细胞。随后，我们用摄像机记录了七鳃鳗在紫外线和绿光照射下的游动运动，并用计算机进行了分析。结果表明，紫外线照射激活了游泳运动，松果体切除术后，紫外线诱导的游泳运动消失。这些结果表明，松果体器官的颜色信息调节了七鳃鳗的游泳运动活动。

It is widely accepted that pineal organ is photosensitive in lower vertebrates. The pineal organ contains photoreceptor cells and photic information obtained by the photoreceptors is transmitted to the central nervous system via second-order neurons, ganglion cells, in the pineal organ. Two types of ganglion cells have been identified, namely, achromatic-and chromatic-type ganglion cell. The achromatic-type ganglion cell is spontaneously active in darkness and is inhibited by visible light. The spike discharge from pineal ganglion cells of chromatic type is suppressed by UV light and excited by light of middle to long wavelengths. The chromatic responses allow the pineal complex to detect the ratio of UV light to visible light in environmental light, which achieves the wavelength-discrimination in the pineal complex independently of eyes. However, the function of the chromatic-type ganglion cell is unknown. We investigated the effect of UV and green light on swimming action using the sand lamprey, Lethenteron reissneri. At first, we electrophysiologically demonstrated that the chromatic ganglion cell was found in the pineal of the sand lamprey. Subsequently, we recorded the swimming movement of the lamprey under irradiation of UV and green light by use of video camera, and analyzed it by the computer. As results, The UV irradiation activated the swimming movement, and the UV-induced swimming movement disappeared by the pinealectomy. Those suggested that the chromatic information form the pineal organ regulated the swimming locomotor activity in the lamprey.