Analysis of circadian rhythms of optic lobe visual interneurons in the cricket.

本研究的主要目的是阐明蟋蟀视叶视觉中间神经元的昼夜节律及其神经基础。在过去两年的研究项目中，我们得到了以下新的发现。通过细胞内记录和荧光染料染色，我们已经确定了视叶中几个适合昼夜节律研究的视觉中间神经元。它们是延髓巨大的中间神经元，其胞体靠近基础延髓，其轴突通过大脑走向对侧延髓，并几乎支配对侧延髓的整个区域。结果：1.根据同侧复合体的感受野，将受试者分为6组。我们已经确定了一些延髓巨型中间神经元的胞浆节律。它们的光诱导反应呈昼夜节律性波动，在主观夜间达到峰值，而自发活动的峰值因神经元类型的不同而不同：有些在主观夜间出现峰值，而另一些则在主观白天出现峰值。HPLC-ECD分析表明，视叶中5-羟色胺的含量呈昼夜波动，在夜间达到峰值。外源性5-羟色胺的应用降低了视觉神经元的敏感性。这些数据表明，视觉系统受到昼夜节律的深刻调节，5-羟色胺可能是参与视觉间神经元敏感性调节的一种神经递质。

The main purpose of this study was to clarify the circadian rhythm of the optic lobe visual interneurons and its neural basis in the cricket Gryllus bimaculatus. During past two years of this research project, we have got the following new findings.1. We have identified several visual interneurons in the optic lobe suitable for circadian rhythm research by intracellular recording and staining with fluorescent dye. They are the medulla giant interneurons with their somata near the basal medulla, their axons runs toward the contralateral medulla through the brain, and innervate the almost whole area of the contralateral medulla. They were classified into 6 groups according to their receptive filed in the ipsilateral compound eye.2. We have characterized the ciradian rhythm in some of the medulla giant interneurons. Their light induced response was fluctuate in a circadian manner, peaking during the subjective night, while the peaks of the spontaneous activity differed according to the neuron types : Some has peaks during the subjective night while others has during the subjective day.3. HPLC-ECD analysis revealed that serotonin content in the optic lobe fluctuates in circadian manner, peaking in the night. The application of exogenous serotonin reduced the sensitivity of the visual interneurons.These data suggest that the visual system is profoundly regulated by the circadian pacemaker and that serotonin is a possible neurotransmitter involved in the regulation of the sensitivity of the visual interneurons.