MUTUAL INTERACTION BETWEEN RIGHT AND LEFT CEREBRAL LOBES IN INSECTS : COUPLING MECHANISM BETWEEN THE OPTIC LOBE CIRCADIAN CLOCKS

研究了两个视叶生物钟之间耦合的机制，特别参考了血清素和色素分散因子的作用。传递耦合信息的双侧髓质神经元（MBNs）的光致电活动呈现日变化，夜间比白天更强烈。将血清素微量注射到视叶中，对自发的和光诱导的反应产生剂量和时间依赖性的抑制，模仿白天的状态。应用美高林，一种非选择性血清素拮抗剂，增加自发活性和光诱发反应，白天效果更高。进一步药理研究表明，5-HT_7样受体介导了5-羟色胺能抑制作用。然后，我们从蟋蟀大脑中纯化PDF，并通过免疫兔子制备抗体。抗体标记了视神经叶的两组神经元，一组位于椎板附近，另一组位于髓质近端。在白天视叶注入PDF增强了MBN的光响应性，而在夜间则几乎没有变化。在白天，PDF的增强作用被血清素所抑制。PDF还诱导了运动节律的相移，其相移依赖于主观日晚到主观夜早的相移和主观夜晚到主观日早的相移。这些事实表明，在蟋蟀的视叶中，血清素在白天释放，并在mbn中设置白天状态，PDF在白天到晚上释放，并增强mbn的光响应性，以设置其夜间状态。5 -羟色胺和PDF对MBNs活动和时钟相位的双重调节可能在两个视叶起搏器之间的稳定耦合中起核心作用。

The mechanism of coupling between the two optic lobe circadian clocks was investigated with special reference to the role of serotonin and pigment-dispersing factor (PDF). Light-induced electrical activities of medulla bilateral neuron (MBNs) that convey coupling information showed daily variations, being more intense during the night than the day. Microinjection of serotonin into the optic lobe caused a dose- and time-dependent inhibition of spontaneous and light-induced responses, mimicking the day state. Application of metergoline, a non-selective serotonin antagonist, increased spontaneous activity and light-evoked responses, with higher effect during the day. Further pharmacological investigation revealed that this serotonergic inhibition was mediated by 5-HT_7 like receptors. We then purified the PDF from the cricket brain and made an antibody by immunizing the rabbit. The antibody labeled two groups of neurons in the optic lobe, one located near the lamina and the other near proximal medulla. PDF injected into the optic lobe enhanced the MBN's photo-responsiveness during the day, while little change was induced during the night. The enhancing effect of PDF during the day was suppressed by serotonin. PDF also induced the phase shifts of the locomotor rhythm in a phase dependent manner : it induces phase advance during the late subjective day to early subjective night and delays during the late subjective night to early subjective day. These facts suggest that in the cricket's optic lobe serotonin is released during the daytime and sets the day state in the MBNs, PDF is released during the late day to night and enhances MBNs' photo-responsiveness to set their night state. The dual regulation of MBNs activity and the clock phase by serotonin and PDF may play central role in the stable coupling between the two optic lobe pacemakers.