IDENTIFICATION AND PHYSIOLOGICAL ANALYSIS OF MEDULLA BILATERAL LARGE NEURONS INVOLVED IN MUTUAL INTERACTION OF BILATERALLY PAIRED CIRCADIAN CLOCKS IN INSECTS

髓质双侧大神经元（MBN）是连接双侧生物钟部位（即视髓质区域）的视觉中间神经元。每侧有 26 个 MBN，根据形态和感​​受野可分为 4 组。在这项研究中，我们研究了 4 组 MBN 中哪一组传输时钟之间相互耦合所需的时钟信息，以及这些神经元如何编码时钟信息。通过 HPLC-ECD，我们首先检查了 MBN 中涉及的生物胺。在包括MBN胞体在内的小组织中，检测到了血清素、多巴胺、章鱼胺和一些未知的胺。由于 MBN 没有被抗血清素和抗多巴胺抗体标记，因此它们的神经递质可能是章鱼胺或未知的胺。然而，血清素能和多巴胺能系统可能在MBN系统的信息传递中发挥重要作用，因为MBN的电刺激降低了对侧视叶中这些胺的水平。与MBN的感受野相对应的复眼的部分破坏表明，感受野位于眼睛的背尾区域的MBN-4s是最有可能的神经元介导候选者时钟耦合所需的时钟信息。它们对光的反应比其他 MBN 弱得多，但可以清楚地看到它们的昼夜差异，这表明它们将时钟信息编码为它们的反应幅度。其他 MBN 的响应能力也表现出昼夜差异，尽管它们的响应模式和昼夜变化彼此不同。这些结果表明，MBN-4 将其一侧的照明信息传递给对侧时钟，并且其他 MBN 在板球昼夜节律系统中也具有与时钟相关的功能。

Medulla bilateral large neurons (MBNs) are visual interneurons connecting the bilateral circadian clock sites, i.e., optic medulla regions. There are 26 MBNs in each side and they could be classified into 4 groups according to their morpholoy and receptive fields. In this study, we examined which of the 4 group of MBNs transmitts the clock information necessary for mutual coupling between the clocks and how those neurons encode the clock information. With HPLC-ECD we first examined the biogenic amines which would be involved in the MBNs. In the small tissue including MBN somata, serotonin, dopamine, octopamine and some unknown amines were detected. Since MBNs were not labelled by anti-serotonin andanti-doapmine antibodies, their neurotransmitter may be either octopamine or the unknown amine. Howeer, serotonergic and dopaminergic system may play an important role in the information transmission in MBN system, since the electricl stimulation of MBNs reduces the level of these amines in the contralateral optic lobe.Partial destruction of the compound eye corresponding to the receptive fields of the MBNs revealed that MBN-4s, whose receptive field lies in the dorso-caudal area of the eye, are the most likely candidates for the neuron mediating the clock information necessary for the clock coupling. Their response to light was rather weaker than those other MBNs, but their day-night difference was clearly seen, suggesting that they encode the clock information as the magnitude of their response. Other MBNs also showed day night difference in their responsiveness, although the pattern of their responses and day night change were different with each other. These results suggest that MBN-4 conveys the lighting information on its side to the contralateral clock and that other MBNs also have clock related functions in the cricket circadian system.