|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1997 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1996 : ¥1,600,000 (Direct Cost : ¥1,600,000)
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.