1999 Fiscal Year Final Research Report Summary
Morphologycal analysses of the neural components of the input and output pathways involved in the Drosophila circadian system, with special reference to the cholinergic neurons.
| Project/Area Number |
09640816
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
動物生理・代謝
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| Research Institution | Kawasaki Medical School |
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Principal Investigator |
YASUYAMA Kouji Medicine, Kawasaki Medical School, Assistant Professor, 医学部, 講師 (60148690)
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| Co-Investigator(Kenkyū-buntansha) |
TOMIOKA Kenji Faculty of Science, Yamaguchi University, Professor, 理学部, 教授 (30136163)
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| Project Period (FY) |
1997 – 1999
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| Keywords | Drosohila / cholinergic / circadian clock / circadian locomotor rhythm / extraretinal photoreceptor / rhodopsin |
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| Research Abstract |
In Drasophila, various lines of evidence suggest that the circadian pacemakers for daily locomotor rhythms reside in the cells called "lateral neurons" (LNs) lying in the anterior rind of the medulla. However, little is known about the neural pathways linking these pacemaker cells to behavioral rhythms. To identify the neural components of the input and output pathways of the Drosophila circadian clock system, we have surveyed the brain using immunocytochemical techniques, especially with reference to cholinergic neurons. A monoclonal antibody against Drosophila choline acetyltransferase (ChAT) stained a group of extraretinal photoreceptors at the posterior margin of the compound eye, which is called the "eyelet". The axons emerging from the eyelet terminated in the region of the anterior medulla, where the possible dendritic field of LNs resides. LNs were immunoreactive to an antibody against Drosophila nAChR, implying cholinergic input to LNs. This circumstantial evidence suggests th
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at the eyelet is involved in an input pathway contributing to circadian entrainment. Transformed flies carrying the transgene composed of ChAT cDNA with 1.2 kb of the cis-regulatory sequence showed obviously reduced ChAT expression in specific subsets of cholinergic neurons, such as the neurons terminating in the distal region of the medulla, where the varicosity of the output fibers of LNs resides. A morphometric study revealed that LN varicosity in the medulla was -significantly larger in the transformants than in the wild-type flies. The transformants entrained to light : dark cycles, and exhibited a double-peaked locomotor activity pattern with morning and evening peaks, as did control flies (white). When the illumination level was low (I.e., 0.24 lux), the transformants showed unusual monophagic locomotor activity exclusively occurring during the entire light phase, in contrast to double-peaked activity in the controls. These observations suggest that defects in ChAT expression resulted in the extraordinary locomotor rhythms in the transformants. Less
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