| Project/Area Number |
63570066
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Neurophysiology and muscle physiology
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| Research Institution | Keio University School of Medicine |
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Principal Investigator |
KAWAMURA Satoru Keio University School of Medicine, Department of Physiology, Lecturer, 医学部, 講師 (80138122)
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| Project Period (FY) |
1988 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1989: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1988: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Photoreceptor / Transmitter / Aspartate / Glutamate / Depolarization / Light stimulation / Calcium ions / アミノ酸 / 灌流 / 高速液体クロマトグラフ |
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| Research Abstract |
Though the transmitter of a vertebrate photoreceptor has not been known yet, circumstantial evidence suggests that aspartate or glutanate could be the transmitter. The purpose of this study is to identify the transmitter substance released from rod photoreceptors.
Rod photoreceptors were isolated with mechanical dissociation of carp retinas. Twenty to eighty percent of the isolated rods retained their axons and 25 - 50 % of then had axon terminals. These cells were perfused with solutions of known chemical and ionic composition. Amino acids which were released from the rods into the perfusion solution were analyzed with high performance liquid chromatography. Though we expected the release of aspartate or glutagate in the dark, we observed the release of almost all of the amino acids. Moreover, the release of these amino acids was not affected by a light stimulation. On the other hand, when the cells were depolarized with a treatment of a high-K^+ solution or a low Ca^<2+>-solution, the release was facilitated. Again, it was none-specific. This "depolarization-induced release" did not require the presence of Ca^<2+> since in the presence of Co^<2+> and in the absence of Ca^<2+>, we still observed the increase in the amino acid release. Though the isolated rod retained axon or axon terminal, we were not sure whether these cells released these amino acids from the cite which is actually involved in the transmitter release in intact cells. It may be true that the population of the intact cells which could release the transmitter in a light-dependent manner was too low in our preparation. However, the present work did indicate that the conventional criteria --release of the substance upon depolarization-- is not sufficient to identify the transmitter and that careful study is needed to solve this issue.
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