1989 Fiscal Year Final Research Report Summary
INTERACTION BETWEEN MUSCARINIC AND NICOTINIC RECEPTORS IN CATECHOLAMINE SECRETION FROM ADRENAL MEDULLARY CELLS
| Project/Area Number |
63480085
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
基礎獣医学
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| Research Institution | OBIHIRO UNIVERSITY OF AGRICULTURE AND VETERINARY MEDICINE |
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Principal Investigator |
NAKAZATO Yoshikazu DEPARTMENT OF VETERINARY PHARMACOLOGY, OBIHIRO UNIVERSITY OF AGRICULTURE AND VETERINARY MEDICINE, 畜産学部, 教授 (60001525)
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| Co-Investigator(Kenkyū-buntansha) |
SATOH Eiki DEPARTMENT OF VETERINARY PHARMACOLOGY, OBIHIRO UNIVERSITY OF AGRICULTURE AND VET, 畜産学部, 助手 (50178711)
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| Project Period (FY) |
1988 – 1989
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| Keywords | Adrenal chromaffin cells / Muscarinic receptor / Nicotinic receptor / Cytosolic free Ca^<2+> / Caffeine / Ryanodine / ライアノジン |
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| Research Abstract |
It is well known that adrenal chromaffin cells possess both muscarinic and nicotinic receptors involved in acetylcholine-induced catecholamine secretion.
We have found that unlike catecholamine secretion induced by nicotinic receptor activation, muscarinic receptor-mediated secretory response was not a result of increased Ca^<2+> influx, but of mobilized Ca^<2+> from some intracellular storage sites. In this experiment, the study was made about, (1) the mode of interaction between muscarinic and nicotinic receptors in causing catecholamine secretion, (2) the nature of intracellular Ca^<2+> store linked to muscarinic receptors and (3) Ca^<2+> releasing mechanism from that hypothetical store. For this purpose, we used perfused adrenal glands of cat and guinea pig, isolated adrenal chromaffin cells of dog and guinea pig and cultured bovine adrenal chromaffin cells. The results are summarized as follows: 1. Catecholamine secretion evoked by nicotine (5xlO^<-5>M) was markedly increased by pr
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eceding application of a pure muscarinic agonist, oxotremorine (10^<-5>M) which caused only a minute secretory response by itself. It appears therefore that both nicotinic and muscarinic receptors interact with each other when acetylcholine releases catecholamine from adrenal chromaffin cells.
2. Adrenal chromaffin cells seem to possess at least two different Ca^<2+> stores responsible for catecholamine secretion as suggested in smooth muscle cells.
One is sensitive to caffeine and the other one is to muscarinic receptor activation of which the second messenger is known to be IP_3. There appears to be a partial overlap in both stores. Similar to that of smooth muscle cells, caffeine-sensitive stores are suggested to be locked by ryanodine in open state. These results suggest that Ca^<2+>-induced Ca^<2+> release mechanism is present as it is in muscle cells.
3. It was confirmed that caffeine and acetylcholine cause increase in cytosolic free Ca^<2+> concentration in cultured bovine adrenal chromaffin cells loaded with Fura 2-AM. Ryanodine selectively blocked the caffeine-induced Increase in the Ca^<2+> concentration. Less
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