1987 Fiscal Year Final Research Report Summary
Studies on the transmembrane signalling mechanism of neurotransmitter receptors and ion channels in Xenopus oocytes injected with rat brain mRNA
| Project/Area Number |
60480460
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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 |
Biological pharmacy
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| Research Institution | Hokkaido University (1987)
Toyama Medical and Pharmaceutical University (1985-1986) |
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Principal Investigator |
NOMURA Yasuyuki Faculty of Pharm. Sci., Hokkaido Univ., 薬学部, 教授 (00034041)
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| Project Period (FY) |
1985 – 1987
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| Keywords | Oocyte / brain mRNA / GTP-binding protein / Serotonin / Inositol Phosphate / Phorbol ester / C1 channel / Caチャネル |
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| Research Abstract |
To clarify the transmembrane signalling mechanism in neurotransmitter receptors and ion channels, we biochemically and electrophysiologically investigated effects of several drugs on acetylcholine (Ach)- or serotonin (5-HT)-induced membrane current and on voltage-sensitive Ca channel (VSCC) activity using Xenopus oocytes injected with rat brain mRNA. We here obtained following results.
Ach/5-HT elicited inward C1 current by activating M_1 or S_1 receptors respectively and pertussis toxinsensitive GTP-binding proteins(G./G ). The involvement of following intracellular events could also be suggested in the Ach/5-HT elicited current responses: 1)inositol phosphate (IP_3) formation by phospholipase C, 2)IP_3-induced release of Ca^<2+> from storage organella and 3)Ca^<2+>. calmodulin-mediated gating of membrane C1 channels. In addition, rapid refractoriness in oocytes to Ach/5-HT could be explained by phosphorylation of receptors and / or G_i/G_o by protein kinase C activated by diacylglycerol and Ca^<2+>.
We also observed expression of VSCC in oocytes injected with brain mRNA and characterized as follows: 1) VSCC seems to be N-type, since w-conotoxin GVTA effectively blocked but organic Ca antagonists did not , 2) protei kinase A stimulates VSCC because of cyclic AMP-induced facilitation of VSCC current, and 3) protein kinase C modulates the channel gating in a biphasic manner, since a phorbol ester (TPA) stimulatorily affected VSCC current at a low concentration but inhibitorily at a high concentration.
Thus we herewith demonstrated Xenopus oocytes microinjected with brain mRNA as a useful model in elucidating the molecular mechanism of signal transduction from receptors to ion channels in the CNS.
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Research Products
(12 results)
