| Project/Area Number |
02670061
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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 | Kurume University |
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Principal Investigator |
TOKIMASA Takayuki Kurume University, School of Medicine, Associate Professor, 医学部, 助教授 (50155511)
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| Co-Investigator(Kenkyū-buntansha) |
HASUO Hiroshi Kurume University, School of Medicine, Assistant Professor, 医学部, 講師 (90172882)
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| Project Period (FY) |
1990 – 1991
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| Project Status |
Completed (Fiscal Year 1991)
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| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1991: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1990: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | Adenylate cyclase / Cyclic AMP / Calmodulin / Phosporylation / Ionic currents / Primary afferent neurons / Sympathetic neurons / Dorsolateral septal nucleus / 背外側中隔核 / 脊椎動物 / パッチ・クランプ / アデニレ-ト・サイクラ-ゼ / フォ-スコリン / プロテインカイネ-ス / ハロセン / 遅延整流 |
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| Research Abstract |
Dissociated vertebrate (frogs & rats) nerve cells were voltage-clamped in the whole-cell configuration. In bull-frog sympathetic and primary afferent neurons, a cationic inward rectifier (H-current, I_H) was identified as the one that can be regulated in a manner connected with phosphorylation of ion channel by cyclic AMP-dependent protein kinase (A-kinase). Thus, bath application of forskolin (1-10 muM) not only increased the maximum H-conductance but caused a depolarizing shift in the I_H activation curve. The basal activity of A-kinase could be inferred from a hyperpolarizing shift in the activation curve when a protein kinase inhibitor, H-8, or A_1-receptor agonists (e. g. N^6-cyclohexyladenosine) was added to the superfusate. Volatile anesthetics (e. g. enflurane, 0.2-0.8 mM) mimicked the H-8 actions on I_H implying that general anesthetics may impair the cyclic AMP-dependence of I^H. In contrast, ion channels responsible for a M-type potassium current (I_M) may have to be phosphorylated by calmodulin-dependent protein kinase in order for them to be open ; these open channels can be closed when they are phosphorylated by calcium-activated phospholipiddependent protein kinase (C-kinase). Any of three types of protein kinase described above did not participate in the regulation of a delayed rectifier potassium current (I_K) ; instead, forskolin (1-10 muM) inhibited I_K in a manner unconnected with adenylate cyclase.
In slice preparations for the rat dorsolateral septal nucleus, the release of glutamate and GABA was markedly enhanced following the A-kinase activation (e. g. by forskolin) ; at the same time, the cell membrane often showed a depolarization which was due presumably to the I_H activation. Since we have succeeded in obtaining dissociated septal neurons, possible mechanisms underlying cyclic AMP-dependent events described above have now been subjected to further investigation by means of the whole-cell patch-clamp.
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