| Project/Area Number |
02670055
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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 | Kumamoto University |
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Principal Investigator |
OGAWA Hisashi KUMAMOTO Univ. Med. Sch., Professor, 医学部, 教授 (20040181)
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| Co-Investigator(Kenkyū-buntansha) |
YAMASHITA Yoshiro KUMAMOTO Univ. Med. Sch., Instructor, 医学部, 助手 (50128328)
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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 |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1991: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1990: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | Rat / Merkel cell / Potassium current / Calcium current Quinacrine / Quinacrine / Patch-clamp / 走査電子顕微鏡 / ラット / カルシウムアンタゴニスト / 静止膜電位 |
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| Research Abstract |
Merkel cells were dissociated enzymatically from the footpad epidermis of 10 to 20-day-old rats pretreated with fluorescent dye, quinacrine, for purposes of staining. Electrical recordings were performed in whole-dell configuration using a conventional patch-clamp technique. The mean resting membrane potential of fluorescent Merkel cells was -54.0 mV, the value being greater than the -26.1 mV of non-fluorescent epidermal cells. The Merkel cells had no Na^+ spike in an external standard solution, but tetrodotoxin-resistant long-lasting action potentials were evoked by depolarization with injection of constant currents in an external solution containing Ba^<2+>. In Merkel cells under voltage-clamp, depolarizing step pulses from a holding potential (V_H) of -80 mV elicited predominantly outward K^+ currents composed of transient and sustained components : the former was selectively inhibited by 4-aminopyridine (4-AP), while the latter. was inhibited by both tetraethylammonium (TEA) and qu
… More
inacrine. The sustained outward K^+ current (I_<KD>) was activated at potentials more positive than -20 or -10 mV at a V^H of -50 mV, at which potential the transient outward K^+ channel was completely inactivated. The transient outward K^+ current (I_A) was activated at potentials more positive than -50 mV at a V_H of -80 mV. When the outward K^+ currents were blocked by adding both TEA and 4-AP, only a sustained inward Ca^<2+> current was observed. In an external solution containing 10 mM-Ca^<2+>, I_<ca> was evoked by potentials more positive than -20 mV at a V^H of -80 mV, and the maximum inward current appeared around +10 mV. Increases of external Ca^<2+> concentration induced a hyperbolic increase of I_<ca>. The selectivity of the Ca^<2+> channel for divalent cations was in the order of Ba^<2+> > Sr^<2+> > Ca^<2+>. It was concluded that Merkel cells have at least three distinct voltage-gated currents : a delayed K^+ current (I_<KD>), a transient A current (I_A) and a high-threshold (L-type) Ca^<2+> current (I_<ca>). Less
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