1994 Fiscal Year Final Research Report Summary
Analysis of mechanism underlying spontaneity in smooth muscle
| Project/Area Number |
05454140
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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 |
General physiology
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| Research Institution | Nagoya University |
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Principal Investigator |
TOMITA Tadao Nagoya University School of Medicine Professor, 医学部, 教授 (50078763)
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| Co-Investigator(Kenkyū-buntansha) |
TOKUNO Hiroyuki Nagoya University School of Medicine Research Assistant, 医学部, 助手 (60155520)
NAKAYAMA Shinsuke Nagoya University School of Medicine Lecturer, 医学部, 講師 (30192230)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Smooth muscle / Stomach / Spontaneity / Na ion / Ca channel blocker / Na pump |
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| Research Abstract |
1. The circular muscle of the guinea-pig gastric antrum produces spontaneous electrical activity, slow wave, at a frequency of 3-5/min, but it has only a very week potential-dependency (Katayama et al., 1993).
2. When a muscle strip was made smaller the frequency of rhythmic activity was reduced and tended to become irregular. This was recovered by hypoosmolarity.
3. Phosphodiesterase inhibitors, usch as caffeine, theophylline reduced slow wave frequency without a clear change in membrane potential, suggesting regulation of slow wave generation by intracellular cAMP but no significant contribution of K^+ channel activation in this inhibition (Tsugeno et at., 1995).
4. Nearly normal pattern of slow wave could be recorded in the presence of ryanodine which is known to interfere with the regulation of intrancellular Ca^<2+> concentration by the sarcoplasmic reticulum (Chowdhury et al., 1995).
5. The membrane was depolarized and slow wave was greatly modified by removal external Na^+ (Sakamoto & Tomita, 1982). These were not affected by Ca-channel blockers. Some activity could be observed in N^+-free solution, but there was a transient inhibition on readmission of Na^+ particularly after a prolonged Na^+ removal.
6. Na^+ seems playing an important role in the generation of slow wave, partly through modification of Na-pump activity, but the underlying mechanism for ther slow wave generation is still not clear.
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