2000 Fiscal Year Final Research Report Summary
Diversity of respiratory rhythm generation and its postnatal alteration
| Project/Area Number |
11670034
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General physiology
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| Research Institution | Chiba University |
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Principal Investigator |
FUKUDA Yasuichiro Chiba University School of Medicine Professor, 医学部, 教授 (10009649)
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| Co-Investigator(Kenkyū-buntansha) |
KUWAKI Tomoyuki Chiba University School of Medicine, Assistant Professor, 医学部, 講師 (80205260)
HAYASHI Fumiaki Chiba Univesity School of Medicine, Associate Professor, 医学部, 助教授 (80173029)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Newborn rat / Respiratory rhythm generation / Asphyxia / hypoxia / Hypoxia tolerance / In vivo and In vitro preparations / postnatal development / Aerobic and Anaerobic Metabolism |
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| Research Abstract |
To clarify a possible functional origin of 'respiratory like' rhythmic activities observed in in vitro brainstem preparation, pattern of respiratory neural activities was analyzed in in vivo newborn and young adult rats during altered chemical stimuli and asphyxia. The phrenic (Phr) and cranial nerve (IX or XII) inspiratory (I) discharges were recorded in halothane-anesthetized, vagotomized and artificially ventilated rats at a low body temperature (25℃). The I discharges of the newborn rat appeared at a regular rhythmic pattern but with short I duration. The I activity responses to CO2 and hyoxia of newborn rats were similar to those in young adult rats. During cessation of artificial ventilation (asphyxia) in the newborn rat, the Phr and cranial nerve I discharges were first augmented, then decreased in rate and finally ceased completely for about 1-2 min. Thereafter rhythmic I activty reappeared at much slower rate with decremental dischage pattern, which persisted for a period more than 50min of asphyxia. A normal respiratory discharge pattern recovered after resumption of artificial ventilation. Similar 'secondary' respiratory activity appeared also in the young adult rat during asphysia but persisted for a period of several min only. It was concluded that the newborn rat is highly capable of displaying asphyxia (hypoxia) tolerant and reversible 'secondary' rhythmic activities for a longer period after cessation of normal respiratory rhythm. The pattern of 'secondary' respiratory activity corresponded well with that of rhythmic activities seen in the isolated medullary preparation of newborn rat incubated with mock CSF at 25℃. The 'respiratory like' activity seen in the isolated medullary tissue may be derived from a similar mechanism that generate 'secondary' respiratory activity in in vivo animals during asphyxia.
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