| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1987: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1986: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
Changes in various respiratory functions with growth and aging were studied in the halothane anesthetized-tracheotomized rat with various ages; 1.5, 3,6,12, above 20 months after birth. Ventilation and metabolism (O_2 consumption and CO_2 prduction) were progressively decreased with growth and aging. Aged animals showed slow respiratory frequency, large tidal volume, large physiological dead space and hypoxemia. Ventilatory response to CO_2 stimulus was also attenuated with aging. There was clear linear correlation between metabolism and alveolar ventilation or the slope of CO_2-ventilatory response line. However, the ratio of increase in ventilation during CO_2 stimulus to the control ventilation was kept fairly constant throught life.Therefore the relative 'reserve' capacity of ventilation to CO_2 stimulus seems not to change significantly with growth and aging. Small respiratory frequency response and large tidal volume response characterize the pattern of ventilatory stimulation in the aged animal.
Other related problems: Carotid chemoreceptor discharge of the rat showed much greter response to hypoxia thn to hypercapnia. Increase in Hb-O_2 affinity with NaOCN adiministration improved the respiratory tolerance to acute hypoxia in young animals. During CO_2 breathing, respiratory frequency response is much facster than tidal volume response in young animals. In the anesthetized young rat, there was a clear dissociation of the onset time between the superior laryngeal (hypoglossal) and phrenic nerve discharges during altered chemical stimuli, which indicates that the process of activation by increased chemical stimuli differs temporally between the superior laryngeal (hypoglossal) inspiratory motoneurons and phrenic driving medullary neurons.
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