Grunstein M M, Hazinski T A, Schlueter M A
J Appl Physiol Respir Environ Exerc Physiol. 1981 Jul;51(1):122-30. doi: 10.1152/jappl.1981.51.1.122.
The mechanism of ventilatory depression during hypoxia in the neonate is unknown. Since endorphins depress ventilation and their actions are antagonized by naloxone, we tested the effect of naloxone on respiration during acute hypoxia in newborn rabbits. In 27 tracheotomized unanesthetized pups, ranging in age from 1 to 15 days, ventilation (VE) was measured in a body plethysmograph. At all ages, inhalation of 5% O2 initially increased VE; thereafter VE became depressed in association with a decrease in CO2 elimination (VCO2). The time constant of VE depression increased with age. During ventilatory and VCO2 depression, saline infusion had no effect. Infusion of naloxone (4 micrograms/g body wt), however, abruptly stimulated both VE and VCO2. Since naloxone acts by competitive blockade of opiate (endorphin) receptors, these data provide evidence that 1) depression in respiration and metabolism during hypoxia is related to the action of endorphins, 2) the degree of endorphin influence decreases with age, and 3) naloxone is effective in reversing hypoxic respiratory depression provided apnea is not established.
新生儿缺氧时通气抑制的机制尚不清楚。由于内啡肽会抑制通气，且其作用可被纳洛酮拮抗，因此我们测试了纳洛酮对新生兔急性缺氧时呼吸的影响。在27只年龄为1至15天、已进行气管切开且未麻醉的幼崽中，通过体容积描记法测量通气量（VE）。在所有年龄段，吸入5%氧气最初会使VE增加；此后，VE会随着二氧化碳排出量（VCO2）的减少而受到抑制。VE抑制的时间常数随年龄增加。在通气和VCO2受到抑制期间，输注生理盐水没有效果。然而，输注纳洛酮（4微克/克体重）会突然刺激VE和VCO2。由于纳洛酮通过竞争性阻断阿片（内啡肽）受体起作用，这些数据表明：1）缺氧时呼吸和代谢的抑制与内啡肽的作用有关；2）内啡肽的影响程度随年龄降低；3）只要未出现呼吸暂停，纳洛酮就能有效逆转缺氧性呼吸抑制。
