THE RESPONSE TO HYPOXIA OF ARTERIAL CHEMORECEPTORS IN FETAL SHEEP AND NEWBORN LAMBS
THE RESPONSE TO HYPOXIA OF ARTERIAL CHEMORECEPTORS IN FETAL SHEEP AND NEWBORN LAMBS
复制标题
DOI：
10.1113/jphysiol.1984.sp015229
复制
发表时间：
1984-01-01
影响因子：
5.5
通讯作者：
MCCOOKE, HB
中科院分区：
文献类型：
--
作者：
BLANCO, CE;DAWES, GS;MCCOOKE, HB
用氟烷或戊巴比妥钠麻醉90~143日龄胎羊14只，分别检测颈动脉化学感受器活性。活动是.apprx。在动脉血氧分压(PaO2)为25 mm Hg5 Hz时，通过压迫脐带或减少用于母羊通风的(FiO2)O2分数，PaO2降低时，PaO2升高。当舌动脉逆行注入1-2ml CO2饱和盐水时，活动迅速增加，但当注入pH值为7.4的生理盐水或胎儿动脉血时，则不明显。在2例胎儿中，在脐带结扎并开始空气呼吸的同时，连续记录近期化学感受器的活动。随着PaO2的下降，活动增加了200-500%，但随着PaO2的上升，活性下降到低于控制水平。这些活动的变化可能反映了出生时自然发生的变化。产后135~146日龄经阴道分娩和剖宫产的12只戊巴比妥钠麻醉羔羊，出生当天均未检测到自发化学感受器活动。然而，在这些羔羊身上可以记录到单一的压力感受器活动，高碳酸血症可以引起化学感受器活动。7日龄7只羔羊中有6只检测到自发化学感受器活性。在8只清醒羔羊中，出生当天对等颅压缺氧的稳态呼吸反应是不同的。在这些羔羊中，有6只在第3天时反应明显更强。动脉化学感受器在胎儿中明显活跃和反应，但在出生当天当PaO2上升时羔羊处于静止状态。在接下来的几天里，化学感受器的低氧敏感度将从胎儿重置到成人范围。
Carotid chemoreceptor activity was detected in each of 14 halothane or pentobarbitone anesthetized exteriorized fetal lambs of 90-143 days gestational age. Activity was .apprx. 5 Hz at a PaO2 [arterial partial pressure of O2] of 25 mmHg and it increased as PaO2 was reduced, either by compressing the umbilical cord or by reducing the (FIO2) O2 fraction of the gas used to ventilate the ewe. Activity increased briskly when 1-2 ml CO2-saturated saline was injected retrogradely into the lingual artery, but not when saline at pH 7.4 or fetal arterial blood was injected. In 2 fetuses near-term chemoreceptor activity was recorded continuously while the umbilical cord was ligated and ventilation with air started. Activity increased 200-500% as PaO2 fell, but then fell to below control as PaO2 rose. These changes in activity may reflect those occurring naturally at birth. No spontaneous chemoreceptor activity could be detected on the day of birth in 12 pentobarbitone anesthetized lambs delivered vaginally or by Cesarean section at 135-146 days. Single baroreceptor activity could however be recorded in these lambs and chemoreceptor activity could be elicited by hypercapnia. Spontaneous chemoreceptor activity was detected in 6 of 7 lambs > 2 days old. In 8 conscious lambs the steady-state respiratory response to isocapnic hypoxia was variable on the day of birth. In 6 of these lambs the response was significantly greater by the 3rd day. Arterial chemoreceptors are evidently active and responsive in the fetus, but quiescent in the lamb on the day of birth when PaO2 has risen. The hypoxic sensitivity of the chemoreceptors is reset from the fetal to the adult range over the next few days.