Development of the arterial chemoreflex and turnover of carotid body catecholamines in the newborn rat.
Development of the arterial chemoreflex and turnover of carotid body catecholamines in the newborn rat.
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新生大鼠动脉化学反射的发展和颈动脉体儿茶酚胺的周转。
DOI：
10.1113/jphysiol.1990.sp018099
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Pequignot,JM
中科院分区：
文献类型：
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作者：
Hertzberg,T;Hellström,S;Lagercrantz,H;Pequignot,JM
1.在胎儿中，颈动脉体中的外周动脉化学感受器是活跃的和有反应的。出生时，当氧合增加时，化学感受器沉默。在接下来的几天里，敏感性被重置为成人水平，化学感受器在正常情况下影响呼吸。为了研究这种重置的潜在机制，我们检查了新生大鼠的化学反射强度，并将其与新生幼崽和近足月胎儿颈动脉体中多巴胺和去甲肾上腺素的含量相关联。此外，通过分析α-甲基-对-酪氨酸合成抑制后的儿茶酚胺减少，测定了1周龄内新生大鼠的多巴胺和去甲肾上腺素转换率。2.在未麻醉的大鼠幼仔中，通过“生理化学去神经”方法评估化学感受器影响，高氧持续时间为15 - 20 s。由高氧引起的通气量的相对变化通过身体体积描记法来确定。我们发现，无论是阴道出生的大鼠还是剖腹产分娩的近足月幼鼠，出生当天的通气量均无变化。1天后，通气量显著降低-19.4 +/-2.3%（平均值+/-S.E.M.）在7日龄时，下降为-28.8 +/-2.2%，表明外周化学感受器的影响增加。3.通过高效液相色谱法测定多巴胺和去甲肾上腺素的含量。多巴胺从胎儿的3.7 +/-0.4 pmol（一对颈动脉体）-1增加到出生后6 - 12 h的峰值15.9 +/-2.6，然后在7天龄时下降到7.1 +/-0.7。去甲肾上腺素水平从胎儿的1.3 +/-0.3增加到4天后的9.6 +/-1.1 pmol（一对颈动脉体）-1。多巴胺的周转率从出生后4.4 pmol（一对颈动脉体）-1 h-1 0 - 6 h降至6 - 12 h时的1.0。去甲肾上腺素的周转率在分娩后的最初几个小时内也有所下降。4.由于多巴胺是一种抑制性的神经调节剂在这个系统中，我们认为，在第一天的生活后看到的敏感性的增加，至少部分是由于多巴胺的释放减少，从而消除了抑制机制。
1. The peripheral, arterial chemoreceptors in the carotid body are active and responsive in the fetus. At birth, when oxygenation increases, the chemoreceptors are silenced. Over the next few days the sensitivity is reset toward the adult level and the chemoreceptors influence breathing during normal conditions. In order to investigate the underlying mechanisms of this resetting we examined the strength of the chemoreflex in newborn rats and correlated this to the contents of dopamine and noradrenaline in the carotid bodies of the newborn pups and near‐term fetuses. Furthermore, turnover rates of dopamine and noradrenaline were determined in newborn rats up to 1 week of age by analysis of catecholamine decreases after inhibition of synthesis with alpha‐methyl‐p‐tyrosine. 2. Chemoreceptor influence was assessed by the method of ‘physiological chemodenervation’ with hyperoxia of 15‐20 s duration in unanaesthetized rat pups. Relative changes in ventilation elicited by hyperoxia were determined by body plethysmography. We found no change in ventilation on the day of birth either in vaginally born rats or in near‐term pups delivered by Caesarean section. After 1 day there was a significant decrease in ventilation of ‐19.4 +/‐ 2.3% (mean +/‐ S.E.M.) and at 7 days of age the decrease was ‐28.8 +/‐ 2.2%, suggesting an increasing influence from the peripheral chemoreceptors. 3. The contents of dopamine and noradrenaline were measured by high‐performance liquid chromatography. Dopamine increased from 3.7 +/‐ 0.4 pmol (pair of carotid bodies)‐1 in the fetus to a peak of 15.9 +/‐ 2.6, 6‐12 h after birth followed by a decline to 7.1 +/‐ 0.7 at 7 days of age. Noradrenaline levels increased from 1.3 +/‐ 0.3 in the fetus to 9.6 +/‐ 1.1 pmol (pair of carotid bodies)‐1 after 4 days. The turnover rate of dopamine decreased from 4.4 pmol (pair of carotid bodies)‐1 h‐1 0‐6 h after birth to 1.0 at 6‐12 h of age. The turnover rate of noradrenaline also decreased over the first hours following delivery. 4. Since dopamine is an inhibitory neuromodulator in this system, we suggest that the increase in sensitivity seen after the first day of life is, at least in part, due to a decrease in the release of dopamine and thus a removal of an inhibitory mechanism.