Woods J R, Dandavino A, Murayama K, Brinkman C R, Assali N S
Circ Res. 1977 Apr;40(4):401-7. doi: 10.1161/01.res.40.4.401.
We studied the autonomic control of resting heart rate of systemic and pulmonary vascular blood pressures (BP) in chronically instrumented neonatal lambs 1-8 weeks of age. The maximum response to ganglionic blockade and sympathetic and parasympathetic antagonists was taken as an index of the magnitude of the total neural, adrenergic, and cholinergic tones. The reactivity of the circulatory parameters to adrenergic and cholinergic agonists also was investigated. All findings were compared with those in adult nonpregnant sheep studied concomitantly and with data previously obtained from term fetal lambs. The results of our studies show: (1) resting heart rate declines spontaneously throughout the 8 weeks of neonatal life approaching that of adult sheep; (2) the progressive bradycardia is not related to changes in the parasympathetic or sympathetic tone; (3) resting systemic BP is under strong neurohumoral control during the first two to three weeks of neonatal life; the control decreases progressively, becoming similar to that of adult sheep; (4) resting pulmonary artery pressure of neonatal and adult sheep has no neurohumoral control; (5) the systemic BP response of the neonate to autonomic agonists is greater than that of the term fetus and is similar to that of the adult; (6) in neonatal and adult sheep, compared to the term fetus, the pressor response to norepinephrine is accompanied by a baroreceptor-mediated bradycardia, and acetylcholine-induced systemci hypotension is accompanied by a "paradoxical" tachycardia mediated through beta-adrenergic stimulation; (7) in contrast to our finding for the fetus, the pulmonary vascular pressure of neonatal and adult sheep is unresponsive to autonomic agonists.
我们研究了1至8周龄长期植入仪器的新生羔羊静息心率、体循环和肺循环血压的自主控制情况。将对神经节阻滞以及交感和副交感拮抗剂的最大反应作为总神经、肾上腺素能和胆碱能张力大小的指标。还研究了循环参数对肾上腺素能和胆碱能激动剂的反应性。所有研究结果均与同期研究的成年未孕绵羊的结果以及先前从足月胎羊获得的数据进行了比较。我们的研究结果表明：（1）在新生期的8周内，静息心率自发下降，接近成年绵羊的心率；（2）逐渐出现的心动过缓与副交感或交感神经张力的变化无关；（3）在新生期的头两到三周，静息体循环血压受到强大的神经体液控制；这种控制逐渐减弱，变得与成年绵羊相似；（4）新生绵羊和成年绵羊的静息肺动脉压不受神经体液控制；（5）新生儿对自主激动剂的体循环血压反应大于足月胎儿，与成年人相似；（6）在新生绵羊和成年绵羊中，与足月胎儿相比，去甲肾上腺素引起的升压反应伴有压力感受器介导的心动过缓，乙酰胆碱引起的体循环低血压伴有通过β-肾上腺素能刺激介导的“反常”心动过速；（7）与我们对胎儿的研究结果相反，新生绵羊和成年绵羊的肺血管压力对自主激动剂无反应。
