Wood C E
Department of Physiology, University of Florida College of Medicine, Gainesville 32610.
Am J Physiol. 1995 Feb;268(2 Pt 2):R343-8. doi: 10.1152/ajpregu.1995.268.2.R343.
In postnatal animals, carotid occlusion does not stimulate reflex hormonal responses, because decreases in carotid arterial baroreceptor activity are balanced by reflex-mediated increases in vagal afferent traffic from aortic and cardiac receptors. The present experiments were designed to test the hypothesis that hormonal responses to carotid occlusion in fetal animals are not inhibited by vagal afferents. In thirteen chronically catheterized fetal sheep (125-146 days), bilateral carotid occlusion (n = 11) increased arterial blood pressure from 44.0 +/- 2.4 to 55.2 +/- 3.3 mmHg, decreased heart rate from 189 +/- 5 to 165 +/- 12 beats/min, increased plasma adrenocorticotropin from 71 +/- 15 to 248 +/- 79 pg/ml and vasopressin from 3.0 +/- 1.0 to 7.4 +/- 2.6 pg/ml but did not significantly alter renin. Plasma hormone concentrations were not significantly altered in control (n = 7) experiments or in response to unilateral carotid occlusion (n = 4). The results of these experiments demonstrate the functional immaturity of the vagal afferent buffering systems in the late-gestation fetus compared with the postnatal animal.
在出生后的动物中，颈动脉闭塞不会刺激反射性激素反应，因为颈动脉压力感受器活动的降低被来自主动脉和心脏感受器的迷走神经传入流量反射介导的增加所平衡。本实验旨在检验以下假设：胎儿动物对颈动脉闭塞的激素反应不受迷走神经传入神经的抑制。在13只长期插管的胎羊（125 - 146天）中，双侧颈动脉闭塞（n = 11）使动脉血压从44.0±2.4 mmHg升高至55.2±3.3 mmHg，心率从189±5次/分钟降至165±12次/分钟，血浆促肾上腺皮质激素从71±15 pg/ml升高至248±79 pg/ml，血管加压素从3.0±1.0 pg/ml升高至7.4±2.6 pg/ml，但肾素没有显著变化。在对照实验（n = 7）或单侧颈动脉闭塞实验（n = 4）中，血浆激素浓度没有显著改变。这些实验结果表明，与出生后的动物相比，妊娠晚期胎儿的迷走神经传入缓冲系统功能不成熟。
