Wagerle L C, Kurth C D, Busija D W
Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia 19104.
J Dev Physiol. 1992 Jan;17(1):51-4.
Cerebral arteries of newborn pigs and baboons constrict to acetylcholine, suggesting that endothelium-dependent dilator mechanisms may be lacking in immature cerebral arteries. The present study tested this possibility in the immature sheep by examining the response of cerebral arterioles in fetal and newborn sheep to endothelium-dependent dilator, acetylcholine. Pial arteriolar diameter was measured in 9 anaesthetized foetuses in utero (4 preterm, 90-111 days gestation and 5 term, 128-143 days gestation) and in 5 anaesthetized, newborn lambs (14 days) using a closed cranial window with intravital microscopy. Application of acetylcholine to the pial surface induced dose-dependent increase in pial arteriolar diameter in all age groups; EC50 for acetylcholine was 0.10 +/- 0.03, 0.28 +/- 0.08 and 0.26 +/- 0.17 microM for preterm fetal, term fetal, and newborn lambs, respectively. The data demonstrate a sensitive dilator response to acetylcholine in immature fetuses as well as newborn lambs suggesting that cholinergic-mediated release of endothelium-dependent relaxing factor is functional early in gestation. The contractile response to acetylcholine observed in newborn pigs and premature baboons may reflect a species difference rather than maturational lack of endothelium-dependent dilator mechanisms.
新生猪和狒狒的脑动脉对乙酰胆碱产生收缩反应，这表明未成熟脑动脉中可能缺乏内皮依赖性舒张机制。本研究通过检测胎儿和新生绵羊脑微动脉对内皮依赖性舒张剂乙酰胆碱的反应，在未成熟绵羊中验证了这种可能性。使用封闭颅窗和活体显微镜，对9只麻醉的子宫内胎儿（4只早产，妊娠90 - 111天；5只足月，妊娠128 - 143天）和5只麻醉的新生羔羊（14天）测量软脑膜微动脉直径。对所有年龄组的软脑膜表面施加乙酰胆碱均引起软脑膜微动脉直径的剂量依赖性增加；早产胎儿、足月胎儿和新生羔羊对乙酰胆碱的半数有效浓度（EC50）分别为0.10±0.03、0.28±0.08和0.26±0.17微摩尔。数据表明未成熟胎儿和新生羔羊对乙酰胆碱有敏感的舒张反应，提示胆碱能介导的内皮依赖性舒张因子释放早在妊娠早期就发挥作用。在新生猪和早产狒狒中观察到的对乙酰胆碱的收缩反应可能反映了物种差异，而非内皮依赖性舒张机制成熟度的缺乏。
