Department of Pediatrics, Division of Neonatology, Loma Linda University School of Medicine, Loma Linda, California, United States of America.
Department of Respiratory Care, Pulmonary Physiology Laboratories, Loma Linda University Medical Center, Loma Linda, California, United States of America.
PLoS One. 2013 Dec 9;8(12):e82326. doi: 10.1371/journal.pone.0082326. eCollection 2013.
Cerebral vessels in the premature newborn brain are well supplied with adrenergic nerves, stemming from the superior cervical ganglia (SCG), but their role in regulation of blood flow remains uncertain. To test this function twelve premature or two-week-old lambs were instrumented with laser Doppler flow probes in the parietal cortices to measure changes in blood flow during changes in systemic blood pressure and electrical stimulation of the SCG. In lambs delivered prematurely at ∼129 days gestation cerebral perfusion and driving pressure demonstrated a direct linear relationship throughout the physiologic range, indicating lack of autoregulation. In contrast, in lambs two-weeks of age, surgical removal of one SCG resulted in ipsilateral loss of autoregulation during pronounced hypertension. Electrical stimulation of one SCG elicited unilateral increases in cerebral resistance to blood flow in both pre-term and two-week-old lambs, indicating functioning neural pathways in the instrumented, anesthetized lambs. We conclude cerebral autoregulation is non-functional in preterm lambs following cesarean delivery. Adrenergic control of cerebral vascular resistance becomes effective in newborn lambs within two-weeks after birth but SCG-dependent autoregulation is essential only during pronounced hypertension, well above the normal range of blood pressure.
早产儿大脑中的血管富含来自颈上神经节（SCG）的肾上腺素能神经，但它们在调节血流中的作用仍不确定。为了测试这一功能，12 只早产或两周大的羔羊被安置了激光多普勒流量探头，以测量全身血压变化和 SCG 电刺激期间大脑皮质血流的变化。在大约 129 天孕龄早产的羔羊中，脑灌注和驱动压在整个生理范围内呈直接线性关系，表明缺乏自动调节。相比之下，在两周大的羔羊中，单侧 SCG 切除导致明显高血压期间同侧自动调节丧失。单侧 SCG 电刺激在早产儿和两周大的羔羊中均引起脑血流阻力单侧增加，表明在仪器化、麻醉的羔羊中存在功能神经通路。我们的结论是，剖宫产分娩后的早产儿大脑自动调节功能丧失。肾上腺素能对脑血管阻力的控制在出生后两周内对新生羔羊有效，但仅在明显高血压（远高于正常血压范围）期间，SCG 依赖性自动调节才是必需的。
