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Changes in ovine renal sympathetic nerve activity and baroreflex function at birth. Am J Physiol 1994 Nov;267(5 Pt 2):H1824-32



Pubmed ID




Scopus ID

2-s2.0-0028112927   43 Citations


The purposes of this study were to characterize the changes in renal sympathetic nerve activity (RSNA) and baroreflex function at birth in conscious sheep. One hour after delivery by cesarean section, RSNA increased by 239 +/- 24% compared with fetuses. The upper and lower plateau values of the baroreflex function curves for RSNA, expressed as the percent maximum achieved in the fetus, were greater (P < 0.05) at 1 h (260 +/- 41 and 142 +/- 40%) and 5 h of age (254 +/- 34 and 100 +/- 19%) than in fetuses (100 and 10 +/- 3%), respectively. Curve midpoint pressures also were higher (P < 0.05) at 1 h (62 +/- 3 mmHg) and 5 h (66 +/- 4 mmHg) than in fetuses (51 +/- 2 mmHg). No changes in the sensitivity (gain) of the RSNA response to baroreceptor stimulation were seen. The baroreflex response curves for heart rate showed similar increases in the curve midpoint pressures, while gain did not change. To determine whether the high circulating levels of angiotensin II (ANG II) in the newborn period contribute to the rise in RSNA or the resetting of the baroreflex toward higher pressures, the angiotensin-converting-enzyme inhibitor, enalaprilat, was administered to five lambs before delivery. No differences in the increase in RSNA after birth were detected between control and treated animals. The curve midpoint pressures of both the RSNA and heart rate baroreflex response curves were significantly less (P < 0.05) in the treated compared with control lambs.(ABSTRACT TRUNCATED AT 250 WORDS)

Author List

Segar JL, Mazursky JE, Robillard JE


Jeffrey L. Segar MD Professor in the Pediatrics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals, Newborn
Blood Pressure
Carbon Dioxide
Cesarean Section
Delivery, Obstetric
Gestational Age
Heart Rate
Hydrogen-Ion Concentration
Partial Pressure
Renal Artery
Sympathetic Nervous System
jenkins-FCD Prod-486 e3098984f26de787f5ecab75090d0a28e7f4f7c0