Faculty Collaboration Database

Mechano- and chemoreceptor modulation of renal sympathetic nerve activity at birth in fetal sheep. Am J Physiol 1999 May;276(5):R1295-301

Date

05/08/1999

Pubmed ID

10233019

DOI

10.1152/ajpregu.1999.276.5.R1295

Scopus ID

2-s2.0-0033007121 (requires institutional sign-in at Scopus site)   7 Citations

Abstract

Physiological responses at birth include increases in heart rate (HR), blood pressure, sympathetic nerve activity, and circulating vasoactive peptides. The factors mediating these responses are not known. To test the hypothesis that afferent input from peripheral mechanoreceptors (arterial and cardiopulmonary baroreceptors) and chemoreceptors contribute to the sympathoexcitatory and hormonal responses at birth, we studied the effects of sinoaortic denervation (SAD) and SAD with vagotomy (Vx) on changes in HR, mean arterial blood pressure (MABP), renal sympathetic nerve activity (RSNA), and catecholamine, arginine vasopressin (AVP), and ANG II levels at birth in term sheep. One hour after delivery by cesarean section, RSNA increased by 168 +/- 49 and 192 +/- 32% (relative to fetal values) in SAD and SAD-Vx animals, respectively. Significant increases in HR (18 +/- 5 and 20 +/- 6%) and MABP (24 +/- 4 and 20 +/- 5%) were also observed 1 h after delivery in SAD and SAD-Vx lambs, respectively. These responses are similar to those seen in intact sheep delivered at the same gestational age. AVP levels markedly increased after birth (19.8 +/- 6.7 to 136.1 +/- 75.9 pg/ml) in SAD-Vx lambs, whereas SAD animals displayed no change in AVP concentrations. Plasma ANG II also did not change after birth in either group, although levels were consistently higher (P < 0.01) in SAD compared with SAD-Vx animals. In the presence of SAD, Vx resulted in significantly greater plasma levels of norepinephrine, although levels did not change after birth in either group. The epinephrine responses at birth were similar in both groups of animals. The present data suggest that afferent input from peripheral chemoreceptors and mechanoreceptors contributes little to the hemodynamic and sympathetic responses after delivery by cesarean section. On the other hand, these peripheral mechanisms appear to be involved in modulating endocrine responses at birth.

Author List

Segar JL, Smith OJ, Holley AT

Author

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

Angiotensin II
Animals
Arginine Vasopressin
Blood Gas Analysis
Blood Pressure
Catecholamines
Chemoreceptor Cells
Female
Fetus
Heart Rate, Fetal
Kidney
Neurosecretory Systems
Pregnancy
Pressoreceptors
Sheep
Sympathetic Nervous System
Vagotomy