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Inhibition of sympathetic responses at birth in sheep by lesion of the paraventricular nucleus. Am J Physiol Regul Integr Comp Physiol 2002 Dec;283(6):R1395-403

Date

10/22/2002

Pubmed ID

12388455

DOI

10.1152/ajpregu.00023.2002

Scopus ID

2-s2.0-0036889028   13 Citations

Abstract

Birth is characterized by a surge in sympathetic outflow, heart rate (HR), mean arterial blood pressure (MABP) and circulating catecholamines. The paraventricular nucleus (PVN) of the hypothalamus is an important central regulatory site of sympathetic activity, but its role in the regulation of sympathoexcitation at birth is unknown. To test the hypothesis that the PVN regulates sympathetic activity at birth, experiments were performed in chronically instrumented near-term (137- to 142-day gestation, term 145 days) sheep before and after delivery by cesarean section. Stereotaxic guided electrolytic lesioning of the PVN (n = 6) or sham lesioning (n = 6) was performed 48 h before study. At 30 min after birth, renal sympathetic nerve activity (RSNA) increased 128 +/- 26% above fetal values in the sham-lesioned animals (P < 0.05). In contrast, at a similar time point, RSNA decreased to 52 +/- 12% of the fetal value in the PVN-lesioned animals. Lesioning of the PVN did not affect the usual postnatal increases in MABP and epinephrine levels although HR failed to rise above fetal values. ANG II but not arginine vasopressin or norepinephrine levels increased in PVN-lesioned animals after birth, whereas all three hormones increased (P < 0.05) in sham-lesioned animals. Fetal and newborn HR baroreflex responses were similar in both groups. However, the usual postnatal attenuation of baroreflex-mediated inhibition of RSNA was blunted in the PVN-lesioned group. The results of this study demonstrate that ablation of the PVN abolishes sympathoexcitation with birth at near-term gestation. The PVN may play a critical role in physiological adaptation at birth.

Author List

Segar JL, Ellsbury DL, Smith OM

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
Animals, Newborn
Arginine Vasopressin
Baroreflex
Blood Gas Analysis
Blood Pressure
Epinephrine
Female
Fetus
Heart Rate
Hydrogen-Ion Concentration
Kidney
Male
Norepinephrine
Paraventricular Hypothalamic Nucleus
Pregnancy
Sheep
Sympathectomy
jenkins-FCD Prod-411 e00897e83867fcfa48419861683711f8d99adb75