title: Ontogeny of baroreflex control of renal sympathetic nerve activity and heart rate.
abstract: The purpose of this study was to characterize the developmental changes in baroreflex function during fetal and postnatal life in sheep. Resting mean arterial blood pressure increased significantly from 55 +/- 2 mmHg in fetuses to 86 +/- 3 mmHg in newborn lambs and to 105 +/- 4 mmHg in 4- to 6-wk-old lambs. The sensitivity (gain) of the renal sympathetic nerve activity (RSNA) response to baroreceptor stimulation was greater (P < 0.05) in fetuses (-7.7 +/- 1.9%/mmHg) than in newborn (-2.9 +/- 0.1%/mmHg) and 4- to 6-wk-old lambs (-2.2 +/- 0.2%/mmHg). The threshold and saturation pressures for the baroreflex function curve were lower (P < 0.05) in fetuses (44 +/- 2 and 61 +/- 2 mmHg) than in newborn (59 +/- 4 and 106 +/- 5 mmHg) or 4- to 6-wk-old lambs (78 +/- 5 and 132 +/- 6 mmHg). Similar findings were observed when the heart rate response to baroreceptor stimulation was examined. Additional experiments were performed in newborn and 4- to 6-wk-old lambs to determine whether the rise in arterial blood pressure associated with postnatal maturation contributed to baroreflex resetting. Sustained elevation of arterial blood pressure by 15-20 mmHg for over 90 min did not reset the baroreflex function curve in either newborn or 4- to 6-wk-old lambs.(ABSTRACT TRUNCATED AT 250 WORDS)
authors: Department of Pediatrics, University of Iowa, Iowa City 52242.
authors: J L
authors: JL
authors: Segar
authors: G
authors: G
authors: Hajduczok
authors: B A
authors: BA
authors: Smith
authors: D C
authors: DC
authors: Merrill
authors: J E
authors: JE
authors: Robillard
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000097:blood / Q000254:growth & development* / Q000502:physiology; D001158:Arteries; D001794:Blood Pressure; D005314:Embryonic and Fetal Development; D005312:Fetal Blood; D006339:Heart Rate; D007668:Kidney / Q000294:innervation*; D011311:Pressoreceptors / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D012146:Rest; D012756:Sheep; D013564:Sympathetic Nervous System / Q000196:embryology / Q000254:growth & development / Q000502:physiology*