TY - JOUR
T1 - Altered heart rate baroreflex during pregnancy
T2 - Role of sympathetic and parasympathetic nervous systems
AU - Brooks, Virginia L.
AU - Kane, Colleen M.
AU - Van Winkle, Donna M.
N1 - Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 1997
Y1 - 1997
N2 - Two studies were performed to determine whether the attenuation of baroreflex control of heart rate during late pregnancy in conscious rabbits is due to changes in parasympathetic (Para) or sympathetic (Sym) control of the heart. In the first, baroreflex relationships between arterial pressure and heart rate were generated before and after treatment with propranolol (Pro) to block Sym or with methscopolamine (Meth) to block Para. Each rabbit was studied in both the pregnant and nonpregnant state. Pregnancy decreased maximum baroreflex gain from 14.9 ± 4.0 to 4.8 ± 0.9 beats · min-1 · mmHg-1 (P < 0.01) and decreased heart rate range from 177 ± 6 to 143 ± 10 beats/min (P < 0.01), primarily by increasing minimum heart rate (114 ± 6 to 134 ± 8 beats/min; P < 0.01). The difference between pregnant and nonpregnant rabbits in baroreflex gain was not altered by Meth but was abolished by Pro, suggesting that it is due to decreased Sym control of the heart. The elevated minimum heart rate of pregnancy persisted after Pro, but was abolished by Meth, suggesting that it is mediated by decreased Para control of the heart. In the second study, isolated buffer-perfused hearts from pregnant and nonpregnant rabbits were treated with increasing doses of isoproterenol (0.3-300 mM) or acetylcholine (0.3-10,000 μM), and the heart rate responses were determined. Hearts from pregnant rabbits were more sensitive to isoproterenol (P < 0.05), but less responsive to acetylcholine (P < 0.05). In conclusion, pregnancy-induced decreases in cardiac reflex gain and range appear to be mediated by alterations in Sym and Para, respectively. The change in Sym occurs proximal to the heart, whereas the decreased contribution of Para may be due, at least in part, to decreased sensitivity of the heart to acetylcholine.
AB - Two studies were performed to determine whether the attenuation of baroreflex control of heart rate during late pregnancy in conscious rabbits is due to changes in parasympathetic (Para) or sympathetic (Sym) control of the heart. In the first, baroreflex relationships between arterial pressure and heart rate were generated before and after treatment with propranolol (Pro) to block Sym or with methscopolamine (Meth) to block Para. Each rabbit was studied in both the pregnant and nonpregnant state. Pregnancy decreased maximum baroreflex gain from 14.9 ± 4.0 to 4.8 ± 0.9 beats · min-1 · mmHg-1 (P < 0.01) and decreased heart rate range from 177 ± 6 to 143 ± 10 beats/min (P < 0.01), primarily by increasing minimum heart rate (114 ± 6 to 134 ± 8 beats/min; P < 0.01). The difference between pregnant and nonpregnant rabbits in baroreflex gain was not altered by Meth but was abolished by Pro, suggesting that it is due to decreased Sym control of the heart. The elevated minimum heart rate of pregnancy persisted after Pro, but was abolished by Meth, suggesting that it is mediated by decreased Para control of the heart. In the second study, isolated buffer-perfused hearts from pregnant and nonpregnant rabbits were treated with increasing doses of isoproterenol (0.3-300 mM) or acetylcholine (0.3-10,000 μM), and the heart rate responses were determined. Hearts from pregnant rabbits were more sensitive to isoproterenol (P < 0.05), but less responsive to acetylcholine (P < 0.05). In conclusion, pregnancy-induced decreases in cardiac reflex gain and range appear to be mediated by alterations in Sym and Para, respectively. The change in Sym occurs proximal to the heart, whereas the decreased contribution of Para may be due, at least in part, to decreased sensitivity of the heart to acetylcholine.
KW - Acetylcholine
KW - Isoproterenol
KW - Langendorff
KW - Methscopolamine
KW - Propranolol
KW - Rabbits
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U2 - 10.1152/ajpregu.1997.273.3.r960
DO - 10.1152/ajpregu.1997.273.3.r960
M3 - Article
C2 - 9321874
AN - SCOPUS:0030798313
SN - 0363-6119
VL - 273
SP - R960-R966
JO - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
JF - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
IS - 3 42-3
ER -