Altered heart rate baroreflex during pregnancy: Role of sympathetic and parasympathetic nervous systems

Virginia Brooks, Colleen M. Kane, Donna M. Van Winkle

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45 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume273
Issue number3 42-3
StatePublished - 1997

Fingerprint

Parasympathetic Nervous System
Baroreflex
Sympathetic Nervous System
Heart Rate
N-Methylscopolamine
Pregnancy
Rabbits
Propranolol
Acetylcholine
Isoproterenol
Reflex
Arterial Pressure
Buffers

Keywords

  • Acetylcholine
  • Isoproterenol
  • Langendorff
  • Methscopolamine
  • Propranolol
  • Rabbits

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

Cite this

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title = "Altered heart rate baroreflex during pregnancy: Role of sympathetic and parasympathetic nervous systems",
abstract = "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.",
keywords = "Acetylcholine, Isoproterenol, Langendorff, Methscopolamine, Propranolol, Rabbits",
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year = "1997",
language = "English (US)",
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journal = "American Journal of Physiology - Renal Fluid and Electrolyte Physiology",
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T1 - Altered heart rate baroreflex during pregnancy

T2 - Role of sympathetic and parasympathetic nervous systems

AU - Brooks, Virginia

AU - Kane, Colleen M.

AU - Van Winkle, Donna M.

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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