Depressed heart rate variability and arterial baroreflex in conscious transgenic mice with overexpression of cardiac G(sα)

Masami Uechi, Kuniya Asai, Motohisa Osaka, Amelia Smith, Naoki Sato, Thomas E. Wagner, Yoshihiro Ishikawa, Hirokazu Hayakawa, Dorothy E. Vatner, Richard P. Shannon, Charles J. Homcy, Stephen F. Vatner

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128 Scopus citations


Recently, we developed a transgenic mouse with cardiac-specific G(sα) overexpression (TG mouse), which exhibits enhanced postsynaptic β-adrenergic receptor signaling, ultimately developing a cardiomyopathy. The goal of the present study was to determine whether cardiac G(sα) overexpression alters autonomic cardiovascular control, which could shed light on the mechanism responsible for the later development of cardiomyopathy. Mean arterial pressure was increased (P<.05) in conscious, chronically instrumented TG mice (123±1 mm Hg) compared with age-matched wild-type (WT) control mice (103±1 mm Hg). Respiratory frequency was increased (P<.05) in TG mice (269±26/min) compared with WT mice (210±20/min). By use of telemetric techniques, baseline heart rate (HR) was elevated (P<.05) in conscious, untethered TG mice (696±13 bpm) compared with WT mice (568±28 bpm). Intrinsic HR, after propranolol and attopine or after ganglienic blockade with hexamethonium, was not different between TG and WT mice. Both the normal minute-to-minute and circadian variations of HR observed in WT mice were markedly blunted in TG mice. HR variability was assessed by the time-domain and frequency-domain methods. At baseline, time-domain analysis indices were reduced (P<.05) in TG mice compared with WT mice. Although the low frequency (LF) component was higher (P<.05) than the high frequency (HF) component in WT mice, the LF component was less (P<.05) than the HF component in TG mice. In addition, arterial baroreflex regulation of HR was markedly blunted in TG mice in response to both nitroglycerin-induced hypotension and phenylephrine-induced hypertension. The reduced LF/HF ratio in TG mice was surprising in view of enhanced β-adrenergic signaling and may be due to reduced neural tone secondary to the elevated arterial pressure or alterations in arterial barereflex control. Dobutamine infusion in WT mice also resulted in depressed HR variability. The combination of elevated baseline HR, arterial pressure, and respiratory frequency suggests that enhanced β-adrenergic signaling in TG mice results in reduced HR variability, in terms of both minute-to-minute variability and the lack of circadian variations in HR. The lack of normal HR variability in general and the failure of HR to decline, even during sleep, may actually be critical mechanisms contributing to the ultimate development of cardiomyopathy in these animals.

Original languageEnglish (US)
Pages (from-to)416-423
Number of pages8
JournalCirculation research
Issue number4
StatePublished - Mar 9 1998
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cardiology and Cardiovascular Medicine


  • Arterial baroreflex
  • Circadian rhythm
  • Spectral analysis
  • Sympathetic nervous system
  • β-adrenergic receptor


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