In vivo demonstration of maturational changes of the chronotropic response to α-adrenergic stimulation

J. McCormack, H. Gelband, J. Villafane, H. Xu, A. Stolfi, A. S. Pickoff

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

In vitro studies suggest that neonates and adults may have different cardiac chronotropic responses to α-adrenergic stimulation. To investigate these differences in vivo, three groups of dogs were studied. Group I = 12 puppies, ages 3-7 days; group II = 12 puppies ages 8-15 days, and group III = seven adult dogs. Heart rate and blood pressure determinations were made in the control setting and then after combined β-adrenergic and parasympathetic blockade (propranolol 0.6 mg/kg and bilateral vagotomies). Alpha-stimulation was then achieved with phenylephrine given in doses of 0.5, 1.0, and 10.0 μg/kg/min. A second, high dose of propranolol (1.0 mg/kg intravenously) was administered after the highest phenylephrine infusion dosage to assure complete β-blockade. Finally, α-blockade was achieved with phentolamine (groups I and II: 0.5 mg intravenously; group III: 5.0 mg intravenously). An α-mediated positive chronotropic effect was observed in 42 and 100% of subjects in groups I and II, respectively, but never observed in the adults. Whereas α-blockade with phentolamine resulted in a large decrease in heart rate of all puppies (groups I and II), it had no effect on adults. Blood pressure responses were similar in all three groups. Thus, there are important maturational changes in the chronotropic response to α-adrenergic stimulation and blockade demonstrable in the intact neonatal canine.

Original languageEnglish
Pages (from-to)50-54
Number of pages5
JournalPediatric Research
Volume24
Issue number1
StatePublished - Jan 1 1988
Externally publishedYes

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Adrenergic Agents
Phentolamine
Phenylephrine
Propranolol
Heart Rate
Blood Pressure Determination
Dogs
Vagotomy
Canidae
Blood Pressure
In Vitro Techniques

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health

Cite this

McCormack, J., Gelband, H., Villafane, J., Xu, H., Stolfi, A., & Pickoff, A. S. (1988). In vivo demonstration of maturational changes of the chronotropic response to α-adrenergic stimulation. Pediatric Research, 24(1), 50-54.

In vivo demonstration of maturational changes of the chronotropic response to α-adrenergic stimulation. / McCormack, J.; Gelband, H.; Villafane, J.; Xu, H.; Stolfi, A.; Pickoff, A. S.

In: Pediatric Research, Vol. 24, No. 1, 01.01.1988, p. 50-54.

Research output: Contribution to journalArticle

McCormack, J, Gelband, H, Villafane, J, Xu, H, Stolfi, A & Pickoff, AS 1988, 'In vivo demonstration of maturational changes of the chronotropic response to α-adrenergic stimulation', Pediatric Research, vol. 24, no. 1, pp. 50-54.
McCormack J, Gelband H, Villafane J, Xu H, Stolfi A, Pickoff AS. In vivo demonstration of maturational changes of the chronotropic response to α-adrenergic stimulation. Pediatric Research. 1988 Jan 1;24(1):50-54.
McCormack, J. ; Gelband, H. ; Villafane, J. ; Xu, H. ; Stolfi, A. ; Pickoff, A. S. / In vivo demonstration of maturational changes of the chronotropic response to α-adrenergic stimulation. In: Pediatric Research. 1988 ; Vol. 24, No. 1. pp. 50-54.
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