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 language | English |
|---|---|
| Pages (from-to) | 50-54 |
| Number of pages | 5 |
| Journal | Pediatric Research |
| Volume | 24 |
| Issue number | 1 |
| State | Published - Jan 1 1988 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health
Cite this
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 journal › Article
}
TY - JOUR
T1 - In vivo demonstration of maturational changes of the chronotropic response to α-adrenergic stimulation
AU - McCormack, J.
AU - Gelband, H.
AU - Villafane, J.
AU - Xu, H.
AU - Stolfi, A.
AU - Pickoff, A. S.
PY - 1988/1/1
Y1 - 1988/1/1
N2 - 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.
AB - 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.
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UR - http://www.scopus.com/inward/citedby.url?scp=0023894732&partnerID=8YFLogxK
M3 - Article
VL - 24
SP - 50
EP - 54
JO - Pediatric Research
JF - Pediatric Research
SN - 0031-3998
IS - 1
ER -