Supersensitivity to acetylcholine of canine sinus and AV nodes after parasympathetic denervation

S. Kaseda, D. P. Zipes

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Supersensitivity of the sinus (SAN) and atrioventricular (AVN) nodes to acetylcholine (ACh) after parasympathetic denervation has not been demonstrated conclusively. In this study, we denervated the SAN and AVN by surgically removing parasympathetic ganglia and painting the area with phenol. Sham dogs underwent thoracotomy without denervation. Four to 9 days later, vagal denervation was proved by supramaximal bilateral vagal stimulation, which prolonged the sinus cycle length (SCL) only 32 ± 7% (means ± SE) and the AVN conduction time (AH interval) 15 ± 7% in denervated dogs. We tested for supersensitivity by obtaining dose-response curves to ACh (1 ml, 10-8.0 to 10-4.0 M in 100.5 steps) infused over 15 s into the sinus nodal and posterior septal arteries in open chest-denervated (Den) dogs and in sham-operated (Sham) dogs that were anesthetized with α-chloralose. ACh concentration (Log[ACh],M) required to prolong SCL 50, 100, and 300% was -5.7 ± 0.1, -5.6 ± 0.1, and -5.4 ± 0.1 in 10 Sham dogs vs. -6.4 ± 0.1 (P < 0.001), -6.3 ± 0.1 (P < 0.001) and -6.1 ± 0.1 (P < 0.001) in 11 Den dogs. ACh concentration necessary to produce second degree and complete AV block was -5.7 ± 0.1 and -5.3 ± 0.1 in 11 Sham dogs vs. -6.3 ± 0.1 (P < 0.001) and -5.8 ± 0.1 (P < 0.01) in 10 Den dogs. Because significantly lower doses of ACh prolonged SCL or produced AV block in Den compared with Sham dogs, we conclude that dogs with vagally denervated SAN and AVN develop a supersensitive response to ACh.

Original languageEnglish
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume255
Issue number3
StatePublished - 1988

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Parasympathectomy
Atrioventricular Node
Sinoatrial Node
Acetylcholine
Canidae
Dogs
Atrioventricular Block
Denervation
Parasympathetic Ganglia
Chloralose
Paintings
Thoracotomy
Phenol

ASJC Scopus subject areas

  • Physiology

Cite this

Supersensitivity to acetylcholine of canine sinus and AV nodes after parasympathetic denervation. / Kaseda, S.; Zipes, D. P.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 255, No. 3, 1988.

Research output: Contribution to journalArticle

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abstract = "Supersensitivity of the sinus (SAN) and atrioventricular (AVN) nodes to acetylcholine (ACh) after parasympathetic denervation has not been demonstrated conclusively. In this study, we denervated the SAN and AVN by surgically removing parasympathetic ganglia and painting the area with phenol. Sham dogs underwent thoracotomy without denervation. Four to 9 days later, vagal denervation was proved by supramaximal bilateral vagal stimulation, which prolonged the sinus cycle length (SCL) only 32 ± 7{\%} (means ± SE) and the AVN conduction time (AH interval) 15 ± 7{\%} in denervated dogs. We tested for supersensitivity by obtaining dose-response curves to ACh (1 ml, 10-8.0 to 10-4.0 M in 100.5 steps) infused over 15 s into the sinus nodal and posterior septal arteries in open chest-denervated (Den) dogs and in sham-operated (Sham) dogs that were anesthetized with α-chloralose. ACh concentration (Log[ACh],M) required to prolong SCL 50, 100, and 300{\%} was -5.7 ± 0.1, -5.6 ± 0.1, and -5.4 ± 0.1 in 10 Sham dogs vs. -6.4 ± 0.1 (P < 0.001), -6.3 ± 0.1 (P < 0.001) and -6.1 ± 0.1 (P < 0.001) in 11 Den dogs. ACh concentration necessary to produce second degree and complete AV block was -5.7 ± 0.1 and -5.3 ± 0.1 in 11 Sham dogs vs. -6.3 ± 0.1 (P < 0.001) and -5.8 ± 0.1 (P < 0.01) in 10 Den dogs. Because significantly lower doses of ACh prolonged SCL or produced AV block in Den compared with Sham dogs, we conclude that dogs with vagally denervated SAN and AVN develop a supersensitive response to ACh.",
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