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July 1, 1998Experimental Physiology

Nitric oxide has an important facilitatory role on both the chronotropic and dromotropic actions of the vagus nerve on the heart, potentially acting as a rate-limiting factor.

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Why the study?

Does nitric oxide modulate the chronotropic and dromotropic actions of the vagus nerve on the ferret heart?

Population

Ferret heart model

Comparison

Nitric oxide synthase inhibitors and NO donors vs Baseline/control responses to vagal stimulation

Design

Preclinical

Key result

Nitric oxide has an important facilitatory role on both the chronotropic and dromotropic actions of the vagus nerve on the heart, potentially acting as a rate-limiting factor.

Authors

KCKelly ConlonTCT CollinsCKC. Kidd

Discussion

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Overview

Nitric oxide may facilitate vagal chronotropic and dromotropic effects; hypothesis-generating in ferrets, clinical relevance unknown.

Key Points

  • To investigate the role of nitric oxide in modulating the chronotropic and dromotropic responses of the heart during parasympathetic vagal stimulation.
  • Assessed cardiac responses to efferent vagal nerve stimulation across multiple frequencies in paced and unpaced ferret hearts.
  • Administered nitric oxide synthase (NOS) inhibitors (L-NAME, L-NOARG), stereospecific substrates (L-arginine, D-arginine), and a nitric oxide donor (sodium nitroprusside).
  • Inhibition of NOS via L-NAME attenuated vagally induced bradycardia, which was reversed by L-arginine but not D-arginine; L-NOARG produced irreversible reduction.
  • The nitric oxide donor sodium nitroprusside enhanced vagally induced bradycardia across all stimulation frequencies tested.
  • L-NAME reduced the vagal-mediated prolongation of atrioventricular conduction delay in both paced and unpaced hearts, whereas sodium nitroprusside magnified this delay.

Structured PICO

Does nitric oxide modulate the chronotropic and dromotropic actions of the vagus nerve on the ferret heart?

P
Population
Ferret heart model
I
Intervention
Nitric oxide synthase (NOS) inhibitors (L-NAME, L-NOARG) and NO donors (sodium nitroprusside)
C
Comparator
Baseline/control responses to vagal stimulation
O
Outcome
Chronotropic (bradycardia) and dromotropic (atrio-ventricular conduction delay) responses to vagal stimulationsurrogate

Nitric oxide plays an important facilitatory role in the chronotropic and dromotropic actions of the vagus nerve on the heart.

Cite This Study

Conlon et al. (1998) studied this question. NOS inhibitors (L-NAME, L-NOARG) and NO donors (sodium nitroprusside) was evaluated on Bradycardia and atrio-ventricular conduction delay induced by vagal stimulation. Nitric oxide has an important facilitatory role on both the chronotropic and dromotropic actions of the vagus nerve on the heart, potentially acting as a rate-limiting factor.

synapsesocial.com/papers/6a942b1f189c14fbc5b9528ehttps://doi.org/10.1113/expphysiol.1998.sp004130
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