What question did this study set out to answer?

To determine how antecedent sympathetic stimulation influences the time course and magnitude of cardiac slowing induced by subsequent vagal stimulation.

April 1, 1994AJP Heart and Circulatory Physiology

Antecedent sympathetic stimulation alters time course of chronotropic response to vagal stimulation in dogs

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Why the study?

Does antecedent sympathetic stimulation alter the chronotropic response to vagal stimulation in anesthetized dogs?

Population

31 anesthetized dogs

Comparison

Antecedent sympathetic stimulation… vs No antecedent stimulation, or administration of…

Design

Preclinical

Authors

TYTiantian YangJiaozuo University JSJerome B. SenturiaCleveland State University MLMatthew N. LevyTechnion – Israel Institute of Technology

Discussion

Member takes

Implication

Antecedent sympathetic blunting of vagal responses in dogs warrants caution in autonomic models; leaves open translation to human chronotropic control.

Key Points

To determine how antecedent sympathetic stimulation influences the time course and magnitude of cardiac slowing induced by subsequent vagal stimulation.
Assessed chronotropic responses to 10-second vagal stimulation trains following sympathetic stimulation, norepinephrine infusion, or atrial pacing in anesthetized dogs across several cohorts (total N=31).
Calculated the reciprocal slope (m⁻¹) of the initial heart rate slowing phase as an index of the time required to attain steady-state vagal responses.
Administered the beta-adrenergic blocker propranolol (1 mg/kg) and alpha-adrenergic blocker phentolamine (2 mg/kg) to identify the receptor mechanism.
Increasing antecedent sympathetic stimulation frequency and duration progressively increased m⁻¹ from 0 to 8.13 ± 2.75 SE and 0 to 8.22 ± 2.26 SE, respectively, indicating delayed vagal slowing.
Antecedent norepinephrine infusion reproduced this delay, while antecedent atrial pacing had no effect, and lengthening the recovery interval between stimuli significantly decreased m⁻¹.
Propranolol abolished the blunting effect on vagal response onset, whereas phentolamine had no noticeable effect, demonstrating postjunctional beta-receptor mediation.

Structured PICO

Does antecedent sympathetic stimulation alter the chronotropic response to vagal stimulation in anesthetized dogs?

Population

31 anesthetized dogs

Intervention

Antecedent sympathetic stimulation (varying frequency and duration), norepinephrine infusion, or atrial pacing

Comparator

No antecedent stimulation, or administration of propranolol (1 mg/kg) or phentolamine (2 mg/kg)

Outcome

Chronotropic response to 10-s strains of vagal stimulation (measured by the reciprocal of the slope, m-1, of the initial portion of the vagal response)surrogate

Antecedent sympathetic stimulation blunts the chronotropic response to vagal stimulation in dogs via postjunctional beta-adrenergic mechanisms.

Cite This Study

Yang et al. (1994) studied this question.

synapsesocial.com/papers/6a8930b96a1d496eee0c4a2e https://doi.org/10.1152/ajpheart.1994.266.4.h1339

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Implication

Antecedent sympathetic blunting of vagal responses in dogs warrants caution in autonomic models; leaves open translation to human chronotropic control.

Antecedent sympathetic stimulation alters time course of chronotropic response to vagal stimulation in dogs

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Antecedent sympathetic stimulation alters time course of chronotropic response to vagal stimulation in dogs

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

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