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Related Experiment Videos

Reflex vascular capacity reduction in the dog

C F Rothe

    Circulation Research
    |November 1, 1976
    PubMed
    Summary
    This summary is machine-generated.

    This study quantifies active reflex venoconstriction in dogs during cardiac fibrillation. Maximal venoconstriction, induced by maximal sympathetic discharge, was found to be 9.0 ml/kg, indicating significant capacity vessel tone.

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    Area of Science:

    • Physiology
    • Cardiovascular Research
    • Autonomic Nervous System

    Background:

    • Understanding the regulation of circulatory filling pressure is crucial for cardiovascular physiology.
    • Active reflex venoconstriction plays a significant role in maintaining blood pressure and organ perfusion.
    • Previous studies have not fully elucidated the maximal capacity of venoconstriction under sympathetic stimulation.

    Purpose of the Study:

    • To determine the maximum degree and time course of active reflex venoconstriction.
    • To quantify the contribution of sympathetic nervous system activity to venoconstriction.
    • To assess basal capacity vessel tone in anesthetized dogs.

    Main Methods:

    • Measurement of mean circulatory filling pressure (Pmc) in chloralose-anesthetized dogs.

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  • Induction of maximal sympathetic discharge via 1-minute cardiac fibrillation.
  • Controlled blood withdrawal to maintain constant Pmc during fibrillation.
  • Comparison of blood withdrawal volumes with and without autonomic nervous system blockade (hexamethonium).

    • Main Results:

    • Maximal active reflex venoconstriction induced by circulatory arrest was 9.0 ml/kg during the first minute of cardiac fibrillation.
    • Autonomic blockade with hexamethonium reduced the required blood withdrawal to 4.8 ml/kg, indicating the role of the sympathetic nervous system.
    • A basal capacity vessel tone equivalent to 10 ml/kg was observed under experimental conditions.

    Conclusions:

    • The sympathetic nervous system significantly contributes to active reflex venoconstriction.
    • Circulatory arrest effectively induces maximal sympathetic discharge, allowing quantification of venoconstrictive capacity.
    • The findings highlight the substantial role of venous tone in cardiovascular regulation.