Reflex cardiovascular response to exercise is modulated by circulating vasopressin

Area of Science:

• Cardiovascular Physiology
• Neuroendocrinology
• Exercise Physiology

Background:

• Peripheral vasopressin (AVP) influences central and peripheral cardiovascular regulation.
• Plasma AVP levels rise during exercise, suggesting a role in exercise-induced cardiovascular adjustments.
• The precise mechanism by which AVP modulates the reflex cardiovascular response to static muscle contraction remains unclear.

Purpose of the Study:

• To investigate the role of vasopressin (AVP) in modulating the reflex cardiovascular response to static muscle contraction.
• To determine whether AVP acts via V1 or V2 receptors to influence pressor, myocardial contractile, and heart rate responses during exercise.

Main Methods:

• Anesthetized cats underwent electrically induced static muscle contraction of hindlimb muscles.
• Cardiovascular responses (mean arterial pressure, myocardial contractility, heart rate) were measured before and after administration of V1 receptor antagonist (V1-x), V1 and V2 receptor antagonists (V1-x + V2-x), or ganglionic blocker (hexamethonium).
• Comparisons were made between different treatment groups and sequential administration protocols.

Main Results:

• Intravenous administration of V1-x significantly augmented the pressor and myocardial contractile responses to muscle contraction.
• Combined V1-x and V2-x administration further augmented these responses, with no significant difference compared to V1-x alone.
• Heart rate responses were not altered by V1-x or V1-x + V2-x. Ganglionic blockade abolished all cardiovascular responses to contraction.

Conclusions:

• Peripheral vasopressin (AVP), acting via V1 receptors, contributes to the modulation of pressor and myocardial contractile responses during static muscle contraction.
• The study suggests that AVP's influence on these responses during exercise is primarily mediated through V1 receptor activation.
• The reflex cardiovascular response to muscle contraction is dependent on autonomic ganglionic transmission.