The effect of dopamine type-2 receptor blockade on autonomic modulation

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Research
• Pharmacology

Background:

• Dopamine2 (D2)-like receptor antagonists, including metoclopramide (MCP), are used for gastroparesis and vomiting.
• MCP's effects on cardiac autonomic modulation are not fully understood.
• The study investigates MCP's impact on the heart's autonomic control.

Purpose of the Study:

• To investigate the effects of metoclopramide (MCP) on cardiac autonomic modulation.
• To assess MCP's influence on sympathovagal balance using heart rate variability.
• To determine MCP's net effect on the heart during supine and standing positions.

Main Methods:

• Healthy male participants underwent intravenous administration of MCP and placebo in a double-blind, crossover design.
• Continuous electrocardiography recorded heart rate variability during prolonged supine and standing phases.
• Power spectral analysis of heart rate variability (HRV) was used to assess low frequency (LF) and high frequency (HF) components.

Main Results:

• MCP administration prevented the decrease in heart rate and sympathetic drive (LFnu) observed with placebo during prolonged supine rest.
• MCP significantly altered LFnu and the LF/HF ratio, indicating increased sympathetic drive.
• MCP augmented sympathetic drive to the heart during the standing phase compared to placebo.

Conclusions:

• Metoclopramide (MCP) exerts a net effect of increased sympathetic drive to the heart.
• MCP maintains sympathetic drive during supine rest and enhances it during postural changes.
• Findings clarify MCP's cardiovascular autonomic effects, relevant for its clinical use.