Evaluation of the effect on heart rate variability of a beta2-adrenoceptor agonist and antagonist using non-linear...

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Regulation
• Pharmacology

Background:

• Heart rate variability (HRV) reflects autonomic nervous system (ANS) activity.
• The cardiac beta2-adrenoceptor's role in modulating HRV is not fully understood.
• Investigating beta2-adrenoceptor modulation of HRV can provide insights into cardiovascular control.

Purpose of the Study:

• To determine the effects of cardiac beta2-adrenoceptor agonism and antagonism on HRV in healthy individuals.
• To analyze changes in HRV using both standard time-domain statistics and advanced non-linear methods.
• To assess the impact of salbutamol (agonist) and ICI 118,551 (antagonist) on autonomic balance.

Main Methods:

• A double-blind, randomized, Latin square design study involving 17 healthy volunteers.
• Administration of placebo, salbutamol, ICI 118,551, or a combination of salbutamol and ICI 118,551.
• HRV assessment using time-domain (SDNN, SDANN) and non-linear (scatterplot, quadrant analysis) methods on sleeping heart rates.

Main Results:

• Salbutamol significantly reduced HRV time-domain indicators (SDNN, SDANN) and scatterplot parameters (length, area) compared to placebo.
• Salbutamol increased cardiac acceleration episodes and reduced beat-to-beat differences.
• ICI 118,551 alone did not affect HRV, but it blocked the effects of salbutamol when administered concurrently.

Conclusions:

• Agonism at the cardiac beta2-adrenoceptor shifts autonomic balance towards sympathetic dominance in healthy volunteers.
• Antagonism with ICI 118,551 alone does not significantly alter HRV, but it counteracts beta2-adrenoceptor agonist effects.
• The beta2-adrenoceptor plays a significant role in modulating HRV, warranting further investigation in cardiovascular disease states.