Dantrolene sodium: effects on isolated cardiac tissues

Area of Science:

• Cardiovascular Pharmacology
• Cardiac Electrophysiology

Background:

• Dantrolene sodium is a muscle relaxant with known effects on calcium handling.
• Its precise impact on cardiac tissue electrophysiology and contractility requires detailed investigation.

Purpose of the Study:

• To investigate the electrophysiological and mechanical effects of dantrolene sodium on different cardiac tissues.
• To elucidate the role of intracellular calcium in mediating dantrolene's cardiac actions.

Main Methods:

• Isolated dog Purkinje fibers and cat atrial and ventricular muscles were utilized.
• Electrophysiological parameters (action potential duration, resting membrane potential, etc.) and contractility were measured.
• Experiments involved varying extracellular calcium concentrations and assessing drug washout effects.

Main Results:

• Dantrolene sodium significantly prolonged action potential duration and decreased contractility in all studied tissues.
• Negative inotropic effects were most prominent in Purkinje fibers, followed by atrial and then ventricular muscle.
• Dantrolene did not significantly alter resting membrane potential, action potential amplitude, or upstroke velocity.
• Reversal of effects was observed with increased extracellular calcium, suggesting a role for intracellular calcium.

Conclusions:

• Dantrolene sodium exerts significant negative inotropic and electrophysiological effects on cardiac tissues.
• These actions are likely mediated, in part, by a reduction in intracellular free calcium concentration.
• The findings have implications for understanding dantrolene's cardiac safety profile and potential therapeutic applications.