Effect of ethanol on guinea pig ventricular action potentials

Area of Science:

• Cardiology
• Pharmacology
• Electrophysiology

Background:

• Ethanol's effects on cardiac function are complex.
• Understanding ethanol's impact on cardiac action potentials is crucial for cardiovascular research.

Purpose of the Study:

• To investigate the effects of low ethanol concentrations on guinea pig ventricular muscle transmembrane potentials.
• To elucidate the mechanisms underlying ethanol's influence on cardiac electrophysiology.

Main Methods:

• Papillary muscles were superfused in vitro and driven at a constant rate.
• Transmembrane potentials were recorded using intracellular microelectrodes.
• Exposure to varying ethanol concentrations (2.5-40 mg/100 ml) was performed, with and without verapamil, propranolol, and norepinephrine.

Main Results:

• Ethanol concentrations of 5 and 40 mg/100 ml enhanced action potential amplitude (AAP) without altering resting membrane potential (MRP) or maximum upstroke velocity (dV/dt).
• Verapamil and propranolol inhibited ethanol's AAP-augmenting effect.
• Ethanol enhanced norepinephrine-restored potentials in high [K+] depolarized fibers, shifting the plateau to more positive values without affecting action potential duration.

Conclusions:

• Low-concentration ethanol augments the slow component of the ventricular action potential upstroke.
• This augmentation appears to be mediated by catecholamines and involves a verapamil- and propranolol-sensitive mechanism.
• Ethanol's effects on cardiac electrophysiology are concentration-dependent and involve modulation of specific ion channel functions.