Effects of alpha adrenergic stimulation on time independent potassium current of isolated ventricular myocytes

The role of alpha adrenergic receptor stimulation on ventricular electrical activity is controversial. The aim of the present paper was to study a wide range of concentrations of alpha adrenergic agonists on the electrical properties of guinea pig's heart isolated ventricular myocytes. The experiments were performed according to the single electrode voltage clamp technique. Phenylephrine and epinephrine (in the presence of propranolol) were used at concentrations from 1 x 10(-9) to 10(-5) M. It was observed that both agonists induce an increase in the time independent inward rectifying potassium current (IK1), that could explain the shortening of the action potential. All the observed effects were dose-dependent and disappeared during washout. These results could explain, at least partially, some of the electrical changes observed during ischemia.