[Effect of a decrease in perfusion pressure on the alpha-adrenergic reactions of the coronary vessels].

Acute dog experiments involving the perfusion of donor coronary arteries demonstrated that alpha-adrenoreceptor stimulation in the presence of a beta-adrenergic block resulted in a 30% drop of coronary flow. This response is maintained at low perfusion coronary blood pressure values (up to 25 +/- 13 mmHg, p less than 0.02), whereas coronary dilatation reserve is already fully depleted at 60 +/- 8 mmHg, suggesting that the degree of coronary arterial stenosis associated with coronary insufficiency may be a decisive factor shaping coronary response to alpha-adrenoreceptor stimulation.