Actions of Mescaline on Isolated Rat Atria

Mescaline at concentrations of 5 x 10⁻⁴ and 1 x 10⁻³ M slowed the heart rate (negative chronotropic effect) and increased the force of contraction (positive inotropic effect) in isolated, spontaneously beating rat atria. When the atria were electrically paced at a constant rate, the increase in contraction force was greatly reduced, suggesting the force increase was secondary to the rate decrease. Pretreatment with histamine antagonists chlorpheniramine and metiamide did not consistently alter these responses.

Study at a glance

Abstract

Mescaline, in concentrations of 5 x 10(-4) and 1 x 10(-3) M, produced negative chronotropic and positive inotropic responses in isolated, spontaneously beating rat atria. In tissues driven at a constant rate, the inotropic response was diminished greatly, indicating that the increment in the force of contraction was secondary to the reduction in rate. These chronotropic and inotropic responses were not altered consistently by pretreatment with the histamine antagonists chlorpheniramine and metiamide.