Mescaline's positive inotropic effect in rat atria is secondary to its negative chronotropic effect and is not mediated by histamine receptors.
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.