Effect of mescaline on cardiopulmonary dynamics. Method for determination of right ventricular pressure in the guinea pig

A simple technique for determining contractility, intraventricular pressure, and heart rate in the anesthetized guinea pig

This paper describes a rapid technique for the continuous recording of intraventricular pressure, dP/dt, and heart rate in the anesthetized guinea pig. A 21g needle, attached to a pressure transducer, is inserted through the chest wall into the left ventricle. This provides continuous monitoring of intraventricular pressure; the first derivative of this pressure pulse is dP/dt, an index of inotropic state. The ventricular signal is also used to trigger a cardiotach for the continuous recording of heart rate. Since major surgery is not required, experimental set-up can be completed in 15-20 min with a minimum of trauma to the animal. This model is ideally suited for the determination of cardiovascular parameters following the administration of drugs by several routes (intravenous, oral, intramuscular, subcutaneous). The effects of three distinct inotropic agents: isoproterenol, AR-L57, and ouabain, have been evaluated in this system. Isoproterenol increased heart rate and dP/dt, and caused a transient increase in peak intraventicular pressure. AR-L57 and ouabain increased dP/dt and intraventricular pressure; their effects on heart rate were minimal. Ouabain was active following either oral or intravenous administration.

Actions of mescaline on isolated rat atria

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.