Comparative Effects of Ouabain Upon Contractile Force of Guinea Pig Diaphragm and Heart.

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Abstract
The action of ouabain upon the force of contraction of isolated diaphragm and ventricular strips of guinea pig was studied. The drug increased the force of contraction of both types of muscle at the lower doses, with a greater effect upon cardiac muscle. Higher concentrations decreased the force of contraction of diaphragm and led to the appearance of spontaneous contractions and other evidence of toxicity in heart. The effective concentrations for production of the above effects were similar in the two types of muscle. Skeletal muscular paralysis was also observed in intact guinea pigs following the administration of non-fatal doses of ouabain. Results are discussed in relation to studies on the mechanism of action of cardiac glycosides, in which skeletal muscle preparations are used.