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Updated: Jun 19, 2026

Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice
Published on: September 17, 2015
Inotropic Effects of Trains of Impulses Applied during the Contraction of Cardiac Muscle
A J Brady1, B C Abbott, W F Mommaerts
1Department of Medicine (The Los Angeles County Heart Association Cardiovascular Research Laboratory), The University of California, Los Angeles.
Abstract:
THE APPLICATION OF A TRAIN OF SUPRAMAXIMAL STIMULI DURING THE ABSOLUTE REFRACTORY PERIOD OF A CARDIAC MUSCLE PREPARATION HAS TWO EFFECTS: a depression of the contraction during which it is applied, and a large potentiation of subsequent contractions. The former is ascribed to a direct effect upon the cell membrane, and is an indication of the continued control of the contractile event by this membrane. The latter is explained as a sudden liberation of norepinephrine by a stimulation of embedded nerve elements, which norepinephrine then distributes itself through the tissue and finally diffuses away.
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