Summary
Characteristics of thrombi produced upon electrical stimulation of mesentery and brain
vessels were studied in five species. Parameters for measuring drug effects were also
evaluated to determine which were sensitive to platelet aggregation inhibitors. The
current required to cause vasoconstriction in 50% of the rat mesentery arteries stimulated
was increased by vasodilators, but not by inhibitors of platelet aggregation. The
threshold of current necessary to cause thrombus formation was increased by Imipramine
in both acute and chronic experiments and by aspirin and papaverine in chronic experiments.
Since these were the only agents tested which inhibit platelet aggregation there appears
to be a relationship between this property and the threshold of current necessary
to cause thrombus formation. This parameter may possibly be used to differentiate
between platelet aggregation inhibitors and streptokinase-like or heparin-like agents.
Changes in mean embolization time under present conditions were not related to activity
in inhibiting platelet aggregation.
