Studies with trimipramine on isolated kitten atria.

The effect of different doses of trimipramine has been studied on the force of contraction of isolated kitten atria. Trimipramine produced dose dependent increase in the force of contraction of the atria. Pretreatment of kitten with reserpine or of the isolated atria with propranolol inhibited the positive inotropic effect of trimpramine. The positive inotropic action of trimipramine is probably due to the release and /or due to blocking the uptake of spontaneously released noradrenaline. Trimipramine was also found to potentiate the positive inotropic action of noradrenaline. This potentiation not only decreased in relation to the time of exposure of the isolated atria to trimipramine but also the action of noradrenaline was antagonised.