Demonstration of an imipramine endacoid in rat brain

The partial purification and characterization of an imipramine endacoid from rat brain is reported. High affinity 3H-imipramine binding as well as 3H-serotonin uptake in both brain and platelet preparations is inhibited in a dose-dependent fashion by the endogenous substance. The effect of the endogenous factor appears to be specific since it does not affect the binding of other drugs to their membrane receptors. The substance is resistant to proteolytic enzymes and is unevenly distributed in rat brain being highly concentrated in the hypothalamus and striatum. Its concentration in rat brain is not changed after repeated electroconvulsive shock treatment.