Biochemical and Electroencephalographic Changes in the Brain of Rabbits Injected With 5-Hydroxytryptophan (Influence of Chlorpromazine Premedication)

Abstract

After the administration of 5HTP (75 mg/kg i.v.) to rabbits, the serotonin concentration increased significantly in the telencephalon, the hippocampus, the medulla-pons and most of all in the midbrain; in the cerebellum the increase was much less. The augmentation of serotonin concentration occurred during the first 2 hours after the injection of 5HTP and reached its maximum at the 2nd hour. At the 3rd hour a decline toward more normal values was observed. During the first 2 hours after the injection of 5HTP behavioral changes (excitation with unresponsiveness to alarming stimuli), as well as EEG changes (monorhythmic diffuse high voltage activity; disappearance of cortical fast rhythms and hippocampal theta waves followed by a generalized depression of voltage) occurred. The administration of chlorpromazine alone does not modify the serotonin content of the brain. But in the various brain parts of chlorpromazine pretreated animals the administration of 5HTP caused increases of serotonin concentration which were of greater magnitude and longer duration than those found in animals treated with only 5HTP. When animals were pretreated with chlorpromazine, the injection of 5HTP did not produce behavioral hyperexcitation and the animals did not arouse from chlorpromazine tranquilization.