Biochemical basis of an animal model of depressive illness--a preliminary report--.

Biochemical analyses of brain samples of an Animal Model of Depression indicate the state of motionlessness observed in response to a conditioned stimulus was due to an excess in functional activity of serotonin. An excess functional activity of serotonin may be directly responsible for human depressive illness. This conflicting conclusion to the currently popular theories of serotonin deficiency was discussed with reference to the animal and clinical data in the literature which are consistent with the conclusion.