[The role of serotonin in one of the types of aggressive behavior--"predatory aggression"]

Electrolytic lesion of the midbrain raphe nuclei in rats, lowering serotonin level in the forebrain, elicited mouse-killing behavior. After the lesion, 50% of previously non-killers rats became mouse-killers. 5-Hydroxytryptophan (100 mg/kg) administration elevated serotonin level to normal values and completely blocked predatory aggression. p-Chlorophenylalanine produced obvious reduction in brain serotonin and slightly stimulated aggressive behavior. These results suggest that the brain serotonin participates as an inhibitory factor in mouse-killing behavior in rats.