Interspecies aggressiveness of rats towards mice after the application of p-chlorophenylalanine.

The administration of pCPA (400 mg/kg) induces in 30% of Wistar rats the potentiation of interspecies aggressiveness and develops in them the instinct to kill mice. It can be supposed that 5-HT system inhibits aggressive behaviour in this type of aggressiveness. Applying mouse killing test it has been stated that cholinergic receptor blockers (atropine, scopolamine) suppress the predatory instinct towards mice in killer rats and the pilocarpine, the cholinomimetic, develops such instinct in rats which previously did not kill mice. The results of the mouse killing test indicate that cholinergic system affects this type of aggressiveness in rats. For the time being, it is difficult to state the correlation between 5-HT and cholinergic system in this type of aggressive behaviour in rats.