[Catalepsy and hyperkinesis induced by the chronic administration of a tetrapeptide into the rat neostriatum].

The effect of bilateral intrastriatal daily microinjection of 5 and 15 micrograms of ley-enkephalin and its synthetic analog tetrapeptide during 3 weeks on behaviour, was investigated. No obvious effect was obtained after ley-enkephalin microinjections. The tetrapeptide produced obvious cataleptic status with plastic rigidity of skeletal muscles. Starting from the 2nd week of tetrapeptide microinjections, the upper arms developed a stereotyped hyperkinesis. No avoidance conditioning was possible. The findings suggest an involvement of the enkephalin neostriatal system in pathological behaviour as an analog of psychopathological disorders in humans.