Catalepsy and hyperkinesis induced by the chronic injection of a tetrapeptide into the neostriatum

The influence on behavior of the chronic (over the course of three weeks) injection of leu-enkephalin and its analog, a tetrapeptide, in doses of 5 and 15 micrograms, into the neostriatum was investigated in experiments on rats. Native enkephalin had little effect, but the tetrapeptide in both doses blocked conditioned reflex avoidance behavior and induced a set of complex changes in behavior. Catalepsy with pronounced waxy rigidity of the skeletal musculature was the main element of the pathological behavior. Stereotypical slow movements of the head and forelimbs began to predominate on the second week of the microinjections. Changes in behavior but without catalepsy and hyperkinesis were observed on the following days. It is hypothesized that the phenomena described are associated with reorganizations of neuromediator systems that accompany the chronic influence on the opiate system of the neostriatum. The role of the enkephalinergic system in the genesis of psychomotor deviations is discussed, as well as the possibility of obtaining through the method utilized of models of neurological and psychopathological deviations.