ORAL STEREOTYPY INDUCED BY AMPHETAMINE MICROINJECTION INTO STRIATUM -AN ANATOMICAL MAPPING STUDY

The ventrolateral striatum has been shown to specifically contribute t o expression of psychostimulant-induced orofacial stereotypies. Adult male Sprague-Dawley rats were implanted with bilateral cannulae direct ed at one of eight striatal subareas, and were injected with saline or amphetamine (20 mu g/0.5 mu l/side) in a counterbalanced order. Behav iors were observed and scored using a time-sampling procedure. In the middle ventrolateral striatum, amphetamine injections produced intense stereotypy, primarily consisting of bar biting, non-injurious self-bi ting and repetitive paw-to-mouth movements, while having no effect on locomotion or rearing. Amphetamine injections 2 mm medial or 1 mm dors al produced no oral stereotypy, while injections 1 mm rostral or cauda l to the effective site produced only low levels of stereotypy. Inject ions into the surrounding sites, particularly in the ventromedial regi on, also had stimulatory effects on locomotion and rearing. In a separ ate experiment, animals were given either unilateral or bilateral inje ction of amphetamine into the ventrolateral striatum. The unilateral i njection produced stereotypy half as intense as that observed with bil ateral injections. These results suggest that the ventrolateral striat um is a discrete neuroanatomical region which is primarily responsible for expression of psychostimulant-induced orofacial stereotypies, and which is likely to be the striatal region controlling normal oral mot or function. Further investigation of this area may provide valuable i nsights concerning the etiology and treatment of orofacial dyskinesias associated with basal ganglia dysfunction.