Multifocal brain sites for apomorphine-induced circling and other stereotyped motor behaviour in the 6-hydroxydopamine-lesioned rat

Abstract Rats pretreated with 6-hydroxydopamine (6-OHDA, 8μg in 4 μl) in one medial forebrain bundle exhibited an assortment of stereotyped activities and pronounced circling towards the unlesioned side when apomorphine was administered either subcutaneously (0.5 mg/kg), or by discrete stereotaxic injection (5 μg in 0.2 μl) into the caudate nucleus, nucleus accumbens, amygdala, lateral habenula, ventromedial thalamus, substantia nigra zona reticulata, periaqueductal grey or superior colliculus (but not a variety of other areas) ipsilateral to the lesion. These rotational responses were absent in unlesioned animals and, where tested, were attenuated by intraperitoneal haloperidol (0.5 mg/kg). It is suggested that multiple brain sites become sensitive to apomorphine following dopamine depletion by 6-OHDA.