Selective down-regulation of D1 dopamine mediated rotational behavior in supersensitive mice

The effects of continuous exposure to selective D1 and D2 agonists on rotational behavior were examined in mice with unilateral 6-hydroxydopamine-induced lesions of the corpus striatum. Continuously exposing mice to the D1 agonist SKF 38393 produced an initial rotational behavioral response which decreased dramatically within 4 hours. At the time these rotations ceased, the mice were totally unresponsive to an acute challenge injection of SKF 38393 but responded normally to an acute injection of the D2 agonist quinpirole. Mice chronically implanted with quinpirole also showed marked rotational behavior, but in contrast to the results with SKF 38393, essentially no diminution of these rotations was seen during a one week period of exposure. The results suggest that there are different mechanisms involved in the long term regulation of D1 and D2 dopamine systems in supersensitive animals.