Dopaminergic mechanisms and motor function: characterization of D-1 and D-2 dopamine receptor interactions.

The effect of selective D-1 and D-2 dopamine receptor agonists (SKF 38393 and LY 171555, respectively) on motor function was studied in rats with unilateral, quinolinic acid-induced striatal lesions. Dose-dependent turning ipsilateral to the side of the lesion was elicited by LY 171555, but not by SKF 38393. When the drugs were given together, however, SKF 38393 was able to increase the total number (but not the duration) of turning induced by LY 171555 in a dose-dependent fashion. Furthermore, either alpha-methyl-paratyrosine pretreatment, a DA-depleting agent, or SCH 23390, a D-1 antagonist, inhibited the LY 171555-induced rotation, which would be restored by SKF 38393. These observations suggest that both the D-1 and D-2 dopamine receptor systems participate in the regulation of rotational behaviors in striatally lesioned rats with normosensitive DA receptors.