D1 dopamine receptors influence Fos immunoreactivity in the globus pallidus and subthalamic nucleus of intact and nigrostriatal-lesioned rats.

Studies of the globus pallidus (GP) and subthalamic nucleus (STN) have emphasized the role of D2 dopamine receptors, although effects of D1 receptor activation on GP firing rate and STN metabolism have been reported, especially in rats with nigrostriatal lesions. This study systematically investigated the effects of D1 and D2 receptor activation on the activity of the GP and STN in intact and 6-OHDA-lesioned rats using immunostaining for the immediate-early gene Fos. In intact rats, the D1 agonist SKF 38393 (20.0 mg/kg) produced a five-fold potentiation of the GP Fos expression due to the D2 agonist quinpirole produced significant Fos expression. In rats with prior nigrostriatal lesions, SKF 38393 (4.0 or 20.0 mg/kg) increased Fos immunostaining in both the GP and STN, while quinpirole increased it only in the GP. SKF 38393 effects in the GP and STN of nigrostriatal-lesioned rats were blocked completely by SCH 23390, and unaffected by eticlopride. These results are a novel demonstration of control of Fos expression by dopaminergic drugs in the STN and by D1 agonists in the GP.