Fig. 3.

Pharmacological blockade of dopamine-induced receptor internalization. Fresh frozen striatal sections were treated with dopamine alone (100 μM) or dopamine plus eticlopride (100 nM) for 30 min as described in Fig. 1. Arrows denote representative staining in medium diameter neurons. Asterisks are placed in the unstained fiber bundles of the descending cortical fibers that penetrate the parenchyma of the rodent striatum. Upper Panels: dopamine pretreatment promotes a loss of receptor immunoreactivity in wild-type tissue and this is blocked by eticlopride. Lower Panels: there is no effect of dopamine on receptor internalization in arrestin3 knockout tissue in the presence of absence of eticlopride. This experiment was performed 2-5 times with the average results presented in Fig. 2.