Fluoxetine potentiation of repeated methylphenidate-induced Zif268 and Homer1a blunting in the middle striatum. Mean density values (mean ± SEM) for Zif268 (A) and Homer1a expression (B) in rats that received 5 injections of vehicle (V), methylphenidate (5 mg/kg; MP), fluoxetine (5 mg/kg; FLX), or methylphenidate + fluoxetine (MP+FLX), followed on day 6 by a vehicle or cocaine challenge (25 mg/kg; C), are given for the medial (m), ventral (v), dorsal (d), central (c), dorsolateral (dl), and ventrolateral (vl) sectors. The potentiation of blunting displayed a medial-lateral gradient, with the most robust effects laterally. *P<0.05, **P<0.01 and ***P<0.001 vs. V/C; #P<0.05, ##P<0.01 and ###P<0.001, MP+FLX/C vs. MP/C (potentiation).