Effect of heroin and pioglitazone on DARPP-32 levels in NAc shell, NAc core, and mPFC. Data are expressed as the positively stained pDARPP-32 cells per square mm in (a) NAc shell, (b) NAc core, and (c) PFC. Animals (n=18) have been trained to self-administer heroin and then divided into two groups and treated with pioglitazone or its vehicle for 3 days before to receive a heroin shot (Her SA/veh/Her shot and Her SA/Pio/Her shot). One more group of rats (n=8) with no history of heroin SA, no Pioglitazone, and no heroin shot has been used as control (veh/veh/veh). Pictures represent p-DARPP-32 immunohistochemistry following heroin self-administration. Scale bar, 100 μm.