Fig. 2

D2R upregulation in D2-MSNs leads to reduced local collateral transmission. a Inhibitory postsynaptic currents (IPSCs) were evoked by blue light illumination of MSNs co-expressing ChR2 and D2R or ChR2 and EGFP in NAc slices. oIPSCs were recorded from neighboring non-fluorescent MSNs. b Individual (gray) and average (black) traces oIPSC traces (gray) from representative MSNs following five 50-ms light pulses (1 Hz). Bicuculline (10 µM) eliminated the oIPSC. c Peak oIPSC amplitude under basal conditions was significantly reduced when D2Rs were overexpressed in D2-MSNs [n = 11 cells (6 mice) or 14 cells (9 mice)]. d, e Treatment with quinpirole (1 µM) reduced oIPSC amplitude in both groups, though to a greater extent in D2R-OE mice [n = 10 cells (6 mice) or 14 cells (9 mice)]. f Quinpirole showed an inhibitory effect on oIPSC amplitude in >90% of cells recorded in both groups. g Sulpiride co-treatment (1 µM) reversed the effect of quinpirole on peak oIPSC amplitude [n = 7 cells (4 mice) or 11 cells (8 mice)]. Error bars = s.e.m.