The expression of STD LTP is mediated by the insertion of GluR2-lacking AMPARs on VTA neurons. A , Time course of mean EPSPs (n = 4) before and after the STD LTP induction protocol indicated by the arrow. The horizontal black bar represents the time of NASPM bath application (100 μm, 15 min). B , Summary of the magnitude of EPSPs in baseline, 25–30 min after LTP induction, and 0–5 min after NASPM exposure. **p < 0.01. Error bars represent SEM.