Behavioral performance on the place discrimination in experiment 1. Each rat received bilateral infusions of saline (Sal) or one of three different doses of Bac–Mus into the Pf 5 min before each test session. The treatments on the x-axis represent the treatment received before acquisition (top) and before reversal learning (bottom). A, Mean ± SEM trials to criterion on place acquisition. Infusion of Bac–Mus had no effect on acquisition. B, Mean ± SEM trials to criterion on place reversal learning. The middle and high dose of Bac–Mus significantly impaired reversal learning. *p < 0.05 versus saline/saline, Bac–Mus/saline, and saline/Bac–Mus low dose. **p < 0.01 versus saline/saline, Bac–Mus/saline, and saline/ Bac–Mus low dose. C, Mean ± SEM perseverative errors committed during reversal learning. Bac–Mus treatment did not affect the number of perseverative errors. D, Mean ± SEM regressive errors committed during reversal learning. The middle and high dose of Bac–Mus significantly increased regressive errors. +p < 0.05 versus saline/saline, Bac–Mus/saline, and saline/Bac–Mus low dose. ++p < 0.01 versus saline/saline, Bac–Mus/saline, saline/Bac–Mus low dose, and saline/Bac–Mus high dose.