Fig. 3. Effects of intravenous anesthetics on passive avoidance performance. Training day (  A , ○); testing day (  B , •). Saline (Sal), propofol (60 mg/kg, Pro), midazolam (5 mg/kg, Mid), or pentobarbital (15 mg/kg, Pen) was injected immediately after training. The step-through retention latencies were measured 24 h later. **  P < 0.01 as compared with each corresponding value in the saline group (midazolam  vs. saline: U = 6.5,  P = 0.0069; propofol  vs. saline: U = 0,  P = 0.0007). ++  P < 0.01 as compared with each corresponding value in the pentobarbital group (midazolam  vs. pentobarbital: U = 5.5,  P = 0.0042; propofol  vs. pentobarbital: U = 0,  P = 0.0006).