FIGURE 5.

Mean (±SEM) active nose pokes, active nose pokes during the stimulus presentation, and inactive nose pokes in late adolescent male and female rats (n = 23–27/sex) during sucrose training and acquisition training for sucrose/fentanyl-rewarded nose pokes. Rats were pre-treated with fentanyl (10 or 100 μg/kg) or saline from PD 4 to PD 9 and started sucrose training on PD 40. Rats first were trained to nose poke for a sucrose solution and then underwent a four-phase sucrose fade out/fentanyl fade in procedure. ST, sucrose training.