The mean (±SEM) unconditioned response (UR), magnitude of the response (a), and magnitude of the area (b) to the 0.25 mA unconditioned stimulus (US) intensity for the first 20 trials of each of four US tests for groups receiving saline or fluoxetine (0.03, 0.3, 3.0 mg/kg). Pretest (white bar) and Post1 (black bar) took place before and following conditioning, respectively, whereas Post2 (gray bar) and Post3 (striped bar) occurred 1 day and 1 week following the cessation of 5 days of drug treatment.