Melatonin does not affect cued fear acquisition. (A) Schematic of the behavioral procedure used. Behavior procedure involved three training phases: habituation, fear conditioning and test. Rats were administrated melatonin 30 min before conditioning phase. (B) Percent freezing during the five cues was shown for the melatonin group (n = 10) and the vehicle group (n = 10) during conditioning phase. (C) Percent freezing to the five cues during test phase. Mel = melatonin group, Veh = vehicle group. All data are represented as mean ± SEM.