Figure 1:

Experimental outline. HAP3 mice were either presented with a three-day juvenile stress regimen (JS) or left undisturbed until behavioral testing started in adulthood (no JS). The conditioning paradigm consisted of a discriminative conditioning phase and a retardation of fear acquisition phase, each lasting 8 days with a 9-day break in between them. During conditioning (1/day, in the afternoon) mice were presented with 5 fear cue-foot shock pairings and 10 unreinforced safety cues. Fear potentiated startle (FPS) was assessed daily in the morning of these 8 days. FPS test sessions contained random presentations of 10 noise alone trials, 10 fear and 10 safety cues, as well as 10 compound safety+fear cues, each followed by the startle noise. During retardation conditioning the former safety cue was now paired with a footshock (5/session, 8 sessions on 8 consecutive days) and during FPS-retardation 10 former safety/now fear cues were followed by the startle noise. A tone (10kHz, 100dB, 20s) and a light (6W, 20s) served as the conditioned stimuli and were counter-balanced across groups and sexes (i.e. for half of each group the light was the safety cue, the tone was the fear cue, and vice versa for the other half). PND: postnatal day, FPS: fear potentiated startle, DC: discriminative conditioning, RET: retardation conditioning, FPS-R: fear potentiated startle-retardation.