Testing was conducted as previously described (Burgdorf et al., 2015b (link)), and the first extinction tests occurred 1 hour postdosing. On the contextual fear training day (D0), animals were placed in a Coulbourn Instruments shock chamber (40 × 40 × 40 cm) for 400 seconds and received three 0.5-mA 1-s footshocks delivered to the floor bars at 90-, 210-, and 330-second timepoints. During extinction, rats were subjected to daily 5-minute nonreinforced (no shock) extinction trials for the first 6 days after training and on day 14 posttraining (consolidation trial). Freezing was quantified via FreezeFrame software (Actimetrics) during the last 3 minutes of each extinction trial. Animals were dosed with a single optimal dose of IGFBP2 (1 µg/kg i.v.), IGF1 (100 µg/kg i.v.), or sterile saline vehicle (1 mL/kg i.v.) 1 hour before the first extinction session (n = 9–11/group).