Fig. 2: The effects of an immediate IV ketamine infusion on fear memory in rats.

A The ketamine group (10 mg/kg) exhibited a significant delay in fear extinction when tested 2 days after ketamine infusion. Fear memory extinction was tested with 12 auditory tone trials (each block represents an average of two trials) in novel Context B (days 2 and 3). B The 10 mg/kg dose significantly increased total freezing based on the area under the curve (AUC) calculation. C The second fear extinction test on day 3 indicates a rapid extinction across all groups and there were no significant differences at the end of the fear extinction. D The total freezing behaviors on day 3 based on the AUC calculation were not different between the groups. E The 10 mg/kg ketamine increased contextual fear recall on day 4. F The 10 mg/kg ketamine also increased cued fear recall on day 4. Contextual fear recall is expressed as % freezing of the initial 180-s in Context A and cued fear recall is expressed as % freezing of 300-s after a single 20-s auditory tone presentation (day 4). Data are shown as mean ± SEM (*p < 0.05, **p < 0.01, ***p < 0.001 vs. saline controls)