Contextual Fear Conditioning

We performed contextual fear conditioning experiments using 12 wild-type mice and 10 Pafah1b1^+/− littermates maintained on a C57BL/6 J background. Mice were moved into the testing room, randomly distributed into five groups (experimenter was blind to animal genotype) and allowed to habituate to light and room for one hour prior to each phase of the experiment. On the first day (training), mice were placed in the fear conditioning apparatus (context A) and monitored for 5 min to measure baseline freezing activity. Then, four 2-second, 0.45 mA foot shocks were presented, separated by 120-second inter-trial intervals during which freezing was monitored, with a 60 second end period following the last foot shock. The next day (context test), mice were placed in the identical fear conditioning chamber for 8 minutes; no shock was presented and the amount of freezing was measured. On the third day (generalization test), mice were placed in a different fear conditioning chamber (context B; altered by inserting a black triangular insert, turning the fan off, spraying trays with acetic acid instead of Simple Green, and inserting a staggered-bar floor grid) and monitored for 8 minutes. At the conclusion of the three day testing period, mice were returned to the animal housing room. A delay test was performed 27 days later by measuring freezing behavior in context A, followed 24 hrs later by context B.