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. 2012 Apr 11;7(4):e34963. doi: 10.1371/journal.pone.0034963

Figure 2. Expression of conditioned fear is altered in GRPR KO mice after single-pairing but not multiple-pairing conditioning.

Figure 2

A,B) Fear conditioning was induced by a single CS-US (tone-shock) pairing in context 1. 24 h and 2 weeks later the freezing response in the same context was tested A and response to the cue alone was tested in a new context B (WT n = 12, GRPR KO n = 11). C,D) To test for extinction of conditioned fear GRPR KO (n = 12) and WT mice (n = 11) were subjected to multiple CS-US (tone-shock) pairing in context 1. Freezing levels during acquisition are shown in the inset in C. C) At the start of extinction training, baseline (pre-cue) and cue-related freezing responses were tested in a new context. D) At the end of 4 days of extinction training, the freezing response to the cue was tested in mice that were handled but not given the training (no Extinction; n = 12) and mice subjected to extinction training (Extinction; 10 presentations of CS alone each day).