Fig. 3: TrkA-KFG mice show attenuated freezing behavior in contextual fear conditioning and extinction.
From: TrkA-cholinergic signaling modulates fear encoding and extinction learning in PTSD-like behavior
A Schematic representation of the protocol used to test fear response and extinction after contextual conditioning. B Quantification of the freezing response after contextual conditioning shows a reduced expression of fear (Fear Res as in day 3 in A) by TrkA-KFG mice (% Freezing 72.43 ± 2.95 in WT and 53.04 ± 5.98 in TrkA-KFG) that is maintained over the course of 9 extinction trials (E1–E9 day 4–12 in A) compared to WT mice. N = 13 for WT and 12 for TrkA-KFG mutants. C Graphical representation of the difference in freezing response measured as difference between the original fear response and last extinction trial (Points Fear Res vs E9 in panel B). Note that both WT and TrkA KFG mice show significant, but similar reduction in fear response at the end of the extinction trials (% Freezing 72.43 ± 2.95 vs 41.33 ± 4.79 in WT mice and 53.04 ± 5.98 vs 28.33 ± 3.23 in TrkA-KFG mice. Data are the Mean ± SEM, p < 0.05 Mann–Whitney Test). D Schematic representation of the protocol used to test the fear response and extinction in the SPS stress model. E In the SPS model of PTSD-like behavior, 6 days after stress, the mice were subjected to fear conditioning and extinction protocol as in C. Similarly to the results obtained with non-stressed animals in B, TrkA-KFG mice show attenuated fear response and reduced freezing during the extinction trials when compared to control mice. % Freezing at each timepoint was analyzed by Mann–Whitney Test. *p < 0.05; n = 10 for WT and n = 11 for TrkA-KFG mice. F Graphical representation of the difference in freezing response between the original fear response and the last extinction trial (Points Fear Res vs E9 in panel E) in WT (% freezing 71.92 ± 2.59 vs 59.99 ± 5.43, p > 0.05 n.s.) and TrkA KFG mice (% freezing response 62.08 ± 3.09 vs 39.39 ± 5.82, Data are the Mean ± SEM, p < 0.05 Mann–Whitney Test). Note that only the TrkA KFG mice show a significant reduction in fear response during the extinction trials.
