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. Author manuscript; available in PMC: 2014 Jun 5.
Published in final edited form as: Sci Transl Med. 2013 Jun 5;5(188):188ra73. doi: 10.1126/scitranslmed.3005656

Fig. 3. Differential regulation of Oprl1 in the amygdala during cued-fear conditioning and cued-fear expression in a PTSD-like mouse model.

Fig. 3

(A) Immobilization-fear conditioning (IMO-FC) and control-fear conditioning (Ctrl-FC) groups equally acquired cued-fear conditioning. IMO in the absence of fear conditioning did not elicit freezing (IMO-NoFC). During the cued-fear expression (Exp) test, the IMO-FC group presented enhanced freezing relative to the nonstressed fear conditioned group (***P ≤ 0.001, IMO-FC versus IMO-NoFC, repeated-measures ANOVA followed by Bonferroni post-test; +P < 0.05, ++P ≤ 0.01, +++P ≤ 0.001, IMO-FC versus Ctrl-FC, repeated-measures ANOVA followed by Bonferroni post-test) (n = 10 mice per group). IMO alone did not induce freezing in the fear expression test. The term “microarray” and the line (under fear expression) denote that at 2 hours after fear expression, microarray analysis was performed to identify differential gene expression in the IMO-FC and Ctrl-FC groups. (B) During fear conditioning, the control-fear conditioning group (Ctrl-FC) presents discrimination of the conditioned stimulus 5 (CS5) presentation versus the intertrial interval (ITI) (period between stimulus) (**P ≤ 0.01, repeated-measures ANOVA followed by Bonferroni post-test), whereas the IMO-fear conditioning group (IMO-FC) does not. (C) mRNA microarray analysis of amygdala tissue showing 45,281 transcripts of amygdala mRNA, obtained 2 hours after fear expression (n = 4 mice per group). (D) Selection of the 1963 probes (4.34%) that present statistically significant changes in control-fear expression (Ctrl-Exp) group versus the IMO-fear expression (IMO-Exp) group. (E) Oprl1 mRNA is down-regulated in the control-fear expression (Ctrl-Exp) group versus the IMO-fear expression (IMO-Exp) group (*P < 0.05, ANOVA followed by Bonferroni post-test). (F) Oprl1 mRNA is highly expressed in the mouse central amygdala (red arrow) (12). (G) In replication studies, fear conditioning induces down-regulation of Oprl1 mRNA in the amygdala of control-fear conditioned (Ctrl-FC) mice [*P < 0.05 versus home cage group (HC), ANOVA followed by Bonferroni post-test, n = 8 mice per group]. The mice in the home cage group were undisturbed in the vivarium and had compensatory handling the same days that the IMO mice were exposed to stress. (H) The cued-fear expression test also induced down-regulation of Oprl1 mRNA in the amygdala of the control-fear conditioning group (Crl-FC) (*P < 0.05 versus HC, **P ≤ 0.01 versus IMO-FC, ANOVA followed by Bonferroni post-test; n = 8 mice per group).