Figure 5.

Between-session extinction is impaired in NPY KO and Y_1/Y₂ receptor double KO mice. (A) Impaired extinction in NPY KO mice shown by higher % of freezing to the first CS of day 2 (early extinction), day 3 (late extinction) and day 4 (extinction recall); (B) a delayed extinction was observed for Y₁ receptor KO mice evidenced by increased % of freezing to the first CS on day 2 but not on day 3 (extinction recall), (C) no change in % of freezing between WT and Y₂ receptor KO mice on all three consecutive extinction days, (D) increased % of freezing of Y_1/Y₂ receptor KO mice is demonstrated on days 3 and 4, indicating impaired between-session extinction. Data shown are means ± SEM, repeated two-way anova with Bonferroni post hoc test, *P < 0.05, ***P < 0.001.