Fig. 5.

An mGlu₃ NAM impairs fear extinction learning in mice. (A) On day 1, mice were fear conditioned with 7 paired CS–US trials. No drug was administered on the conditioning day. (B) On day 2, mice received an i.p. injection of vehicle or the mGlu₃ NAM VU0477950 (3–100 mg/kg) and then were trained on fear extinction with 20 CS-alone trials. Data are presented as mean freezing across 4 consecutive trials. * indicates P < 0.05, 100-mg/kg Bonferroni posttest vs. vehicle-treated mice. (C) Extinction learning criterion was established by examining asymptotic learning (shaded horizontal line) across all 20 CS-alone trials in vehicle-treated animals. Freezing behavior of mice treated with 100 mg/kg is plotted for comparison. (D) Quantification of the learning impairment induced by VU0477950 as measured by trials to criterion. Numbers within the individual bars indicate number of mice within the respective group. * indicates P < 0.05 Tukey posttest vs. vehicle and 3-mg/kg–treated mice. Data are expressed as mean ± SEM.