Chronic Flx treatment before fear conditioning leads to fear erasure when combined with extinction training. (A) Flx treatment started 3 weeks before and continued throughout the experiment. (B) Control and Flx groups (n = 31 to 34 mice per group) exhibited similar levels of fear acquisition (extinction day 1, first block of 2 CS) and extinction (extinction day 2, last block of 2 CS). One week later (n = 21 per group) only control group showed spontaneous recovery and fear renewal. In the fear renewal test, the Flx-extinction group froze less than either control-extinction or Flx–no-extinction group (NoExt, n = 5). *P < 0.05, **P < 0.01, ***P < 0.001. Error bars indicate mean ± SEM.