Metyrapone blocked the enhancement of long-term memory formation or persistence induced by stress after fear conditioning.

<p>(A) Rats were pretreated with the corticosterone synthesis inhibitor metyrapone 40 min before exposure to cold water stress 1 or 12 h after weak contextual fear conditioning (CFC) and then tested for long-term memory (LTM) on day 2 and day 7. (B) Metyrapone blocked the effects of stress 1 h after CFC on LTM formation on day 2 and reduced the persistence of LTM tested on day 7. (C) Metyrapone blocked the effects of stress 12 h after CFC on the persistence of LTM tested on day 7, leaving LTM formation tested on day 2 intact. The data are expressed as mean ± SEM (<i>n</i> = 6 per group). *<i>p</i><0.05, compared with Vehicle-No stress group.