Stress and corticosterone administered 12 h after fear conditioning selectively enhanced the persistence but not formation of long-term memory.

<p>(A) Rats were exposed to cold water stress or administered corticosterone 1, 12, or 24 h after weak contextual fear conditioning (CFC) and then tested for long-term memory (LTM) on day 2 and day 7. (B) Stress exposure 1 h after CFC enhanced LTM formation tested on day 2, whereas stress exposure 12 h after CFC selectively enhanced the persistence of LTM tested on day 7 but did not affect LTM formation tested on day 2. (C) Corticosterone administration 1 h after CFC enhanced LTM formation tested on day 2, whereas corticosterone administration 12 h after CFC selectively enhanced the persistence of LTM tested on day 7 but did not affect LTM formation tested on day 2. The data are expressed as mean ± SEM (<i>n</i> = 6–9 per group). *<i>p</i><0.05, compared with Control group.