The retrieval of a consolidated memory results into a labile phase, which is vulnerable to the interference by benzodiazepines. The aim of the present study was to assess MDZ vulnerability after retrieval of a strong contextual fear memories or after retrieval of a contextual fear memory in animals that had experienced a stressful situation prior to acquisition.
Male Wistar rats were subjected on day 1 to a stressful session and on day 2 submitted to a contextual fear conditioning paradigm (3 shocks, 0.25 mA) and 7 days after training re-exposed to the training context (A) for 3 or 5 min. A separate group of rats were conditioned with a strong training protocol (5 shocks, 0.25 mA) and 7 days after re-exposed to the training context (A) for 3 or 5 min .Immediately after retrieval all rats were administered (i.p.) either with SAL or MDZ 1.5 mg/kg,. One day later, rats were tested in A. The results showed that MDZ does not affect reconsolidation of a 7-day fear memory in stressed animals and in stronger memories regardless of the duration of the re-exposure period and the MDZ doses used. In addition, we tested the influence of pre-reactivation D-cycloserine (DCS) on MDZ´s effect on fear memory reconsolidation. Our evidence showed that: a) Previous stress or a strong memory prevents MDZ?s disruptive effect on fear memory reconsolidation and b) DCS prior to reactivation promotes retrieval-induced lability in such resistant memory traces.
