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 of contextual fear memories after retrieval in animals that had experienced multiple reactivation sessions.
Male Wistar rats were subjected on day 1 to a contextual fear conditioning paradigm (3 shocks, 0.5 mA). On day 3 and day 5 one group of rats (3R) were re-exposed to the training context (A) for 3min. The control group (1R) remained in the home cage. Seven days after training, both groups were re-exposed to A for 3min. and immediately administered (i.p.) either with SAL or MDZ 3 mg/kg,. One day later, rats were tested in A. The results showed that MDZ does not affect reconsolidation only in 3R rats. In addition, we tested the influence of pre-reactivation D-cycloserine (DCS) on MDZ´s effect on fear memory reconsolidation.
We then asked whether the process of retrieval induced-lability would mediate the resistance to disruption. To answer this, another group (2R-90s) were trained on day 1 and briefly (90 s) re-exposed to A on day 3 and day 5.
The results showed that MDZ does not affect reconsolidation only in rats subjected to multiple reactivation sessions of 3 min. duration (3R).
Our evidence showed that: a) Multiple reactivation-labilitation session prevents MDZ?s disruptive effect on fear memory reconsolidation b) DCS prior to reactivation promotes retrieval-induced lability in such resistant memory trace and (c) retrieval-induced fragility enables such memory resistance upon reactivation.
