Resumo

Introduction: Consolidation is a temporal graded post-acquisition stabilization of memory trace, in which long-term memory becomes resistant to interferences and treatments, such as anisomycin (ANI), a drug which blocks the wave of protein synthesis necessary for memory stabilization. The dorsal hippocampus (DH), structure primarily related to the cognitive process of learning and memory associations, appears to have a critical role on this process. Rats retested in the elevated plus-maze express further avoidance to open-arms, which is thought to reflect a retrieval of an aversive memory acquired on testing. Objective: The aim of the present study was to investigate the contribution of DH protein synthesis in the consolidation of the aversive memory using the elevated plus-maze test/retest protocol. Methods: Male Wistar rats, aged three-months, were bilaterally implanted with guide cannulas aimed at the DH. One-week later, they were allocated to eight groups (n=7-10/group) based on the drug treatment [phosphate buffered-saline (vehicle) or ANI (80 μg) in 0.8 μl/side] and the moment of these infusions (15 min pre-test, immediately after, 3 or 6 h after test) into the DH. On the next day, all groups were retested in the EPM. Behavioral measures scored during 5 min in both test and retest were the percentage of open-arms entries (%OAE) and time (%OAT), stretched-attend postures (SAPs) and enclosed-arms entries (EAE). The ANI dose selection was based on studies published elsewhere and experimental design abovementioned was approved by the local Ethical Committee in Animal Research (068/CEUA/PRPe/UFSC/2008). Results: Repeated-measures analysis of variance showed that vehicle- and ANI-treated groups, independent of infusion time point, expressed more avoidance to open-arms during the elevated plus-maze retest when compared to their respective level on testing, characterized by reduced %OAT [F(1,68) = 116.16; P < 0.0001; test (mean ± S.E.M) = 15.2 ± 1.4 % and retest = 1.4 ± 0.3 %] and %OAE [F(1,68) = 119.74; P < 0.0001; test = 29.6 ± 1.8 % and retest = 7.0 ± 1.3 %]. Importantly, these results were observed in the absence of changes in EAE, an elevated plus-maze index of general exploratory activity. No statistically significant differences were observed for SAPs. Discussion: Neither the DH protein synthesis inhibition induced by ANI before testing (15 min) nor post-testing (0, 3 or 6 h) was able to interfere with the additional avoidance to open-arms demonstrated on elevated plus-maze retesting, suggesting the critical molecular steps necessary for consolidation of this aversive memory may take place outside DH.