Resumo

Introduction: Benzodiazepines such as diazepam (DZP) have amnestic properties, while GABA antagonists such as pentylenetetrazole (PTZ) improve memory in rats submitted to learning tasks. A relationship between these results with anxiolytic and anxiogenic effects, at least for acquisition of memory, has been suggested. The present study aimed to verify the effects of DZP and PTZ on retrieval of aversive memories and anxiety, concomitantly, verifying a possible relationship between these two variables on the elevated plus-maze discriminative avoidance task. Methods and Results: The modified elevated plus-maze – a model designed to assess anxiety and memory simultaneously, consists of two open opposite of two enclosed arms. One of enclosed arm is paired with aversive stimuli (light and noise) which were produced every time the animal entered the aversive arm. During the Training Session, Female Wistar Rats were placed in the center of the apparatus, for 10 min. In order to avoid one-trial-tolerance (OTT) phenomenon upon subsequent test session, transparent glass walls were used to block open arms entries. After 24h, during the test, the glass walls were removed and no aversive stimuli was presented. The animals received DZP, PTZ or Saline (i.p.) twenty minutes before this test session. The time spent in each arm and the distance traveled were registered. In the test session the animals treated with DZP presented an increase in the distance travelled (mean+-PE 26.0+-1.6m to DZP and 17.4+-2.3m to SAL) and in the exploration of open arms (19.6+-5.8% to DZP and 6,8+-2,5% to SAL), revealing an anxiolytic effect, while animals treated with PTZ presented reduction in distance travelled (10.2+-2.6m to PTZ and 28.8+-3.4m to SAL) and exploration of open arms (2.6+-2.4% to PTZ and 27.2+-3.8% to SAL), exhibiting an anxiogenic effect. As well, an increase in the exploration of aversive arms was detected for the DZP group (57.6+-7.4% to DZP and 30.2+-5.6% to SAL), but not for the PTZ group. Thus, a memory impairment was verified by the DZP treated group. The Pearson’s test did not show statistical correlation between open arms and aversive arms exploration for any of the groups. Conclusion: DZP impaired memory retrieval, suggesting that benzodiazepines can induce retrograde amnesia as well. Despite the fact that the DZP-treated animals presented memory impairment and anxiety reduction, these variables did not correlate, suggesting that the memory impairing is not a secondary effect of the anxiolysis induced by the drug. In addition, both DZP and PTZ group presented, respectively, anxiolytic and anxiogenic effects in the test session, indicating that previous exposition to the apparatus did not induced the OTT phenomenon in the test session. Therefore, the suggested model is efficient in avoiding OTT phenomenon in a second exposition to the apparatus and might be an useful model to the study relationships between anxiety and the retrieval of aversive memories.