EFFECTS OF ANXIETY ON THE ESCAPE BEHAVIOR INDUCED BY THE MICROINJECTION OF NMDA IN THE DORSAL PERIAQUEDUCTAL GRAY Introduction Among the emotional disorders, anxiety and panic attack have been affecting in different levels a great number of individuals, although those mechanisms are being studied for a long time the full comprehension of such phenomena’s have been a challenge. The relationship between anxiety and panic is still unclear. Some authors sustain that anxiety increases the occurrence of panic episodes, while there are clinical reports showing an inverse correlation between anxiety and panic attacks. Animal models have been used as a powerful tools to understand and investigate the systems underlying the mechanisms of anxiety and panic attack. By further understanding the animal defense response we can also determine neural circuits in those syndromes. Objectives The present study investigated the inverse correlation between anxiety and panic attacks in animal models of anxiety. Methodology The escape response induced by local NMDA microinjection in the dorsal periaqueductal grey (dPAG) was employed as an animal model of panic. Freezing to contextual cues previously associated with electric shocks was used as an animal model of anxiety. The relationship between anxiety and panic was studied in Wistar male rats (250g; 12hours light/dark). All the subjects were implanted with a 12,5mm cannula, aimed to dPAG (AP=2.3; DV=4.5; ML=1.7) under standard stereotaxic surgery (Tribromoethanol, 250mg/Kg). Six days later, the animals were randomly assigned to one of two groups: with or without contextual fear conditioning (1sec¡V1,0mA current). Six hours later, half of the rats in each group were microinjected with 0,5ƒÝl NMDA (15ug/ul) or saline solution (0,9%). Immediately after the injection, every rat was allowed to explore an open field (30 minutes). The frequency of jumping and running behavior was analyzed using a computer program. Results None of the animals trained in the contextual fear conditioning ran or shown significant results after the NMDA microinjection, while all the animals without the training ran. Histology The histological analysis shown that the cannulas were located inside or at the border of dPAG, making possible the correct NMDA microinjection in the designed region. Discussion The contextual fear conditioning was capable to inhibit or atenuate the activity burst mechanism induced by NMDA microinjection into dPAG. The activation of such brain mechanisms related to anxiety shown an inhibitory effect in panic attack Conclusion In conclusion, our results suggest that the fear produced by contextual fear conditioning is capable to inhibit or attenuate inate defense reactions induced by NMDA microinjection into dPAG. Those results support the point of view of an inverse correlation between anxiety and panic attacks. Acknowledgements: This work was supported by CNPq Galvão, B.O. (1); Larrubia, B.C. (1); Cardenas, F.P. (2); Landeira-Fernandez, J. (1,3);. (1) Pontifícia Universidade Católica do Rio de Janeiro, RJ, Brasil, (2) Universidad de Los Andes, Bogotá, Colômbia (3) Universidade Estácio de Sá, RJ The underlined area indicate the specific site for microinjection The underlined area indicate the site affected by NMDA microinjection