EFFECTS OF ANXIETY ON THE ESCAPE BEHAVIOR INDUCED BY THE MICROINJECTION OF NMDA IN THE DORSAL PERIAQUEDUCTAL GRAY

1
EFFECTS OF ANXIETY ON THE ESCAPE BEHAVIOR INDUCED
BY THE MICROINJECTION OF NMDA IN THE DORSAL
PERIAQUEDUCTAL GRAY
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

• 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 phenomenas 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
  (AP2.3 DV4.5 ML1.7) 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 (1secV1,0mA
  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
The underlined area indicate the specific site
for microinjection
The underlined area indicate the site affected by
NMDA microinjection