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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

Defensive behavioral responses are contingent upon threat intensity, proximity, and context of exposure. Based on these factors, we developed a classical conditioning paradigm that elicits clear transitions between conditioned freezing and flight behavior within individual subjects. This model is crucial for the understanding the pathologies involved in anxiety, panic, and post-traumatic stress disorders.

Abstract

Fear- and anxiety-related behaviors significantly contribute to an organism’s survival. However, exaggerated defensive responses to perceived threat are characteristic of various anxiety disorders, which are the most prevalent form of mental illness in the United States. Discovering the neurobiological mechanisms responsible for defensive behaviors will aid in the development of novel therapeutic interventions. Pavlovian fear conditioning is a widely used laboratory paradigm to study fear-related learning and memory. A major limitation of traditional Pavlovian fear conditioning paradigms is that freezing is the only defensive behavior monitored. We recently developed a modified Pavlovian fear conditioning paradigm that allows us to study both conditioned freezing and flight (also known as escape) behavior within individual subjects. This model employs higher intensity footshocks and a greater number of pairings between the conditioned stimulus and unconditioned stimulus. Additionally, this conditioned flight paradigm utilizes serial presentation of pure tone and white noise auditory stimuli as the conditioned stimulus. Following conditioning in this paradigm, mice exhibit freezing behavior in response to the tone stimulus, and flight responses during the white noise. This conditioning model can be applied to the study of rapid and flexible transitions between behavioral responses necessary for survival.

Introduction

Fear is an evolutionarily conserved adaptive response to an immediate threat1,2. While organisms possess innate defensive responses to a threat, learned associations are crucial to elicit appropriate defensive responses to stimuli predictive of danger3. Dysregulation in brain circuits controlling defensive responses is likely to contribute to maladaptive reactions associated with multiple debilitating anxiety disorders, such as post-traumatic stress disorder (PTSD), panic disorder4, and specific phobias5,6

Protocol

The following steps/procedures were conducted in accordance with institutional guidelines after approval from the Institutional Animal Care & Use Committee of Tulane University.

1. Preparation of mice

  1. Use male and/or female adult mice aged between 3-5 months. In the present study, we used male C57BL/6J mice obtained from Jackson Laboratory, but any mouse strain from a reputable supplier can be used.
  2. At least one week before the experiment, house all the mice individua.......

Representative Results

As described in the diagram (Figure 1A), the session starts with pre-exposure (Day 1), followed by fear conditioning (Days 2 and 3), and then either extinction or retrieval (Day 4).

Presentations of the SCS in the pre-exposure (Day 1) session did not elicit flight or freezing response in the mice (Figure 2A-2B). Behavioral analysis during conditioning (Days 2 and 3) revealed that the tone component of the SCS signific.......

Discussion

The described sound and shock parameters are important elements of this protocol. It is critical, therefore, to test the shock amplitude and sound pressure level before starting the experiments. Fear conditioning studies typically use 70-80 dB sound pressure levels and 0.1-1 mA shock intensity18; thus, the described parameters are within the bounds of traditional fear conditioning paradigms. In a previous CS-only (no footshock) control experiment, we did not observe flight or freezing responses in.......

Acknowledgements

This work was supported by the Louisiana Board of Regents through the Board of Regents support fund (LEQSF(2018-21)-RD-A-17) and the National Institute of Mental Health of the National Institutes of Health under award number R01MH122561. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

....

Materials

NameCompanyCatalog NumberComments
Neutral contextPlexiglass cylinder 30 X 30 cm 
Fear conditioning boxMed Associates, Inc.VFC-00825 X 30 X 35 cm dimentions
Audio generator Med Associates, Inc.ANL-926 
ShockerMed Associates Inc.ENV-414SStainless steel grid
SpeakerMed Associates, Inc.ENV-224AMSuitable for pure tone and white noise 
C57/BL6J miceJackson laboratory, USA664Aged 3-5 month
Cineplex software (Editor/ studio)PlexonCinePlex Studio v3.8.0For video tracking and behavioral scoring analysis
MedPC software VMed Associates, Inc.SOF-736
NeuroexplorerPlexonUsed to extract the freezing data scored in PlexonEditor
GraphPad Prism 8GraphPad Software, Inc.Version 8Statistical analysis software

References

  1. Gross, C. T., Canteras, N. S. The many paths to fear. Nature Reviews Neuroscience. 13 (9), 651-658 (2012).
  2. LeDoux, J. Rethinking the Emotional Brain. Neuron. , (2012).
  3. Maren, S.

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