Send to:

Choose Destination
See comment in PubMed Commons below
Front Behav Neurosci. 2012 Oct 29;6:69. doi: 10.3389/fnbeh.2012.00069. eCollection 2012.

Not all stressors are equal: behavioral and endocrine evidence for development of contextual fear conditioning after a single session of footshocks but not of immobilization.

Author information

  • 1Institut de Neurociències, Universitat Autònoma de Barcelona Bellaterra, Barcelona, Spain ; Red de trastornos adictivos (RTA), Instituto de Salud Carlos III Madrid, Spain ; Unitat de Fisiologia Animal (Facultat de Biociències), Universitat Autònoma de Barcelona Bellaterra, Barcelona, Spain.


Exposure of animals to footshocks (FS) in absence of any specific cue results in the development of fear to the compartment where shocks were given (contextual fear conditioning), and this is usually evaluated by time spent freezing. However, the extent to which contextual fear conditioning always develops when animals are exposed to other stressors is not known. In the present work we firstly demonstrated, using freezing, that exposure of adult rats to a single session of FS resulted in short-term and long-term contextual fear conditioning (freezing) that was paralleled by increased hypothalamic-pituitary-adrenal (HPA) activation. In contrast, using a similar design, no HPA or behavioral evidence for such conditioning was found after exposure to immobilization on boards (IMO), despite this stressor being of similar severity as FS on the basis of standard physiological measures of stress, including HPA activation. In a final experiment we directly compared the exposure to the two stressors in the same type of context and tested for the development of conditioning to the context and to a specific cue for IMO (the board). We observed the expected high levels of freezing and the conditioned HPA activation after FS, but not after IMO, regardless of the presence of the board during testing. Therefore, it can be concluded that development of fear conditioning to context or particular cues, as evaluated by either behavioral or endocrine measures, appears to be dependent on the nature of the aversive stimuli, likely to be related to biologically preparedness to establish specific associations.


contextual fear conditioning; footshock; freezing; hypothalamic-pituitary-adrenal axis; immobilization; stress

Free PMC Article
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Frontiers Media SA Icon for PubMed Central
    Loading ...
    Write to the Help Desk