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  • Title: Reinstatement of extinguished fear by beta-adrenergic arousal elicited by a conditioned context.
    Author: Morris RW, Westbrook RF, Killcross AS.
    Journal: Behav Neurosci; 2005 Dec; 119(6):1662-71. PubMed ID: 16420169.
    Abstract:
    Five experiments examined the reinstatement of fear (freezing) produced by recent reexposure to a dangerous context. Rats were trained to fear a conditioned stimulus (CS) and a distinctive context with shock. The CS was then extinguished. A 2-min interval between reexposure to the dangerous context and presentation of the extinguished CS in a different context reinstated freezing when the CS was tested the next day. Propranolol (a beta-adrenergic antagonist) blocked reinstatement of extinguished fear without decreasing freezing to a nonextinguished CS. Administration of epinephrine (an adrenergic agonist) reinstated extinguished fear without reexposure to the dangerous context. The results suggest a role for beta-adrenergic activity elicited by exposure to a conditioned context in the reinstatement of extinguished fear.
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