Reinstatement of extinguished fear by β-adrenergic arousal elicited by a conditioned context.

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 β-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 β-adrenergic activity elicited by exposure to a conditioned context in the reinstatement of extinguished fear. (PsycINFO Database Record (c) 2010 APA, all rights reserved)