title: The effect of yohimbine on the extinction of conditioned fear: a role for context.
abstract: Six experiments with rat subjects examined the effect of yohimbine, an alpha-2 adrenergic autoreceptor antagonist, on the extinction of conditioned fear to a tone. Experiments 1 and 2 demonstrated that systemic administration of yohimbine (1.0 mg/kg) facilitated a long-term decrease in freezing after extinction, and this depended on pairing drug administration with extinction training. However, Experiments 3 and 4 demonstrated that yohimbine did not eradicate the original fear learning: Freezing was renewed when the tone was tested outside of the extinction context. Experiments 5 and 6 found that the contextually specific attenuation of fear produced by yohimbine transferred to another extinguished conditional stimulus (CS) and not to a nonextinguished CS. The results suggest that yohimbine, when administered in the presence of a neutral context, creates a form of inhibition in that context that allows that specific context to reduce fear of an extinguished CS.
authors.affiliation: Department of Psychology, University of Vermont, Burlington, VT 05401, USA.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Morris
authors.forename: Mark E
authors.initials: ME
authors.lastname: Bouton
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D003213:Conditioning, Psychological / Q000187:drug effects*; D003463:Cues; D004305:Dose-Response Relationship, Drug; D005108:Extinction, Psychological / Q000187:drug effects*; D005239:Fear; D005260:Female; D046352:Freezing Reaction, Cataleptic / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D015016:Yohimbine / Q000494:pharmacology*
chemical_list: D000317:Adrenergic alpha-Antagonists; D015016:Yohimbine