Effects of D-cycloserine on extinction of learned fear to an olfactory cue.

Full Abstract

D-cycloserine (DCS), a partial NMDA receptor agonist, facilitates extinction of learned fear in rats and has been used to treat anxiety disorders in clinical populations. However, research into the effects of DCS on extinction is still in its infancy, with visual cues being the primary fear-eliciting stimuli under investigation. In both human and animal subjects odors have been found to associate strongly with aversive events. Therefore, this study examined the generality of the effects of DCS on extinction by testing odor cues. Sprague-Dawley rats were conditioned and extinguished to an odor using varying parameters, injected with either saline or DCS (15 mg/kg) following extinction, and then tested for a freezing response 24 h later. Experiment 1 demonstrated that after 3 odor-shock pairings, rats did not display short-term extinction and DCS had no effect on long-term extinction. Experiment 2 demonstrated that after 3 odor-noise pairings, rats displayed significant short-term extinction and DCS significantly facilitated long-term extinction. Following 2 odor-shock pairings in Experiment 3, half the rats displayed short-term extinction ("extinguishers") and half did not ("non-extinguishers"). DCS facilitated long-term extinction in the "extinguishers" condition but not in the "non-extinguishers" condition. In Experiment 4, following 2 odor-shock pairings and an extra extinction session, DCS had a significant facilitatory effect on long-term extinction. Thus, extinction of freezing to an odor cue was facilitated by systemic injections of DCS, but only when some amount of within-session extinction occurred prior to injection.

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Author information

Author/s: Weber, Marianne (M); Hart, Joe (J); Richardson, Rick (R);

Affiliation: School of Psychology, University of New South Wales, Sydney, Australia.

Journal and publication information

Publication Type: Journal Article

Journal: Neurobiology of learning and memory (Neurobiol Learn Mem), published in United States. (Language: eng)

Reference: 2007-May; vol 87 (issue 4) : pp 476-82

Dates: Created 2007/04/02; Completed 2007/07/16; Revised 2007/10/17;

PMID: 17275356, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Analysis of Variance
Animals
Association Learning - drug effects
Conditioning, Classical - drug effects
Cues
Cycloserine - pharmacology
Excitatory Amino Acid Agonists - pharmacology
Extinction, Psychological - drug effects

Fear
Generalization, Stimulus - drug effects
Male
Rats
Rats, Sprague-Dawley
Receptors, N-Methyl-D-Aspartate - agonists
Smell - physiology
Startle Reaction - drug effects

Associated Chemicals: Excitatory Amino Acid Agonists (0) ; Receptors, N-Methyl-D-Aspartate (0) ; Cycloserine (68-41-7)

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