D-cycloserine facilitates extinction but does not eliminate renewal of the conditioned emotional response

Behav Neurosci. 2006 Oct;120(5):1159-62. doi: 10.1037/0735-7044.120.5.1159.


The effect of D-cycloserine (DCS), an NMDA partial agonist, on extinction of fear was investigated in rats using the conditioned emotional response preparation. Fear extinction was facilitated when the first 4 trials occurred with a 30-mg/kg dose of DCS. However, extinguished fear was "renewed" regardless of the drug treatment when the rats were returned to the context in which fear had been conditioned. Additional results suggest that DCS's facilitation of extinction is a small but meaningful effect in the current method. The results suggest caution regarding the use of DCS as an adjunct to extinction: Although the drug may modestly facilitate extinction learning, it does not necessarily destroy the potential for relapse. Behavioral mechanisms are discussed.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Antimetabolites / pharmacology*
  • Association Learning / drug effects
  • Conditioning, Classical / drug effects*
  • Cycloserine / pharmacology*
  • Dose-Response Relationship, Drug
  • Extinction, Psychological / drug effects*
  • Fear / drug effects*
  • Female
  • Mental Recall / drug effects
  • Nitroso Compounds / agonists*
  • Rats
  • Rats, Wistar


  • Antimetabolites
  • Nitroso Compounds
  • 4-nitrosodimethylaniline
  • Cycloserine