Effects of D-cycloserine on extinction of conditioned freezing

Behav Neurosci. 2003 Apr;117(2):341-9. doi: 10.1037/0735-7044.117.2.341.


The present study tested the prediction that D-cycloserine (DCS), a partial N-methyl-D-aspartate agonist, would facilitate extinction of conditioned freezing in male Sprague-Dawley rats. Rats received 5 light-shock pairings (conditioning). The following day, rats received 6 light-alone presentations (extinction training). Twenty-four hours later, rats received 1 light-alone presentation (test). Subcutaneous DCS injection before or after extinction training significantly enhanced extinction, and the dose-response curve for this effect was linear. Increasing the delay of DCS administration after extinction training led to a linear decrease in the facilitatory effect. The effect of systemic administration was replicated by intra-basolateral amygdala infusion. These results suggest that DCS facilitates extinction of conditioned freezing by acting on consolidation processes partly mediated by the basolateral amygdala.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amygdala / drug effects
  • Analysis of Variance
  • Animals
  • Brain Mapping
  • Conditioning, Psychological / drug effects*
  • Conditioning, Psychological / physiology
  • Cycloserine / pharmacology*
  • Dose-Response Relationship, Drug
  • Drug Administration Routes / veterinary
  • Excitatory Amino Acid Agonists / pharmacology*
  • Extinction, Psychological / drug effects*
  • Extinction, Psychological / physiology
  • Male
  • Rats
  • Rats, Sprague-Dawley
  • Reflex, Startle / drug effects*
  • Reflex, Startle / physiology
  • Time Factors


  • Excitatory Amino Acid Agonists
  • Cycloserine