Accumbal opioid receptors modulate cue competition in one-trial overshadowing

Brain Res. 2013 Jun 23;1517:57-67. doi: 10.1016/j.brainres.2013.04.019. Epub 2013 Apr 17.


The contribution of opioid receptors in the nucleus accumbens to contextual and auditory fear conditioning was examined. Impairment in contextual fear conditioning was found when training occurred under accumbal infusions of the opioid receptor agonist morphine in a dose-dependent and receptor specific fashion, only when shock onset coincided with auditory stimulus offset. Contextual fear conditioning was spared, however when the delivery of shock was not signalled by an auditory stimulus, the auditory stimulus was of low intensity (70dB), or an interval (10s or 30s) was interpolated between auditory stimulus offset and shock onset. These results provide evidence that opioid receptors in the nucleus accumbens regulate competition between contextual and discrete auditory stimuli for association formation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acoustic Stimulation / adverse effects
  • Analgesics, Opioid / pharmacology
  • Analysis of Variance
  • Animals
  • Conditioning, Psychological / physiology*
  • Cues*
  • Dose-Response Relationship, Drug
  • Electroshock / adverse effects
  • Fear / drug effects
  • Fear / physiology*
  • Freezing Reaction, Cataleptic / drug effects
  • Freezing Reaction, Cataleptic / physiology
  • Learning Disabilities / chemically induced
  • Male
  • Morphine / pharmacology
  • Naloxone / pharmacology
  • Narcotic Antagonists / pharmacology
  • Nucleus Accumbens / drug effects
  • Nucleus Accumbens / metabolism*
  • Psychoacoustics
  • Rats
  • Rats, Wistar
  • Reaction Time / drug effects
  • Receptors, Opioid / metabolism*


  • Analgesics, Opioid
  • Narcotic Antagonists
  • Receptors, Opioid
  • Naloxone
  • Morphine