Effect of Leu-enkephalin on the memory reactivation produced by blockade of the benzodiazepine/GABA-chloride ionophore receptor complex

Brain Res. 1995 Jan 30;670(2):347-50. doi: 10.1016/0006-8993(94)01361-k.


This investigation sought to characterize the interaction between GABA/benzodiazepine and opioid systems in memory retrieval deficit induced by detaining an animal in the training apparatus after acquisition. Mice pretreated with saline or Leu-enkephalin (0.2 mg/kg) were trained in one-trial passive avoidance test with following detention. Pre-testing administration of bicuculline (1 mg/kg), picrotoxin (1 mg/kg), or flumazenil (10 mg/kg) produced the memory-enhancing effect in the saline-pretreated mice. Pretraining treatment with Leu-enkephalin blocked the reactivation of memory produced by bicuculline and picrotoxin, but not flumazenil. The present investigation suggest that both benzodiazepine/GABA and opioid systems are important modulators of memory retrieval and that a specific interaction between these systems is responsible for the observed recovery of impaired memory trace.

MeSH terms

  • Analysis of Variance
  • Animals
  • Avoidance Learning / drug effects
  • Bicuculline / pharmacology
  • Enkephalin, Leucine / pharmacology*
  • Flumazenil / pharmacology
  • GABA-A Receptor Antagonists*
  • Male
  • Memory Disorders / drug therapy*
  • Mice
  • Mice, Inbred BALB C
  • Picrotoxin / pharmacology
  • Receptors, Opioid, delta / drug effects*


  • GABA-A Receptor Antagonists
  • Receptors, Opioid, delta
  • Picrotoxin
  • Flumazenil
  • Enkephalin, Leucine
  • Bicuculline