Effects of the combination of metyrapone and oxazepam on cocaine and food self-administration in rats

Pharmacol Biochem Behav. 2008 Nov;91(1):181-9. doi: 10.1016/j.pbb.2008.07.005. Epub 2008 Jul 19.


For several years, our laboratory has investigated the role for the HPA axis in cocaine reinforcement. Two classes of drugs that we have studied include corticosterone synthesis inhibitors (e.g., metyrapone) and benzodiazepine receptor agonists (e.g., oxazepam). In the experiments described in this manuscript, we tested the effects of various doses of metyrapone and oxazepam against several doses of self-administered cocaine. Behavioral, endocrine and pharmacokinetic measures of the effects of the combination of metyrapone and oxazepam on cocaine reward are presented. Combinations of metyrapone and oxazepam at doses that produced no observable effects when administered separately significantly reduced cocaine self-administration without affecting food-maintained responding during the same sessions. Changes in pharmacokinetics or endocrine function do not appear to mediate these effects, suggesting a central mechanism of action. Therefore, although these drugs produce their effects through distinct mechanisms, an additive effect on cocaine self-administration is obtained when these drugs are administered together, suggesting that combinations of low doses of metyrapone and oxazepam may be useful in reducing cocaine seeking with a reduced incidence of unwanted side effects and a decreased potential for abuse.

Publication types

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

MeSH terms

  • Animals
  • Cocaine-Related Disorders / psychology*
  • Conditioning, Operant / drug effects
  • Corticosterone / metabolism
  • Dose-Response Relationship, Drug
  • Drug Combinations
  • Eating / drug effects*
  • Enzyme Inhibitors / pharmacokinetics
  • Enzyme Inhibitors / pharmacology*
  • Extinction, Psychological / drug effects
  • Hypnotics and Sedatives / pharmacokinetics
  • Hypnotics and Sedatives / pharmacology*
  • Male
  • Metyrapone / pharmacokinetics
  • Metyrapone / pharmacology*
  • Oxazepam / pharmacokinetics
  • Oxazepam / pharmacology*
  • Rats
  • Rats, Wistar
  • Self Administration
  • Substance Abuse, Intravenous / psychology


  • Drug Combinations
  • Enzyme Inhibitors
  • Hypnotics and Sedatives
  • Oxazepam
  • Corticosterone
  • Metyrapone