Heroin and cocaine intravenous self-administration in rats: mediation by separate neural systems

Psychopharmacology (Berl). 1982;78(3):204-9. doi: 10.1007/BF00428151.


The hypothesis that separate neural systems mediate the reinforcing properties of opiate and psychomotor stimulant drugs was tested in rats trained to lever-press of IV injections of either cocaine or heroin during daily 3-h sessions. Pretreatment with the opiate receptor antagonist drug naltrexone produced dose-dependent increases in heroin self-administration, but had no effect on the rate or pattern of cocaine self-administration. Similarly, pretreatment with low doses of the dopamine antagonist drug alpha-flupenthixol produced dose-dependent increases in cocaine but not heroin self-administration. High doses of alpha-flupenthixol eliminated all responding for cocaine and slightly reduced heroin self-administration. The specificity with which the two antagonist drugs exerted their behavioral effects strongly suggests that independent neural substrates are responsible for the reinforcing actions of heroin and cocaine.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cocaine / administration & dosage*
  • Conditioning, Operant / drug effects*
  • Dose-Response Relationship, Drug
  • Flupenthixol / administration & dosage
  • Heroin / administration & dosage*
  • Infusions, Parenteral
  • Male
  • Motor Activity / drug effects
  • Naltrexone / administration & dosage
  • Rats
  • Rats, Inbred Strains
  • Receptors, Dopamine / drug effects
  • Receptors, Opioid / drug effects
  • Self Administration


  • Receptors, Dopamine
  • Receptors, Opioid
  • Naltrexone
  • Heroin
  • Flupenthixol
  • Cocaine