Heroin and cocaine intravenous self-administration in rats: mediation by separate neural systems.
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.
D000818:Animals; D003042:Cocaine / Q000008:administration & dosage*; D003216:Conditioning, Operant / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005475:Flupenthixol / Q000008:administration & dosage; D003932:Heroin / Q000008:administration & dosage*; D007263:Infusions, Parenteral; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009271:Naltrexone / Q000008:administration & dosage; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects; D011957:Receptors, Opioid / Q000187:drug effects; D012646:Self Administration
D011954:Receptors, Dopamine; D011957:Receptors, Opioid; D009271:Naltrexone; D003932:Heroin; D005475:Flupenthixol; D003042:Cocaine