Factors affecting voluntary morphine intake in self-maintained  addicted rats.
D000818:Animals; D001522:Behavior, Animal; D001562:Benzimidazoles / Q000494:pharmacology; D003061:Codeine / Q000494:pharmacology*; D004361:Drug Tolerance; D006801:Humans; D007263:Infusions, Parenteral; D008614:Meperidine / Q000494:pharmacology*; D009020:Morphine / Q000008:administration & dosage*; D009021:Morphine Dependence; D009269:Nalorphine / Q000494:pharmacology*; D051381:Rats; D013375:Substance Withdrawal Syndrome
D001562:Benzimidazoles; D009020:Morphine; D008614:Meperidine; D009269:Nalorphine; D003061:Codeine