The discriminative stimulus properties of legal, over-the-counter stimulants administered singly and in binary and ternary combinations.
Ninety-six male Sprague-Dawley rats were trained in one of seven drug versus saline (SAL) discrimination (DD) tasks under a variable-ratio 5-15 schedule of food-motivated lever press responding. Three groups of rats (n = 12/group) were trained to discriminate between one of the legal over-the-counter (OTC) stimulants--caffeine (CAF), ephedrine (EPHED), phenylpropanolamine (PPA), and SAL. Three other groups (n = 12/group) were trained to discriminate between one of three binary stimulant combinations--CAF+EPHED, CAF+PPA, EPHED+PPA, and SAL. The seventh group of rats (n = 24) was trained to discriminate between SAL and a ternary combination of the OTC stimulants, CAF+EPHED+PPA. Generalization tests were conducted with each of the OTC stimulants and the controlled stimulants--amphetamine (AMPHET) and cocaine (COC). The data suggest: 1) there is cross-generalization between some OTC combinations and controlled stimulants; 2) full generalization between the OTC and controlled stimulants were demonstrated in rats trained to discriminate two of the binary stimulant combinations from SAL; 3) drug mixtures are not perceived as new entities distinct from their component elements; 4) training dose-ratio may influence the characteristics of mixture discriminations; 5) stimulus overshadowing may be a factor determining drug mixture cues, and 6) the DD properties of aggregate drug compounds may function within a euclidean metric space. We propose that some binary OTC stimulant combinations may effectively function as a methadone-like replacement therapy in cocaine dependence.
Department of Psychiatry and Behavioral Sciences, University of Oklahoma Health Sciences Center, Oklahoma City 73190-3000.
D V
DV
Gauvin
K R
KR
Moore
B D
BD
Youngblood
F A
FA
Holloway
D000661:Amphetamine / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003042:Cocaine / Q000494:pharmacology; D004192:Discrimination, Psychological / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004809:Ephedrine / Q000494:pharmacology; D005795:Generalization, Stimulus / Q000187:drug effects; D008297:Male; D010665:Phenylpropanolamine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012055:Reinforcement Schedule
D000697:Central Nervous System Stimulants; D004338:Drug Combinations; D010665:Phenylpropanolamine; D002110:Caffeine; D000661:Amphetamine; D004809:Ephedrine; D003042:Cocaine