Retention of sequential drug discriminations under fixed-interval schedules for long time periods without training.
The experiments showed that sequential drug discriminations can be learned and retained under a fixed-interval (FI) schedule for more than 18 months without additional training under a complex three-choice procedure. Pigeons were trained to discriminate among 5 mg/kg pentobarbital, 2 mg/kg D-amphetamine, and saline. After responding stabilized, dose-response curves were determined for other drugs. Subsequently, pentobarbital was replaced with 5 mg/kg morphine as a training drug, and D-amphetamine was replaced with 30 mg/kg caffeine. After the pigeons learned these new discriminations, dose-response curves were redetermined. Initially, chlordiazepoxide substituted for pentobarbital, cocaine substituted for D-amphetamine, and nicotine partially substituted for D-amphetamine. Morphine, Delta9-tetrahydrocannabinol, and caffeine did not substitute for either drug. After retraining with morphine and caffeine, responding occurred on the pentobarbital/morphine key after pentobarbital, chlordiazepoxide and morphine and on the D-amphetamine/caffeine key after D-amphetamine, cocaine and caffeine. After nicotine and Delta9-tetrahyrdocannabinol, responding occurred on the saline key. These data show that drug discriminations learned under fixed-interval schedules are retained for long time periods, even when discrimination training with other drugs occurs during the retention period.
Li
Mi
M
Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205, USA.
McMillan
Donald E
DE
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D002110:Caffeine / Q000008:administration & dosage / Q000494:pharmacology; D002492:Central Nervous System Depressants / Q000008:administration & dosage / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage / Q000494:pharmacology*; D002707:Chlordiazepoxide / Q000008:administration & dosage / Q000494:pharmacology; D003042:Cocaine / Q000008:administration & dosage / Q000494:pharmacology; D010856:Columbidae; D003913:Dextroamphetamine / Q000008:administration & dosage / Q000494:pharmacology; D004193:Discrimination Learning / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000008:administration & dosage / Q000494:pharmacology; D005793:Generalization, Psychological; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology; D010424:Pentobarbital / Q000008:administration & dosage / Q000494:pharmacology; D012055:Reinforcement Schedule
D002492:Central Nervous System Depressants; D000697:Central Nervous System Stimulants; D002110:Caffeine; D009538:Nicotine; D002707:Chlordiazepoxide; D009020:Morphine; D013759:Dronabinol; D010424:Pentobarbital; D003042:Cocaine; D003913:Dextroamphetamine