Ratio size and cocaine concentration effects on oral cocaine-reinforced behavior.
Monkeys were given a choice between cocaine solutions and water under concurrent fixed-ratio reinforcement schedules. The operant response was spout contact. Six rhesus monkeys served as subjects. The cocaine concentration was varied from 0.0125 to 0.8 mg/ml, and the fixed-ratio value was varied from 8 to 128. Cocaine maintained higher response rates than did water over a wide range of conditions. Response rate and number of cocaine deliveries per session were inverted U-shaped functions of concentration. These functions were shifted to the right as the fixed ratio was increased. The number of cocaine deliveries was more persistent as fixed-ratio value was increased when the unit dose was larger rather than smaller. Cocaine consumption was analyzed as a function of unit price (fixed-ratio value divided by cocaine concentration), and unit price accounted for between 77% and 92% of the variance in cocaine consumption for individual monkeys. The current data support the claim that a drug's reinforcing effects increase directly with dose and underscore the need to gather parametric data when examining the effects of experimental manipulations on a drug-reinforced baseline.
University of Texas-Houston Health Science Center, USA.
M J
MJ
Macenski
R A
RA
Meisch
D000818:Animals; D016739:Behavior, Addictive / Q000503:physiopathology*; D003042:Cocaine / Q000008:administration & dosage* / Q000494:pharmacology; D003216:Conditioning, Operant / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D016014:Linear Models; D008253:Macaca mulatta; D008297:Male; D008960:Models, Psychological; D009294:Narcotics / Q000008:administration & dosage* / Q000494:pharmacology; D012055:Reinforcement Schedule
D009294:Narcotics; D003042:Cocaine