Modifying drug-reinforced behavior by altering the economic conditions of the drug and a nondrug reinforcer

Behavioral economics and drug choice: effects of unit price on cocaine self-administration by monkeys

The application of microeconomic theory to the experimental analysis of behavior has been termed behavioral economics. There has been an increasing interest in applying the concepts of behavioral economics to the study of drug self-administration. In a previously published experiment (Nader and Woolverton, 1992), rhesus monkeys (N = 3) were trained in a discrete-trials choice procedure and allowed to choose between intravenous injections of cocaine (0.03-1.0 mg/kg/injection) and food presentation (1 or 4 pellets; 1 g/pellet) during daily 7-h experimental sessions. When cocaine or food was available under a fixed-ratio (FR) 30 schedule, cocaine intake increased in a dose-related manner for all monkeys. When the response requirement (FR) for cocaine was differentially increased by doubling or quadrupling, the frequency of cocaine choice decreased, shifting the cocaine dose-response function to the right. The present paper is a reanalysis of data from that experiment. Several mathematical models, differentially incorporating the effects of FR, dose and number of food pellets, were compared. When cocaine consumption was analyzed using a multiple linear regression analysis with FR, dose and number of pellets as separate main effects (model I), the R2 was 0.82. When FR and dose were combined into one factor, unit price (UP, responses/mg/kg), and cocaine consumption was analyzed as a linear function of UP (model IIA), the R2 was 0.54. When cocaine consumption was analyzed as a curvilinear, negatively accelerated function of UP (model IIB), the R2 was 0.53. The difference between models I and IIA was statistically significant while models IIA and IIB were not different.(ABSTRACT TRUNCATED AT 250 WORDS)

The economic context of drug and non-drug reinforcers affects acquisition and maintenance of drug-reinforced behavior and withdrawal effects

The focus of this review is to examine the effect of non-drug alternative reinforcers on drug-reinforced behavior. An increasing number of animal laboratory as well as human clinical studies have demonstrated the effectiveness of non-drug reinforcers in reducing steady-state levels of drug self-administration. One goal of this review was to determine what behavioral economic conditions are optimal for reducing drug-reinforced behavior. Variables such as price of the drug and non-drug reinforcer have been manipulated by changing fixed-ratio (FR) value of these commodities. Income has been changed by limiting the amount of access to the commodities or by changing session length. Substitution was evaluated by determining whether decreased demand for a drug (due to increased price) was related to increased demand for a non-drug reinforcer. A second goal of this review was to investigate transition states in the drug addiction process with respect to the role of alternative non-drug reinforcers. Animal models of acquisition and withdrawal were examined to identify behavioral economic conditions under which acquisition may be prevented or withdrawal effects (and potential for relapse) may be alleviated.

Autoshaping i.v. cocaine self-administration in rats: effects of nondrug alternative reinforcers on acquisition

The purpose of this experiment was to examine the effects of a nondrug alternative reinforcer and feeding conditions on the acquisition of cocaine self-administration. Rats were autoshaped to press a lever that resulted in a 0.2 mg/kg i.v. cocaine infusion. Responses on the lever were monitored during six consecutive autoshaping sessions that occurred each day. A retractable lever was inserted into the operant chamber on a random time 60 s schedule 10 times per session for six sessions that began each hour. Each day the six autoshaping sessions were followed by a 6-h cocaine self-administration session. During self-administration the lever remained extended, and each response on the lever resulted in a cocaine infusion (0.2 mg/kg). The criterion for acquisition of cocaine-reinforced behavior was met when there were 5 consecutive days during which the mean number of infusions during the 6-h self-administration session was at least 100. This procedure was repeated daily until the criterion was met or 30 days elapsed. The rats were also trained to respond on lick-operated automatic drinking devices that delivered 0.05 ml water or a glucose and saccharin solution (G + S) contingent upon each lick response. Five groups of 12-14 rats were compared. The first four groups constituted a 2 x 2 factorial design whereby either G + S or water was available in the home cage for 3 weeks before autoshaping began and G + S or water was available in the operant chamber during autoshaping. These groups were limited to 20 g food per day and all had free access to water.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of increasing response requirement on choice between cocaine and food in rhesus monkeys

Rhesus monkeys were trained in a discrete-trials choice procedure and allowed to choose between intravenous injections of cocaine (0.01-1.0 mg/kg/injection) and food presentation (1 or 4 pellets; 1 g/pellet) during daily 7-h experimental sessions. When each reinforcer was available under a fixed-ratio (FR) 30 schedule, the frequency of cocaine choice and the total drug intake increased in a dose-related manner for all monkeys. When the FR for cocaine was differentially increased, the frequency of cocaine choice decreased, shifting the cocaine dose-response function to the right and/or downward. When the FR for cocaine was at least 480, cocaine preference could not be recovered up to doses of 1.0 mg/kg/injection. In a second experiment, when the response requirement for food was differentially increased, the frequency of cocaine choice increased. These results demonstrate that altering the response requirement for cocaine or for alternative reinforcers that are available can substantially affect cocaine self-administration.