Effects of triazolam on drinking in baboons with and without an oral self-administration history: a reinstatement phenomenon

Effect of response-independent candy on responding maintained by candy using a novel model of commodity acquisition and consumption in nonhuman primates

Ingestive behavior consists of appetitive or foraging behavior, i.e., "acquisition," followed by consummatory behavior. Responding of six adult rhesus monkeys, living in three-chambered enclosures, was studied under an operant chain schedule that simulated commodity acquisition and commodity consumption. Responding during the initial acquisition component was reinforced by stimuli paired with that commodity, while responding during the following consumption component was reinforced with that commodity. Throughout the 10-h experimental day, monkeys experienced multiple candy (plain M & Ms) and fruit-drink (Kool-Aid) sessions in different end chambers. The effects of response-independent candy reinforcement, in the context of extinction, were examined when monkeys received a daily food ration of 8 or 20 chow. Response-independent candy increased responding during the acquisition components of candy sessions when monkeys received a daily food ration of 8 chow but not when the food ration was 20 chow. Furthermore, response-independent candy increased candy choice over fruit-drink during choice opportunities and increased the length of time spent in the candy chamber when the candy stimulus lights were illuminated under both food ration conditions, i.e., location preference. The present procedure, which combines operant and place preference measures of commodity acquisition, when used in combination with methods of studying reinstatement of responding, may prove useful in analyzing factors affecting relapse.

Oral drug self-administration: an overview of laboratory animal studies

Many abused drugs can be established as orally delivered reinforcers for rhesus monkeys and other animals. Benzodiazepines, barbiturates, opioids, psychomotor stimulants, dissociative anesthetics, and ethanol can come to serve as reinforcers when taken by mouth. The principal problems in establishing drugs as reinforcers by the oral route of administration are (1) aversive taste, (2) delay in onset of central nervous system effects, and (3) consumption of low volumes of drug solution. Strategies have been devised to successfully overcome these problems, and orally delivered drugs can be established as effective reinforcers. Reinforcing actions are demonstrated by consumption of greater volumes of drug solution than volumes of the water vehicle, and supporting evidence for reinforcing effects consists of the maintenance of behavior under intermittent schedules of reinforcement and the generation of orderly dose-response functions. This article presents an overview of studies of behavior reinforced by oral drug reinforcement. Factors that control oral drug intake include dose, schedule of reinforcement, food restriction, and alternative reinforcers. Many drugs, administered by the experimenter, can alter oral drug reinforcement. Relative reinforcing effects can be assessed by choice procedures and by persistence of behavior across increases in schedule size. In general, reinforcing effects increase directly with dose. Rhesus monkeys prefer combinations of reinforcing drugs to the component drugs. The taste of drug solutions may act as a conditioned reinforcer and a discriminative stimulus. Consequences of drug intake include tolerance and physiological dependence. Findings with orally self-administered drugs are similar to many findings with other positive reinforcers, including intravenously self-administered drugs.