Social Contact Reinforces Cocaine Self-Administration in Young Adult Male Rats: The Role of Social Reinforcement in Vulnerability to Drug Use

Drug-using peers are recognized as a leading factor influencing drug use among adolescents and young adults. One mechanism by which peers influence drug use is by providing social reinforcement for using drugs. Social reinforcement may be provided in multiple ways, including by making social contact contingent on drug use (i.e., an individual must use drugs to gain/maintain access to a peer). The purpose of this study was to develop a preclinical model in which intravenous cocaine self-administration was positively reinforced by access to a social partner. Young adult male rats were trained to self-administer cocaine in operant conditioning chambers with a guillotine door that could be opened to an adjacent compartment housing either a social partner or a non-social stimulus. Once cocaine self-administration was established, the guillotine door was activated, and cocaine intake was reinforced by brief access to either a social (age- and sex-matched peer) or non-social (black-and-white athletic sock) stimulus. Contingent access to a social partner rapidly increased cocaine self-administration. Total cocaine intake was 2- to 3-fold greater in rats assigned to the social versus non-social condition across a 100-fold dose range. Cocaine intake rapidly increased when rats in the original non-social group were later provided with social partners, whereas cocaine intake resisted change and remained elevated when rats in the original social group had their partners removed. These data indicate that contingent access to a social partner increases drug intake and suggest that social reinforcement may represent a vulnerability factor that is particularly resistant to psychosocial interventions.

A Versatile Automated-Guillotine-Door Design for Application in Small Animal Research

The versatile design of a reliable door which can be employed with nonaquatic and aquatic small animals is described.

Influence of Conditions at the Time of Reinforcement upon the Strength of a Secondary Reinforcement Effect

Animals were trained to run through a guillotine door into an adjacent compartment for water reinforcement. They were then given access to the compartment as a consequence of bar-pressing, but no water. At the time of testing for bar-pressing various changes were made in the type of response required. For other groups of animals variations were made in the relative sizes of the two compartments during both training and testing. It was found that “getting into the starting box” was as reinforcing as “getting out of the starting box,” that learning in the testing situation did not occur unless previous water reinforcement had been given in one of the compartments, and that changes in the type of response required at the time of testing did not diminish the learning effect.