Drug use typically occurs in social contexts, and data from epidemiological (Schinke et al., 2008, Sieving et al., 2000, Bahr et al., 2005, Biederman et al., 2000, Chassin et al., 1996), human laboratory (Caudill and Marlatt, 1975, Collins et al., 1985), and preclinical (Smith, 2012, Robinson et al., 2016) studies indicate the behavior of other individuals (i.e., whether other individuals are using drugs) influences the drug use of the subject. In most studies, the presence of peers not using drugs decreases drug intake, whereas the presence of peers using drugs increases drug intake (see reviews by Pelloux et al., 2019; Strickland and Smith, 2014, Strickland and Smith, 2015). The degree to which the social context interacts with manipulations that mimic treatment interventions (e.g., pharmacotherapies) are not known.

The purpose of this study was to examine the influence of social contact on the effects of dextroamphetamine (d-amphetamine) on the reacquisition of cocaine self-administration. D-amphetamine reduces cocaine intake in preclinical (Chiodo et al., 2008, Czoty et al., 2011, Negus and Mello, 2002, Peltier et al., 1996), human laboratory (Rush et al., 2010), and human clinical (Grabowski et al., 2004) contexts. In this study, rats self-administered cocaine during 6-hr daily test sessions prior to extinction and reacquisition testing. During reacquisition, d-amphetamine- and saline-treated rats were randomized to three social groups in which each rat (1) remained isolated, (2) was partnered with a rat that self-administered cocaine, or (3) was partnered with a rat that did not have access to cocaine.

The a priori predictions were (1) d-amphetamine treatment would decrease the reacquisition of cocaine self-administration, (2) the effects of d-amphetamine would be attenuated in rats that re-acquired in the presence of a rat also self-administering cocaine, and (3) the effects of d-amphetamine would be enhanced in rats that reacquired in the presence of a rat without access to cocaine.