Dopamine D1- and D2-Like Receptor Mechanisms in Relapse to Cocaine-Seeking Behavior: Effects of Selective Antagonists

Dopaminergic mechanisms are thought to be critical in medi-ating relapse to cocaine-seeking behavior. This study exam-ined the different roles of D1- and D2-like receptor mechanisms in the relapse process. Squirrel monkeys were given extended histories of i.v. cocaine self-administration under conditions in which responding was maintained jointly by response-contin-gent cocaine injections and a cocaine-paired visual stimulus (second-order schedule). Responding was then extinguished by substituting saline for cocaine injections and omitting pre-sentations of the cocaine-paired stimulus. Subsequently, non-contingent priming injections of cocaine combined with resto-ration of the cocaine-paired stimulus induced dose-dependent reinstatement of drug-seeking behavior, with response rates approaching those maintained by active cocaine self-adminis