Cocaine and dependence and D₂ receptor availability in the functional subdivisions of the striatum: Relationship with cocaine-seeking behavior

Striatal dopamine D₂ receptors have been implicated in the neurobiology of cocaine addiction. Previous imaging studies showed reduced striatal D₂ receptor availability in chronic cocaine abusers, and animal studies suggested that low D₂ receptor availability promotes cocaine self-administration. Here, D₂ receptor availability was assessed with positron emission tomography (PET) and [¹¹C]raclopride in the limbic, associative, and sensori-motor subdivisions of the striatum in 17 recently detoxified chronic cocaine-dependent (CCD) subjects and 17 matched healthy control (HC) subjects. In addition, the relationship between regional D₂ receptor availability and behavioral measures obtained in cocaine self-administration sessions was investigated in CCD subjects. [ ¹¹C]Raclopnde binding potential was significantly reduced by 15.2% in the limbic striatum, 15.0% in the associative striatum, and 17.1% in the sensori-motor striatum in CCD subjects compared to HC subjects. In CCD subjects, no relationship was detected between D₂ availability in striatal regions and either the positive effects of smoked cocaine or the choice of cocaine over an alternative reinforcer (money) following a priming dose of cocaine (a laboratory model of relapse). Thus, this study confirms previous reports of a modest decrease in D₂ receptor availability in CCD subjects, and establishes that this decrease is generalized throughout the striatum, However, this study failed to demonstrate a relationship between D₂ receptor availability and cocaine-induced cocaine-taking behavior. Additional research is warranted to unravel potential neurobiological traits that might confer vulnerability to relapse in detoxified CCD subjects.