Comparing nucleus accumbens and dorsal striatal dopamine responses to self-administered cocaine in naïve rats

Dopamine (DA) responses in the nucleus accumbens (NAcc) and dorsal striatum (DS) are commonly associated with different aspects of cocaine effects. Enhanced NAcc DA has been most convincingly linked with the positive reinforcing effects of cocaine, while DS DA is thought to mediate cocaine-induced motoric effects. Though several studies have shown NAcc DA enhancement following cocaine self-administration, very little work has examined the effects of cocaine self-administration on DS DA. In this study, DA levels in the NAcc and DS, and locomotor responses to a single self-administered cocaine injection (1.5 mg/kg) were assessed in operant-trained, drug-naïve Sprague-Dawley rats. Locomotor activity, NAcc and DS DA levels increased significantly over baseline activity immediately after cocaine injection. However, while basal and cocaine-stimulated NAcc DA concentrations (nM) were significantly greater than DS DA levels, the magnitude of response was statistically comparable between brain regions. These findings indicate that, though both the NAcc and DS are importantly involved in the dopaminergic response to self-administered cocaine in drug-naïve rats, basal DA differences in dialysis data are obscured by statistical conversions to baseline percentages.