Effects of cocaine on dopamine in subregions of the rat prefrontal cortex and their efferents to subterritories of the nucleus accumbens

The present study sought to investigate the contributions of the ventral prelimbic/infralimbic cortices and shell subterritory of the nucleus accumbens as well as the dorsal prelimbic/anterior cingulate cortices and core subregion of the nucleus accumbens to the acute systemic effects of cocaine (20 mg/kg i.p.) on both locomotor activity and simultaneous dialysate dopamine levels using a dual-probe microdialysis design. Basal dopamine levels were significantly higher in the ventral medial prefrontal cortex compared with the dorsal medial prefrontal cortex and higher concentrations of dopamine were also observed in the core of the nucleus accumbens compared with its shell counterpart. Cocaine produced a significant decrease in dopamine levels in both the ventral and dorsal medial prefrontal cortices. In contrast, cocaine significantly increased dialysate dopamine in the shell of the nucleus accumbens, whereas only a slight increase in dopamine was observed in the core subregion of the nucleus accumbens. A significant negative relationship between dopamine levels in the ventral and dorsal medial prefrontal cortices and dialysate dopamine concentrations in the shell and core of the nucleus accumbens was observed. Finally, in both the ventral and dorsal medial prefrontal cortices, the magnitude of the locomotor response to cocaine was inversely related to dialysate dopamine levels. In contrast, the magnitude of the locomotor response to cocaine became progressively larger as dopamine levels increased in the shell of the nucleus accumbens. These results show a dissociation in the pattern of dopamine release in subterritories of both the medial prefrontal cortex and nucleus accumbens in response to the acute systemic administration of cocaine.