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 pr elimbic/infralimbic cortices and shell subterritory of the nucleus accumben s as well as the dorsal prelimbic/anterior cingulate cortices and core subr egion 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 s hell counterpart. Cocaine produced a significant decrease in dopamine level s in both the ventral and dorsal medial prefrontal cortices. In contrast, c ocaine significantly increased dialysate dopamine in the shell of the nucle us accumbens, whereas only a slight increase in dopamine was observed in th e core subregion of the nucleus accumbens. A significant negative relations hip between dopamine levels in the ventral and dorsal medial prefrontal cor tices and dialysate dopamine concentrations in the shell and core of the nu cleus accumbens was observed. Finally, in both the ventral and dorsal media l prefrontal cortices, the magnitude of the locomotor response to cocaine w as inversely related to dialysate dopamine levels. In contrast, the magnitu de of the locomotor response to cocaine became progressively larger as dopa mine 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. (C) 1999 Elsevier Science B.V. A ll rights reserved.