Our voltammetric recordings also revealed increases in dopamine release in the shell prior to and following the response for cocaine. However shell increases in dopamine were of higher concentration, less synchronized to the response, and of longer duration than in the core. As noted above, a cause of this variation may be related to the existence of more potent dopamine uptake in the core than the shell allowing dopamine to diffuse further from its release site in the shell (Jones et al., 1996). Additionally, sub-region differences in release dynamics may be related to differences in afferent projections to the core and shell. For example, the medial shell of the NAc (where measurements were made here) receive dopamine inputs from more medial portions of the VTA, compared to the core where projections originate in the lateral VTA (Ikemoto, 2007). Moreover, intertwined within this dopamine projection system are highly complex neuroanatomical ‘loops’ involving distinct cortical and subcortical structures (Haber et al., 2000; Everitt et al., 2008), as well as direct connections between the core and shell (van Dongen et al., 2005). Indeed,
