Dopamine likely exerts complex effects on waiting in the 5CSRTT. For example, within the medial prefrontal cortex, activation of D1-like receptors leads to reduced anticipatory responding;157 additionally, depletion of dopamine in the ventral striatum decreases, while systemic or local application of amphetamine increases, this behavior.158, 159 Heightened anticipatory responding has been associated with low dopamine content and reduced dopamine D2-like receptor availability in the ventral striatum.83, 160 Pharmacological manipulation of D2-like receptors affects this form of impulsivity and its modulation by amphetamine,159, 161 with baseline impulsivity affecting sensitivity to D2 manipulations.162 Moreover, the core and shell subregions of the nucleus accumbens may exert opposing influences on the relationship between dopamine D2-like receptors and premature responding, with D2-like receptor antagonism increasing and decreasing impulsivity in the shell and core, respectively.163
