Low dopamine D_2/3 receptor availability in the nucleus accumbens shell is associated with highly impulsive behavior in rats as measured by premature responses in a cued attentional task. However, it is unclear whether dopamine D_2/3 receptor availability in the nucleus accumbens is equally linked to intolerance for delayed rewards, a related form of impulsivity.

We investigated the relationship between D_2/3 receptor availability in the nucleus accumbens and impulsivity in a delay-discounting task where animals must choose between immediate, small-magnitude rewards and delayed, larger-magnitude rewards. Corticostriatal D_2/3 receptor availability was measured in rats stratified for high and low impulsivity using in vivo [¹⁸F]fallypride positron emission tomography and ex vivo [³H]raclopride autoradiography. Resting-state functional connectivity in limbic corticostriatal networks was also assessed using fMRI.

Delay-discounting task impulsivity was inversely related to D_2/3 receptor availability in the nucleus accumbens core but not the dorsal striatum, with higher D_2/3 binding in the nucleus accumbens shell of high-impulsive rats compared with low-impulsive rats. D_2/3 receptor availability was associated with stronger connectivity between the cingulate cortex and hippocampus of high- vs low-impulsive rats.

We conclude that delay-discounting task impulsivity is associated with low D_2/3 receptor binding in the nucleus accumbens core. Thus, two related forms of waiting impulsivity—premature responding and delay intolerance in a delay-of-reward task—implicate an involvement of D_2/3 receptor availability in the nucleus accumbens shell and core, respectively. This dissociation may be causal or consequential to enhanced functional connectivity of limbic brain circuitry and hold relevance for attention-deficit/hyperactivity disorder, drug addiction, and other psychiatric disorders.