Ventral Striatal D(2/3) Receptor Availability Is Associated with Impulsive Choice Behavior As Well As Limbic Corticostriatal Connectivity

BACKGROUND: 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. METHODS: 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 [(18)F]fallypride positron emission tomography and ex vivo [(3)H]raclopride autoradiography. Resting-state functional connectivity in limbic corticostriatal networks was also assessed using fMRI. RESULTS: 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. CONCLUSIONS: 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.