Striatal Dopamine D2/ D3 Receptors Mediate Response Inhibition and Related Activity in Frontostriatal Neural Circuitry in Humans

Impulsive behavior is thought to reflect a traitlike characteristic that can have broad consequences for an individual's success and well-being, but its neurobiological basis remains elusive. Although striatal dopamine D-2-like receptors have been linked with impulsive behavior and behavioral inhibition in rodents, a role for D-2-like receptor function in frontostriatal circuits mediating inhibitory control in humans has not been shown. We investigated this role in a study of healthy research participants who underwent positron emission tomography with the D-2/D-3 dopamine receptor ligand [ F-18] fallypride and BOLD fMRI while they performed the Stop-signal Task, a test of response inhibition. Striatal dopamine D-2/D-3 receptor availability was negatively correlated with speed of response inhibition (stopsignal reaction time) and positively correlated with inhibition-related fMRI activation in frontostriatal neural circuitry. Correlations involving D-2/D-3 receptor availability were strongest in the dorsal regions (caudate and putamen) of the striatum, consistent with findings of animal studies relating dopamine receptors and response inhibition. The results suggest that striatal D-2-like receptor function in humans plays a major role in the neural circuitry that mediates behavioral control, an ability that is essential for adaptive responding and is compromised in a variety of common neuropsychiatric disorders.