Prefrontal cortical–striatal dopamine receptor m RNA expression predicts distinct forms of impulsivity

Variation in dopamine receptor levels has been associated with different facets of impulsivity. To further delineate the neural substrates underlying impulsive action (inability to withhold a prepotent motor response) and impulsive choice (delay aversion), we characterised rats in the D ifferential R einforcement of L ow R ates of R esponding task and a delay discounting task. We also measured performance on an effort‐based discounting task. We then assessed D 1 and D 2 dopamine receptor m RNA expression in subregions of the prefrontal cortex and nucleus accumbens using in situ hybridisation, and compared these data with behavioral performance. Expression of D 1 and D 2 receptor m RNA in distinct brain regions was predictive of impulsive action. A dissociation within the nucleus accumbens was observed between subregions and receptor subtypes; higher D 1 m RNA expression in the shell predicted greater impulsive action, whereas lower D 2 m RNA expression in the core predicted greater impulsive action. We also observed a negative correlation between impulsive action and D 2 m RNA expression in the prelimbic cortex. Interestingly, a similar relationship was present between impulsive choice and prelimbic cortex D 2 m RNA , despite the fact that behavioral indices of impulsive action and impulsive choice were uncorrelated. Finally, we found that both high D 1 m RNA expression in the insular cortex and low D 2 m RNA expression in the infralimbic cortex were associated with willingness to exert effort for rewards. Notably, dopamine receptor m RNA in these regions was not associated with either facet of impulsivity. The data presented here provide novel molecular and neuroanatomical distinctions between different forms of impulsivity, as well as effort‐based decision‐making.