Catecholamine receptors differentially mediate impulsive choice in the medial prefrontal and orbitofrontal cortex

Impulsivity is characteristic of several mental health disorders and is largely mediated by the prefrontal cortex subregions: the medial prefrontal cortex (mPFC) and the orbitofrontal cortex (OFC). Dopamine (DA) and norepinephrine (NE) are known to modulate activity of the prefrontal cortex, however their direct role in impulsive choice is not known. The aim of the present study was to investigate the effect of microinjecting DA or NE compounds in the mPFC or OFC on impulsive choice as measured by a delayed reinforcement (DR) task in male Wistar Kyoto rats. Following training in the DR task, rats were pretreated with DA D(1) and D(2) receptor antagonists (SCH23390 3 μg/side, raclopride 3 or 6 μg/side) or NE α(1) and α(2) receptor agonists (phenylephrine 0.1 or 0.3 μg/side, guanfacine 1 or 3 μg/side, respectively) into the mPFC or OFC and the effect on impulsive behavior was assessed. Pretreatment with raclopride into the mPFC or OFC significantly increased impulsive choice, however only pretreatment with SCH23390 into the mPFC, and not the OFC, significantly increased impulsive choice. Pretreatment with the NE receptor agonists had no effect on impulsive choice. This study suggests that DA receptors, but not NE receptors, differentially mediate impulsive choice in sub-regions of the prefrontal cortex.