The effects of the dopamine D2/3 agonist quinpirole on incentive value and palatability-based choice in a rodent model of attention-deficit/hyperactivity disorder

Rationale Palatability and incentive value influence animal food choice. Dopamine D2/3 receptor signaling may mediate the effects of palatability and incentive value on choice. Dopamine signaling is disrupted in attention-deficit hyperactivity disorder (ADHD). Investigating behavioral choice processes under D2/3 receptor agonists will help elucidate behavioral and pharmacological correlates of ADHD. Objectives To determine (1) how changes in incentive value affects choice of actions for outcomes that differ in palatability; (2) the effects of the D2/3 agonist quinpirole on choice based on palatability and incentive value; (3) how choice differs in spontaneously hypertensive rats (SHR; ADHD model) compared with control strains. Methods Rats responded instrumentally for two food outcomes (chocolate and grain pellets) that differed in palatability. Following specific satiety of one outcome, rats underwent a choice test. Prior to the choice test, rats were given intra-peritoneal quinpirole (0.01–0.1 mg/kg) body weight. These manipulations were conducted in three strains of rats: SHR rats; the normotensive Wistar-Kyoto (WKY) controls; and Wistar outbred (WIS) controls. Results All rat strains responded more vigorously for chocolate pellets compared with grain pellets. Quinpirole reduced the effects of palatability and dose-dependently increased the effects of incentive value on choice. SHR rats were the least influenced by incentive value, whereas WKY rats were the least influenced by palatability. Conclusions These results show that D2/3 signaling modulates choice based on palatability and incentive value. Disruption of this process in SHR rats may mirror motivational impairments observed in ADHD.