Mesolimbic dopamine involvement in Pavlovian and operant approach behaviors.

摘要

Previous research has yielded conflicting results regarding the involvement of mesolimbic dopamine in Pavlovian and operant tasks. While there is abundant evidence that an operant lever press requires intact dopamine (DA) D1 transmission in the nucleus accumbens (ACB) and in the basolateral amygdala (BLA), there is conflicting evidence regarding the specific brain sites at which DA mediates a Pavlovian approach response. The present study was designed to compare the effects of ACB and BLA D1 receptor-blockade on an operant and Pavlovian task, while minimizing differences in behavioral response topography. Animals were trained on either a Pavlovian cued approach task or an operant cued nosepoke task. In the Pavlovian approach task, a tone signaled a pellet delivery to which animals responded with a head entry into a food compartment. In the operant nosepoke task, animals were trained to emit a nosepoke in response to the same tone, in order to trigger a pellet delivery. Bilateral microinfusions of the D1 antagonist SCH 23390 (0, 1 or 2 mug/side) into either the ACB or the BLA produced a dose-dependent disruption of the operant nosepoke. In contrast, the Pavlovian cued approach response was unaffected by D1 antagonist microinfusions into either the ACB or the BLA. In addition, infusion of SCH 23390 into either site suppressed general locomotion. The results suggest a dissociation of the anatomical substrates mediating an operant nosepoke and a Pavlovian approach, despite similar response topographies. These findings are consistent with the notion that D1 activity at the ACB and BLA plays a role in the expression of operant responses, but not in the expression of Pavlovian approach responses.