Shifting motivational states: The effects of nucleus accumbens dopamine and opioid receptor activation on a modified effort-based choice task

Stimulation of nucleus accumbens 5-HT6 receptors increases both appetitive and consummatory motivation in an effort-based choice task

“…Furthermore, this pattern of findings in the effort-based choice task suggests differential impacts on effort-based choice performance across different receptor types within the NAc. For instance, stimulation of mu-opioid receptors in the NAc core also increases progressive ratio performance and food intake when tested separately [19,20], but when both are tested in the same task, mu-opioid receptor stimulation shifts food-motivated behavior towards consumption of the rat chow and inhibits the effort expended to earn the sugar reward [13]. In contrast, dopamine receptor manipulations reduced appetitive motivation without affecting consumption of the pabulum diet.…”

“…Behavioral training involved acclimating the rats to a progressive ratio 2 (PR-2) operant task through successive approximations [13]. Briefly, operant training proceeded for three daily sessions each on FR-1, FR-3, and FR-5 schedules of reinforcement.…”

“…gives rats the option to lever press for a preferred food (sugar pellets) at the same time as a pabulum diet (standard rat chow) is available for free consumption. Dopamine receptor manipulations tend to impact appetitive motivation (as measured by progressive ratio breakpoint for earning sugar), while mu-opioid receptor stimulation shifts behavior away from food-seeking and towards increased consumption of the rat chow [13]. Much less is known about how individual serotonin receptors may similarly primarily impact appetitive versus consummatory processes within the NAc.…”

“…In our prior experiments, rats were tested separately under conditions of free-feeding or during effortful response to receiving food. We have recently utilized an effort-based choice task to demonstrate differential effects of dopamine and opioid receptor manipulations within the NAc on appetitive and consummatory aspects of motivation [13]. This task, adapted from Randall et al [14].…”

Intra-NAc insulin reduces the motivation for food and food intake without altering cue-triggered food-seeking

“…For example, reducing activity in the NAc shell, [ 7 , 36 , 44 , 53 , 59 ] increases food intake, whereas reducing activity in the NAc core attenuates cue- or sugar-primed food-seeking [ 3 , 25 , 40 ]. Furthermore, increasing dopamine activity within the NAc core selectively enhances the motivation to work for food [ 11 , 38 ] while actions of dopamine in the shell increase food intake [ 31 ]. Taken together, these data demonstrate the importance of the NAc in driving cue-induced food-seeking, the willingness to work for food, and food consumption.…”