Role of Central Amygdala Opioids in Incentive Motivation: TranslatingLearning into Focused and Amplified 'Wanting'.

[摘要] Wanting a reward like food is different from liking it, and the brain processes these sensations separately.Components of the limbic system mediate both, and here I examined how different neurochemical signals (opioids and cannabinoids) in particular limbic structures [central amygdala (CeA), basolateral amygdala (BLA), and nucleus accumbens (NAc)] process Pavlovian ;;wanting,’ and hedonic ;;liking.’Experiment 1 examined how CeA activation targets incentive motivational ;;wanting’ upon particular cues (e.g., an extending lever that signals sucrose reward delivery), to make them stronger ;;motivational magnets.’Microinjecting the drug DAMGO to stimulate µ opioid receptors in CeA of rats enhanced approach and food consummatory behaviors directed at cues. Experiment 2 examined how amygdala mediates cue-induced motivation to obtain rewards themselves (cue-triggered reward ;;wanting’).Opioid activation of CeA, but not BLA enhanced such cue-triggered motivation, integrating Pavlovian and instrumental learning to create sharper bursts of ;;wanting’ for the predicted reward. ;;Wanting’ is distinguishable from ;;liking,’ so Experiment 3 used taste reactivity procedures to examine if amygdala opioid stimulation also altered the hedonic impact of food when it is consumed.Strikingly, opioid stimulation reduced hedonic ;;liking’ reactions to sweetness, even when it enhanced food ;;wanting.’This points to a specialized role for amygdala opioids in enhancing reward ;;wanting’ focused by learning, but not hedonic ;;liking’ of the same reward. Experiment 3 raised the question of what brain substrates do enhance reward ;;liking’ (and made it important for me to show that I can identify ;;liking’ enhancement when it does occur using the present methodologies).The nucleus accumbens shell is known to process food ;;liking,’ and so in experiment 4, I found that microinjection of the endocannabinoid anandamide within the dorsomedial shell enhances hedonic ;;liking.’This is the first demonstration of a brain endocannabinoid ;;hotspot’ for stimulation of sensory pleasure. Altogether, these experiments demonstrated that amygdala opioids play a specialized role in amplifying and focusing ;;wanting’ based on prior learning, while nucleus accumbens endocannabinoids amplify hedonic ;;liking.’These findings expand our knowledge of how the limbic system produces distinct components of reward and motivation, and carries implications for understanding appetitive disorders including addiction and obesity.

[发布机构] University of Michigan

[效力级别] Incentive Salience

[关键词] Amygdala;Incentive Salience;Pavlovian Learning;Cannabinoid;Nucleus Accumbens;Reward;Neurosciences;Psychology;Health Sciences;Science;Social Sciences;Psychology