Opioid reward 'liking' and 'wanting' in the nucleus accumbens.

Whether we 'like' and 'want' stimuli depends partially on opioid neurotransmission within the nucleus accumbens. But how are 'liking' and 'wanting' organized within this neural substrate? Do 'liking' and 'wanting' originate from the same nucleus accumbens subregions? Or are there specific localized sites for opioid enhancement of reward 'liking' and 'liking'? The present review aims to summarize recent advances in the identification of brain substrates for food 'liking' and 'wanting' with a focus on opioid hotspots in the nucleus accumbens. Our findings suggest that 'liking' and 'wanting' are anatomically dissociable: i) the nucleus accumbens contains a highly localized subregion corresponding to the rostro-dorsal quarter of the medial accumbens shell dedicated to hedonic processing; ii) by contrast, 'wanting' is widely distributed throughout the nucleus accumbens. As a specific mechanism of 'wanting', opioid neurotransmission within the nucleus accumbens might increase incentive salience attribution to conditioned cues that predict reward. These findings provide insight into the identity of the nucleus accumbens mechanism of 'liking' and 'wanting' and suggest that opioid circuits in much of the accumbens outside the 'liking' hotspot may stimulate food intake by a neurobehavioral mechanism that is separable from hedonic impact.