Figure 1.

Hedonic hotspots in nucleus accumbens (NAc) and ventral pallidum (VP). Top: Sagittal views of NAc medial shell showing functional maps of opioid-stimulated hedonic enhancements, as measured by taste reactivity to sucrose. Microinjections that stimulated mu (left), delta (middle) or kappa (right) opioid receptors in the rostrodorsal quadrant of NAc medial shell increased hedonic “liking” reactions to sucrose, compared to vehicle baselines in the same rats. A single map showing shared opioid hotspot includes any site where agonist microinjection increased hedonic reactions by at least 250% compared to baseline (overlapping sites shown adjacently). Mu effects are depicted in red, delta in orange, and kappa in yellow (Modified from Castro and Berridge, 2014). Bottom: Horizontal maps of VP similarly show sites where mu opioid (left) or orexin stimulation increased hedonic reactions. A shared hedonic hotspot is revealed in posterior VP, where either mu opioid or orexin stimulation increased hedonic reactions by at least 150% compared to vehicle baseline in the same rats. Mu is colored red, and orexin is colored yellow (Modified from Ho and Berridge, 2013).