Orexin or Acetylcholine Mediated Augmentation of "Liking" versus "Wanting" in the Nucleus Accumbens Hotspot
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The rostrodorsal quadrant of nucleus accumbens medial shell has been shown to contain a pleasure generating hedonic hotspot. Orexin, a neurotransmitter that is projected into the accumbens by the lateral hypothalamus, has been shown to increase liking and eating behavior when injected into caudal ventral pallidum, another region in which the hedonic component of food can be manipulated. In this study, we show that targeted microinjections into the NAc hotspot of orexin, but not scopolamine, can alter affective oro facial reactions of 'liking' reactions elicited by sucrose. Conversely, scopolamine, but not orexin, can robustly change food intake behaviors in the same location. The mapped sites suggest that orexin-induced increases in sucrose hedonic impact do overlap with the opioid-induced increases, thus the orexin hotspot and the opioid hotspot in the medial accumbens shell are likely anatomically the same or very similar. We also show that disparate neurochemical systems can mediate hedonic versus motivated behavior.