title: Endocannabinoid hedonic hotspot for sensory pleasure: anandamide in nucleus accumbens shell enhances 'liking' of a sweet reward.
abstract: Cannabinoid drugs such as Delta9-THC are euphoric and rewarding, and also stimulate food intake in humans and animals. Little is known about how naturally occurring endogenous brain cannabinoids mediate pleasure from food or other natural sensory rewards. The taste reactivity paradigm measures effects of brain manipulations on affective orofacial reactions to intraorally administered pleasant and unpleasant tastes. Here we tested if anandamide microinjection into medial nucleus accumbens shell enhances these affective reactions to sweet and bitter tastes in rats. Anandamide doubled the number of positive 'liking' reactions elicited by intraoral sucrose, without altering negative 'disliking' reactions to bitter quinine. Anandamide microinjections produced Fos plumes of approximately 0.02-1 mm3 volume. Plume-based maps, integrated with behavioral data, identified the medial shell of accumbens as the anatomical hotspot responsible for hedonic amplification. Anandamide produced especially intense hedonic enhancement in a roughly 1.6 mm3 'hedonic hotspot' in dorsal medial shell, where anandamide also stimulated eating behavior. These results demonstrate that endocannabinoid signals within medial accumbens shell specifically amplify the positive hedonic impact of a natural reward (though identification of the receptor specificity of this effect will require future studies). Identification of an endocannabinoid hotspot for sensory pleasure gives insight into brain mechanisms of natural reward, and may be relevant to understanding the neural effects of cannabinoid drugs of abuse and therapeutic agents.
authors.affiliation: Department of Psychology, The University of Michigan, Ann Arbor, MI 48109, USA. svmahler@umich.edu
authors.forename: Stephen V
authors.initials: SV
authors.lastname: Mahler
authors.forename: Kyle S
authors.initials: KS
authors.lastname: Smith
authors.forename: Kent C
authors.initials: KC
authors.lastname: Berridge
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D063385:Cannabinoid Receptor Modulators / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D063388:Endocannabinoids; D005247:Feeding Behavior / Q000187:drug effects; D005518:Food Preferences / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects; D008297:Male; D008845:Microinjections / Q000379:methods; D009714:Nucleus Accumbens / Q000187:drug effects*; D016761:Oncogene Proteins v-fos / Q000378:metabolism; D053284:Polyunsaturated Alkamides / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D012201:Reward; D013395:Sucrose / Q000008:administration & dosage; D013549:Sweetening Agents / Q000008:administration & dosage; D013649:Taste / Q000187:drug effects* / Q000502:physiology
chemical_list: D001095:Arachidonic Acids; D063385:Cannabinoid Receptor Modulators; D063388:Endocannabinoids; D016761:Oncogene Proteins v-fos; D053284:Polyunsaturated Alkamides; D013549:Sweetening Agents; D013395:Sucrose; C078814:anandamide