XXXX D2-Like Receptors and Behavioral Economics of Food Reinforcement.

@entity935 @entity19 @entity53612
UNASSIGNED: Previous studies suggest @entity935 (DA) D2-like receptor involvement in the reinforcing effects of food. To determine contributions of the three D2-like receptor subtypes, knockout (KO) @entity19 completely lacking DA D2, D3, or D4 receptors (D2R, @entity53612 , or D4R KO @entity19 ) and their wild-type (WT) littermates were exposed to a series of fixed-ratio (FR) food-reinforcement schedules in two contexts: an open economy with additional food provided outside the experimental setting and a closed economy with all food earned within the experimental setting. A behavioral economic model was used to quantify reinforcer effectiveness with food pellets obtained as a function of price (FR schedule value) plotted to assess elasticity of demand. Under both economies, as price increased, food pellets obtained decreased more rapidly (ie, food demand was more elastic) in DA D2R KO @entity19 compared with WT littermates. Extinction of responding was studied in two contexts: by eliminating food deliveries and by delivering food independently of responding. A hyperbolic model quantified rates of extinction. Extinction in DA D2R KO @entity19 occurred less rapidly compared with WT @entity19 in both contexts. Elasticity of food demand was higher in DA D4R KO than WT @entity19 in the open, but not closed, economy. Extinction of responding in DA D4R KO @entity19 was not different from that in WT littermates in either context. No differences in elasticity of food demand or extinction rate were obtained in D3R KO @entity19 and WT littermates. These results indicate that the D2R is the primary DA D2-like receptor subtype mediating the reinforcing effectiveness of food.Neuropsychopharmacology advance online publication, 19 August 2015; doi:10.1038/npp.2015.223.
