| Abstract: | When rats are forced to drink a morphine solution as their only source of fluid, they eventually reverse their initial preference and drink more morphine than water in a 2-bottle preference test. Two experiments with 13 male Holtzman rats examined the cause of this shift in preference using the taste reactivity test, which involves the analysis of fixed action patterns elicited by taste solutions infused into Ss' mouths. Three morphine concentrations (0.03, 0.6, and 1.5 mg/ml) and 2 levels of motivation (drug-replete and drug-withdrawal states) were studied. A greater percentage of ingestive taste reactivity responses occurred to the oral morphine infusion in morphine-raised than in water-raised Ss. Data are inconsistent with the idea that enhanced morphine ingestion is caused by anticipation of positive consequences. Instead, they support the idea that rats come to "like" the flavor of the morphine solution; in other words, the palatability evaluation of the morphine changes, possibly through an association between the flavor and the hedonically positive effects of the morphine. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
