title: Chronic morphine treatment exaggerates the suppressive effects of sucrose and cocaine, but not lithium chloride, on saccharin intake in Sprague-Dawley rats.
abstract: Three experiments examined the effect of chronic morphine treatment on cocaine-, sucrose-, and lithium chloride (LiCl)-induced suppression of saccharin intake in Sprague-Dawley rats. All rats were either water- or food-deprived and then implanted subcutaneously with 1 morphine (75 mg) or vehicle pellet for 5 days. They were then given brief access to 0.15% saccharin and soon thereafter injected with either cocaine (10 mg/kg s.c.), LiCl (0.009 M, 1.33 ml/100 g body weight i.p.), or saline, or, in Experiment 2, given a 2nd access period to either a preferred 1.0 M sucrose solution or the same 0.15% saccharin solution. There was 1 taste-drug or taste-taste pairing per day for a number of days. The results showed that a history of chronic morphine treatment exaggerated the suppressive effects of a rewarding sucrose solution and cocaine but not those of the aversive agent, LiCl. These data provide further support for the reward comparison hypothesis.
authors.affiliation: Department of Behavioral Science, Pennsylvania State University College of Medicine, Hershey 17033, USA. psg6@psu.edu
authors.forename: P S
authors.initials: PS
authors.lastname: Grigson
authors.forename: R A
authors.initials: RA
authors.lastname: Wheeler
authors.forename: D S
authors.initials: DS
authors.lastname: Wheeler
authors.forename: S M
authors.initials: SM
authors.lastname: Ballard
mesh_terms: D000818:Animals; D001245:Association Learning / Q000187:drug effects; D003042:Cocaine / Q000494:pharmacology*; D003214:Conditioning, Classical / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004326:Drinking / Q000187:drug effects*; D018021:Lithium Chloride / Q000494:pharmacology*; D008297:Male; D009021:Morphine Dependence / Q000523:psychology*; D009042:Motivation; D009714:Nucleus Accumbens / Q000187:drug effects / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D012439:Saccharin; D013395:Sucrose / Q000494:pharmacology*; D013649:Taste / Q000187:drug effects*; D013681:Tegmentum Mesencephali / Q000187:drug effects / Q000503:physiopathology
chemical_list: D013395:Sucrose; D012439:Saccharin; D018021:Lithium Chloride; D003042:Cocaine