title: CCK-8 and CCK-58 differ in their effects on nocturnal solid meal pattern in undisturbed rats.
abstract: Various molecular forms of CCK reduce food intake in rats. Although CCK-8 is the most studied form, we reported that CCK-58 is the only detectable endocrine peptide form in rats. We investigated the dark-phase rat chow intake pattern following injection of CCK-8 and CCK-58. Ad libitum-fed male Sprague-Dawley rats were intraperitoneally injected with CCK-8, CCK-58 (0.6, 1.8, and 5.2 nmol/kg), or vehicle. Food intake pattern was assessed during the dark phase using an automated weighing system that allowed continuous undisturbed monitoring of physiological eating behavior. Both CCK-8 and CCK-58 dose dependently reduced 1-h, dark-phase food intake, with an equimolar dose of 1.8 nmol being similarly effective (-49% and -44%). CCK-58 increased the latency to the first meal, whereas CCK-8 did not. The intermeal interval was reduced after CCK-8 (1.8 nmol/kg, -41%) but not after CCK-58. At this dose, CCK-8 increased the satiety ratio by 80% and CCK-58 by 160%, respectively, compared with vehicle. When behavior was assessed manually, CCK-8 reduced locomotor activity (-31%), whereas grooming behavior was increased (+59%). CCK-58 affected neither grooming nor locomotor activity. In conclusion, reduction of food intake by CCK-8 and CCK-58 is achieved by differential modulation of food intake microstructure and behavior. These data highlight the importance of studying the molecular forms of peptides that exist in vivo in tissue and circulation of the animal being studied.
authors.affiliation: CURE: Digestive Diseases Research Center, Digestive Diseases Division, Department of Medicine, University of California, Los Angeles 90073, USA.
authors.forename: Miriam
authors.initials: M
authors.lastname: Goebel-Stengel
authors.forename: Andreas
authors.initials: A
authors.lastname: Stengel
authors.forename: Lixin
authors.initials: L
authors.lastname: Wang
authors.forename: Gordon
authors.initials: G
authors.lastname: Ohning
authors.forename: Yvette
authors.initials: Y
authors.lastname: Taché
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Reeve
mesh_terms: D000818:Animals; D002766:Cholecystokinin / Q000008:administration & dosage*; D002940:Circadian Rhythm / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects*; D005247:Feeding Behavior / Q000187:drug effects*; D006120:Grooming / Q000187:drug effects; D007274:Injections, Intraperitoneal; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D017440:Photoperiod; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D012528:Satiety Response / Q000187:drug effects; D012844:Sincalide / Q000008:administration & dosage*; D013997:Time Factors
chemical_list: C038823:cholecystokinin 58; D002766:Cholecystokinin; D012844:Sincalide