title: Ovarian hormones inhibit fat intake under binge-type conditions in ovariectomized rats.
abstract: Binge eating is more common in females than in males. This study investigated the effects of ovarian hormones on binge-eating behavior in a diet-related rat model. Six groups of ovariectomized Sprague-Dawley rats were used (n=13/group). All rats had continuous access to chow and water throughout the study. One half of the rats were injected every fourth day with estradiol benzoate (2 microg/100 microl sesame oil) and progesterone (500 microg/100 microl sesame oil); the other half received only the sesame oil vehicle. Three feeding protocols were tested in each hormone injection condition: (1) chow only: no additional dietary fat access; (2) low-restriction: 1-h fat access every day; (3) high-restriction: 1-h fat access on Monday, Wednesday, and Friday. As previously reported in intact male and female rats, the high-restriction groups exhibited binge-like increases in 1-h energy intake during fat access. The major new finding of this study is that 1-h energy intake was tonically, but not cyclically, reduced in the hormone-treated high-restriction (binge) rats. Specifically, both low- and high-restriction hormone-treated rats consumed significantly less energy than did the oil-treated rats during the 1-h fat period (p<0.0001) and overall (p<0.0001), indicating a tonic inhibition of eating. However, food intake during the 1-h fat access period was also cyclically reduced in the hormone-treated low-restriction rats, but not in the hormone-treated high-restriction rats. These results indicate that the normal cyclic inhibitory influence of ovarian hormones on eating, but not their normal tonic inhibitory influence, is disrupted by conditions leading to binge-type eating.
authors.affiliation: Department of Nutritional Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Yu
authors.forename: Nori
authors.initials: N
authors.lastname: Geary
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Corwin
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D001823:Body Composition / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D002032:Bulimia / Q000188:drug therapy* / Q000503:physiopathology; D004041:Dietary Fats / Q000008:administration & dosage*; D004195:Disease Models, Animal; D004435:Eating / Q000187:drug effects*; D002149:Energy Intake / Q000187:drug effects; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives*; D005260:Female; D010052:Ovariectomy; D011374:Progesterone / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D004041:Dietary Fats; C074283:estradiol 3-benzoate; D011374:Progesterone; D004958:Estradiol