title: Individual effects of estradiol and progesterone on food intake and body weight in ovariectomized binge rats.
abstract: The individual roles of estradiol (E) and progesterone (P) in the control of food intake and body weight in ovariectomized (OVX) rats were investigated. Six groups of OVX Sprague-Dawley rats (n=9/group) were assigned to one of three 4-day cyclic hormone treatments: two groups were treated with E benzoate; two groups were treated with P; two groups were treated with both (EP). All rats had continuous access to chow and water throughout this 4-week study. One group of rats within each hormone treatment condition was fed chow ad libitum, and the second was subjected to a binge schedule: chow ad libitum plus 1-h access to an optional fat source on Monday, Wednesday, and Friday. A seventh OVX group (n=8) received the oil vehicle and chow. This group was included to monitor body weight and to verify hormone efficacy. The main findings were: (1) relative to rats receiving only P, E alone or EP attenuated 24-h chow intake tonically and cyclically, i.e. intake on Day 4, which models estrus, was lower in E and EP than in P, and also was lower than intake on Day 2, which models diestrus. In contrast, (2) neither E nor EP detectably affected optional fat intake during the 1-h fat access period relative to rats receiving only P when data were collapsed across the entire study. However, (3) E and EP had large effects on fat intake relative to P during the 1-h fat access period at the start of the study, but not at the end, when bingeing was fully established. (4) E and EP led to lower and apparently normal levels of body weight compared to rats receiving only the oil vehicle or only P. These results indicate that (1) administration of E alone has similar effects as co-administration of E and P on feeding and body weight in rats bingeing on fat, (2) with or without P, the inhibitory effects of E on meal size are compromised when bingeing on fat, and (3) the effects of E on binge size change dynamically as bingeing develops.
authors.affiliation: Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA 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; D001835:Body Weight / Q000187:drug effects*; D004338:Drug Combinations; D004435:Eating / Q000187:drug effects*; D004958:Estradiol / Q000494:pharmacology*; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D010052:Ovariectomy; D011374:Progesterone / Q000494:pharmacology*; D011372:Progestins / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D004338:Drug Combinations; D004967:Estrogens; D011372:Progestins; D011374:Progesterone; D004958:Estradiol