354 Brain Research, 624 (1993) 354-35(> © 1993 Elsevier Science Publishers B.V. All rights reserved 0006-8993/93/$06.00 BRES 25859 Antagonism of estrogenic effects on feeding behavior by central implants of anisomycin Peter C. Butera *, Robert B. Campbell 1, Dawn M. Bradway 2 Department of Psychology, PO Box 2208, Niagara University, Niagara, NY 14109, USA (Accepted 6 July 1993) Key words: Estradiol; Anisomycin;Paraventricular nucleus; Protein synthesis; Food intake; Bodyweight; Lordosis The followingexperiment determined whether the estrogenic suppression of food intake is dependent upon changes in protein synthesis within neurons of the paraventricular nucleus of the hypothalamus(PVN). Ovariectomized rats were treated centrally with anisomycin-filledor empty (control) cannulae in the PVN. Females were injected with either 2.0 ~zg of estradiol benzoate (EB) or the oil vehicle and the inner cannulae were removed 2 h later. EB injections significantly lowered food and water intake in the central control group but not in animals given PVN implants of anisomycin. Body weight gain decreased for all females. EB induced comparable levels of female sexual behavior in both groups, demonstrating that anisomycin implants did not affect the ability of estradiol to stimulate lordosis. These findings indicate that the effects of estradiol on food intake require the activation of protein synthesis in estrogen-sensitive PVN neurons. In addition to their effects on reproductive physiol- ogy and behavior, ovarian hormones affect food intake, body weight, and other regulatory processes involved in energy balance (see ref. 12 for a review). Although the biochemical mechanism is unknown, it appears that steroidal actions within the paraventricular nucleus of the hypothalamus (PVN) mediate the effects of estra- diol on food intake 1'2'3'7. In contrast, the biochemical and cellular events that underlie the activation of lordosis by ovarian steroids are clearer. One important finding is that the effects of estradiol on sexual behavior are mediated by its actions on the genome. Studies have shown that RNA or protein synthesis inhibitors applied to the ventromedial nucleus of the hypothalamus (VMN) diminish lordosis produced by injections of estradiol and progester- one 6'9'1° (see ref. 6 for a review). The present study was conducted to determine whether a comparable mechanism produces estrogenic effects on feeding behavior. Specifically, it was hypoth- esized that PVN implants of anisomycin will attenuate the effects of estradiol on feeding behavior but not lordosis. The tests for sexual behavior allowed us to assess any general deficit in activity caused by the drug, and also served as a bioassay for the spread of protein synthesis inhibition to the VMN. Thirty-six adult, female rats (Long-Evans strain) obtained from Blue Spruce Breeding Farms (Altamont, NY) served as experimental subjects. All females were approximately 70 days of age and were housed individ- ually on a 12/12 h light/dark cycle (lights on between 07.00 and 19.00 h). All animals were ovariectomized and fitted with bilateral, stainless steel cannula using previously re- ported procedures 1. The coordinates used for the PVN implants were obtained from an atlas of the rat brain 8. Food cups and water bottles were filled daily at 10.00 h with powdered rat chow and tap water, weighed to the nearest tenth of a gram on an Ohaus electronic balance, and re-weighed 24 h later. All tests for female sexual behavior were conducted between 15.00 and 16.00 h. Lordosis quotients (number of lordoses/ * Corresponding author. Fax: (1) (716) 286-8581 I Robert Campbell is currently in the Department of Biophysicsat Roswell Park Memorial Institute, Buffalo, NY, USA. 2 Dawn Bradway is currently in the Biobehavioral Sciences Graduate Program at the University of Connecticut, Storrs, CT, USA.