LESIONS OF HYPOTHALAMIC PARAVENTRICULAR NUCLEI DO NOT PREVENT THE EFFECT OF ESTRADIOL ON ENERGY AND FAT BALANCE

The chronic effects of estradiol (E(2)) on energy balance have been investigated in ovariectomized rats with hypothalamic paraventricular nuclei (PVH) lesions. Body weight and food intake were monitored throughout the E(2) treatment, which lasted 26 days. At the end of this treatment, rats were decapitated, and their carcasses were processed to determine the body contents in energy, fat, and protein. Plasma adrenocorticotropic hormone (ACTH) and corticosterone were determined by radioimmunoassay and protein-binding assay at the end of the study. Regardless of whether they were sham- or PVH-lesioned, E(2)-treated rats ate, expended, and gained significantly less energy than untreated animals. In addition, E(2)-treated rats deposited less fat and protein than the rats not receiving E(2). In contrast to the E(2) treatment, PVH lesions accelerated the gains in energy and fat regardless of whether the rats were treated with E(2) or with a placebo. There were no interaction effects of PVH lesions and the E(2) treatment on energy or fat gains. Plasma levels of corticosterone and ACTH were higher in E(2)-treated rats than in animals receiving the placebo treatment. The present results provide evidence that the hypothalamic PVH is not an essential neuroanatomical structure in the effects of E(2) on energy and fat balances.