There are many animal models for studying different aspects of neurodegeneration. Lipopolysaccharide (LPS) injected in rats intracerebroventricularly induces neuroinflammation quite similar to the inflammatory component of chronic neurodegenerative conditions such as Alzheimer's disease. We used this model to examine the effect of estradiol on neuroinflammation. LPS or pyrogen-free saline were injected intracerebroventricularly (i.c.v.) into the lateral ventricle of male Wistar rats and estradiol was administered (200 micrograms/kg s.c.) 48 h before or 24 h after LPS injection. LPS-induced body weight loss was partially postponed by the treatment, especially in the rats pretreated with estradiol. When analyzing GFAP glial cell morphology in the CA3c area of the hippocampus and corpus callosum, as well as the number of astroglial cells in CA3c and CA1, GFAP expression was found to be reduced. This was true especially in the animals pretreated with estradiol and to a much lesser extent in the posttreated ones. The data support the possible existence of a neuroimmunomodulatory effect of estradiol administration in neurodegenerative conditions, which influences the inflammatory component.