Staphylococcal enterotoxin B induces fever, brain c-Fos expression, and serum corticosterone in rats

The paraventricular nucleus of the hypothalamus (PVH) occupies a pivotal po int within the network of brain nuclei coordinating critical host-defense r esponses. In mice, T cell-dependent immune stimuli, including the bacterial superantigen staphylococcal enterotoxin B (SEB), can activate the PVH. To determine whether T cell-dependent immune stimuli activate the PVH in rats, we assessed plasma corticosterone (Cort) levels, fever responses, and c-Fo s expression in the PVH in animals treated with intraperitoneal injections of SEB. In animals with previously implanted abdominal thermisters, intrape ritoneal injection of 1 mg/kg SEB resulted in a significant rise in body te mperature, with a latency of 3.5-4 h. In separate animals, intraperitoneal injection of 1 mg/kg SEB resulted in a significant elevation of plasma Cort and induced c-Fos expression in parvocellular neurons within the PVH. Thes e results support the idea that T cell-dependent immune stimuli activate br ain pathways mediating host-defense responses such as fever and neuroendocr ine changes.