Systemic endotoxin induces Fos-like immunoreactivity in rat spinal sympathetic regions

Immunocytochemical detection of Fos protein was used to evaluate the activation of neurons in sympathetic preganglionic regions of rat spinal cord after systemic treatment with endotoxin. Administration of relatively low doses of bacterial lipopolysaccharide (LPS) to conscious rats caused transient hypotension and stress hormone elevation. Three hours after LPS injection, Fos protein was detected in large numbers of neurons throughout the thoracic spinal cord. Fos-immunoreactive neurons were found in spinal cord segments T3-T13 in the four sympathetic preganglionic nuclei: the intermediolateral cell column (77.7%), the intercalated nucleus (10.6%), the central autonomic nucleus (10.1%) and the lateral funiculus (1.5%). These regions in control animals showed no Fos staining. We conclude that sublethal endotoxemia is a potent stimulus causing Fos expression in sympathetic preganglionic regions.