SYSTEMIC ENDOTOXIN INDUCES FOS-LIKE IMMUNOREACTIVITY IN RAT SPINAL SYMPATHETIC REGIONS

Immunocytochemical detection of Fos protein was used to evaluate the a ctivation of neurons in sympathetic preganglionic regions of rat spina l cord after systemic treatment with endotoxin. Administration of rela tively low doses of bacterial lipopolysaccharide (LPS) to conscious ra ts caused transient hypotension and stress hormone elevation. Three ho urs after LPS injection, Fos protein was detected in large numbers of neurons throughout the thoracic spinal cord. Fos-immunoreactive neuron s were found in spinal cord segments T3-T13 in the four sympathetic pr eganglionic nuclei: the intermediolateral cell column (77.7%), the int ercalated nucleus (10.6%), the central autonomic nucleus (10.1%) and t he lateral funiculus (1.5%). These regions in control animals showed n o Fos staining. We conclude that sublethal endotoxemia is a potent sti mulus causing Fos expression in sympathetic preganglionic regions.