Expression of NADPH-diaphorase in nucleus tractus solitarius after peripheral injection of E. coli endotoxin in rats

The possibility that peripheral exogenous pyrogens can activate brainstem nuclei by abdominal viscera aAerents was studied using the NADPH-diaphorase method in E. coli lipopolysaccharide treated rats with and without ibu- profen pre-treatment. 2. NADPH-d staining revealed: (i) a significant increase in the number of NADPH-d labeled neurons in the subpos- tremal area of the nucleus tractus solitarius lipopolysaccharide treated rats compared with control animals (p < 0.05), and (ii) an almost similar number of NADPH-d positive neurons in both control and ibuprofen pre- treated rats (p = 0.091). 3. These data indicate that peripheral administration of an exogenous pyrogen stimulates the synthesis of nitric oxide in the nucleus tractus solitarius, and are consistent with the hypothesis of a direct neural link between the periphery and the hypothalamus.