Cytokine-induced activation of the neuroendocrine stress axis persists in endotoxin-tolerant mice.

Chronic administration of lipopolysaccharide (LPS) to mice markedly reduced activation of the neuroendocrine stress axis elicited by an acute challenge dose of LPS. LPS-induced elevation in norepinephrine turnover in the hypothalamus showed complete tolerance whereas elevation of plasma corticosterone showed only partial tolerance. Challenge-induced increased turnover of dopamine in hypothalamus persisted in LPS-tolerant animals. Neuroendocrine activation persisted following acute challenge with interleukin-1 and tumor necrosis factor following chronic LPS exposure.