PERIPHERAL CATECHOLAMINES ARE INVOLVED IN THE NEUROENDOCRINE AND IMMUNE EFFECTS OF LPS

There is evidence for bidirectional communication between the brain an d the immune system. The immune system is subjected to neuroendocrine influences and reciprocally the hypothalamo-pituitary-adrenal axis is modulated by immune signals. Lipopolysaccharides (LPS), used to mimic infectious/inflammatory diseases, induce a series of stress markers, i ncluding modifications of monoaminergic transmission, enhancement of H PA axis activity, and decreased immune activity. In the present work w e investigated the participation of peripheral catecholamines in the i mmune and endocrine responses to LPS in vivo. We studied the effects o f LPS after chemical sympathectomy using 6-hydroxydopamine (6-OHDA), w hich does not cross the brain-blood barrier (BBB) in adults when perip herally injected. 6-OHDA administration was able to interfere with the effects of LPS on immune cells; however, the effects depended on the lymphoid tissue tested. In fact, the depression of mitogenesis induced by LPS was reversed by 6-OHDA in the spleen but not in the thymus. Mo reover, 6-OHDA also interfered with the endocrine modifications induce d by LPS. This neurotoxin completely or partially inhibited the effect of LPS on ACTH and corticosterone secretion, respectively. Taken toge ther, these results clearly demonstrate that in vivo, the peripheral s ympathetic nervous system participates in the immune and endocrine eff ects of LPS. (C) 1995 Academic Press, Inc.