In vivo evidence that arginine vasopressin is involved in the adrenocorticotropin response induced by interleukin-6 but not by tumor necrosis factor-alpha in the rat.

We examined whether arginine vasopressin (AVP) is involved in the adrenocorticotropin (ACTH) response induced by interleukin (IL)-6 or tumor necrosis factor (TNF)-alpha in the rat. To accomplish this, we employed immunoneutralization of brain AVP by injecting anti-AVP antiserum intracerebroventricularly (i.c.v., 3rd ventricle). For comparison, we also tested the effect of immunoneutralization of corticotropin-releasing hormone (CRH) in the brain. Anti-CRH antibody, anti-AVP antibody, or normal rabbit serum (control) was given i.c.v. 15 min before an i.c.v. administration of human recombinant IL-6 (100 ng) or TNF-alpha (100 ng). Both IL-6 and TNF-alpha significantly elevated plasma ACTH levels. The IL-6-induced ACTH response was significantly suppressed by both anti-CRH and anti-AVP antibodies. On the other hand, the TNF-alpha-induced ACTH response was not significantly affected by anti-AVP antibody, although anti-CRH antibody could suppress the response. These results suggest that the IL-6-induced ACTH response may be mediated by both CRH and AVP, whereas the ACTH response to TNF-alpha is only via CRH.