1 Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Austria; 2 Research Department, BRAHMS AG, Biotechnology Centre, Hennigsdorf, Germany; and 3 Department of Dermatology, University Hospital Münster, Münster, Germany Submitted 3 March 2008 ; accepted in final form 26 June 2008 Oxytocin is a hormone and neurotransmitter found to have anti-inflammatory functions in rodents. Here we used experimental bacterial endotoxinemia to examine the role of exogenous oxytocin administration on innate immune responses in humans. Ten healthy men received, in a randomized, placebo-controlled, crossover design, placebo, oxytocin, LPS, and LPS + oxytocin. Oxytocin treatment resulted in a transient or prolonged reduction of endotoxin-induced increases in plasma ACTH, cortisol, procalcitonin, TNF- , IL-1 receptor antagonist, IL-4, IL-6, macrophage inflammatory protein-1 , macrophage inflammatory protein-1β, monocyte chemoattractant protein-1 (MCP-1), interferon-inducible protein 10, and VEGF. In vitro, oxytocin had no impact on LPS effects in releasing TNF- , IL-6, and MCP-1 in monocytes and peripheral blood mononuclear cells from healthy human donors. In summary, oxytocin decreases the neuroendocrine and cytokine activation caused by bacterial endotoxin in men, possibly due to the pharmacological modulation of the cholinergic anti-inflammatory pathway. Oxytocin might be a candidate for the therapy of inflammatory diseases and conditions associated with high cytokine and VEGF levels. neuroendocrinology; hypothalamic-pituitary-adrenal; cytokines Address for reprint requests and other correspondence: M. Clodi, Dept. of Medicine III, Medical Univ. of Vienna, Waehringer Guertel 18-20, A-1090, Vienna, Austria (e-mail: martin.clodi{at}meduniwien.ac.at )