Melatonin modulates mesenteric blood flow and TNF alpha concentrations after lipopolysaccharide challenge

Objective: To investigate the effect of various doses of melatonin on reduc tion in mesenteric blood flow (MBF) and increase in tumour necrosis factor alpha (TNF alpha) concentration caused by injection of lipopolysaccharide ( LPS). Design: University Hospital, Turkey. Setting: Open experimental study. Animals: 59 Swiss albino mice. Interventions: Animals were injected with melatonin solvent or 1, 10, 100, or 500 mg/kg melatonin. Ten minutes later control animals were injected wit h saline, and the experimental group with LPS. Main outcome measures: Mesenteric blood flow and serum TNF alpha concentrat ion. Results: In control animals, 100 and 500 mg/kg melatonin reduced MBF. LPS r educed MBF in solvent, I, and 10 mg/kg melatonin groups. The concentration of TNF alpha was considerably increased in the mice given LPS. Melatonin re duced this response significantly. Conclusion: In high doses melatonin directly reduces MBF. It has no protect ive effect on the LPS-induced decrease in MBF. In lower doses it blocks, bu t at higher doses reduces, LPS-induced TNF alpha production.