Inhibitory effects of oxytocin on the inflammatory parameters and vascular endothelial growth factor (VEGF) in the rat air pouch model of inflammation

Introduction: The aim of the present study was to evaluate the effect of oxytocin on the angiogenesis and inflammatory parameters in air pouch model of inflammation. Methods: Inflammation was induced by injection of carrageenan into pouches in male Wistar rats. Oxytocin (4.25, 8.5 and 17 µg) was administered intra pouch at the same time as the carrageenan and then for 2 consecutive days. After 72 h, the pouches fluid was collected to determine exudates volume, interleukin 1-beta (IL-1B) and vascular endothelial growth factor (VEGF) concentrations. Then, the pouches were dissected out, weighed and the hemoglobin concentration was assessed. Results: All three doses of oxytocin (4.25, 8.5 and 17 µg) significantly decreased volume of exudates (P < 0.05, P < 0.01 and P < 0.001, respectively) while leukocyte accumulation in the pouch fluid was diminished by 8.5 and 17 µg oxytocin. The granulation tissue weight was also markedly reduced in comparison with the control group. A significant reduction in the angiogenesis rate in oxytocin-treated rats by all doses was seen. Interestingly, there was no significant difference between the effect of oxytocin and diclofenac on the inhibition of angiogenesis, VEGF concentration and inflammatory parameters except leukocyte accumulation. In addition, administration of oxytocin (17 µg/pouch) significantly decreased IL-1B level (47%) compared to the control group (P < 0.05). Conclusion: Oxytocin has an anti-inflammatory effect and inhibits cell influx and exudation to the site of the inflammatory response. The anti-angiogenesis effect of oxytocin may be related to the local inhibition of VEGF levels as similarly shown by diclofenac.