Objective        To observe the effect of antenatal dexamethasone (DEX) treatment on expression of toll-like receptor 4 (TLR4) in neonatal rats with necrotizing enterocolitis (NEC)

and to explore its protective effect and potential mechanisms.       Methods        Twelve pregnant Sprague-Dawley (SD) rats were randomly divided into three groups with 4 rats in each group

including a normal control group (NC group)

a DEX group and a normal saline group (NS group). On the gestational days 16

17 and 18

rats of the DEX group and the NS group were intramuscularly injected with DEX [0.5 mg/(kg·d)] and normal saline (0.3 ml/d)

respectively. All rats of the three groups were delivered spontaneously (term=22 d). Neonatal rats of the DEX group and NS group (except NC group) were selected to establish NEC models by artificial feeding

cold exposure after hypoxic-reoxygenation and LPS intragastric administration. General conditions of neonatal rats were observed in each group. All the neonatal rats were sacrificed on the 5th day after birth and proximal intestine tissues of rat ileocecal junction were obtained. Pathological changes of the tissues were examined by pathological sectioning and hematoxylin and eosin (HE) staining

and protein expression of TLR4 was detected by immunohistochemical method. Total RNA was extracted from the rest of intestinal tissues

and mRNA expression of TLR4 was detected by Quantitative Real-time PCR (Q-PCR).       Results         Incidence of NEC in the DEX group was lower than that in the NS group. Typical NEC symptoms were observed in rats of the NS group but not the NC group

while the symptoms were later and milder in rats of the DEX group. Histopathologic scores and TLR4 expressions of the DEX and NS groups were significantly higher than those of the NC group (P0.05)

and the two indicators of the DEX group were significantly lower than those of the NS group (P0.05).       Conclusion        Antenatal DEX has a protective effect on rat model of NEC probably by downregulating TLR4 expression to exert an anti-inflammatory effect.