Abstract: Three models of necrotizing enterocolitis ( NEC) in rats of different ages were
established to study the differences of brain injury. Method Sixty newborn SD rats were divided into 6
groups: 1-day-old control group, 1 day old model group, 3 day old control group, 3 day old model
group, 5 day old control group and 5 day old model group, with 10 rats in each group. NEC models were
established in all model groups by artificial feeding, hypoxia, cold stimulation and lipopolysaccharide
( LPS) induction. Rats in the control group were fed with breast milk in normal environment. During the
modeling period, the activity, abdominal distension and diarrhea of rats were observed, and the weight
changes were monitored. After the rats were killed, the overall morphology of intestinal tissue was observed. HE staining was used to observe the pathological changes of small intestine tissue, and the
injury score was performed. Nissl staining was used to observe the number of nissl bodies in brain tissue.
TUNEL staining was used to observe the level of apoptosis in brain tissue. Result Compared with the
control group at the same age, the rats in the model group had abdominal distension, diarrhea, poor
activity, the weight decreased significantly ( P<0. 05) , swelling, gas accumulation and necrotic foci in
the intestinal tissue. The pathological damage of small intestinal tissue was serious, the injury score was
significantly increased (P<0. 05) , the number of Nissi bodies in brain tissue was significantly decreased
(P<0. 05) , and the cell apoptosis in the brain tissue was increased. Moreover, the intestinal tissue and
brain tissue injuries of 1-day-old NEC rats were the most serious. Conclusion There are differences in
intestinal and brain tissue injuries among NEC rats at different ages. The younger the age, the more
severe the injury, suggesting that the age of onset may be one of the risk factors for brain injury in NEC
rats.

Key words: necrotizing enterocolitis, rat, age, brain injury

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