Effects of environmental stimulation on learning and memory in young rats with hypoxic-ischemia brain damage

Objective To explore the effects of enriched environment and neonatal handling on the reference learning and memory test and the number of neurons in hippocampal CA1 region in young rats with the hypoxia ischemia brain damage(HIBD).Methods The HIBD model was established in Sprague-Dawley(SD)rats aged 7 days.Then the HIBD rats were randomly divided into five groups:sham(n = 14),HIBD(n = 14),HIBD with enriched environment(HIBDE,n = 14),HIBD with neonatal handling(HIBDN,n = 14),HIBD with combined intervention(HIBDC,n = 14).After 7 days of HIBD,the different interventions were implemented.At 35 days old,the Morris Water Maze test was performed,the number of neurons in hippocampal CA1 was detected by Nissl staining.Results In the Morris water hidden platform test,the latency to the platform in HIBDE and HIBDC were significantly shorter than that in HIBD and HIBDN(P all 0.05).However,there was no significant difference between HIBD and HIBDN.In the Morris water exploratory test,the percentage of the time in target quadrant in HIBDE and HIBDC were significantly higher than that in HIBD(P all 0.01).However,there was no significant difference between HIBDN and HIBD.The number of neurons in the damaged side of hippocampus was significantly less in HIBD than that in sham group(P 0.001).The number of neurons in the damaged side was significantly increased in HIBDC and HIBDE than that in HIBD and HIBDN(P 0.0.5).The number of neurons in the un-damaged side was significantly increased in HIBDE than that in HIBD,HIBDN and HIBDC(all P 0.05).Conclusions The enriched environment implemented one week after HIBD could promote the recovery of neonatal rats'brain damage.The short time neonatal handling immediately after HIBD could not further enhance the effect of enriched environment.