BACKGROUND: The present study analyzed the effect of 3 days (2 h/d) intrauterine hypoxia on leing and memory in juvenile rats, as well as the therapeutic effects of Angelica sinensis on dentate gyrus neurons, as well as leing and memory.OBJECTIVE: To explore the effects of intrauterine hypoxia on hippocampal dentate gyrus neurons, as well as leing and memory, in juvenile rats; to explore N-methyI-D-aspartate receptor-1 (NMDAR1) expression in the dentate gyrus of neonatal rats following intrauterine hypoxia, as well as prolonged hypoxia; to investigate the regulatory mechanisms of Angelica sinensis.DESIGN, TIME AND SETTING: A randomized and controlled experiment based on developmental neurobiology was performed at the Department of Histology and Embryology in Luzhou Medical College from October 2007 to October 2008.MATERIALS: Angelica sinensis solution (250 g/L) was obtained from Central South Hospital of Wuhan University, China. Neuron-specific enolase and NMDAR1 mRNA in situ hybridization reagents were provided by Wuhan Boster Biological Technology, China. Image-Pro Plus 6.0 analysis system was purchased from Media Cybetics, USA.METHODS: Healthy pregnant Sprague Dawley rats (n = 30) were randomly divided into control (n = 10), hypoxia (n = 10), and Angelica (n = 10) groups. The Angelica and hypoxia pregnant rats were placed in a three-gas incubator (oxygen concentration: 13%) starting with day 14 of pregnancy for 2 hours/day for 5 consecutive days to establish a fetal rat intrauterine hypoxia model. One hour prior to modeling, the pregnant rats from the Angelica and hypoxia groups received Angelica sinensis and normal saline (8 mL/kg) injections, respectively, through the caudal vein. The control group procedures were identical to the hypoxia group, but lacked the hypoxic conditions.MAIN OUTCOME MEASURES: Brain tissues of neonatal rats were used to detect expression of NMDAR1 mRNA, and brain tissues of juvenile rats aged 30 days were used to determine neuron-specific enolase mRNA expression by in situ hybridization. Microscopic images (400x) of the hippocampal dentate gyrus were collected. The integral optical density (IOD) value of positive NMDAR1 mRNA cells in the dentate gyrus of neonatal rats, as well as the quantity and the IOD value of positive neuron-specific enolase mRNA cells in the dentate gyrus of juvenile rats, were analyzed with Image-Pro IPP6.0 software. At 30 days after birth, leing and memory parameters were measured in the juvenile rats using Morris water maze.RESULTS: The quantity and the IOD value of positive neuron-specific enolase mRNA cells in the dentate gyrus of the hypoxia group juvenile rats were significantly less than the control group (P <0.05), and also less than the Angelica group (P < 0.05). The IOD value of positive NMDAR1 mRNA cells in the dentate gyrus of the hypoxia group neonatal rats was significantly greater than the control group, and also greater than the Angelica group (P < 0.05). In the Morris water maze,the searching time during the probe trial and reversal probe trial was shorter in the hypoxia group juvenile rats compared with the control group, and the Angelica group was prolonged compared with the hypoxia group (P < 0.05).CONCLUSION: Intrauterine hypoxia increased expression of NMDAR1 mRNA in the dentate gyrus of neonatal rats, reduced the number of dentate gyrus neurons, and negatively affected leing and memory in juvenile rats. In contrast, Angelica sinensis injection improved the intrauterine hypoxic condition, increased the number of dentate gyrus neurons, and improved the leing and memory deficits of the juvenile rats.