母婴分离所致的慢性内脏痛对成年大鼠空间学习记忆能力和旷场行为的影响

Effects of chronic visceral pain caused by neonate-mother separation on the ability of spatial learning memory and behavior in open field in adult rats

目的：观察母婴分离所致的慢性内脏痛对成年大鼠空间学习记忆能力和旷场行为的影响。方法：模型组大鼠于出生后第3~21 d,每天接受3 h母婴分离,对照组大鼠不做分离处理;8周龄时,使用腹壁撤退反射评分和痛阈测定方法筛选出有慢性内脏痛的大鼠;Morris水迷宫检测成年大鼠的空间学习记忆能力;旷场实验评估成年大鼠的旷场行为;Western Blot方法检测大鼠海马脑源性神经营养因子（brain derived neurotrophic factor,BDNF）的表达变化。结果：（1）母婴分离成年大鼠分别在20、40、60、80 mm Hg压力下的腹壁撤退反射评分均显著高于对照大鼠（P〈0.05）,而其痛阈显著低于对照大鼠（P〈0.05）。（2）与对照组相比,母婴分离大鼠水迷宫的寻台潜伏期与平均平台象限滞留时间均无显著差异（P〉0.05）。（3）与对照大鼠相比,母婴分离大鼠旷场运动的总路程和总速度无显著差异（P〉0.05）,但中心路程和中心路程时间显著减少（P〈0.05）。（4）Western Blot结果显示母婴分离大鼠海马内BDNF的表达与对照相比显著降低（P〈0.05）。结论：母婴分离所致的慢性内脏痛对成年大鼠空间学习记忆能力和自主探究行为无显著影响,但能引发成年大鼠的心理焦虑,该效应可能与海马BDNF的表达减少有关。

Objective： To observe effects of chronic visceral pain caused by neonate-mother separation（ NMS） on the ability of spatial learning,memory and behavior in open field in adult rats. Methods： The neonates of the NMS group were accepted maternal separation every day for 3 h in the first 3 ~ 21 d after birth,and the neonates of the control group were not separated. At eight weeks old,the rats with visceral hypersensitivity were assessed by the scores of abdominal withdrawal reflex（ AWR） and the measurement of pain threshold. The ability of spatial learning memory was tested by Morris Water Maze（ MWM） and the anxiety disorder was evaluated by the Open Field Test（ OFT）. Western Blot was used to detect the protein expression change of brain derived neurotrophic factor（ BDNF） in the hippocampus. Results：（ 1） Scores of abdominal withdrawal reflex of NMS rats were significantly increased under different pressures of colorectal distensions（ 20,40,60 and 80 mm Hg,P〈0. 05） and the pain thresholds were significantly lowered than those of con-trol rats（ P〈0. 05）.（ 2） There were no significant difference in search platform latency（ SPL） and the decrease of average residence time in the platform quadrant between control and NMS rats（ P〈0. 05）.（ 3） There were no significant difference in the total distance and speed between control and NMS rats（ P〈0. 05）. But the center distance and the time were shortened significantly in the rats with NMS（ P〈0. 05）.（ 4） The Western Blot showed that the expression of brainderived neurotrophic factor（ BDNF） was significantly decreased in hippocampus of NMS rats comparing with control rats（ P〈0. 05）. Conclusion： Chronic visceral pain caused by NMS has no effect on the ability of spatial learning memory and spontaneous activity in open field,but can increase the level of anxiety,which may be related with the decreased expression of BDNF in hippocampus.