大鼠应激后下颌骨骨皮质变化的微型CT观察

Analysis of cortical bone of the mandibular body in psychological stressed rats by micro-CT

目的 探讨大鼠接受心理应激后下颌骨骨皮质的骨密度变化.方法 100只成年雄性SD大鼠分为心理应激组（PS组,40只）、空白对照组（C组,40只）和足部电击组（FS组,20只）,其中PS组和C组按实验时间等分为1、2、3、4和5周亚组,每亚组8只.PS组在交流箱内接受心理应激,FS组仅做为应激源接受足部电击.高架十字迷宫实验观察C组和PS组各实验时间行为变化,并应用微型CT观察分析大鼠下颌骨颊、舌两侧近远中向六等分线与对应颌骨上下界平分线的交点处（A、B、C、D、E位点）骨皮质的骨密度.结果 大鼠接受心理应激后,各时间点（1、2、3、4、5周）的开臂停留时间分别为（16.6±2.3）、（17.1±2.4）、（15.8±1.6）、（15.8±2.2）、（17.9±2.6）s;开臂停留时间百分比分别为（30.5±3.7）％、（30.3±2.5）％、（26.8±3.8）％、（26.5±2.0）％、（27.4±2.6）％;开臂进入次数百分比分别为（34.1±4.4）％、（34.6±4.1）％、（32.6土3.9）％、（34.5±4.8）％、（31.8±3.3）％.以上数据均显著低于C组（P＜0.05）;而应激不同时间组之间两两比较,差异均无统计学意义（P＞0.05）.PS 5周组下颌骨颊侧D位点骨皮质骨密度[（1 085.4±88.5） mg/cm3]明显高于C组[（782.3±53.7） mg/cm3]和PS1周组[（825.2±88.5） mg/cm3]（P＜0.05）,E位点的骨密度表现为PS 5周组[（657.2±101.7）mg/cm3]显著高于C组[（415.9±99.7） mg/cm3]和PS 1周[（348.1±111.3）mg/cm3]、2周组[（339.3±74.0） mg/cm3] （P＜0.05）;应激大鼠下颌骨舌侧的骨密度变化主要集中在磨牙下方的感兴趣区域,表现为B、C位点PS 5周组[（1 755.6±156.6）、（1 367.8±115.8） mg/cm3]显著高于C组[（1 364.6±120.2）、（922.6±102.6） mg/cm3]和PS1周组[（1 299.7±172.9）、（1 052.3±107.9） mg/cm3]（P＜0.05）;PS组和C组其他位点比较,差异无统计学意义（P＞0.05）.结论 心理应激后大鼠下颌骨颊、舌侧局部区域骨皮质骨密度升高.

Objective To calculate the bone mineral density（BMD） of buccal and lingual mandibular cortical bone in psychological stressed rats.Methods One hundred adult male SD rats were randomly divided into psychological stress group（PS group,40 rats）,control group （C group,40 rats） and foot shock group（FS group,20 rats）.In addition,the PS group and C group were equally divided into week 1,week 2,week 3,week 4 and week 5 subgroup at random.The animals placed intervally in the communication box to receive the psychological stimuli were considered as the PS group animals.The stressors were from their neighboring FS group rats which were receiving foot shock.After observing the behavioral changes of the PS group rats and C group rats with elevated plus maze test,the mandibles were removed carefully and BMD of regions of interest（ROI） in the mandible were calculated by Micro-CT.The ROI were located at the equidistant five points,i.e.A,B,C,D and E,along the anteroposterior border and approximately halfway between the superior and inferior border of the mandible.Results Significant decrease of time spent in the open arms,ratio of open arms time and ratio of open arms entries were observed in PS group [time spent in the open arms：（16.6±2.3）,（17.1 ±2.4）,（15.8± 1.6）,（15.8±2.2）,（17.9±2.6） s]; ratio of open arms time：[（30.5 ± 3.7）%,（30.3 ± 2.5）%,（26.8 ± 3.8）%,（26.5 ± 2.0）%,（27.4 ± 2.6）%]; ratio of open arms entries：[（34.1±4.4）%,（34.6±4.1）%,（32.6±3.9）%,（34.5±4.8）%,（31.8±3.3）%] compared with control group at each time point（P〈0.05）,no differeces were observed among PS groups（P〉0.05）.On the buccal side of mandibular body,BMD in point D of week 5 PS group[（1 085.4±88.5） mg/cm3] was higher than that of matched control group [（782.3±53.7） mg/cm3）]and week 1 PS group [（825.2±88.5） mg/cm3]（P〈0.05）.Similar results of BMD were obtained in point E between week 5 PS group [（657.2± 101.7） mg/cm3] and control group [（415.9±99.7） mg/cm3],week 1 and 2 PS group [（348.1± 111.3）,（339.3±74.0） mg/cm3] （P〈0.05）.On the lingual side of mandibular body,the alterations of BMD were observed in point B and C between week 5 PS group [（1 755.6±156.6）,（1 367.8±115.8） mg/cm3]and matched control group [（1 364.6±120.2）,（922.6±102.6） mg/cm3] and week 1 PS group [（1 299.7± 172.9）,（1 052.3± 107.9） mg/cm3] （P〈O.05）.No differeces of BMD were observed in the other points between PS group and control group at each time point（P〉0.05）.Conclusions Psychological stress induced by communication box could result in the anxious behavior of SD rats and increase the BMD of cortical bone in certain regions of the mandibular body.