中文摘要：

目的观察正畸初期不同矫治力对三叉神经节中PPTA mRNA（Preprotachykinin-A，前速激肽原A）的影响。方法采用反转录一聚合酶链反应（RT-PCR）技术检测来观察正畸初期阶段不同正畸力值作用下大鼠三叉神经节中PPTA mRNA的变化情况。结果实验组大鼠三叉神经节PPTA mRNA的表达发生了明显的变化，并呈现一定的规律性。加力2hPPTA mRNA的表达量开始增加；加力3d达到最高；之后逐渐下降，但7天仍然高于对照组（P〈0．05）；不同正畸力组之间，20g组和50g组大鼠三叉神经节PPTA mRNA的动态变化相似，各时间点两组之间无统计学差异（P〉0．05）；80g组在各个时间点PPTA mRNA的表达明显高于其它两组（P〈0．05），并且峰值有相对提前的趋势。结论本研究提示正畸初期力值的大小对疼痛的表达可能有不同程度的影响。

英文摘要：

Objective To investigate the changes of PPTA mRNA in rats trigeminal ganglion with various initial orthodontic forces. Methods SD rats were randomly divided into control group and experimental group, experimental group according to different orthodontic force was divided into 20g group, 50g group and 80g group. The first maxillary molar was moved mesially by an orthodontic force for 2 hours,1 days,3 days, 5 days and 1 week ,The expression of PPTA mRNA in trigeminal ganglion were detected with reverse transcription-polymerasa chain reaction （RT-PCR）. Results The expression of PPTA mRNA in the experimental group were stronger than that in control group at all the time points; PPTA mRNA level was increased after 2 hours and reached the peak level around 3 days during tooth movement, 7 days after tooth movement PPTA mRNA level was still higher than that in the controls （P〈0.05）; The dynamic changes of PPTA mRNA in rats＇trigeminal ganglion of 20g group was similar to that of 50g group and no statistically significant difference was found between the two groups at each time point （P〉0.05）. But the expression of PPTA mRNA of 80g group was significantly higher than the other two groups at each time point （P〈0.05）, and the peak of expression was relatively advanced. Conclusion The results suggested various initial orthodontic forces may influnce the expression of pain.