中文摘要：

目的检测不同硬度食物喂养下，大鼠在离乳后不同发育阶段咬肌脑源性神经营养因子（brain-derived neurotrophic factor，BDNF）及其受体酪氨酸蛋白激酶B（Tyrosine KinaseB，TrkB）mRNA的表达变化。方法出生后18d刚离乳的大鼠4JD只，分为硬食组、软食组，分别喂养营养成分相同的固体、粉状鼠粮，于大鼠3、4、6、9周龄时取表层咬肌，利用半定量RT-PCR方法检测BDNF及其受体TrkBmRNA的表达变化情况。结果3—9周龄2组大鼠咬肌均有BDNF／TrkBmRNA表达，3周龄时，2组表达均较低，没有显著差异；4周龄时，2组大鼠咬肌BDNF／TrkB mRNA均较3周时有显著的增加，但软食组增加幅度低于硬食组；6—9周龄时BDNF／TrkBmRNA表达降低，2组间没有显著差异。结论BDNF／TrkBmRNA在咀嚼形成关键期（P3—4周）表达显著增强，软食喂养能够降低此阶段大鼠咬肌BDNF／TrkBmRNA表达，BDNF／TrkB可能与咀嚼形成有密切关系。

英文摘要：

Objective To observe the mRNA expression of brain-derlved neurotrophic factor/ receptor in masseter muscle of rat fed with soft and solid diet. Methods Forty rats soon after weaning （ 18 days after birth） were fed with ordinary solid or soft diet, and the superficial masseter muscle was dissected when rats were 3, 4, 6 and 9 weeks old after birth. The expression of BDNF/TrkB mRNA was evaluated with semi-quantitive RT-PCR. Results From 3 to 9 weeks after birth, the BDNF/TrkB mRNA in rat masseter muscle was detected in both groups. 3 weeks after birth, the expressions of BDNF/TrkB mRNAs in both groups were relatively low. 4 weeks after birth, the levels of BDNF and TrkB mRNA in both groups increased dramatically（ P 〈 0.05）. However,both of them in soft diet group were significantly lower than that in solid diet group （ P 〈 0.05 ）. From 6 to 9 weeks, the levels of BDNF and TrkB mRNA in both groups decreased, and there were no differences between two groups （P 〉 0.05）. Conclusion The notable increase of BDNF/ TrkB mRNA level happened at the same time as mastication formation （P3-P4 w）, which could be decreased by soft-diet feeding, so BDNF/TrkB might have a close relationship with mastication formation.