损伤内侧前额叶抑制豚鼠听觉惊吓反射的研究

Lesions of the medial prefrontal cortex of guinea pig inhibit acoustic startle reflex

目的观察分析内侧前额叶（mPFC）不同亚区在惊吓反射表达中的作用。方法24只健康雄性英国种白化豚鼠随机分成4组：前扣带回损伤（n=6）及似损伤（n=6）（实验1）；缘前皮质损伤／缘前皮质＋前扣带回联合损伤（n=6）及假损伤（n=6）（实验2）。分别注射利多卡因或生理盐水。采用条件刺激（CS，声音）与非条件刺激（US，气流冲击角膜）配对训练，观察各组听觉惊吓反射（acoustic startle reflex，ASR）变化。结果实验1表明前扣带回损伤后SR率无显著变化（时间效应F=15．421，P=0．098；组间效应F=14．753，P=0．084）。实验2表明单独缘前皮质注射利多卡因后SR率无显著变化（时间效应F=14．975，P=0．178；组间效应F=18．643，P=0．089）；但缘前皮质和前扣带回同时沣射利多卡冈后，SR发生率则有显著下降，并且没有随着训练而恢复（组间效应F=67．743，P=0．009）。结论mPFC中缘前皮质和前扣带回联合损伤导致ASR发生率显著下降，且没有随着训练而恢复，表明mPFC参与了对听觉惊吓反射的调控，但其调控机制有待探讨。

Objective To observe and analyze the role of different subfields of medial prefrontal cortex （mPFC） in the expression course of startle reflex. Methods 24 healthy male British kind of albino guinea pigs were randomly divided into 4 groups ： anterior cingulated cortex lesion（ n = 6 ） and sham-lesion（ n = 6 ） （ Experiment 1 ） ; prelimbic cortex lesion/joint lesion of prelimbic cortex and anterior cingulated cortex （ n = 6） and sham-lesion （ n = 6）（ Experiment 2 ）. The animals were injected lidocaine （lesion） or physiological saline （sham-lesion）. Each group received paired training of conditioned stinm]us（ CS, a tone） and unconditioned stimulus （US, a air puff） , to observe the acoustic startle reflex（ ASR） change of these groups. Results As the results of experiment 1 suggested, SR rate did not change significantly after anterior cingulated cortex lesion（ time effect： F= 15. 421, P= 0. 098 ;group effect ： F = 14. 753, P = 0. 084 ）. As the results of experiment 2 suggested, SR rate did not change significantly after prelimbie cortex lesion （ time effect ： F = 14. 975, P = 0. 178 ; group effect ： F = 18. 643, P = 0. 089）. When prelimbie cortex and anterior cingulated cortex were lesioned at the same time, SR rate declined significantly and didn ＇ t recover with the following training （ group effect： F = 67. 743, P = 0. 009 ）. Conclusion Lesions of the prelimbie cortex and anterior cingulated cortex in mPFC cause the significantly decline of acoustic startle reflex（ASR）, which don＇t recover with the following training. This study indicates that mPFC involves in the regulation of ASR, but the regulation mechanism needs to be discussed.