大鼠脑中隔核毁损对关联性条件化恐惧的影响

目的：中隔核(Septum)在实验大鼠对关联性刺激所产生的条件化恐惧的获得(Acquisi-tion)已经证明具有重要的作用，但对关联性刺激所产生的条件化恐惧的表达(Expression)的作用至今仍未阐明。方法：实验组大鼠分别采用射频(Radiofrequency)技术对双侧中隔核区行组织毁损术，对照组大鼠完全按照实验组大鼠的手术程序，但不采用射频技术进行组织破坏，然后均接受经典的条件化恐惧的实验训练。实验1：实验大鼠(n=18)在手术后第11d，经采用足部电击(Footshocks)方法产生与之关联的条件化恐惧，然后在24h后，在相同条件下但不予以足部电击的情况下评定其僵滞(Freezing)行为；实验2：实验大鼠(n=16)在手术前24h，先采用足部电击方法产生与之关联的条件化恐惧，然后在手术后第11d在相同条件下但不予以足部电击的情况下评定僵滞行为。结果:在训练前接受双侧中隔核毁损的大鼠既不阻断也不增强关联性条件化僵滞，而在训练后接受双侧中隔核毁损的大鼠则明显阻断关联性条件化僵滞的表达，同时因关联性条件化恐惧所致非粪的数量也明显减少。结论:双侧中隔核的毁损并不引起关联性条件化恐惧的增强，而是明显减弱关联性条件化恐惧的表达水平，因此，中隔核具有潜在增强关联性条件化恐惧的表达的作用。

Effects of septal lesions on contextual fear conditioning in rats

Objective: The septum plays an important role for acquisition of conditioned fear responding to contextual stimuli in rats, but its role for expression of contextual conditioned fear remains uclear. Methods: Rats were given the bilateral septal lesions with radiofrequency or sham lesions at the bilateral septum, and were trained in a classical conditioned fear paradigm. Experiment 1: 11 days following the surgery, footshocks were used in 18 rats to induce conditioned fear, and 24 hours later, freezing behavior was measured in a shock chamber without shocks. Experiment 2: twenty-four hour before surgery, the rats (n=16) were conditioned for rear in the same procedure as above and 11 days after surgery, freezing behavior was assessed in a shock chamber sithout shocks. Results: Rats did bilateral septal lesions before training did not showed blocked or enhanced contextual conditioned freezing, but those had bilateral septal lesions after training demonstrated blocked expression of contextual conditioned freezing. Moreover, posttaining bilateral septal lesions reduced the amounts of defecation induced by contextual conditioned fear significantly. Conclusion: Take together, the results suggest that the septal lesions do not produce an enhancement of contextual fear conditioning, but obviously attenuate the level of expression of contextual conditioned fear by two measures of fear, freezing and defecation, i.e. the septum has a potential enhanced effect on the expression of contextual conditioned fear.