延长创伤环境暴露时间对条件性恐惧表达的影响

Effect of prolonged traumatic context exposure on conditioned fear response

目的明确延长创伤后创伤环境的暴露时间对单一线索条件性恐惧表达的影响。方法灯光线索条件性恐惧训练后延长动物在训练环境中的停留时间。结果创伤后延长环境暴露时间能够消除动物对环境的恐惧，使之不能自发恢复，并因此抑制了对单一线索的条件性恐惧反应，主要表现为在创伤环境中，延长暴露组动物对灯光线索的条件性恐惧反应低于非延长暴露组[恐惧水平分别为（19．531±6．073）％，（46．094±10．427）％]，达到边缘显著水平（P=0．085），且这种恐惧下调可以持续至少35d[延长暴露组与非延长暴露组的恐惧水平分别为（21．094±4．897）％，（74．219±9．481）％，P〈0．01]。结论延长创伤环境暴露时间改变了对创伤环境的“恐惧”表征，从而使创伤环境作为“安全场景设置者”降低了对单一线索条件性恐惧的表达，提示在创伤后延长创伤环境的停留时间，使受害者对环境的恐惧消失，可能有助于预防创伤后应激障碍的形成。

Objective To understand the effect of immediately prolonged context exposure on cued condi- tioning. Methods Prolonged or not prolonged traumatic context exposure（rats stayed 90 minutes or 2 minutes in train context after the last light-shock trial,that was 90 min group or 2 rain group respectively） immediately after visual Pavlov fear conditioning train to extinct the fear response to traumatic context. Results Results showed that contextual fear memory was an important factor modulating cued conditioned fear response of rats. In traumatic context,the fear response to conditioned light of 90 min group was marginally significant low compared with 2 min group [ freezing levels were （ 19. 531 ± 6. 073 ） % , （46. 094 ± 10. 427 ） % respectively, P = 0. 085 ] , and the de- crease of fear expression of 90 rain group could last at least 35 days [ freezing levels were （21. 094 ± 4. 897 ） % , （74. 219 ± 9. 481 ） % respectively for groups, P 〈 0.01 ]. Conclusion Immediately prolonged context exposure transfer the traumatic context as a ＂safe occasion setter＂ ,then decreased the fear response to discrete conditioned cues. This suggests that immediately prolong the traumatic environment exposure time might be a favorable way to prevent posttraumatic stress disorder.