Nithianantharajah Jess, Murphy Mark
Department of Anatomy and Cell Biology, University of Melbourne, Vic., Australia.
Neurobiol Learn Mem. 2008 Jul;90(1):36-43. doi: 10.1016/j.nlm.2007.12.002. Epub 2008 Jan 28.
Auditory fear conditioning is one of the most well characterized models used in studies of learning and memory. In order to ensure the animals have been conditioned to fear the auditory stimulus, animals are generally tested for their response to this stimulus in a different context to that used for training. For this reason it is often unclear how much contextual fear conditioning the animals also acquire when they are trained. In this study, we have established a protocol for fear conditioning in mice which is explicit for auditory cues; mice trained using this protocol, show a very low fear response to contextual cues encountered during training. We have undertaken analysis to look for potential brain changes associated with this model by measuring levels of the synaptic vesicle protein, synaptophysin, in the basolateral nuclei of the amygdala following auditory fear conditioning. Our results show levels of synaptophysin were significantly higher in mice which learnt to associate the auditory stimulus with fear, in comparison to all non-learning control animals. These findings support the idea that synaptic plasticity associated with formation of fear conditioning to a single specific conditioned stimulus occurs within the basolateral nuclei of the amygdala. Furthermore, our results demonstrate the usefulness of this model in looking for changes in the brain specific for a defined learning event.
听觉恐惧条件反射是学习与记忆研究中最具特征的模型之一。为确保动物已被条件化至恐惧听觉刺激，通常会在与训练环境不同的情境中测试动物对该刺激的反应。因此，在训练时动物同时获得了多少情境恐惧条件反射往往并不明确。在本研究中，我们建立了一种针对小鼠的恐惧条件反射实验方案，该方案对听觉线索有明确规定；使用此方案训练的小鼠，对训练期间遇到的情境线索表现出极低的恐惧反应。我们通过测量听觉恐惧条件反射后杏仁核基底外侧核中突触囊泡蛋白突触素的水平，进行分析以寻找与该模型相关的潜在大脑变化。我们的结果显示，与所有非学习对照动物相比，学会将听觉刺激与恐惧联系起来的小鼠中突触素水平显著更高。这些发现支持了这样一种观点，即与针对单一特定条件刺激形成恐惧条件反射相关的突触可塑性发生在杏仁核基底外侧核内。此外，我们的结果证明了该模型在寻找特定学习事件中大脑变化方面的有用性。
