Weisskopf M G, LeDoux J E
Center for Neural Science, New York University, New York City, New York 10003, USA.
J Neurophysiol. 1999 Feb;81(2):930-4. doi: 10.1152/jn.1999.81.2.930.
Fear conditioning involves the transmission of sensory stimuli to the amygdala from the thalamus and cortex. These input synapses are prime candidates for sites of plasticity critical to the learning in fear conditioning. Because N-methyl-D-aspartate (NMDA)-dependent mechanisms have been implicated in fear learning, we investigated the contribution of NMDA receptors to synaptic transmission at putative cortical and thalamic inputs using visualized whole cell recording in amygdala brain slices. Whereas NMDA receptors are present at both of these pathways, differences were observed. First, the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-receptor-mediated component of the synaptic response, relative to the NMDA component, is smaller at thalamic than cortical input synapses. Second, thalamic NMDA responses are more sensitive to Mg2+. These findings suggest that there are distinct populations of NMDA receptors at cortical and thalamic inputs to the lateral amygdala. Differences such as these might underlie unique contributions of the two pathways to fear conditioning.
恐惧条件反射涉及感觉刺激从丘脑和皮层传递至杏仁核。这些输入突触是对恐惧条件反射学习至关重要的可塑性位点的主要候选者。由于依赖N-甲基-D-天冬氨酸（NMDA）的机制与恐惧学习有关，我们使用杏仁核脑片的可视化全细胞记录，研究了NMDA受体对假定的皮层和丘脑输入处突触传递的贡献。虽然这两条通路都存在NMDA受体，但观察到了差异。首先，相对于NMDA成分，丘脑输入突触处突触反应的α-氨基-3-羟基-5-甲基-4-异恶唑丙酸受体介导成分比皮层输入突触处的小。其次，丘脑NMDA反应对Mg2+更敏感。这些发现表明，外侧杏仁核的皮层和丘脑输入处存在不同群体的NMDA受体。诸如此类的差异可能是这两条通路对恐惧条件反射做出独特贡献的基础。
