Linke R, Faber-Zuschratter H, Seidenbecher T, Pape H-C
Institut für Anatomie, Otto-von-Guericke Universität Magdeburg, Leipziger Str. 44, D-39120 Magdeburg, Germany.
Brain Res Bull. 2004 Jul 15;63(6):461-9. doi: 10.1016/j.brainresbull.2004.04.012.
Stimulation of amygdaloid nuclei and emotionally relevant stimuli are known to influence the induction and maintenance of long-term potentiation in the hippocampal formation and the formation of long-term declarative memories. Because the thalamic projection from the posterior paralaminar thalamic nuclei is an important sensory afferent projection to amygdaloid nuclei mediating the fast acquisition of fear-potentiated behavior, we were interested in verifying whether this projection establishes synaptic contacts on amygdala neurons that project to the hippocampal formation. Thalamic afferents were labeled with the anterograde tracer Phaseolus vulgaris leucoagglutinin and amygdalo-hippocampal neurons were identified by injection of the retrograde tracer Fluorogold into the lateral entorhinal cortex. A massive overlap of both projection systems was observed especially in the anterior basomedial nucleus of the amygdala. Light microscopic examination revealed that single anterogradely labeled boutons were in close apposition to retrogradely labeled neurons suggesting synaptic contacts. The occurrence of such synaptic contacts was confirmed with electron microscopy. However, despite the massive overlap of anterogradely labeled axons and retrogradely labeled neurons observed at the light microscopic level, electron microscopy revealed that only 10% of all labeled profiles make direct contacts on each other; anterogradely labeled boutons predominantly contacted unlabeled profiles but synapses with direct contact between labeled profiles were rare. Altogether the findings demonstrate that the thalamic connection with the basomedial nucleus of the amygdala may represent an anatomical substrate for modulating amygdala output to the hippocampal formation.
已知刺激杏仁核和与情绪相关的刺激会影响海马结构中长时程增强的诱导和维持以及长时陈述性记忆的形成。由于来自丘脑后旁层核的丘脑投射是介导恐惧增强行为快速习得的杏仁核的重要感觉传入投射，我们感兴趣的是验证该投射是否在投射至海马结构的杏仁核神经元上建立突触联系。用顺行示踪剂菜豆白细胞凝集素标记丘脑传入纤维，并通过向外侧内嗅皮质注射逆行示踪剂荧光金来识别杏仁核 - 海马神经元。观察到两个投射系统大量重叠，尤其在杏仁核的前基底内侧核。光学显微镜检查显示，单个顺行标记的终末与逆行标记的神经元紧密相邻，提示存在突触联系。电子显微镜证实了这种突触联系的存在。然而，尽管在光学显微镜水平观察到顺行标记的轴突和逆行标记的神经元大量重叠，但电子显微镜显示，所有标记的结构中只有10% 相互直接接触；顺行标记的终末主要与未标记的结构接触，标记结构之间直接接触的突触很少见。总之，这些发现表明丘脑与杏仁核基底内侧核的连接可能是调节杏仁核向海马结构输出的解剖学基础。
