Synaptic mechanisms of amygdala-dependent behaviors

杏仁核中的神经活动构成了情绪行为表达的基础，杏仁核在焦虑和条件性恐惧中的作用正在调查中。我们的主要目标是了解杏仁核回路如何触发恐惧行为，以及神经元活动在从正常状态向病理状态转变的过程中如何变化。这些知识将提供有助于开发与病理性恐惧相关的精神障碍的治疗方法的信息。杏仁核通过分析传入的带有情绪内容的信息并触发防御反应来运作。我们研究杏仁核如何在突触水平上整合处理感觉和情感信息的传入信号以及提供执行控制的信号。为了解决这个问题，我们通过有选择地刺激来自特定大脑区域的神经纤维来询问特定的输入。为了解决这个问题，我们建立了基于视蛋白的技术来选择性地激活或抑制杏仁核的输入，杏仁核的输入来自传递感觉信息的周边皮质区TEA和与情感、疼痛和认知有关的前扣带回(ACC)。这两种输入都针对杏仁核内单个混合的神经元。我们发现这两条输入通路在突触可塑性方面存在显著差异。虽然从周边皮质传入的突触传递的长时程增强(LTP)需要抑制GABA-A受体介导的抑制，但ACC-杏仁核通路中的LTP不需要。此外，切断外囊和杏仁核之间的联系，即使在存在GABA-A受体介导的抑制的情况下，也能使来自周边皮质的LTP进入。此外，我们发现这两种输入与杏仁核抑制神经元的连接方式不同。ACC能更有效地激活表达5-羟色胺受体3的中间神经元，而TEA能更有效地招募囊周细胞。 我们的研究表明，小的GTPase Rap1抑制了杏仁基底外侧核皮质输入中谷氨酸的释放。我们通过成像原代皮质神经元的突触前释放，同时操纵Rap1-ERK1/2信号通路来研究这种抑制的分子机制。研究表明，RAP1-ERK1/2信号通路通过阻止L类钙通道参与突触前释放而抑制突触前释放，可能是通过阻止通道插入质膜实现的。 我们继续研究杏仁核去抑制的机制，并将重点放在局部微电路的多巴胺能调制上。使用转基因Cre-鼠的神经元间特异性系，我们选择性地激活杏仁基底外侧核中的小白蛋白阳性神经元，发现多巴胺选择性地抑制向主细胞释放GABA，但不抑制向中间神经元释放GABA。我们的发现解释了这种选择性：在小白蛋白阳性神经元中，cAMP信号调节以主细胞为目标的突触处的GABA释放，而不是中间神经元。

Neural activity in the amygdala forms the basis for expression of emotional behavior, and the role of the amygdala in anxiety and conditioned fear is under investigation. Our main goal is to understand how amygdala circuitry triggers fear behaviors and how neuronal activity changes during transition from normal to pathological states. This knowledge will provide information that will help in developing treatments for mental disorders associated with pathological fear.
 The amygdala operates by analyzing incoming information with emotional content and triggering defensive responses. We study how the amygdala integrates, at the synaptic level, incoming signals that process sensory and affective information and signals that provide executive control. To address this question, we interrogate a specific input by selectively stimulating nerve fibers coming from a specific brain area. To address this question, we established opsin-based techniques for selective activation or silencing of amygdala inputs from perirhinal cortical area TeA, which transmits sensory information, and from the anterior cingulate cortex (ACC), which is implicated in affect, pain and cognition. Both inputs target individual intermingled neurons within the amygdala. We found a significant difference in synaptic plasticity between the two input pathways. While long-term potentiation (LTP) of synaptic transmission in the input from perirhinal cortex required suppression of GABA-A receptor-mediated inhibition, LTP in the ACC-amygdala pathway did not. Moreover, severing connections between external capsule and amygdala enabled LTP in the input from perirhinal cortex even in the presence of GABA-A receptor-mediated inhibition. In addition, we found that these two inputs exhibit differential connectivity to the amygdala inhibitory neurons. The ACC input was more effective in activating interneurons that express serotonin receptor 3, whereas the TeA input was more effective in recruiting the pericapsular cells. Our studies revealed that small GTPase Rap1 suppresses release of glutamate in the cortical inputs to the basolateral amygdala. We investigated molecular mechanisms of this suppression by imaging presynaptic release in primary cortical neurons, while manipulating the Rap1-Erk1/2 signaling pathway. The study revealed that the Rap1-Erk1/2 signaling suppressed presynaptic release by preventing participation of the L-type calcium channel in presynaptic release, possibly by preventing insertion of the channel into the plasma membrane. We continued to investigate the mechanisms responsible for amygdala disinhibition and focused on dopaminergic modulation of local microcircuits. Using interneuron-specific lines of transgenic Cre-mice, we selectively activated parvalbumin positive neurons in the basolateral amygdala and found that dopamine selectively suppressed GABA release towards principal cells, but not towards interneurons.
 The selectivity was explained by our finding that in parvalbumin-positive neurons, cAMP signaling regulated GABA release at synapses that targeted principal cells but not interneurons.