The acquisition of fear memories involves plasticity of the thalamic and cortical pathways to the lateral amygdala (LA). In turn, the maintenance of synaptic plasticity requires the interplay between input-specific synaptic tags and the allocation of plasticity-related proteins. Based on this interplay, weakly activated synapses can express long-lasting forms of synaptic plasticity by cooperating with strongly activated synapses. Increasing the number of activated synapses can shift cooperation to competition. Synaptic cooperation and competition can determine whether two events, separated in time, are associated or whether a particular event is selected for storage. The rules that determine whether synapses cooperate or compete are unknown. We found that synaptic cooperation and competition, in the LA, are determined by the temporal sequence of cortical and thalamic stimulation and that the strength of the synaptic tag is modulated by the endocannabinoid signaling. This modulation is particularly effective in thalamic synapses, supporting a critical role of endocannabinoids in restricting thalamic plasticity. Also, we found that the availability of synaptic proteins is activity-dependent, shifting competition to cooperation. Our data present the first evidence that presynaptic modulation of synaptic activation, by the cannabinoid signaling, functions as a temporal gating mechanism limiting synaptic cooperation and competition.

中文翻译：

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大麻素受体激活对杏仁核突触竞争的时间门控。

恐惧记忆的获得涉及到外侧杏仁核 (LA) 的丘脑和皮质通路的可塑性。反过来，突触可塑性的维持需要输入特定的突触标签和可塑性相关蛋白质的分配之间的相互作用。基于这种相互作用，弱激活的突触可以通过与强激活的突触合作来表达持久形式的突触可塑性。增加激活的突触数量可以将合作转变为竞争。突触合作和竞争可以确定时间上分开的两个事件是否相关联，或者是否选择特定事件进行存储。决定突触是合作还是竞争的规则是未知的。我们发现在洛杉矶的突触合作和竞争，由皮质和丘脑刺激的时间顺序决定，突触标签的强度受内源性大麻素信号调节。这种调节在丘脑突触中特别有效，支持内源性大麻素在限制丘脑可塑性方面的关键作用。此外，我们发现突触蛋白的可用性依赖于活动，将竞争转变为合作。我们的数据提供了第一个证据，即通过大麻素信号传导对突触激活的突触前调节，起到限制突触合作和竞争的时间门控机制的作用。支持内源性大麻素在限制丘脑可塑性方面的关键作用。此外，我们发现突触蛋白的可用性依赖于活动，将竞争转变为合作。我们的数据提供了第一个证据，即通过大麻素信号传导对突触激活的突触前调节，起到限制突触合作和竞争的时间门控机制的作用。支持内源性大麻素在限制丘脑可塑性方面的关键作用。此外，我们发现突触蛋白的可用性依赖于活动，将竞争转变为合作。我们的数据提供了第一个证据，即通过大麻素信号传导对突触激活的突触前调节，起到限制突触合作和竞争的时间门控机制的作用。