Metaplasticity refers to the persistent modification, by previous activity, in the ability to induce synaptic plasticity. Accumulated evidence has proposed that metaplasticity contributes to network function and cognitive processes such as learning and memory. In this regard, it has been observed that training in several behavioral tasks modifies the possibility to induce subsequent synaptic plasticity, such as long-term potentiation (LTP) and long-term depression (LTD). For instance, our previous studies have shown that conditioned taste aversion (CTA) training prevents the induction of in vivo LTP in the projection from the basolateral nucleus of the amygdala to the insular cortex (BLA-IC). Likewise, we reported that extinction of CTA allows induction but not maintenance of LTP in the same pathway. Besides, we showed that it is possible to express in vivo low-frequency stimulation LTD in the BLA-IC projection and that its induction prior to CTA training facilitates the extinction of this task. However, until now, little is known about the participation of LTD on metaplastic processes. The present study aimed to analyze whether CTA training modifies the expression of in vivo LTD in the BLA-IC projection. To do so, animals received low-frequency stimulation to induce IC-LTD 48 h after CTA training. Our results show that CTA training occludes the subsequent induction of LTD in the BLA-IC pathway in a retrieval-dependent manner. These findings reveal that CTA elicits a metaplastic regulation of long-lasting changes in the IC synaptic strength, as well as that specific phases of learning differentially take part in adjusting the expression of synaptic plasticity in neocortical regions.

元可塑性是指通过先前的活动对诱导突触可塑性的能力进行持续修改。积累的证据表明，元可塑性有助于网络功能和认知过程，如学习和记忆。在这方面，已经观察到在几个行为任务中的训练改变了诱导随后突触可塑性的可能性，例如长期增强 (LTP) 和长期抑制 (LTD)。例如，我们之前的研究表明，条件性味觉厌恶（CTA）训练可以防止体内诱导从杏仁核基底外侧核到岛叶皮质的投射中的 LTP (BLA-IC)。同样，我们报道了 CTA 的消失允许在同一途径中诱导而不是维持 LTP。此外，我们证明了在 BLA-IC 投影中表达体内低频刺激 LTD 是可能的，并且它在 CTA 训练之前的诱导有助于消除这项任务。然而，直到现在，人们对 LTD 参与化生过程知之甚少。本研究旨在分析 CTA 训练是否会改变体内表达LTD 在 BLA-IC 投影中。为此，动物在 CTA 训练后 48 小时接受低频刺激以诱导 IC-LTD。我们的结果表明，CTA 训练以检索依赖的方式阻止了 BLA-IC 通路中 LTD 的后续诱导。这些发现表明，CTA 引发了对 IC 突触强度长期变化的化生调节，以及学习的特定阶段不同地参与调节新皮质区域突触可塑性的表达。