The nucleus accumbens shell (NAcSh) regulates emotional and motivational responses, a function mediated, in part, by integrating and prioritizing extensive glutamatergic projections from limbic and paralimbic brain regions. Each of these inputs is thought to encode unique aspects of emotional and motivational arousal. The projections do not operate alone, but rather are often activated simultaneously during motivated behaviors, during which they can interact and coordinate in shaping behavioral output. To understand the anatomic and physiological bases underlying these interprojection interactions, the current study in mice of both sexes focused on how the basolateral amygdala projection (BLAp) to the NAcSh regulates, and is regulated by, projections from the medial prefrontal cortex (mPFCp) and paraventricular nucleus of the thalamus (PVTp). Using a dual-color SynaptoTag technique combined with a backfilling spine imaging strategy, we found that all three afferent projections primarily targeted the secondary dendrites of NAcSh medium spiny neurons, forming putative synapses. We detected a low percentage of BLAp contacts closely adjacent to mPFCp or PVTp presumed synapses, and, on some rare occasions, the BLAp formed heterosynaptic interactions with mPFCp or PVTp profiles or appeared to contact the same spines. Using dual-rhodopsin optogenetics, we detected signs of dendritic summation of BLAp with PVTp and mPFCp inputs. Furthermore, high-frequency activation of BLAp synchronous with the PVTp or mPFCp resulted in a transient enhancement of the PVTp, but not mPFCp, transmission. These results provide anatomic and functional indices that the BLAp interacts with the mPFCp and PVTp for informational processing within the NAcSh.

SIGNIFICANCE STATEMENT The nucleus accumbens regulates emotional and motivational responses by integrating extensive glutamatergic projections, but the anatomic and physiological bases on which these projections integrate and interact remain underexplored. Here, we used dual-color synaptic markers combined with backfilling of nucleus accumbens medium spiny neurons to reveal some unique anatomic alignments of presumed synapses from the basolateral amygdala, medial prefrontal cortex, and paraventricular nucleus of thalamus. We also used dual-rhodopsin optogenetics in brain slices, which reveal a nonlinear interaction between some, but not all, projections. These results provide compelling anatomic and physiological mechanisms through which different glutamatergic projections to the nucleus accumbens, and possibly different aspects of emotional and motivational arousal, interact with each other for final behavioral output.

伏伏核壳（NAcSh）调节情绪和动机反应，这一功能部分是通过整合和优先考虑来自边缘和上肢大脑区域的广泛谷氨酸能投射而介导的。这些输入中的每一个都被认为编码了情感和动机唤醒的独特方面。这些投影并非单独运行，而是经常在动机行为期间同时激活，在此期间它们可以相互作用并协调以塑造行为输出。为了理解这些相互投射相互作用背后的解剖学和生理学基础，目前在男女小鼠中的研究都集中在基底外侧杏仁核投射（BLAp）到NAcSh的调控以及如何受内侧前额叶皮层（mPFCp）和丘脑室旁核（PVTp）。使用双色SynaptoTag技术与回填脊柱成像策略相结合，我们发现所有三个传入投影主要针对NAcSh中棘状神经元的次级树突，形成假定的突触。我们检测到与mPFCp或PVTp假定的突触紧密相邻的BLAp接触的百分比较低，在极少数情况下，BLAp与mPFCp或PVTp谱形成异突触相互作用，或似乎接触相同的棘。使用双视紫红质光遗传学，我们检测到PVTp和mPFCp输入对BLAp的树突求和的迹象。此外，与PVTp或mPFCp同步的BLAp的高频激活会导致PVTp传输的瞬时增强，但不会导致mPFCp传输的瞬时增强。

重要性声明伏伏核通过整合广泛的谷氨酸能投射调节情绪和动机反应，但这些投射整合和相互作用的解剖和生理基础仍未得到开发。在这里，我们使用双色突触标记物与伏伏核中棘神经元的回填相结合，揭示了基底外侧杏仁核，内侧前额叶皮层和丘脑室旁核的突触的一些独特的解剖学排列。我们还在脑切片中使用了双视紫红质光遗传学，这揭示了一些但不是全部投影之间的非线性相互作用。这些结果提供了令人信服的解剖学和生理学机制，通过这些机制，不同的谷氨酸能投射到伏隔核，以及可能在情感和动机唤醒的不同方面，