Abnormal fear and anxiety can manifest as psychiatric disorders. The bed nucleus of the stria terminalis (BNST) is implicated in sustained responding to, or anticipation of, an aversive event which can be expressed as anticipatory anxiety. The BLA is also active during anticipatory anxiety and sends projections to the BNST. However, little is known about the role for BLA neurons that project to BNST (BLA-BNST) in anticipatory anxiety in rodents. To address this, we tested whether chemogenetic inactivation of the BLA-BNST pathway attenuates sustained conditioned responses produced by anticipation of an aversive stimulus. For comparison, we also assessed BLA-BNST inactivation during social interaction, which is sensitive to unlearned anxiety. We found that BLA-BNST inactivation reduced conditioned sustained freezing and increased social behaviors, but surprisingly, only in males. To determine whether sex differences in BLA-BNST neuronal activity contribute to the differences in behavior, we used in vivo and ex vivo electrophysiological approaches. In males, BLA-BNST projection neurons were more active and excitable, which coincided with a smaller after-hyperpolarization current (I_AHP) compared with other BLA neurons; whereas in females, BLA-BNST neurons were less excitable and had larger I_AHP compared with other BLA neurons. These findings demonstrate that activity of BLA-BNST neurons mediates conditioned anticipatory anxiety-like behavior in males. The lack of a role of BLA-BNST in females in this behavior, possibly because of low excitability of these neurons, also highlights the need for caution when generalizing the role of specific neurocircuits in fear and anxiety.

SIGNIFICANCE STATEMENT Anxiety disorders disproportionately affect women. This hints toward sex differences within anxiety neurocircuitry, yet most of our understanding is derived from male rodents. Furthermore, debilitating anticipation of adverse events is among the most severe anxiety symptoms, but little is known about anticipatory anxiety neurocircuitry. Here we demonstrated that BLA-BNST activity is required for anticipatory anxiety to a prolonged aversive cue, but only in males. Moreover, BLA-BNST neurons are hypoactive and less excitable in females. These results uncover BLA-BNST as a key component of anticipatory anxiety circuitry, and cellular differences may explain the sex-dependent role of this circuit. Uncovering this disparity provides evidence that the assumed basic circuitry of an anxiety behavior might not readily transpose from males to females.

异常的恐惧和焦虑可以表现为精神疾病。终纹床核 (BNST) 与对厌恶事件的持续反应或预期有关，可表示为预期焦虑。BLA 在预期焦虑期间也很活跃，并向 BNST 发送预测。然而，关于投射到 BNST (BLA-BNST) 的 BLA 神经元在啮齿动物的预期焦虑中的作用知之甚少。为了解决这个问题，我们测试了 BLA-BNST 通路的化学灭活是否会减弱因预期厌恶刺激而产生的持续条件反应。为了比较，我们还评估了社交互动过程中的 BLA-BNST 失活，这对未习得的焦虑很敏感。我们发现 BLA-BNST 失活减少了条件性持续冻结并增加了社会行为，但令人惊讶的是，仅在男性中。为了确定 BLA-BNST 神经元活动的性别差异是否会导致行为差异，我们使用体内和体外电生理学方法。在男性中，BLA-BNST投射神经元更加活跃和兴奋，同时与其他BLA神经元相比，超极化后电流（ I _{AHP ）更小；}而在女性中，与其他 BLA 神经元相比，BLA-BNST 神经元的兴奋性较低且I _AHP较大。这些发现表明，BLA-BNST 神经元的活动介导了男性的条件性预期焦虑样行为。BLA-BNST 在女性中缺乏这种行为的作用，可能是因为这些神经元的低兴奋性，也突出了在概括特定神经回路在恐惧和焦虑中的作用时需要谨慎。

重要性声明焦虑症不成比例地影响女性。这暗示了焦虑神经回路中的性别差异，但我们的大部分理解来自雄性啮齿动物。此外，对不良事件的衰弱预期是最严重的焦虑症状之一，但对预期焦虑神经回路知之甚少。在这里，我们证明了 BLA-BNST 活性是对长期厌恶线索的预期焦虑所必需的，但仅限于男性。此外，BLA-BNST 神经元在女性中是低活性的并且不太容易兴奋。这些结果揭示了 BLA-BNST 作为预期焦虑回路的关键组成部分，细胞差异可以解释该回路的性别依赖性作用。发现这种差异提供了证据，表明焦虑行为的假定基本电路可能不容易从男性转移到女性。