Humans often rank craniofacial pain as more severe than body pain. Evidence suggests that a stimulus of the same intensity induces stronger pain in the face than in the body. However, the underlying neural circuitry for the differential processing of facial versus bodily pain remains unknown. Interestingly, the lateral parabrachial nucleus (PB_L), a critical node in the affective pain circuit, is activated more strongly by noxious stimulation of the face than of the hindpaw. Using a novel activity-dependent technology called CANE developed in our laboratory, we identified and selectively labeled noxious-stimulus-activated PB_L neurons and performed comprehensive anatomical input-output mapping. Surprisingly, we uncovered a hitherto uncharacterized monosynaptic connection between cranial sensory neurons and the PB_L-nociceptive neurons. Optogenetic activation of this monosynaptic craniofacial-to-PB_L projection induced robust escape and avoidance behaviors and stress calls, whereas optogenetic silencing specifically reduced facial nociception. The monosynaptic circuit revealed here provides a neural substrate for heightened craniofacial affective pain.

中文翻译：

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颅面特异性单突触回路可加剧情感疼痛。

人类通常认为颅面疼痛比身体疼痛更严重。有证据表明，与身体相比，相同强度的刺激会在面部引起更强烈的疼痛。然而，面部与身体疼痛的差异处理的潜在神经回路仍然未知。有趣的是，臂旁外侧核 (PB _L ) 是情感疼痛回路中的一个关键节点，面部的伤害性刺激比后爪的刺激更强烈。使用我们实验室开发的一种称为 CANE 的新型活性依赖技术，我们识别并选择性标记了有害刺激激活的 PB _L神经元并进行全面的解剖输入输出映射。令人惊讶的是，我们发现了颅感觉神经元和 PB _L伤害性神经元之间迄今未表征的单突触连接。这种单突触颅面到 PB _L投射的光遗传学激活诱导了强烈的逃避和回避行为以及压力呼叫，而光遗传学沉默特别减少了面部伤害感受。这里揭示的单突触回路为颅面情感性疼痛加剧提供了神经基质。