Zhao Junli, Furutani Kenta, McGinnis Aidan, Mathew Joseph P, Wang Fan, Ji Ru-Rong
Center for Translational Pain Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina.
Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina.
Anesthesiology. 2025 Aug 1;143(2):383-403. doi: 10.1097/ALN.0000000000005553. Epub 2025 May 7.
General anesthesia, such as isoflurane, induces analgesia (loss of pain) and loss of consciousness through mechanisms that are not fully understood. A distinct population of γ-aminobutyric acid-mediated neurons has been recently identified in the central amygdala (CeA) that can be activated by general anesthesia (CeA GA ) and exert antinociceptive functions. In this study, the authors aimed to explore the underlying cellular mechanisms of CeA GA neurons across different phases of nerve injury-induced nociceptive sensitization in mice.
This study used 107 mice, including 57 males and 50 females. The authors induced c-fos activation in the mice brains using 1.2% isoflurane and validated Fos expression via RNAscope (Advanced Cell Diagnostics, USA) in situ hybridization. Unlike previous studies using the capturing activated neuronal ensembles method, CeA GA neurons (tdTomato + ) were labeled using the Fos-Targeted Recombination in Active Populations (TRAP2) method. The authors then performed ex vivo electrophysiologic recordings to assess the properties of both Fos-positive/CeA GA neurons and Fos-negative CeA neurons. Using chemogenetic strategy to selectively activate the CeA GA neurons, the authors investigated pain-like behaviors and associated comorbidities in mice after spared nerve injury (SNI).
Isoflurane induced robust Fos expression in CeA γ-aminobutyric acid-mediated neurons. Electrophysiologic recordings in brain slices revealed that compared to Fos-negative CeA neurons, CeA GA neurons had higher excitability and exhibited distinct patterns of action potentials. Chemogenetic activation of Fos-TRAPed CeA GA neurons increased nociceptive thresholds in naive mice and in mice 2 weeks after SNI, but demonstrated modest antinociception 8 weeks after SNI. Finally, Fos-negative CeA neurons, but not CeA GA neurons, exhibited increased excitability in the chronic phase of SNI, which was correlated with a downregulation of K + -Cl - cotransporter-2 (KCC2) in the CeA (sham vs . SNI 8 weeks).
These results validate the antinociceptive power of CeA GA neurons using a different approach. Additionally, the authors highlight distinct roles of CeA GA neurons in governing physiologic pain, acute pain, and the transition to chronic pain through KCC2 dysregulation.
全身麻醉，如异氟烷，通过尚未完全明确的机制诱导镇痛（痛觉丧失）和意识丧失。最近在中央杏仁核（CeA）中发现了一群由γ-氨基丁酸介导的神经元，它们可被全身麻醉激活（CeA GA）并发挥抗伤害感受功能。在本研究中，作者旨在探讨CeA GA神经元在小鼠神经损伤诱导的伤害性感受敏化不同阶段的潜在细胞机制。
本研究使用了107只小鼠，包括57只雄性和50只雌性。作者使用1.2%异氟烷诱导小鼠大脑中的c-fos激活，并通过RNAscope（美国高级细胞诊断公司）原位杂交验证Fos表达。与以往使用捕获激活神经元群体方法的研究不同，CeA GA神经元（tdTomato +）使用活性群体中的Fos靶向重组（TRAP2）方法进行标记。然后作者进行离体电生理记录，以评估Fos阳性/CeA GA神经元和Fos阴性CeA神经元的特性。使用化学遗传学策略选择性激活CeA GA神经元，作者研究了保留神经损伤（SNI）后小鼠的疼痛样行为和相关合并症。
异氟烷在CeAγ-氨基丁酸介导的神经元中诱导了强烈的Fos表达。脑片电生理记录显示，与Fos阴性CeA神经元相比，CeA GA神经元具有更高的兴奋性，并表现出不同的动作电位模式。Fos-TRAPed CeA GA神经元的化学遗传学激活增加了未受伤小鼠和SNI后2周小鼠的伤害性感受阈值，但在SNI后8周表现出适度的抗伤害感受作用。最后，Fos阴性CeA神经元而非CeA GA神经元在SNI慢性期表现出兴奋性增加，这与CeA中K + -Cl - 共转运体-2（KCC2）的下调相关（假手术组与SNI 8周组）。
这些结果使用不同方法验证了CeA GA神经元的抗伤害感受能力。此外，作者强调了CeA GA神经元在通过KCC2失调控制生理性疼痛、急性疼痛以及向慢性疼痛转变中的不同作用。
