N-acylethanolamines (NAEs) are endogenous lipid-signaling molecules derived from fatty acids that regulate numerous biological functions, including in the brain. Interestingly, NAEs are elevated in the absence of fatty acid amide hydrolase (FAAH) and following CO₂-induced ischemia/hypercapnia, suggesting a neuroprotective response. Tetracosahexaenoic acid (THA) is a product and precursor to docosahexaenoic acid (DHA), however, the NAE product - tetracosahexaenoylethanolamide (THEA) - has never been reported. Presently, THEA was chemically synthesized as an authentic standard to confirm THEA presence in biological tissues. Whole brains were collected and analyzed for unesterified THA, total THA and THEA in wild-type and FAAH-KO mice that were euthanized by either head-focused microwave fixation, CO₂ + microwave or CO₂ only. PPAR activity by transient transfection assay and ex vivo neuronal output in medium spiny neurons (MSN) of the nucleus accumbens by patch clamp electrophysiology were determined following THEA exposure. THEA in the wild-type mice was nearly doubled (p<0.05) following ischemia/hypercapnia (CO₂ euthanization) and up to 12-times higher (p<0.001) in the FAAH-KO compared to wild-type. THEA did not increase (p>0.05) transcriptional activity of PPARs relative to control, but 100nM THEA increased (p<0.001) neuronal output in MSN of the nucleus accumbens. Here were identify a novel NAE, THEA, in the brain that is elevated upon ischemia/hypercapnia and by knockout of the FAAH enzyme. While THEA did not activate PPAR, it augmented the excitability of MSN in the nucleus accumbens. Overall, our results suggest THEA is a novel NAE that is produced in the brain upon ischemia/hypercapnia and regulates neuronal excitation.

中文翻译：

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Tetracosahexaenoylethanolamide 是一种新型的 n-酰基乙醇酰胺，在缺血时升高并增加神经元输出。

N-酰基乙醇胺 (NAE) 是源自脂肪酸的内源性脂质信号分子，可调节多种生物功能，包括在大脑中。有趣的是，在不存在脂肪酸酰胺水解酶 (FAAH) 和 CO ₂诱导的缺血/高碳酸血症后，NAE 升高，表明存在神经保护反应。四十二碳六烯酸 (THA) 是二十二碳六烯酸 (DHA) 的产物和前体，然而，从未报道过 NAE 产物——四十二碳六烯酰乙醇酰胺 (THEA)。目前，THEA 已被化学合成，作为确认生物组织中存在 THEA 的可靠标准。收集全脑并分析野生型和 FAAH-KO 小鼠的未酯化 THA、总 THA 和 THEA，这些小鼠通过头部聚焦微波固定、CO 安乐死₂ +仅微波或 CO ₂。在 THEA 暴露后测定通过瞬时转染测定法测定的 PPAR 活性和通过膜片钳电生理学测定伏隔核中等多刺神经元 (MSN) 中的离体神经元输出。缺血/高碳酸血症（CO ₂安乐死）并且在 FAAH-KO 中比野生型高 12 倍（p<0.001）。相对于对照，THEA 没有增加 (p>0.05) PPARs 的转录活性，但 100nM THEA 增加了 (p<0.001) 伏隔核 MSN 中的神经元输出。这里鉴定了大脑中的一种新型 NAE，THEA，它在缺血/高碳酸血症和通过敲除 FAAH 酶时升高。虽然 THEA 没有激活 PPAR，但它增强了伏隔核中 MSN 的兴奋性。总体而言，我们的结果表明 THEA 是一种新型 NAE，在缺血/高碳酸血症时在大脑中产生并调节神经元兴奋。