Baratta Annalisa M, Viechweg Shaun S, Mong Jessica A, Pocivavsek Ana
Maryland Psychiatric Research Center, Department of Psychiatry, University of Maryland School of Medicine.
Department of Pharmacology, University of Maryland School of Medicine.
J Vis Exp. 2018 Aug 19(138):58129. doi: 10.3791/58129.
The kynurenine pathway (KP) of tryptophan degradation has been implicated in psychiatric disorders. Specifically, the astrocyte-derived metabolite kynurenic acid (KYNA), an antagonist at both N-methyl-d-aspartate (NMDA) and α7 nicotinic acetylcholine (α7nACh) receptors, has been implicated in cognitive processes in health and disease. As KYNA levels are elevated in the brains of patients with schizophrenia, a malfunction at the glutamatergic and cholinergic receptors is believed to be causally related to cognitive dysfunction, a core domain of the psychopathology of the illness. KYNA may play a pathophysiologically significant role in individuals with schizophrenia. It is possible to elevate endogenous KYNA in the rodent brain by treating animals with the direct bioprecursor kynurenine, and preclinical studies in rats have demonstrated that acute elevations in KYNA may impact their learning and memory processes. The current protocol describes this experimental approach in detail and combines a) a biochemical analysis of blood kynurenine levels and brain KYNA formation (using high-performance liquid chromatography), b) behavioral testing to probe the hippocampal-dependent contextual memory (passive avoidance paradigm), and c) an assessment of sleep-wake behavior [telemetric recordings combining electroencephalogram (EEG) and electromyogram (EMG) signals] in rats. Taken together, a relationship between elevated KYNA, sleep, and cognition is studied, and this protocol describes in detail an experimental approach to understanding function outcomes of kynurenine elevation and KYNA formation in vivo in rats. Results obtained through variations of this protocol will test the hypothesis that the KP and KYNA serve pivotal roles in modulating sleep and cognition in health and disease states.
色氨酸降解的犬尿氨酸途径（KP）与精神疾病有关。具体而言，星形胶质细胞衍生的代谢产物犬尿喹啉酸（KYNA）是N-甲基-D-天冬氨酸（NMDA）和α7烟碱型乙酰胆碱（α7nACh）受体的拮抗剂，与健康和疾病状态下的认知过程有关。由于精神分裂症患者大脑中的KYNA水平升高，谷氨酸能和胆碱能受体的功能障碍被认为与认知功能障碍存在因果关系，而认知功能障碍是该疾病心理病理学的核心领域。KYNA可能在精神分裂症患者中发挥病理生理学上的重要作用。通过用直接生物前体犬尿氨酸治疗动物，可以提高啮齿动物大脑中的内源性KYNA，并且在大鼠中的临床前研究表明，KYNA的急性升高可能会影响它们的学习和记忆过程。本实验方案详细描述了这种实验方法，并结合了以下内容：a）对血液中犬尿氨酸水平和大脑中KYNA形成的生化分析（使用高效液相色谱法），b）用于探究海马依赖性情境记忆的行为测试（被动回避范式），以及c）对大鼠睡眠-觉醒行为的评估[结合脑电图（EEG）和肌电图（EMG）信号的遥测记录]。综合来看，本研究探讨了KYNA升高、睡眠和认知之间的关系，并且该方案详细描述了一种实验方法来理解犬尿氨酸升高和KYNA在大鼠体内形成的功能结果。通过改变该方案获得的结果将检验以下假设：KP和KYNA在调节健康和疾病状态下的睡眠和认知方面起关键作用。
