Amygdalic levels of monoamines, amino acids and nitric oxide rise upon exposure to conditioned fear stress without elevation of amino acids

条条性恐惧是一种人为的压力，由刺激引起，比如声音，这在本质上不会引起恐惧。杏仁核被认为是与获取、巩固和回忆恐惧有关的区域。本研究旨在利用体内微透析方法，连续监测第1天条件恐惧习得和第2天条件刺激下声调恐惧回忆时杏仁核中谷氨酸、NO_3^-、多巴胺和血清素的细胞外水平变化。谷氨酸仅在第1天升高，而多巴胺、血清素和NO_3^-均在第2天升高。此外，我们采用体内脑微透析方法，研究了锂、丙咪嗪和地西泮腹腔注射对大鼠杏仁核NO_3^-水平的影响。与对照组相比，锂组明显降低了NO_3^水平，而丙咪嗪组提高了NO_3^水平。这表明锂和丙咪嗪对大脑中一氧化氮相关系统的影响是相反的。我们还研究了外周给药干扰素- α对大脑中氨基酸水平的影响。一天的干扰素治疗没有引起这些氨基酸的显著变化。注射干扰素4天后，大鼠额叶皮质、纹状体、海马、杏仁核和丘脑中的谷氨酸、甘氨酸、牛磺酸和γ -氨基丁酸水平显著高于对照组。然而，经过14天的治疗，这些氨基酸中的大多数恢复到大约基础水平，甚至更低。

Conditioned fear is an artificial stress, induced by a stimulus, such as a tone, that does not elicit fear in nature. The amygdala is considered to be the area involved in acquisition, consolidation and recall of fear. The present study was designed to continuously monitor changes in extracellular levels of glutamate, NO_3^-, dopamine and serotonin in the amygdala, at the acquisition of conditioned fear on Day 1 and at fear recall in response to a tone as a conditioned stimulus on Day 2, using the in vivo microdialysis method. Glutamate was elevated only on Day 1, while dopamine, serotonin and NO_3^- rose on both days. Using a in-vivo brain microdialysis method, in addition, we investigated effects of intraperitoneal administration with lithium, imipramine, and diazepam on NO_3^- levels in the rat amygdala. Lithium significantly declined, but that of imipramine raised NO_3^- levels as compared with control. These suggest that lithium and imipramine induce contrastive effects on nitric oxide related systems in the brain. We also investigated the influence of peripherally administered interferon-alpha on amino acid levels in the brain. One day of interferon-alpha treatment induced no significant changes in any of these amino acids. After 4 days of interferon-alpha injections, glutamate, glycine, taurine and gamma-aminobutyric acid levels were significantly higher than those in the control frontal cortex, striatum, hippocampus, amygdala, and thalamus. However, most of these amino acids returned to approximately basal levels, or even lower, with 14-day-treatment.