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

条件性恐惧是一种人为的压力，由一种刺激（如音调）引起，这种刺激在本质上不会引起恐惧。杏仁核被认为是参与获得，巩固和回忆恐惧的区域。本研究采用体内微透析方法，连续监测大鼠杏仁核内谷氨酸、NO_3^-、多巴胺和5-羟色胺细胞外水平的变化，分别在第1天获得条件性恐惧和第2天对作为条件刺激的音调的恐惧回忆。谷氨酸仅在第1天升高，而多巴胺、5-羟色胺和NO_3^-在两天均升高。此外，我们采用在体脑微透析方法，研究了腹腔注射锂、丙咪嗪和地西泮对大鼠杏仁核NO_3^-水平的影响。与对照组相比，锂显著降低，丙咪嗪显著升高NO_3^-水平。这表明锂和丙咪嗪对脑中的一氧化氮相关系统产生对比效应。我们还研究了外周给药α干扰素对大脑中氨基酸水平的影响。一天的干扰素-α治疗诱导任何这些氨基酸没有显着变化。注射干扰素α 4天后，谷氨酸、甘氨酸、牛磺酸和γ-氨基丁酸水平显著高于对照组额叶皮质、纹状体、海马、杏仁核和丘脑。然而，这些氨基酸中的大多数在14天处理后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.