Department of Neurochemistry, Institute of Psychiatry and Neurology, 02-957 Warsaw, 9 Sobieskiego Street, Poland.
Neurobiol Learn Mem. 2010 Nov;94(4):499-508. doi: 10.1016/j.nlm.2010.09.001. Epub 2010 Sep 15.
In this paper we used a model of individual differences in fear responses in rats selected according to their low and high freezing response in the contextual fear test and termed these animals "low- and high anxiety" rats, respectively. We studied differences in the density of GABA-A receptor alpha-2 subunits and gephyrin in the brain structures of low (LR) and high (HR) anxiety rats subjected to extinction trials and re-learning of a conditioned fear response. We found different patterns of spontaneous (western blotting) and fear-stimulated expression of alpha-2 subunits and gephyrin (western blotting and immunocytochemistry) in brain structures of HR and LR animals. Increased basal concentrations of alpha-2 subunits in the amygdala were observed in HR rats (compared to unconditioned control group). The density of alpha-2 subunits in the amygdala negatively correlated with freezing response duration in the aversive context on re-learning in the same group of animals. This finding supports data on the role of GABA-A receptor alpha-2 subunits in the amygdala in modulation of anxiety-like behaviour. Western blotting revealed that exposure of HR animals to fear-conditioned context upon re-test of the conditioned fear test elevated the concentration of alpha-2 subunits in the amygdala and prefrontal cortex. In addition, immunocytochemistry showed that conditioned fear increased the number of cells co-expressing alpha-2 subunits and gephyrin in the basolateral amygdala and dentate gyrus of the hippocampus in the HR group. Together, these findings suggest that animals that are more vulnerable to stress differ in the intracellular mechanisms that control GABA-A receptor trafficking in limbic structures (hippocampus and amygdala), which are involved in the control of emotional behaviour. These data indicate a possible mechanism for the variable effects of benzodiazepines among patients with anxiety disorders. The obtained data may also help to better explain the neurobiological mechanisms that operate in clinical situations where anxious patients subjected to exposure therapy are exposed to an aversive, contextual and conditioning stimulus.
在这项研究中，我们使用了根据其在情境恐惧测试中的低冻结反应和高冻结反应选择的恐惧反应个体差异模型，将这些动物分别命名为“低焦虑”和“高焦虑”大鼠。我们研究了在消退试验和重新学习条件性恐惧反应后，大脑结构中 GABA-A 受体 α-2 亚基和 gephyrin 的密度在低（LR）和高（HR）焦虑大鼠中的差异。我们发现 HR 和 LR 动物大脑结构中α-2 亚基和 gephyrin 的自发（western blotting）和恐惧刺激表达存在不同模式（western blotting 和免疫细胞化学）。在 HR 大鼠的杏仁核中观察到 α-2 亚基的基础浓度增加（与未条件对照组相比）。在同一组动物的重新学习中，杏仁核中 α-2 亚基的密度与厌恶环境中的冻结反应持续时间呈负相关。这一发现支持了 GABA-A 受体 α-2 亚基在杏仁核中在调节焦虑样行为中的作用的数据。Western blotting 显示，在重新测试条件性恐惧测试时，将 HR 动物暴露于恐惧条件环境中，会导致杏仁核和前额叶皮层中 α-2 亚基的浓度升高。此外，免疫细胞化学显示，在 HR 组中，条件性恐惧增加了基底外侧杏仁核和海马齿状回中共同表达 α-2 亚基和 gephyrin 的细胞数量。总之，这些发现表明，对压力更敏感的动物在控制边缘结构（海马体和杏仁核）中 GABA-A 受体转运的细胞内机制上存在差异，这与情绪行为的控制有关。这些数据表明，在焦虑障碍患者中，苯二氮䓬类药物的作用存在差异，可能存在一种机制。这些数据还可能有助于更好地解释在焦虑患者接受暴露疗法时暴露于厌恶、情境和条件刺激的临床情况下起作用的神经生物学机制。
