Institute of Pharmacology, Polish Academy of Sciences, Department of Brain Biochemistry, 31-343 Krakow, Smętna Street 12, Poland.
Free University Maria Ss. Assunta (LUMSA), Department of Human Sciences, Rome, Italy.
Prog Neuropsychopharmacol Biol Psychiatry. 2019 Jul 13;93:221-231. doi: 10.1016/j.pnpbp.2019.04.001. Epub 2019 Apr 3.
Disturbances in fear-evoked signal transduction in the hippocampus (HP), the nuclei of the amygdala (AMY), and the prefrontal cortex (PFC) underlie anxiety-related disorders. However, the molecular mechanisms underlying these effects remain elusive. Heterotrimeric G proteins (GPs) are divided into the following four families based on the intracellular activity of their alpha subunit (Gα): Gα(s) proteins stimulate cyclic AMP (cAMP) generation, Gα(i/o) proteins inhibit the cAMP pathway, Gα(q/11) proteins increase the intracellular Ca concentration and the inositol trisphosphate level, and Gα(12/13) proteins activate monomeric GP-Rho. In the present study, we assessed the effects of a fear memory procedure on the mRNA expression of the Gα subunits of all four GP families in the HP, AMY and PFC. C57BL/6 J mice were subjected to a fear conditioning (FC) procedure followed by a contextual or cued fear memory test (CTX-R and CS-R, respectively). Morphine (MOR, 1 mg/kg/ip) was injected immediately after FC to prevent the fear consolidation process. Real-time quantitative PCR was used to measure the mRNA expression levels of Gα subunits at 1 h after FC, 24 h after FC, and 1 h after the CTX-R or CS-R. In the HP, the mRNA levels of Gα(s), Gα(12) and Gα(11) were higher at 1 h after training. Gα(s) levels were slightly lower when consolidation was stabilized and after the CS-R. The mRNA levels of Gα(12) were increased at 1 h after FC, returned to control levels at 24 h after FC and increased again with the CTX-R. The increase in the Gα(11) level persisted at 24 h after FC and after CTX-R. In the AMY, no specific changes were induced by FC. In the PFC, CTX-R was accompanied by a decrease in Gα(i/o) mRNA levels; however, only Gα(i2) downregulation was prevented by MOR treatment. Hence, the FC-evoked changes in Gα mRNA expression were observed mainly in the HP and connected primarily to contextual learning. These results suggest that the activation of signaling pathways by Gα(s) and Gα(12) is required to begin the fear memory consolidation process in the HP, while signal transduction via Gα(11) is implicated in the maintenance of fear consolidation. In the PFC, the downregulation of Gα(i2) appears to be related to the contextual learning of fear.
在海马体（HP）、杏仁核（AMY）核和前额叶皮层（PFC）中，恐惧诱发的信号转导障碍是焦虑相关障碍的基础。然而，这些影响的分子机制仍然难以捉摸。异三聚体 G 蛋白（GPs）根据其α亚基（Gα）的细胞内活性分为以下四个家族：Gα(s)蛋白刺激环腺苷酸（cAMP）的产生，Gα(i/o)蛋白抑制 cAMP 途径，Gα(q/11)蛋白增加细胞内 Ca 浓度和肌醇三磷酸水平，Gα(12/13)蛋白激活单体 GP-Rho。在本研究中，我们评估了恐惧记忆程序对 HP、AMY 和 PFC 中所有四个 GP 家族的 Gα 亚基 mRNA 表达的影响。C57BL/6J 小鼠接受恐惧条件反射（FC）程序，然后进行情境或线索恐惧记忆测试（CTX-R 和 CS-R，分别）。MOR（1mg/kg/ip）在 FC 后立即注射，以防止恐惧巩固过程。实时定量 PCR 用于测量 FC 后 1 小时、FC 后 24 小时和 CTX-R 或 CS-R 后 1 小时 Gα 亚基的 mRNA 表达水平。在 HP 中，训练后 1 小时 Gα(s)、Gα(12)和 Gα(11)的 mRNA 水平较高。当巩固稳定后和 CS-R 后，Gα(s)水平略有下降。FC 后 1 小时 Gα(12)的 mRNA 水平升高，FC 后 24 小时恢复到对照水平，CTX-R 后再次升高。FC 后 24 小时后 Gα(11)水平持续升高，CTX-R 后再次升高。在 AMY 中，FC 没有引起特定的变化。在 PFC 中，CTX-R 伴随着 Gα(i/o)mRNA 水平的降低；然而，只有 MOR 处理才能防止 Gα(i2)下调。因此，FC 诱导的 Gα mRNA 表达变化主要发生在 HP 中，主要与情境学习有关。这些结果表明，Gα(s)和 Gα(12)的信号通路激活对于开始 HP 中的恐惧记忆巩固过程是必需的，而 Gα(11)的信号转导与恐惧巩固的维持有关。在 PFC 中，Gα(i2)的下调似乎与恐惧的情境学习有关。
