Ponce-Lina Renata, Serafín Norma, Carranza Martha, Arámburo Carlos, Prado-Alcalá Roberto A, Luna Maricela, Quirarte Gina L
Departamento de Neurobiología Conductual y Cognitiva, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, Mexico.
Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, Mexico.
Front Behav Neurosci. 2020 Feb 13;14:12. doi: 10.3389/fnbeh.2020.00012. eCollection 2020.
Aversive events induce the release of glucocorticoid stress hormones that facilitate long-term memory consolidation, an effect that depends on the activation of glucocorticoid receptors (GRs). GRs are distributed widely in the hippocampus. The dorsal region of the hippocampus has been related to cognitive functions and the ventral region to stress and emotion. GR acts as a transcription factor which after hormone binding becomes phosphorylated, affecting its cellular distribution and transcriptional activity. Two functionally well-described GR phosphorylation sites are serine 232 (pSer232), which enhances gene expression, and serine 246 (pSer246), having the opposite effect. Since gene expression is one of the plastic mechanisms needed for memory consolidation, we investigated if an aversive learning task would induce GR phosphorylation in the dorsal (DH) and the ventral (VH) hippocampus. We trained rats in contextual fear conditioning (CFC) using different foot-shock intensities (0.0, 0.5, or 1.5 mA). One subgroup of animals trained with each intensity was sacrificed 15 min after training and blood was collected to quantify corticosterone (CORT) levels in serum. Another subgroup was sacrificed 1 h after training and brains were collected to evaluate the immunoreactivity (IR) to GR, pSer232 and pSer246 by SDS-PAGE/Western blot in DH and VH, and by immunohistochemistry in dorsal and ventral CA1, CA2, CA3, and dentate gyrus (DG) hippocampal regions. The conditioned freezing response increased in animals trained with 0.5 and 1.5 mA during training and extinction sessions. The degree of retention and CORT levels were directly related to the intensity of the foot-shock. Although total GR-IR remained unaffected after conditioning, we observed a significant increase of pSer246-IR in the dorsal region of CA1 and in both dorsal and ventral DG. The only region in which pSer232-IR was significantly elevated was ventral CA3. Our results indicate that fear conditioning training is related to GR phosphorylation in specific subregions of the hippocampus, suggesting that its transcriptional activity for gene expression is favored in ventral CA3, whereas its repressor activity for gene-silencing is increased in dorsal CA1 and in both dorsal and ventral DG.
厌恶事件会诱导糖皮质激素应激激素的释放，这些激素有助于长期记忆巩固，这一效应依赖于糖皮质激素受体（GRs）的激活。GRs广泛分布于海马体中。海马体的背侧区域与认知功能有关，而腹侧区域与应激和情绪有关。GR作为一种转录因子，在与激素结合后会发生磷酸化，从而影响其细胞分布和转录活性。两个功能已被充分描述的GR磷酸化位点分别是丝氨酸232（pSer232），它能增强基因表达；以及丝氨酸246（pSer246），其作用相反。由于基因表达是记忆巩固所需的可塑性机制之一，我们研究了厌恶学习任务是否会在背侧（DH）和腹侧（VH）海马体中诱导GR磷酸化。我们使用不同的足部电击强度（0.0、0.5或1.5毫安）对大鼠进行情境恐惧条件反射（CFC）训练。每个强度训练的一组动物在训练后15分钟被处死，并采集血液以量化血清中的皮质酮（CORT）水平。另一组动物在训练后1小时被处死，并采集大脑，通过SDS-PAGE/蛋白质免疫印迹法评估DH和VH中GR、pSer232和pSer246的免疫反应性（IR），并通过免疫组织化学法评估背侧和腹侧CA1、CA2、CA3以及齿状回（DG）海马区的免疫反应性。在训练和消退阶段，接受0.5和1.5毫安训练的动物的条件性僵住反应增加。记忆保持程度和CORT水平与足部电击强度直接相关。虽然条件反射后总GR-IR保持不变，但我们观察到CA1背侧区域以及背侧和腹侧DG中的pSer246-IR显著增加。pSer232-IR显著升高的唯一区域是腹侧CA3。我们的结果表明，恐惧条件反射训练与海马体特定亚区域的GR磷酸化有关，这表明其在腹侧CA3中有利于基因表达的转录活性，而在背侧CA1以及背侧和腹侧DG中其基因沉默的抑制活性增加。
