The gastrin-releasing peptide regulates stress-enhanced fear and dopamine signaling

Fear extinction is an adaptive behavioral process critical for organism’s survival, but deficiency in extinction may lead to PTSD. While the amygdala and its neural circuits are critical for fear extinction, the molecular identity and organizational logic of cell types that lie at the core of these circuits remain unclear. Here we report that mice deficient for amygdala-enriched gastrin-releasing peptide gene (Grp-/-) exhibit enhanced neuronal activity in the basolateral amygdala (BLA) and stronger fear conditioning, as well as deficient extinction in stress-enhanced fear learning (SEFL). rAAV2-retro-based tracing combined with visualization of the GFP knocked in the Grp gene showed that BLA receives several GRPergic conditioned stimulus projections: from the indirect auditory thalamus-to-auditory cortex pathway, medial prefrontal cortex, ventral hippocampus and ventral tegmental area. Transcription of dopamine-related genes was decreased in BLA of Grp-/- mice following SEFL extinction recall, suggesting that the GRP may mediate fear extinction regulation by dopamine. RNA-seq from mouse brain tissue. Gene expression from 4 replicates each from 4 separate conditions were compared. The sample names are WT or KO (for wild type or Grp -/- mice), an S indicates the mouse had undergone stress treatment (a lack of S indicates no stress treatment), and the mouse number.

恐惧消退是对生物体生存至关重要的适应性行为过程，而消退缺陷可引发创伤后应激障碍（Post-Traumatic Stress Disorder, PTSD）。尽管杏仁核及其神经环路在恐惧消退中发挥关键作用，但构成这些环路核心的细胞类型的分子特性与组织逻辑仍有待阐明。本研究发现，杏仁核富集的胃泌素释放肽基因（gastrin-releasing peptide gene, Grp）敲除小鼠（Grp-/-）的基底外侧杏仁核（basolateral amygdala, BLA）神经元活动增强、恐惧条件反射增强，且在应激增强恐惧学习（stress-enhanced fear learning, SEFL）模型中出现恐惧消退障碍。基于rAAV2-retro的逆行示踪技术，结合对Grp基因敲入的绿色荧光蛋白（green fluorescent protein, GFP）的可视化检测显示，基底外侧杏仁核接收多条GRP能条件刺激投射，其来源包括间接听觉丘脑-听觉皮层通路、内侧前额叶皮层、腹侧海马及腹侧被盖区。在SEFL消退回忆后，Grp-/-小鼠基底外侧杏仁核内多巴胺相关基因的转录水平显著下调，提示GRP可能通过多巴胺信号通路介导恐惧消退的调控。本研究采用小鼠脑组织进行RNA测序，对4组独立实验条件下各4个生物学重复的基因表达谱进行了对比分析。样本命名规则如下：WT或KO分别代表野生型小鼠或Grp敲除小鼠；带有S标识的小鼠接受过应激处理，无S标识则表示未进行应激处理，样本后缀为小鼠编号。