Chen Y, Hatalski C G, Brunson K L, Baram T Z
Department of Anatomy & Neurobiology and Pediatrics, University of California at Irvine, CA 92697-4475, USA.
Brain Res Mol Brain Res. 2001 Nov 30;96(1-2):39-49. doi: 10.1016/s0169-328x(01)00265-0.
The mechanisms of the molecular and neuroendocrine responses to stress in the immature rat have been a focus of intense investigation. A principal regulator of the these responses in both mature and developing rat is the neuropeptide corticotropin releasing hormone (CRH), and levels of hypothalamic CRH mRNA are enhanced by stress. In vitro, transcription of the CRH gene is governed by binding of the phosphorylated form of cAMP responsive element binding protein (pCREB) to the promoter. Here we tested the hypothesis that rapid, stress-induced CRH transcription occurred during the first two postnatal weeks, and is associated with pCREB expression. The time-course of induction of unedited, heteronuclear CRH RNA (CRH hnRNA) was examined in hypothalamic paraventricular nucleus (PVN) of immature rats subjected to both modest and strong acute stressors using in situ hybridization; pCREB abundance was determined in individual neurons in specific PVN sub-nuclei using immunocytochemistry and unbiased quantitative analysis. CRH hnRNA signal was negligible in PVN of immature rats sacrificed under stress-free conditions, but was readily detectable within 2 min, and peaked at 15 min, in PVN of stressed animals. Enhanced pCREB immunoreactivity was evident within 2 min of stress onset, and was enhanced specifically in stress-responsive, CRH-expressing medial parvocellular neurons. These data support the notion that, already during early postnatal life, stress induces rapid CREB phosphorylation, interaction of pCREB-containing transcription complexes with the CRE element of the CRH gene promoter, and initiation of CRH hnRNA production in stress-responsive neurons of rat PVN.
幼鼠对应激的分子和神经内分泌反应机制一直是深入研究的重点。在成熟和发育中的大鼠中，这些反应的主要调节因子是神经肽促肾上腺皮质激素释放激素（CRH），应激会提高下丘脑CRH mRNA的水平。在体外，CRH基因的转录受cAMP反应元件结合蛋白（pCREB）的磷酸化形式与启动子结合的调控。在此，我们检验了这样一个假设：快速的、应激诱导的CRH转录发生在出生后的前两周，并且与pCREB的表达有关。使用原位杂交技术，研究了遭受适度和强烈急性应激源的未成熟大鼠下丘脑室旁核（PVN）中未经编辑的异核CRH RNA（CRH hnRNA）诱导的时间进程；使用免疫细胞化学和无偏定量分析确定了特定PVN亚核中单个神经元的pCREB丰度。在无应激条件下处死的未成熟大鼠的PVN中，CRH hnRNA信号可忽略不计，但在应激动物的PVN中，2分钟内即可轻易检测到，15分钟时达到峰值。应激开始后2分钟内，pCREB免疫反应性增强，并且在应激反应性的、表达CRH的内侧小细胞神经元中特异性增强。这些数据支持这样一种观点，即在出生后早期，应激就会诱导快速的CREB磷酸化、含pCREB的转录复合物与CRH基因启动子的CRE元件相互作用，并在大鼠PVN的应激反应性神经元中启动CRH hnRNA的产生。
