Diurnal corticotropin-releasing hormone mRNA variation in the hypothalamus exhibits a rhythm distinct from that of plasma corticosterone.
Diurnal corticotropin-releasing hormone mRNA variation in the hypothalamus exhibits a rhythm distinct from that of plasma corticosterone.
复制标题
下丘脑中促肾上腺皮质激素释放激素 mRNA 的昼夜变化表现出与血浆皮质酮不同的节律。
DOI：
10.1159/000126099
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发表时间：
1992
影响因子：
4.1
通讯作者：
Akil,H
中科院分区：
文献类型：
--
作者：
Kwak,SP;Young,EA;Morano,I;Watson,SJ;Akil,H
下丘脑垂体-肾上腺轴呈现昼夜节律，血浆皮质酮的日波动可证明这一点。这种节律似乎主要是由下丘脑室旁核（PVN）CRH神经元的刺激介导的。在本研究中，我们研究了昼夜节律对下丘脑室旁区CRH mRNA水平的影响。在24小时内处死动物，以建立CRH mRNA波动的详细时程。同时测量该区域I型和II型皮质酮受体mRNA的水平，以观察其变化是否与CRH mRNA的变化相关。血浆ACTH水平定量作为CRH肽分泌的指标。结果表明，ACTH的变化密切相关的皮质酮水平的变化与增加的趋势开始于下午1时，这表明，昼夜分泌驱动开始在这个时候左右。通过RNA酶保护测定确定的CRH mRNA节律似乎以预期的方式改变这些内分泌波动，在光照阶段增加，并在天黑前（5-6 PM）达到最大水平。突然下降30%的CRH mRNA含量在下丘脑中检测到黑暗后2小时内（8 PM），正好与血浆皮质酮水平的峰值。然而，CRH mRNA含量的其他周期性变化并不伴随着血浆皮质酮的变化。这两种类型的皮质酮受体的mRNA表现出任何昼夜变化，表明类固醇受体在下丘脑的表达不受昼夜节律的影响。我们的结论是CRH mRNA水平波动昼夜，但呈负相关的皮质酮水平仅在傍晚。
The hypothalamopituitary-adrenal axis exhibits a diurnal rhythm as witnessed by the daily excursion of corticosterone in plasma. The rhythm appears to be mediated largely by the stimulation of CRH neurons in the paraventricular nucleus (PVN) of the hypothalamus. In the present study, we investigated the effects of circadian influence on CRH mRNA levels in the paraventricular hypothalamus. Animals were sacrificed through a 24-hour period to establish a detailed time course of CRH mRNA fluctuations. Levels of both type I and type II corticosterone receptor mRNAs were also measured in this area to see whether changes correlate with that of CRH mRNA. Plasma levels of ACTH were quantified as an index for CRH peptide secretion. The results indicate that changes in ACTH closely paralleled alterations in corticosterone levels with an increasing trend starting at 1 PM, suggesting that the diurnal secretory drive commences around this time. The CRH mRNA rhythm as determined by RNase protection assays appeared to change in an anticipatory fashion to these endocrine fluctuations, increasing during the light phase and reaching maximal levels just prior to dark (5-6 PM). An abrupt decrease of 30% in the CRH mRNA content was detected in the hypothalamus within 2 h after dark (8 PM) and coincided with the peak of plasma corticosterone levels. However, other periodic variations in the CRH mRNA content were not accompanied by changes in plasma corticosterone. Neither types of corticosterone receptor mRNAs showed any diurnal change suggesting that the expression of steroid receptors in the hypothalamus is not regulated by circadian influences. We conclude that CRH mRNA levels fluctuate diurnally but are inversely related to corticosterone levels only in the early evening.