Chao H M, McEwen B S
Rockefeller University, Laboratory of Neuroendocrinology, New York, New York 10021.
Endocrinology. 1990 Jun;126(6):3124-30. doi: 10.1210/endo-126-6-3124.
Glucocorticoids regulate the level of preproenkephalin mRNA expression in a number of cell systems. This study investigated the expression of preproenkephalin mRNA in the brain and its regulation by glucocorticoids in vivo. Two different methods for mRNA quantitation were employed. Total RNA isolated from dissected brain tissue was analyzed in an RNAse T2 protection assay. In addition, we have used in situ hybridization to brain sections to assess the expression of preproenkephalin mRNA. The results demonstrate that in the striatum the preproenkephalin mRNA is expressed at a high level and is regulated by glucocorticoids. There is a decrease in striatal preproenkephalin mRNA after adrenalectomy (ADX), and ADX animals replaced with corticosterone express higher levels of striatal preproenkephalin mRNA than ADX animals. By in situ hybridization we have determined that the corticosterone-induced increase in striatal preproenkephalin mRNA is evident after 16 h, but not after 2 h, of corticosterone replacement of ADX animals. Elevation of circulating corticosterone levels in intact rats by 2-3 h of restraint stress, a multiple daily stress regimen over 1-21 days, or corticosterone injection did not change the level of preproenkephalin mRNA in the striatum; however, a single 16-h restraint stress resulted in a decreased level of expression. In intact rats there was a diurnal variation in the level of striatal preproenkephalin mRNA expression; ADX resulted in a decrease in the mRNA level, but did not abolish the diurnal variation in expression. Thus, while there is clearly regulation of striatal preproenkephalin mRNA by glucocorticoids, our results provide evidence for regulation by nonglucocorticoid mechanisms as well.
糖皮质激素可调节多种细胞系统中前脑啡肽原mRNA的表达水平。本研究调查了前脑啡肽原mRNA在脑内的表达及其在体内受糖皮质激素的调节情况。采用了两种不同的mRNA定量方法。从解剖的脑组织中分离出的总RNA在核糖核酸酶T2保护试验中进行分析。此外，我们还利用原位杂交技术检测脑切片中前脑啡肽原mRNA的表达。结果表明，纹状体中前脑啡肽原mRNA表达水平较高且受糖皮质激素调节。肾上腺切除术后（ADX）纹状体前脑啡肽原mRNA水平下降，用皮质酮替代的ADX动物比ADX动物表达更高水平的纹状体前脑啡肽原mRNA。通过原位杂交我们确定，在对ADX动物进行皮质酮替代16小时后，皮质酮诱导的纹状体前脑啡肽原mRNA增加明显，但2小时后不明显。通过2 - 3小时的束缚应激、1 - 21天的每日多次应激方案或注射皮质酮来提高完整大鼠循环皮质酮水平，并未改变纹状体中前脑啡肽原mRNA的水平；然而，单次16小时的束缚应激导致表达水平下降。在完整大鼠中，纹状体前脑啡肽原mRNA表达水平存在昼夜变化；ADX导致mRNA水平下降，但并未消除表达的昼夜变化。因此，虽然糖皮质激素对纹状体前脑啡肽原mRNA有明显调节作用，但我们的结果也为非糖皮质激素机制的调节提供了证据。
