Priest C A, Eckersell C B, Micevych P E
Department of Anatomy and Cell Biology, UCLA School of Medicine 90024-1763, USA.
Brain Res Mol Brain Res. 1995 Feb;28(2):251-62. doi: 10.1016/0169-328x(94)00213-x.
Numerous studies suggest that the ventromedial nucleus of the hypothalamus is a primary locus of control for reproductive behavior in the female rat. The display of lordosis behavior is estrogen dependent and its regulation appears to involve the activity of endogenous opioid circuits in the mediobasal hypothalamus and brainstem. Hypothalamic levels of preproenkephalin-A mRNA and the neuropeptide which it encodes, methionine-enkephalin, are dramatically up-regulated by estrogen. To characterize the temporal and cellular aspects of the effect of an acute exposure to estrogen on preproenkephalin-A mRNA levels in the ventromedial nucleus and arcuate nucleus of the hypothalamus, ovariectomized female rats were injected with 50 micrograms estradiol benzoate and used for quantitative in situ hybridization histochemistry of preproenkephalin-A mRNA. In the ventromedial nucleus, estrogen treatment caused a biphasic increase in the number of preproenkephalin-A mRNA cells. Maximal numbers of cells expressing preproenkephalin-A mRNA were observed at 1 and 48 h after estrogen injection. At 4 and 96 h after estrogen injection, the numbers of preproenkephalin-A mRNA cells were similar to that which was seen in the ovariectomized female. The induction of preproenkephalin-A mRNA expression in cells of the arcuate nucleus followed a similar pattern that peaked 48 h after exposure to estrogen. Levels of preproenkephalin-A mRNA per cell did not change in either nucleus as a function of estrogen treatment. Thus, acute estrogen treatment induces expression of preproenkephalin-A mRNA in populations of cells in the ventromedial hypothalamus and arcuate nucleus in which preproenkephalin-A mRNA expression is undetectable by in situ hybridization in the absence of circulating estrogen.
大量研究表明，下丘脑腹内侧核是雌性大鼠生殖行为的主要控制位点。脊柱前凸行为的表现依赖于雌激素，其调节似乎涉及中基底下丘脑和脑干中内源性阿片肽回路的活动。雌激素可显著上调前脑啡肽原-A mRNA及其编码的神经肽甲硫氨酸脑啡肽在下丘脑的水平。为了表征急性暴露于雌激素对下丘脑腹内侧核和弓状核中前脑啡肽原-A mRNA水平影响的时间和细胞方面，对去卵巢的雌性大鼠注射50微克苯甲酸雌二醇，并用于前脑啡肽原-A mRNA的定量原位杂交组织化学研究。在腹内侧核中，雌激素处理导致前脑啡肽原-A mRNA细胞数量呈双相增加。在雌激素注射后1小时和48小时观察到表达前脑啡肽原-A mRNA的细胞数量最多。在雌激素注射后4小时和96小时，前脑啡肽原-A mRNA细胞数量与去卵巢雌性大鼠中的数量相似。弓状核细胞中前脑啡肽原-A mRNA表达的诱导遵循类似模式，在暴露于雌激素后48小时达到峰值。每个细胞的前脑啡肽原-A mRNA水平在两个核中均未随雌激素处理而改变。因此，急性雌激素处理可诱导下丘脑腹内侧核和弓状核中细胞群体表达前脑啡肽原-A mRNA，而在缺乏循环雌激素的情况下，通过原位杂交无法检测到这些细胞中前脑啡肽原-A mRNA的表达。
