Segarra A C, Acosta A M, González J L, Angulo J A, McEwen B S
University of Puerto Rico, Department of Physiology, School of Medicine, San Juan, PR 00936, Puerto Rico.
Brain Res Mol Brain Res. 1998 Sep 18;60(1):133-9. doi: 10.1016/s0169-328x(98)00160-0.
Opioids have been implicated in sexual differentiation of the brain and in the regulation of reproductive behavior and endocrinology of mammals. Previous studies have indicated that estrogen administration in adults regulates preproenkephalin MRNA levels in several hypothalamic brain nuclei. We have determined preproenkephalin mRNA levels in estrogen-treated juvenile male and female rats to investigate the developmental pattern of estrogenic regulation of enkephalinergic neurons in the medial preoptic area. Rats were treated with estradiol benzoate (20 microgram/kg/day) or oil from day 21 to 23. Sections of the medial preoptic area (mPOA) were studied by in situ hybridization histochemistry at the single cell level and quantified with the assistance of an image analysis system. Our data indicate that males contain higher levels of preproenkephalin mRNA per neuron than females. In addition, our results indicate that estrogen causes an upward shift in the amount of mRNA expressed per cell, females demonstrating a greater response to estrogen than males. An increase in soma cell area following estrogen treatment was observed only in female mPOA enkephalinergic neurons. Taken together, these results indicate a sex difference in total preproenkephalin levels and in estrogenic regulation of preproenkephalin mRNA in the POA of juvenile rats. These results are discussed in relation to the differential role opioids may play in male and female reproductive physiology.
阿片类物质与大脑的性别分化以及哺乳动物生殖行为和内分泌的调节有关。先前的研究表明，成年动物体内雌激素的施用可调节几个下丘脑脑核中前脑啡肽原mRNA的水平。我们测定了经雌激素处理的幼年雄性和雌性大鼠的前脑啡肽原mRNA水平，以研究雌激素对内侧视前区脑啡肽能神经元调节的发育模式。从第21天到23天，用苯甲酸雌二醇（20微克/千克/天）或油对大鼠进行处理。通过单细胞水平的原位杂交组织化学研究内侧视前区（mPOA）的切片，并借助图像分析系统进行定量分析。我们的数据表明，雄性大鼠单个神经元中的前脑啡肽原mRNA水平高于雌性。此外，我们的结果表明，雌激素会使每个细胞表达的mRNA量向上偏移，雌性对雌激素的反应比雄性更大。仅在雌性mPOA脑啡肽能神经元中观察到雌激素处理后体细胞面积增加。综上所述，这些结果表明幼年大鼠POA中前脑啡肽原的总水平以及雌激素对前脑啡肽原mRNA的调节存在性别差异。本文结合阿片类物质在雄性和雌性生殖生理学中可能发挥的不同作用对这些结果进行了讨论。
