Neuroendocrine mechanism mediating the nutritional infertility

葡萄糖的供应可能是哺乳动物在营养不良下生殖功能受到抑制的主要因素之一。本研究探讨了葡萄糖利用率对雌性大鼠促性腺激素释放激素（GnRH）/促黄体生成激素（LH）释放的调节作用。大鼠的下丘脑和延髓被认为是通过检测血糖水平来调节LH分泌和摄食行为的感受器。本研究应用Fos免疫组织化学方法检测了去卵巢大鼠下丘脑最后区（AP）、孤束核（NTS）和室旁核（paraventricular nucleus，下丘脑室旁核）内Fos蛋白的表达，结果表明：2-脱氧葡萄糖（2-deoxyglucose，2DG）可诱导Fos蛋白在AP、NTS和室旁核大量表达。Fos和各种细胞标记物如GFAP和MAP-2的双重免疫组织化学显示AP中Fos表达细胞是神经元而不是胶质细胞。这些细胞不是儿茶酚胺能的，因为AP中的任何Fos样免疫反应性与酪氨酸羟化酶免疫反应性不共定位。NTS内部分Fos阳性神经元为儿茶酚胺能神经元，提示AP内存在一群非儿茶酚胺能神经元，它们可能参与低葡萄糖利用的感受，从而调节雌性大鼠的生殖功能和摄食行为。

Glucose availability would be one of the major factors involved in the suppressed reproductive functions under malnutrition in mammalian species. In the present study, the role of glucose availability in regulating gonadotropin-releasing hormone (GnRH)/Iuteinizing hormone (LH) release in female rats. The sensors for detecting the blood glucose level to regulate LH secretion and feeding behavior have been considered to be located in the hypothalamus and medulla oblongata in rats. The present study focussed on the localization of glucose sensors in the area postrema using Fos immunohistochemistry as a marker of neuronal activation.Peripheral administration of a glucose antagonist, 2-deoxyglucose (2DG), induced a massive expression of Fos protein in the area postrema (AP), solitary tract nucleus (NTS) and paraventricular nucleus of the hypothalamus in ovariectomized and estradiol-primed ovariectomized rats. Dual immunohistochemistry with Fos and various cell markers, such as GFAP and MAP-2, showed that Fos-expressing cells in the AP would be neuronal but not glial cells. These cell were not catecholaminergic because any Fos-like immunoreactivities in the AP were not co-localized with tyrosine hydroxy lase immunoreactivity. A part of the Fos-expressing neruons in the NTS was catecholaminergic.These results indicate that a population of non-catecholaminergic neurons in the AP could be involved in sensing low glucose availability to regulate reproductive functions as well as feeding behavior n female rats.