Jansen H T, Hileman S M, Lubbers L S, Jackson G L, Lehman M N
Department of Cell Biology, Neurobiology, and Anatomy, University of Cincinnati College of Medicine, Ohio 45267, USA.
J Neuroendocrinol. 1996 Dec;8(12):921-7. doi: 10.1111/j.1365-2826.1996.tb00822.x.
The neural pathways responsible for conveying the steroid feedback signals that ultimately affect reproductive neuroendocrine function remain largely undefined. One possibility involves a direct projection from estrogen receptor (ER)-containing neurons to the median eminence (ME), a site of neuroendocrine peptide release. To examine this possibility, 8 ewes received stereotaxic injections of the retrograde neuronal tract-tracing compound cholera toxin-beta subunit (CT beta) into the ME. Neurons sending projections to the ME and containing ER were identified using a dual-label immunoperoxidase method. Double-labeled cells were found in distinct regions: (1) the ER-rich arcuate nucleus (ARC) that contained the greatest number of double-labeled cells, and (2) the organum vasculosum of the lamina terminalis (OVLT) which contained a very consistent, but low, number of double-labeled cells. While a fairly large number of retrogradely-labeled ARC neurons containing ER were identified, the majority of ER-containing ARC neurons were unlabeled and thus send projections elsewhere. Other regions containing high concentrations of ER-positive cells such as the medial preoptic area (MPOA), anterior hypothalamic area, and ventrolateral portion of the ventromedial hypothalamic nucleus, were devoid of double-labeled cells. Similarly, regions rich in neuroendocrine neurons such as the periventricular hypothalamus and paraventricular and supraoptic hypothalamic nuclei contained no double-labeled cells. These results suggest that modulation of neuroendocrine secretory activity may occur directly at the level of the ME by ER-containing neurons located within restricted regions of the hypothalamus and forebrain. However, the relatively low proportion of ER-containing neurons projecting to the ME suggests that the influence of estradiol upon neuroendocrine function also may include target sites other than the ME.
负责传递最终影响生殖神经内分泌功能的类固醇反馈信号的神经通路在很大程度上仍不明确。一种可能性是从含雌激素受体（ER）的神经元直接投射到正中隆起（ME），即神经内分泌肽释放的部位。为了检验这种可能性，8只母羊接受了立体定位注射逆行神经元示踪化合物霍乱毒素β亚基（CTβ）到正中隆起。使用双重标记免疫过氧化物酶方法鉴定向正中隆起投射且含雌激素受体的神经元。在不同区域发现了双重标记的细胞：（1）富含雌激素受体的弓状核（ARC），其中双重标记细胞数量最多；（2）终板血管器（OVLT），其中双重标记细胞数量非常稳定但较少。虽然鉴定出了相当数量含雌激素受体的逆行标记弓状核神经元，但大多数含雌激素受体的弓状核神经元未被标记，因此向其他部位投射。其他含有高浓度雌激素受体阳性细胞的区域，如内侧视前区（MPOA）、下丘脑前区和腹内侧下丘脑核的腹外侧部分，没有双重标记细胞。同样，富含神经内分泌神经元的区域，如下丘脑室周区以及下丘脑室旁核和视上核，也没有双重标记细胞。这些结果表明，神经内分泌分泌活动的调节可能直接在下丘脑和前脑受限区域内的含雌激素受体神经元作用于正中隆起的水平发生。然而，投射到正中隆起的含雌激素受体神经元比例相对较低，这表明雌二醇对神经内分泌功能的影响可能还包括正中隆起以外的靶位点。
