Centre for Neuroendocrinology, Department of Physiology, University of Otago School of Medical Sciences, P.O. Box 913, Dunedin, New Zealand.
Endocrinology. 2011 Dec;152(12):4906-14. doi: 10.1210/en.2011-1522. Epub 2011 Sep 20.
GnRH neuron activity is dependent on gonadal steroid hormone feedback. Altered synaptic input may be one mechanism by which steroids modify GnRH neuron activity. In other neuronal populations, steroid hormones have been shown to elicit profound effects on dendritic spine density, a measure of excitatory synaptic input. The present study examined gonadal steroid feedback effects on GnRH neuron spine density in female GnRH-green fluorescent protein (GFP) mice. Immunocytochemical labeling of GFP in this model reveals fine morphological details of GnRH neurons. Spine density and other features were quantified by confocal analysis. Ovariectomy resulted in a significant reduction in somatic spine density (27%, P < 0.05) compared with sham-operated diestrous females. However, dendritic spine density was unaltered. Positive feedback effects of estradiol on spine density were investigated using a protocol to mimic the GnRH/LH surge. Ten GnRH-GFP mice underwent an established protocol, receiving either estradiol benzoate (1 μg per 20 g body weight) or vehicle (n = 5/group) 32 h prior to being killed during the expected surge. Double-label immunofluorescence showed that all estradiol-treated females expressed cFos in a subpopulation of GnRH neurons. Spine density was determined by confocal analysis of activated (cFos-positive, n = 10 neurons/animal) and nonactivated (cFos-negative, n = 10 neurons/animal) GnRH neurons from estradiol-treated animals and for GnRH neurons (n = 20 neurons/animal) from nonsurged controls (all cFos negative). Activated GnRH neurons (cFos positive) showed a dramatic 60% increase in total spine density (0.78 ± 0.06 spines/μm) compared with nonactivated GnRH neurons (0.50 ± 0.01 spines/μm) in estradiol-treated animals (P < 0.001). Both somatic and dendritic spine density was significantly increased. Spine density was not different between nonactivated GnRH neurons from surged animals (0.50 ± 0.01 spines/μm) and GnRH neurons from nonsurged animals (0.51 ± 0.06 spines/μm). These data demonstrate that positive feedback levels of estradiol stimulate a robust increase in spine density specifically in those GnRH neurons that are activated at the time of the GnRH/LH surge.
GnRH 神经元的活动依赖于性腺类固醇激素的反馈。突触输入的改变可能是类固醇调节 GnRH 神经元活动的一种机制。在其他神经元群体中，类固醇激素已被证明对树突棘密度产生深远影响，树突棘密度是兴奋性突触输入的一种衡量标准。本研究检查了雌性 GnRH-绿色荧光蛋白 (GFP) 小鼠中性腺类固醇激素反馈对 GnRH 神经元棘密度的影响。在该模型中，GFP 的免疫细胞化学标记揭示了 GnRH 神经元的精细形态细节。通过共聚焦分析对棘密度和其他特征进行量化。与假手术的发情期雌性相比，卵巢切除术导致体细胞棘密度显著降低（27%，P<0.05）。然而，树突棘密度没有改变。使用模拟 GnRH/LH 激增的方案研究了雌二醇的正反馈对棘密度的影响。10 只 GnRH-GFP 小鼠接受了一个既定的方案，在预期激增期间被杀之前 32 小时，每 20 克体重接受 1 μg 苯甲酸雌二醇（n = 5/组）或载体（n = 5/组）。双重标记免疫荧光显示，所有接受雌二醇治疗的雌性在 GnRH 神经元的亚群中表达 cFos。通过共聚焦分析来自雌二醇处理动物的激活（cFos-阳性，n = 10 个神经元/动物）和非激活（cFos-阴性，n = 10 个神经元/动物）的 GnRH 神经元以及来自未激增对照的 GnRH 神经元（n = 20 个神经元/动物）（均为 cFos 阴性）来确定棘密度。与雌二醇处理动物中的非激活 GnRH 神经元（0.50 ± 0.01 个棘/μm）相比，激活的 GnRH 神经元（cFos 阳性）的总棘密度显著增加了 60%（0.78 ± 0.06 个棘/μm）（P<0.001）。体细胞和树突棘密度均显著增加。激增动物的非激活 GnRH 神经元（0.50 ± 0.01 个棘/μm）和未激增动物的 GnRH 神经元（0.51 ± 0.06 个棘/μm）之间的棘密度没有差异。这些数据表明，雌二醇的正反馈水平刺激了 GnRH/LH 激增时激活的 GnRH 神经元中棘密度的显著增加。
