Jansen Heiko T, Cutter Christopher, Hardy Steven, Lehman Michael N, Goodman Robert L
Department of Veterinary and Comparative Anatomy, Washington State University College of Veterinary Medicine, Pullman, Washington 99164-6520, USA.
Endocrinology. 2003 Aug;144(8):3663-76. doi: 10.1210/en.2002-0188.
The annual reproductive cycle in sheep may reflect a functional remodeling within the GnRH system. Specifically, changes in total synaptic input and association with the polysialylated form of neural cell adhesion molecule have been observed. Whether seasonal changes in a specific subset(s) of GnRH inputs occur or whether glial cells specifically play a role in this remodeling is not clear. We therefore examined GnRH neurons of breeding season (BS) and nonbreeding season (anestrus) ewes and tested the hypotheses that specific (i.e. gamma-aminobutyric acid, catecholamine, neuropeptide Y, or beta-endorphin) inputs to GnRH neurons change seasonally, and concomitant with any changes in neural inputs is a change in glial apposition. Using triple-label immunofluorescent visualization of GnRH, glial acidic fibrillary protein and neuromodulator/neural terminal markers combined with confocal microscopy and optical sectioning techniques, we confirmed that total numbers of neural inputs to GnRH neurons vary with season and demonstrated that specific inputs contribute to these overall changes. Specifically, neuropeptide Y and gamma-aminobutyric acid inputs to GnRH neurons increased during BS and beta-endorphin inputs were greater during either anestrus (GnRH somas) or BS (GnRH dendrites). Associated with the changes in GnRH inputs were seasonal changes in glial apposition, glial acidic fibrillary protein density, and the thickness of glial fibrils. These findings are interpreted to suggest an increase in net stimulatory inputs to GnRH neurons during the BS contributes to the seasonal changes in GnRH neurosecretion and that this increased innervation is perhaps stabilized by glial processes.
绵羊的年度生殖周期可能反映了促性腺激素释放激素（GnRH）系统内的功能重塑。具体而言，已观察到总突触输入的变化以及与神经细胞黏附分子多唾液酸化形式的关联。GnRH输入的特定亚组是否发生季节性变化，或者神经胶质细胞是否在这种重塑中发挥特定作用尚不清楚。因此，我们检查了繁殖季节（BS）和非繁殖季节（发情间期）母羊的GnRH神经元，并测试了以下假设：GnRH神经元的特定（即γ-氨基丁酸、儿茶酚胺、神经肽Y或β-内啡肽）输入会随季节变化，并且伴随着神经输入的任何变化，神经胶质细胞的贴附也会发生变化。通过将GnRH、神经胶质酸性纤维蛋白和神经调质/神经末梢标记物的三重标记免疫荧光可视化与共聚焦显微镜和光学切片技术相结合，我们证实了GnRH神经元的神经输入总数随季节变化，并表明特定输入导致了这些总体变化。具体而言，在繁殖季节，GnRH神经元的神经肽Y和γ-氨基丁酸输入增加，而β-内啡肽输入在发情间期（GnRH胞体）或繁殖季节（GnRH树突）更大。与GnRH输入的变化相关的是神经胶质细胞贴附、神经胶质酸性纤维蛋白密度和神经胶质纤维厚度的季节性变化。这些发现被解释为表明在繁殖季节，GnRH神经元的净刺激输入增加有助于GnRH神经分泌的季节性变化，并且这种增加的神经支配可能通过神经胶质细胞的过程得以稳定。
