Ishizaki Mami, Iigo Masayuki, Yamamoto Naoyuki, Oka Yoshitaka
Misaki Marine Biological Station, Graduate School of Science, The University of Tokyo, Miura, Kanagawa, Japan.
Endocrinology. 2004 Apr;145(4):2092-103. doi: 10.1210/en.2003-0960. Epub 2004 Jan 8.
It has become a general notion that there are multiple GnRH systems in the vertebrate brains. To measure GnRH release activities from different GnRH systems, we conducted a static incubation of brain-pituitary slices under various conditions, and GnRH released into the incubation medium was measured by RIA. The slices were divided into two parts, one containing GnRH neurons in the preoptic area and axon terminals in the pituitary (POA-GnRH slices), and the other containing the cell bodies and fibers of terminal nerve-GnRH neurons and midbrain tegmentum-GnRH neurons (TN-TEG-GnRH slices). We demonstrated that GnRH release was evoked by high K(+) depolarizing stimuli (in both POA-GnRH and TN-TEG-GnRH slices) via Ca(2+) influx through voltage-gated Ca(2+) channels. The most prominent result was the presence of conspicuous sexual difference in the amount of GnRH release in the POA-GnRH slices. The GnRH release from TN-TEG-GnRH slices also showed a small sexual difference, which was by far more inconspicuous than that of POA-GnRH slices. Immunohistochemical analysis using an antiserum specific to the seabream GnRH (sbGnRH; suggested to be specific to POA-GnRH neurons) revealed the presence of a much larger number of POA-GnRH neurons in males than in females. This clear morphological sexual difference is suggested to underlie that of GnRH release in the POA-GnRH slices.
脊椎动物大脑中存在多种促性腺激素释放激素（GnRH）系统已成为一种普遍观念。为了测量不同GnRH系统的GnRH释放活性，我们在各种条件下对脑垂体切片进行了静态孵育，并通过放射免疫分析（RIA）测量释放到孵育培养基中的GnRH。切片被分成两部分，一部分包含视前区的GnRH神经元和垂体中的轴突终末（视前区 - GnRH切片），另一部分包含终末神经 - GnRH神经元和中脑被盖 - GnRH神经元的细胞体和纤维（终末神经 - 中脑被盖 - GnRH切片）。我们证明，通过电压门控钙通道的钙内流，高[K⁺]（o）去极化刺激可诱发GnRH释放（在视前区 - GnRH切片和终末神经 - 中脑被盖 - GnRH切片中均如此）。最显著的结果是视前区 - GnRH切片中GnRH释放量存在明显的性别差异。终末神经 - 中脑被盖 - GnRH切片中的GnRH释放也显示出较小的性别差异，远不如视前区 - GnRH切片明显。使用对鲷鱼GnRH（sbGnRH；提示对视前区 - GnRH神经元具有特异性）特异的抗血清进行免疫组织化学分析表明，雄性视前区 - GnRH神经元的数量比雌性多得多。这种明显的形态学性别差异被认为是视前区 - GnRH切片中GnRH释放性别差异的基础。
