Dubois E A, Florijn M A, Zandbergen M A, Peute J, Goos H J
Faculty of Biology, Department of Experimental Zoology, Research Group of Comparative Endocrinology, University of Utrecht, Padualaan 8, Utrecht, 3584 CH, The
Gen Comp Endocrinol. 1998 Dec;112(3):383-93. doi: 10.1006/gcen.1998.7141.
The effects of two endogenous steroids on the maturation of the catfish GnRH and the chicken GnRH-II system in the African catfish were investigated. Immature fish (2 weeks of age, which is before sexual differentiation; thus male and female genotypes present) were fed with food pellets containing either testosterone (T), 11beta-hydroxyandrostenedione (OHA) or no steroid (control). After 2 and 4 weeks of treatment, the effects on the two GnRH systems were investigated immunocytochemically, using specific antibodies against the respective GnRH-associated peptides. By means of fluorescence microscopy the number of GnRH perikarya and the cell surfaces were determined. Confocal laser scanning microscopy was applied to verify spatial distribution and staining intensity. After 2 weeks of treatment no difference in any of the parameters between the groups was observed. However, 4 weeks T treatment resulted in significantly more cfGnRH-ir perikarya in the brain compared to the OHA and control groups. In addition, in the T group the number of immunoreactive fibers was markedly higher and the staining of the perikarya and axons was more intense. The distribution of cfGnRH-ir neurons over the ventral forebrain differed between the two age groups: in 4-week-old fish, the largest concentration of neurons was localized in the ventral telencephalon, while 2 weeks later the number of neurons in the supraoptic area had markedly increased, suggesting that the cfGnRH system is still undergoing developmental changes during this period. In 6-week-old fish the average volume of the cfGnRH perikarya (expressed as surface size in the microscopical sections) in both the OHA and the T group was significantly bigger than that in the control group. The cGnRH-II-ir neurons in the midbrain tegmentum showed strong immunoreactivity in all groups, both treated and nontreated. In contrast to the cfGnRH neurons, the staining intensity and the number of cGnRH-II neurons did not change after steroid treatment. The results of this study show that T is able to accelerate the development of the cfGnRH system, whereas OHA has only minimal effects; the cGnRH-II system develops independent from these steroids.
研究了两种内源性类固醇对非洲鲶鱼中鲶鱼促性腺激素释放激素（GnRH）和鸡促性腺激素释放激素II（GnRH-II）系统成熟的影响。将未成熟的鱼（2周龄，处于性别分化之前，因此存在雄性和雌性基因型）喂食含有睾酮（T）、11β-羟基雄烯二酮（OHA）或不含类固醇的食物颗粒（对照组）。在处理2周和4周后，使用针对各自GnRH相关肽的特异性抗体，通过免疫细胞化学方法研究对两种GnRH系统的影响。借助荧光显微镜确定GnRH核周体的数量和细胞表面。应用共聚焦激光扫描显微镜来验证空间分布和染色强度。处理2周后，各实验组之间在任何参数上均未观察到差异。然而，与OHA组和对照组相比，T处理4周后，脑中cfGnRH免疫反应性核周体显著增多。此外，在T组中，免疫反应性纤维的数量明显更高，核周体和轴突的染色更强。两个年龄组中，cfGnRH免疫反应性神经元在前脑腹侧的分布有所不同：在4周龄的鱼中，神经元的最大集中区域位于腹侧端脑，而2周后，视上区域的神经元数量显著增加，这表明在此期间cfGnRH系统仍在经历发育变化。在6周龄的鱼中，OHA组和T组中cfGnRH核周体的平均体积（以显微镜切片中的表面大小表示）均显著大于对照组。中脑被盖中的cGnRH-II免疫反应性神经元在所有组（处理组和未处理组）中均显示出强烈的免疫反应性。与cfGnRH神经元不同，类固醇处理后cGnRH-II神经元的染色强度和数量没有变化。本研究结果表明，T能够加速cfGnRH系统的发育，而OHA的影响极小；cGnRH-II系统独立于这些类固醇发育。
