Hamano K, Yosida K, Suzuki M, Ashida K
Division of Biofunction, National Research Institute of Fisheries Science, Yokohama, Kanagawa, Japan
Gen Comp Endocrinol. 1996 Mar;101(3):275-81.
Changes in concentration of thyrotropin-releasing hormone (TRH) in various regions of the brain of female and male chum salmon Oncorhynchus keta during their spawning migration toward the home stream were examined to determine the physiological role of TRH. In the same specimens, serum levels of prolactin (PRL) and thyroxin (T4) were also examined and compared with the change of TRH concentration. TRH concentration in the olfactory bulb of males increased significantly just before the upstream migration or entering the river and dropped after entering the home stream. TRH concentration in the olfactory lobe was also slightly higher in Class 2 salmons with nuptial coloration captured in coastal water than in the other groups. TRH concentrations in hypothalamus and pituitary remained relatively low during the spawning migration. The change of TRH concentration in females was similar to that in males, but was smaller and with a wider range. The serum level of PRL was extremely low in both males and females collected in coastal waters (Classes 1 and 2) and increased after the fish entered the river. The serum level of T4 in both males and females tended to be low, as did the TRH concentration in the hypothalamus and pituitary. Immunohistochemistry of the brain using anti-proTRH serum revealed many proTRH cell bodies in the olfactory bulb and olfactory lobe. These results indicate that TRH in the homing salmon is produced mainly in the olfactory bulb and lobe and that its production may be related to changes in olfactory function during migration.
为确定促甲状腺激素释放激素（TRH）的生理作用，研究了在向家乡河流洄游产卵过程中，雌、雄大麻哈鱼（Oncorhynchus keta）大脑不同区域TRH浓度的变化。在同一批样本中，还检测了催乳素（PRL）和甲状腺素（T4）的血清水平，并与TRH浓度变化进行比较。雄鱼嗅球中的TRH浓度在上游洄游前或进入河流时显著增加，进入家乡河流后下降。在沿海水域捕获的具有婚姻色的2级鲑鱼的嗅叶中，TRH浓度也略高于其他组。在产卵洄游期间，下丘脑和垂体中的TRH浓度相对较低。雌鱼TRH浓度的变化与雄鱼相似，但变化较小且范围更广。在沿海水域（1级和2级）采集的雄鱼和雌鱼的血清PRL水平都极低，进入河流后升高。雄鱼和雌鱼的血清T4水平以及下丘脑和垂体中的TRH浓度都趋于较低。用抗proTRH血清对大脑进行免疫组织化学分析，发现在嗅球和嗅叶中有许多proTRH细胞体。这些结果表明，洄游鲑鱼中的TRH主要在嗅球和嗅叶中产生，其产生可能与洄游过程中嗅觉功能的变化有关。
