Yamamoto N, Uchiyama H, Ohki-Hamazaki H, Tanaka H, Ito H
Department of Anatomy, Nippon Medical School, Tokyo, Japan.
Brain Res Dev Brain Res. 1996 Sep 2;95(2):234-44. doi: 10.1016/0165-3806(96)00078-8.
Previous studies suggest that gonadotropin-releasing hormone (GnRH) neurons appear in the olfactory placode and subsequently migrate into the brain during embryonic development. The aim of the present study was to obtain direct evidence for migration of GnRH neurons from the olfactory placode into the brain. Olfactory placodes from quail embryos were transplanted isotopically and isochronically, to replace the unilaterally ablated olfactory placodes of chick embryos. The chimeric embryos were allowed to develop for several days until they reached the embryonic stages when GnRH neurons are seen in the brain in normal embryos. Quail olfactory epithelia were formed in the host chick embryos. Quail olfactory nerves were also formed and reached the olfactory bulb or primordial olfactory bulb. GnRH-immunoreactive cells of quail origin revealed by a triple staining method were observed in the quail olfactory epithelium, quail olfactory nerve, chick olfactory bulb, and septo-preoptic area. These results indicate that GnRH neurons originate in the olfactory placode and migrate into the telencephalon including the septo-preoptic area. A migratory route of GnRH neurons was well documented by the use of a quail neuron-specific antibody, QN. The migratory route in the brain is discussed with special reference to the terminal nerve. A GnRH-immunoreactive neuronal group of chick origin appeared in the diencephalon of chimeric embryos. These diencephalic neurons may be of non-placodal origin. FMRFamide-immunoreactive neurons of quail origin were also found in the quail olfactory nerve and the host olfactory bulb, suggesting that FMRFamide neurons also originate in the olfactory placode and migrate into the brain.
先前的研究表明，促性腺激素释放激素（GnRH）神经元在胚胎发育过程中出现在嗅基板，随后迁移至脑内。本研究的目的是获得GnRH神经元从嗅基板迁移至脑内的直接证据。将鹌鹑胚胎的嗅基板进行同基因、同时期移植，以替代单侧切除嗅基板的鸡胚。使嵌合胚胎发育数天，直至达到正常胚胎中GnRH神经元出现在脑内的胚胎阶段。在宿主鸡胚中形成了鹌鹑嗅上皮。也形成了鹌鹑嗅神经并延伸至嗅球或原始嗅球。通过三重染色法显示的鹌鹑来源的GnRH免疫反应性细胞在鹌鹑嗅上皮、鹌鹑嗅神经、鸡嗅球和隔区-视前区中均有观察到。这些结果表明，GnRH神经元起源于嗅基板并迁移至包括隔区-视前区在内的端脑。利用鹌鹑神经元特异性抗体QN很好地记录了GnRH神经元的迁移途径。结合终神经对脑中的迁移途径进行了讨论。在嵌合胚胎的间脑中出现了鸡来源的GnRH免疫反应性神经元群。这些间脑神经元可能起源于非基板。在鹌鹑嗅神经和宿主嗅球中也发现了鹌鹑来源的FMRF酰胺免疫反应性神经元，这表明FMRF酰胺神经元也起源于嗅基板并迁移至脑内。
