Histochemical and molecular biological studies on the physiological roles of the caudal neurosecretory system

尾侧神经分泌系统（CNS）合成并释放至少两种肽激素，尿紧张素I和II （UI和II）。虽然这些神经肽已被证明具有各种各样的生物活性，但它们在鱼类中的协调功能的清晰图像尚未出现。我们和其他人对这些肽的测序拓宽了我们对它们可能功能的思考，因为UI和UI分别与促肾上腺皮质激素释放因子（CRF）和生长抑素具有序列同源性。考虑到UI和UI可能的垂体功能，我们进行了组织化学和分子生物学研究来阐明CNS的生理功能。首先，我们合成了UI和UI，并开发了两种肽的放射免疫测定方法。这使我们能够测量中枢神经系统和其他组织中UI和UI的含量。其次，我们建立了一种用于UI和UI的原位杂交（ISH）组织化学方法，该方法在表达的遗传信息和表达该信息的细胞的鉴定方面具有很强的特异性。我们证明UI和UI在几乎所有可识别的尾侧神经分泌神经元中表达。此外，我们发现UI在下丘脑核中表达，其位置与产生crf的神经元不同。这强烈提示UI具有垂体功能。第三，我们还建立了一种联合ISH和免疫组织化学鉴定同一神经元中UI转录本和UI肽的方法。这提供了基因表达、激素合成和释放的动态方面的信息。利用上述方法，我们正在研究不同环境和条件下正常和去垂体鱼各组织中UI和UI基因表达和含量的变化，以阐明UI和UI的促垂体功能。

The caudal neurosecretory system (CNS) synthesizes and releases at least two peptide hormones, urotensins I and II (UI and UII). While these neuropeptides have been shown to have a wide variety of biological activities, a clear picture of their coordinated functions in fish has not yet emerged. The sequencing of these peptides by us and others has broadened our thinking about their possible functions since UI and UII have been found to have sequence homology to corticotropin-releasing factor (CRF) and somatostatin, respectively. Taking the possible hypophysiotropic functions of UI and UII into consideration, we carried out histochemical and molecular biological studies to elucidate the physiological functions of the CNS.First, we synthesized UI and UII, and developed radioimmunoassays for both peptides. This enables us to measure contents of UI and UII in the CNS and other tissues. Second, we established an in situ hybridization (ISH) histochemistry for UI and UII, which has the advantage of great specificity in terms of both the genetic information expressed and identification of the cells in which that information is expressed. We demonstrated that UI and UII are expressed in almost all identifiable caudal neurosecretory neurons. Further, we found that UI is expressed in the hypotalamic nuclei, the locations of which differ from those of CRF-producing neurons. This strongly suggests that UI has a hypophysiotropic function. Third, we also established a method for identification of UI transcripts and UI peptides in the same neurons by combined ISH and immunohistochemistry. This provides information on the dynamic aspects of gene expression, and synthesis and release of hormones.Using the methods mentioned above, we are now investigating changes in the gene expressions and contents of UI and UII in various tissues in normal and hypophysectomized fish subjected to various environments and conditions to elucidate the hypophysiotropic functions of UI and UII.