Aguilar-Roblero R, Morin L P, Moore R Y
Departmento de Neurociencias, Universidad Nacional Autónoma de México, Mexico.
Exp Neurol. 1994 Dec;130(2):250-60. doi: 10.1006/exnr.1994.1203.
A compelling body of evidence indicates that the suprachiasmatic nucleus (SCN) of the hypothalamus is a pacemaker in the rodent circadian timing system. Two important components of this evidence are studies showing that SCN lesions abolish circadian rhythms and others demonstrating restoration of circadian activity rhythms after transplantation of fetal SCN into the brains of arrhythmic hosts. In the present study, we evaluated what has remained a persisting issue in this transplant literature, the extent to which the exact localization and organization of the transplants is critical to their capacity to restore circadian function in the hamster. The data obtained indicate that the location of the graft in the ventricular system is not crucial to outcome. Grafts in the lateral ventricle, dorsal third ventricle, interventricular foramen, and caudal third ventricle are as capable of restoring circadian function as ones placed in the ventral third ventricle in the vicinity of the lesion. Restoration of rhythmicity does require that the grafts contain a minimum volume of SCN-like tissue as defined by cytoarchitecture and the presence of vasopressin--and vasoactive intestinal polypeptide (VIP)--immunoreactive cells and fibers. There is also an indication that VIP-immunoreactive elements are the component critical to functional recovery. Connections between graft and host are evident in the immunohistochemical material but are quite variable in extent and often very limited. Thus, the data obtained in this study are consistent with the view that restoration of circadian function by fetal grafts requires the presence of SCN, and probably VIP-containing neurons, but does not depend upon the exact location of the graft or the presence of specific connections between graft and host.
大量令人信服的证据表明，下丘脑的视交叉上核（SCN）是啮齿动物昼夜节律计时系统中的起搏器。这一证据的两个重要组成部分是：研究表明SCN损伤会消除昼夜节律，以及其他研究表明，将胎儿SCN移植到无节律宿主的大脑中后，昼夜活动节律得以恢复。在本研究中，我们评估了移植文献中一直存在的一个问题，即移植的确切定位和组织对其恢复仓鼠昼夜节律功能的能力的关键程度。获得的数据表明，移植物在脑室系统中的位置对结果并不关键。侧脑室、第三脑室背侧、室间孔和第三脑室尾侧的移植物与放置在损伤附近的第三脑室腹侧的移植物一样，都有能力恢复昼夜节律功能。节律性的恢复确实要求移植物包含由细胞结构以及抗利尿激素和血管活性肠肽（VIP）免疫反应性细胞及纤维所定义的最小体积的SCN样组织。也有迹象表明，VIP免疫反应性成分是功能恢复的关键组成部分。移植物与宿主之间的连接在免疫组织化学材料中很明显，但在范围上变化很大，而且往往非常有限。因此，本研究获得的数据与以下观点一致：胎儿移植物恢复昼夜节律功能需要存在SCN，可能还需要含VIP的神经元，但不依赖于移植物的确切位置或移植物与宿主之间特定连接的存在。
