Canbeyli R S, Lehman M, Silver R
Psychology Department, Barnard College of Columbia University, New York, NY 10027.
Brain Res. 1991 Jul 19;554(1-2):15-21. doi: 10.1016/0006-8993(91)90166-s.
The suprachiasmatic nuclei (SCN) regulate circadian rhythmicity in many biological and behavioral responses. Hamsters are made permanently arrhythmic by bilateral destruction of the SCN. Circadian locomotor rhythmicity is restored by fetal tissue transplants placed in the 3rd ventricle (3V). If intact animals are implanted with fetal SCN grafts, they maintain locomotor activity rhythms when the host SCN are subsequently destroyed. The mechanism(s) whereby the SCN (either grafted or in situ) regulate locomotor rhythmicity is not known. Evidence from other graft models point to the possibility of efferents to appropriate targets in the host. In the present study, efferent connections of transplanted fetal SCN were examined using the carbocyanine dye, Dil. Intact or SCN-lesioned animals were sacrificed 7 or 40 days after receiving fetal SCN grafts into 3V. Dil crystals were placed on the grafts in fixed brains which were then incubated for 3-6 weeks before sectioning. Sections bearing Dil-labelled efferents from the graft were photographed and then stained for immunoreactive VIP and NP cells to locate donor SCN. Although labelled efferents were observed in a majority of the grafts, most were confined to the limits of the graft. The few labelled efferents that entered the host tissue when the graft seemed to merge with the host did not extend very far regardless of whether the graft contained immunohistochemical evidence for donor SCN or not. The observation of limited graft-host connectivity suggests either that a limited number of efferents is sufficient to support circadian locomotor rhythmicity, or that the mechanism mediating restoration of function entails a diffusible substance.
视交叉上核（SCN）调节许多生物和行为反应中的昼夜节律。通过双侧破坏SCN可使仓鼠永久性地失去节律。将胎儿组织移植到第三脑室（3V）可恢复昼夜运动节律。如果给完整的动物植入胎儿SCN移植物，当宿主SCN随后被破坏时，它们仍能维持运动活动节律。SCN（无论是移植的还是原位的）调节运动节律的机制尚不清楚。来自其他移植模型的证据表明，有可能存在向宿主中适当靶标的传出神经。在本研究中，使用羰花青染料Dil检查移植的胎儿SCN的传出连接。将完整或SCN损伤的动物在将胎儿SCN移植到3V中7天或40天后处死。将Dil晶体置于固定大脑中的移植物上，然后在切片前孵育3 - 6周。拍摄带有来自移植物的Dil标记传出神经的切片，然后对免疫反应性VIP和NP细胞进行染色以定位供体SCN。尽管在大多数移植物中观察到了标记的传出神经，但大多数都局限于移植物范围内。当移植物似乎与宿主融合时，少数进入宿主组织的标记传出神经无论移植物是否含有供体SCN的免疫组织化学证据，都不会延伸很远。有限的移植物 - 宿主连接性的观察结果表明，要么有限数量的传出神经足以支持昼夜运动节律，要么介导功能恢复的机制需要一种可扩散的物质。
