Sandow S L, Whitehouse D, Hill C E
Division of Neuroscience, John Curtin School of Medical Research, Australian National University, A.C.T., Australia.
J Anat. 1998 Jan;192 ( Pt 1)(Pt 1):45-57. doi: 10.1046/j.1469-7580.1998.19210045.x.
Vascular sympathetic neuroeffector associations have been examined in rat iris arterioles using serial section electron microscopy and reconstruction techniques. Examination of random sections showed that, of all profiles of varicosities (199) seen to lie closer than 4 microns to vascular smooth muscle cells, only a small proportion (29/199) were found in close association with vascular smooth muscle cells, where adjacent membranes were separated by less than 100 nm. However, serial section examination, from intervaricose region to intervaricose region, of 79 varicosities similarly observed lying within 4 microns of vascular smooth muscle cells showed that 54 formed close associations with vascular smooth muscle cells. In serial sections, all these varicosities were also closely associated with melanocytes and of the 25 remaining varicosities, 22 formed close associations with melanocytes alone, whilst 3 did not come into close association with any effector cell. The increased observation of close associations with vascular smooth muscle cells in serial sections, compared with random sections, is consistent with the demonstration that the area of contact only occupies, on average, a small percentage (5%) of the total surface area of the varicosity as seen in the 3-dimensional reconstructions. In both random and serial sections, close associations were observed between varicosities and vascular smooth muscle cells or melanocytes irrespective of whether fibres were present singly or in small nerve bundles. Three-dimensional reconstruction of associations of varicosities and vascular smooth muscle cells demonstrated several common features, such as accumulations of synaptic vesicles and loss of Schwann cell covering at the region of membrane facing the effector cell. The similarity in the appearance of the neuroeffector association seen in this study and those described in previous studies provides evidence for the existence of a common sympathetic neuroeffector association, irrespective of the receptor subtype involved in neurotransmission.
利用连续切片电子显微镜和重建技术，对大鼠虹膜小动脉中的血管交感神经效应器关联进行了研究。对随机切片的检查显示，在所有距离血管平滑肌细胞小于4微米的曲张体轮廓（199个）中，只有一小部分（29/199）与血管平滑肌细胞紧密关联，相邻膜之间的距离小于100纳米。然而，对79个同样观察到位于血管平滑肌细胞4微米范围内的曲张体从曲张体间区域到曲张体间区域进行连续切片检查发现，有54个与血管平滑肌细胞形成了紧密关联。在连续切片中，所有这些曲张体也都与黑素细胞紧密关联，在其余25个曲张体中，22个仅与黑素细胞形成紧密关联，而3个未与任何效应细胞形成紧密关联。与随机切片相比，连续切片中与血管平滑肌细胞紧密关联的观察结果增加，这与三维重建中所显示的接触面积仅平均占曲张体总表面积的一小部分（5%）是一致的。在随机切片和连续切片中，无论纤维是单独存在还是成小神经束存在，都观察到曲张体与血管平滑肌细胞或黑素细胞之间存在紧密关联。曲张体与血管平滑肌细胞关联的三维重建显示了几个共同特征，如突触小泡的聚集以及在面向效应细胞的膜区域施万细胞覆盖的缺失。本研究中所见的神经效应器关联外观与先前研究中描述的相似，这为存在共同的交感神经效应器关联提供了证据，而与神经传递中涉及的受体亚型无关。
