Segu L, Calas A
Brain Res. 1978 Sep 29;153(3):449-64. doi: 10.1016/0006-8993(78)90331-1.
In vitro uptake of labeled serotonin (5-HT) has allowed the radioautographic detection of serotoninergic fibers in the cat spinal cord at thoracic and lumbar levels. The specificity of labeling was ensured by the conditions of incubation ([3H]5-HT was 10(-7) M) and by test control experiments with concomitant 10(-6) M NA or 2 X 10(-6) M fluoxetine which led respectively to an unmodified or a negative radioautographic pattern. Macroscopic radioautography with [14C]5-HT gave the framework for analysis of 5-HT innervation at this level which appeared dense in the grey matter and more scattered in white matter except in the periphery. In the grey matter labeled structures appeared at histological level as randomly oriented fibers. They displayed enlargements which were identified by electron microscopy as varicosities (mean diameter 0.7 micrometer) containing clear and large granular vesicles. To estimate the density of 5-HT varicosities in grey matter, semi-automatic counting was performed on histological radioautographs, using an image analyzer. Maximal concentrations of boutons were found in the periependymal region, the sympathetic lateral column, the whole dorsal horn and the motor neuron area of ventral horn. In a densely innervated region, the number of boutons was estimated to be at least 2.65 X 10(6)/cu.mm. In white matter, labeled fibers were longitudinally oriented in the periphery and obliquely in other regions, except in the dorsal funiculus, where they were nearly absent. Previous histofluorescence and biochemical data are confirmed and completed by the results of this approach which displays several advantages in resolution, sensitivity and possibilities of automated quantification. Moreover owing to the dynamic abilities of the radioautographic method, the spinal cord provides a good model for the study of the properties (namely the axonal flow) and the functions of the serotoninergic neurons.
对标记的血清素（5-羟色胺，5-HT）进行体外摄取，已能通过放射自显影检测猫胸段和腰段脊髓中的5-羟色胺能纤维。通过孵育条件（[3H]5-HT为10^(-7) M）以及与10^(-6) M去甲肾上腺素（NA）或2×10^(-6) M氟西汀同时进行的试验对照实验确保标记的特异性，这两种对照实验分别导致放射自显影模式未改变或呈阴性。用[14C]5-HT进行的宏观放射自显影为分析该水平的5-羟色胺神经支配提供了框架，5-羟色胺神经支配在灰质中显得密集，在白质中则较为分散，除了在外周区域。在灰质中，标记结构在组织学水平上表现为随机取向的纤维。它们呈现出膨大，通过电子显微镜鉴定为含有清亮和大颗粒小泡的曲张体（平均直径0.7微米）。为了估计灰质中5-羟色胺曲张体的密度，使用图像分析仪在组织学放射自显影片上进行半自动计数。在室管膜周围区域、交感神经外侧柱、整个背角和腹角的运动神经元区域发现了最高浓度的终扣。在一个神经支配密集的区域，终扣数量估计至少为2.65×10^6/立方毫米。在白质中，标记纤维在外周纵向排列，在其他区域倾斜排列，除了在背索中几乎不存在。以前的组织荧光和生化数据通过该方法的结果得到了证实和补充，该方法在分辨率、灵敏度和自动定量可能性方面具有几个优点。此外，由于放射自显影方法的动态能力，脊髓为研究5-羟色胺能神经元的特性（即轴浆运输）和功能提供了一个良好的模型。
