Beaudet A, Descarries L
Brain Res. 1976 Jul 30;111(2):301-9. doi: 10.1016/0006-8993(76)90775-7.
Serotonin (5-HT) nerve terminals, specifically labeled with [3H]5-HT have been counted in light microscope radioautographs from the fronto-parietal neocortex of adult rats, following prolonged superfusions with relatively high concentrations of tracer (10(-5) M or 10(-4) M), and after 15 or 30 days of radioautographic exposure. Comparative analysis of the results indicated that all 5-HT varicosities did not possess the same capacity to accumulate the exogenous amine. Nevertheless, superfusions with 10(-4) M[3H]5-HT provided a sufficient loading of 5-HT boutons to allow their complete detection within any given layer of the neocortex. The labeled varicosities were found to be present within all cortical layers, except layer VI. Their total number was extrapolated to be approximately 1 X 10(6)/cu.mm of cortex. This figure represented a mean incidence of one 5-HT nerve terminal/850-1400 cortical synapses (0.07-0.12%). The intralaminar density of 5-HT innervation increased progressively from layer V to layer I, in a distribution pattern suggestive of unspecific afferents. Based on endogenous 5-HT levels of 346 +/- 32 ng/g for the fronto-parietal neocortex, the mean 5-HT content per varicosity could be estimated to be 0.35 X 10(-3) pg, and the concentration 1900 ng/g wet weight of terminal or 0.2%. In view of their particular ultrastructural features7, ubiquitous repartition and endogenous amine content, 5-HT nerve endings may be considered as capable of exerting a rather widespread influence in the neocortex.
在用相对高浓度的示踪剂（10⁻⁵M或10⁻⁴M）进行长时间灌流后，以及在放射自显影曝光15或30天后，已对成年大鼠额顶叶新皮质光镜放射自显影片中用[³H]5-羟色胺特异性标记的5-羟色胺（5-HT）神经终末进行了计数。结果的比较分析表明，并非所有5-HT曲张体积累外源性胺的能力都相同。然而，用10⁻⁴M[³H]5-HT灌流能使5-HT终扣充分负载，从而在新皮质的任何给定层内实现其完全检测。发现标记的曲张体存在于除VI层外的所有皮质层中。其总数经推断约为1×10⁶/立方毫米皮质。这个数字代表每850 - 1400个皮质突触中有一个5-HT神经终末的平均发生率（0.07 - 0.12%）。5-HT神经支配的层内密度从V层到I层逐渐增加，其分布模式提示为非特异性传入。根据额顶叶新皮质内源性5-HT水平为346±32 ng/g，每个曲张体的平均5-HT含量估计为0.35×10⁻³pg，浓度为1900 ng/g湿重的终末或0.2%。鉴于其特殊的超微结构特征、普遍分布和内源性胺含量，5-HT神经末梢可被认为能够在新皮质中发挥相当广泛的影响。
