Goldberg J I, Mills L R, Kater S B
Department of Zoology, University of Alberta, Edmonton, Canada.
J Neurobiol. 1991 Mar;22(2):182-94. doi: 10.1002/neu.480220208.
The neurotransmitter serotonin has been shown to inhibit neurite outgrowth in specific identified neurons isolated from adult Helisoma. While in vivo experiments on Helisoma embryos have supported the hypothesis that endogenous serotonin regulates neurite outgrowth during embryonic development, direct effects of serotonin on embryonic neurons have not been measured. In the present study, cultures of dissociated embryonic neurons were used to test the direct actions of serotonin on developing embryonic neurons. Serotonin arrested neurite outgrowth in a significant percentage of elongating neurites in a dose-dependent manner. Furthermore, analysis of neurons with stable, nonelongating neurites revealed a novel response. Serotonin caused the reinitiation of neurite outgrowth in a significant percentage of nonelongating neurites. The arrestment of outgrowth and reinitiation of outgrowth occurred in similar percentages of elongating and nonelongating neurites, respectively. Parallel experiments on cultures of dissociated adult neurons were carried out to determine whether serotonin could also induce both inhibitory and stimulatory responses in adult cells. Serotonin arrested neurite outgrowth in a similar percentage of neurites to that observed in cultures of embryonic neurons. In contrast, serotonin did not reinitiate neurite outgrowth in a significant percentage of adult neurites. These data support the hypothesis that serotonin regulates neurite outgrowth in developing embryonic neurons. Furthermore, only some of these regulatory effects appear to be conserved from embryonic to adult neurons.
神经递质5-羟色胺已被证明可抑制从成年椎实螺分离出的特定已鉴定神经元的神经突生长。虽然对椎实螺胚胎的体内实验支持了内源性5-羟色胺在胚胎发育过程中调节神经突生长的假说，但尚未测量5-羟色胺对胚胎神经元的直接作用。在本研究中，使用解离的胚胎神经元培养物来测试5-羟色胺对发育中的胚胎神经元的直接作用。5-羟色胺以剂量依赖的方式使相当比例的正在伸长的神经突停止生长。此外，对具有稳定的、不伸长的神经突的神经元的分析揭示了一种新的反应。5-羟色胺使相当比例的不伸长的神经突重新开始生长。生长的停止和重新开始分别发生在相似比例的正在伸长和不伸长的神经突中。对解离的成年神经元培养物进行了平行实验，以确定5-羟色胺是否也能在成年细胞中诱导抑制和刺激反应。5-羟色胺使神经突生长停止的神经突比例与在胚胎神经元培养物中观察到的相似。相比之下，5-羟色胺并没有使相当比例的成年神经突重新开始生长。这些数据支持了5-羟色胺调节发育中的胚胎神经元神经突生长的假说。此外，这些调节作用中只有一些似乎从胚胎神经元到成年神经元是保守的。
