Glover J C, Stuart D K, Cline H T, McCaman R E, Magill C, Stent G S
J Neurosci. 1987 Feb;7(2):581-94. doi: 10.1523/JNEUROSCI.07-02-00581.1987.
We have investigated the development of neurotransmitter metabolism in embryos of the glossiphoniid leech Haementeria ghilianii. The neurotransmitter content of dissected embryonic tissues was measured by means of radioenzymatic assays, while the presence of neurotransmitters in individual identified neurons was detected by means of immunocytochemical and monoamine histofluorescence techniques. The capacity for synthesis of neurotransmitters was measured by incubating dissected embryonic tissues in radiolabeled neurotransmitter precursors. A specific neurotransmitter uptake system present in some neurons was detected by means of an autoradiographic technique. At an early stage of development of the nervous system, when most neurons are just beginning process outgrowth, the nerve cord acquires the capacity to synthesize ACh, 5-HT, and GABA from their immediate precursors, and contains ACh. Moreover, 5-HT-immunoreactive neurons and neurons that are capable of GABA uptake can be identified. Dopamine-containing neurons are first detected by their histofluorescence at a slightly later stage, after process outgrowth is under way. As development continues, the content of and capacity for synthesis of these neurotransmitters increase, as does the number of neurons capable of GABA uptake. During the earlier stages of development, ACh content exceeds 5-HT content, which in turn exceeds dopamine content. By the end of embryogenesis, however, 5-HT and dopamine contents have greatly increased relative to ACh content, with 5-HT content exceeding ACh content by a factor of 2. Of the neurotransmitters thus far studied, 5-HT is present in the highest amount in the juvenile and adult nerve cord. Our results indicate that in the development of the leech nervous system neurotransmitter metabolism is one of the first neuronal characters to differentiate and that the subsequent levels of the different neurotransmitters are differentially regulated.
我们研究了舌蛭科水蛭海地蛭胚胎中神经递质代谢的发育情况。通过放射酶法测定解剖后的胚胎组织中的神经递质含量，同时利用免疫细胞化学和单胺组织荧光技术检测单个已鉴定神经元中神经递质的存在。通过将解剖后的胚胎组织与放射性标记的神经递质前体一起孵育来测量神经递质的合成能力。利用放射自显影技术检测某些神经元中存在的特定神经递质摄取系统。在神经系统发育的早期阶段，当大多数神经元刚开始长出突起时，神经索就获得了从其直接前体合成乙酰胆碱（ACh）、5-羟色胺（5-HT）和γ-氨基丁酸（GABA）的能力，并且含有ACh。此外，可以鉴定出5-HT免疫反应性神经元和能够摄取GABA的神经元。含多巴胺的神经元在突起生长开始后的稍晚阶段首先通过其组织荧光被检测到。随着发育的继续，这些神经递质的含量和合成能力增加，能够摄取GABA的神经元数量也增加。在发育的早期阶段，ACh含量超过5-HT含量，而5-HT含量又超过多巴胺含量。然而，到胚胎发育结束时，相对于ACh含量，5-HT和多巴胺含量大幅增加，5-HT含量比ACh含量高出2倍。在迄今为止研究的神经递质中，5-HT在幼年和成年神经索中的含量最高。我们的结果表明，在水蛭神经系统的发育中，神经递质代谢是最早分化的神经元特征之一，并且不同神经递质的后续水平受到不同的调节。
