Stuart D K, Blair S S, Weisblat D A
J Neurosci. 1987 Apr;7(4):1107-22. doi: 10.1523/JNEUROSCI.07-04-01107.1987.
The nervous system of the glossiphoniid leech includes segmentally iterated neurons that contain serotonin (5-HT) and dopamine. These have been investigated in Helobdella triserialis, Theromyzon rude, and Haementeria ghilianii. Five types of 5-HT neurons are identified by immunocytochemistry in the abdominal ganglia of the ventral nerve cord: the bilaterally paired Retzius, anteromedial, ventrolateral and dorsolateral neurons, and the unpaired posteromedial (pm) neuron. Three types of bilaterally paired dopamine neurons are identified by glyoxylic acid-induced fluorescence in the segmental body wall: MD, LD1, and LD2. Each left or right half of the segmental complement of the leech nervous system is known to develop from 6 distinct ectodermal primary blast cells (ns, nf, o, p, qs, and qf). To identify the blast cells of origin of the 5-HT and dopamine neurons, fluorescent cell lineage tracers were injected into the various precursors of the blast cells in early (stage 6) embryos. The embryos were then raised until their 5-HT and dopamine neurons could be scored (stage 11) for the presence or absence of lineage tracer. We find that the Retzius, anteromedial, and posteromedial 5-HT neurons are derived from the ns blast cell, while the ventrolateral and dorsolateral 5-HT neurons are derived from the nf blast cell. The unpaired pm 5-HT neuron arises as one of a bilateral pair of neurons, of which one later dies. Whether the left or right pm neuron survives in any given ganglion is the consequence of some form of competitive interaction between cells derived from the left and right n primary blast cells, possibly between the left and right pm neurons themselves. We find that, of the dopamine neurons, the LD1 neuron is derived from the o blast cell, the LD2 neurons from the p blast cell, and the MD neuron from one of the 2 kinds of q blast cells. These results show that the 5-HT and dopamine neurons arise from 5 different primary blast cells in a highly determinate manner, and they support the view that cells of a similar phenotype need not be closely related in the developmental cell lineage tree.
舌蛭科水蛭的神经系统包含节段重复的、含有5-羟色胺（5-HT）和多巴胺的神经元。这些神经元已在三链索蛭、粗尾蛭和吉利尼血蛭中得到研究。通过免疫细胞化学方法，在腹神经索的腹神经节中鉴定出5种类型的5-HT神经元：双侧成对的雷丘斯神经元、前内侧神经元、腹外侧神经元和背外侧神经元，以及不成对的后内侧（pm）神经元。通过乙醛酸诱导荧光法，在节段体壁中鉴定出3种类型的双侧成对多巴胺神经元：MD、LD1和LD2。已知水蛭神经系统节段互补的每一侧（左或右）均由6个不同的外胚层初级胚细胞（ns、nf、o、p、qs和qf）发育而来。为了鉴定5-HT和多巴胺神经元的起源胚细胞，在早期（6期）胚胎中，将荧光细胞谱系示踪剂注射到胚细胞的各种前体细胞中。然后将胚胎饲养至其5-HT和多巴胺神经元能够被标记（11期），以观察是否存在谱系示踪剂。我们发现，雷丘斯神经元、前内侧神经元和后内侧5-HT神经元源自ns胚细胞，而腹外侧和背外侧5-HT神经元源自nf胚细胞。不成对的pm 5-HT神经元最初是一对双侧神经元中的一个，其中一个随后死亡。在任何给定的神经节中，左侧还是右侧的pm神经元存活，是源自左侧和右侧n初级胚细胞的细胞之间某种形式的竞争性相互作用的结果，可能是在左侧和右侧pm神经元自身之间。我们发现，多巴胺神经元中，LD1神经元源自o胚细胞，LD2神经元源自p胚细胞，MD神经元源自2种q胚细胞中的一种。这些结果表明，5-HT和多巴胺神经元以高度确定的方式源自5种不同的初级胚细胞，并且支持这样一种观点，即具有相似表型的细胞在发育细胞谱系树中不一定密切相关。
