Abstract—The suprachiasmatic nucleus (SCN) regulates functions in accordance with circadian rhythms thanks to the pacemaker neurons present in it and afferents modulating their activity. One type of afferent is nerve fibers containing only tyrosine hydroxylase (TH) and secreting (L-dihydroxyphenylalanine) L-DOPA. The aim of this work was to test the hypothesis that L-DOPA comes from TH-containing fibers into neurons containing only aromatic L-amino acid decarboxylase (AAAD), where dopamine is synthesized. The synthesis of dopamine was evaluated by its content in SCN in intact rats on the 10th postnatal day (P10) and on P60, as well as by the total dopamine content in SCN and in the incubation medium after incubation of this nucleus in the medium with or without L-DOPA. It was shown that in intact rats SCN contains dopamine at the same concentration at P10 and P60. Some of the experiments with incubation of SCN slices were performed with rats injected with neurotoxins of monoaminergic neurons to exclude the synthesis of dopamine from L-DOPA in monoaminergic structures. At P10, during incubation of SCN in L-DOPA-containing medium, an increase in dopamine synthesis was observed equally in animals in control (normal) and after exposure to neurotoxins, which indicates synthesis of dopamine only in monoenzymatic AAAD-containing neurons. In a similar experiment at P60, the addition of L-DOPA into the incubation medium also led to an increase in the synthesis of dopamine, however, in animals exposed to neurotoxins to a lesser extent than in the control. This means that in adult animals, dopamine is synthesized in SCN mainly in monoenzymatic AAAD-containing neurons and to a lesser extent in monoaminergic structures. Thus, it was shown that dopamine in SCN is synthesized in monoenzymatic AAAD-containing neurons from L-DOPA secreted by monoenzymatic TH-containing fibers.

中文翻译：

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大鼠发育前上核中含有芳香氨基酸脱羧酶的非多巴胺能神经元合成多巴胺

摘要-视交叉上核（SCN）可以根据昼夜节律调节功能，这要归功于其中存在的起搏器神经元和传入物质来调节其活动。一种类型的传入神经纤维是仅包含酪氨酸羟化酶（TH）和分泌（L-二羟基苯丙氨酸）L-DOPA的神经纤维。这项工作的目的是检验以下假设：L-DOPA来自含TH的纤维进入仅包含芳族L-氨基酸脱羧酶（AAAD）的神经元，在该神经元中合成了多巴胺。通过在出生后第10天（P10）和P60在完整大鼠的SCN中评估其多巴胺的合成，并通过在该核中在培养液中孵育该细胞核后，在该SCN和孵育介质中的多巴胺总含量进行评估。或不使用L-DOPA。结果表明，在完整大鼠中，SCN在P10和P60处含有相同浓度的多巴胺。用注射了单胺能神经元神经毒素的大鼠进行了一些SCN切片孵育实验，以排除单胺能结构中L-DOPA合成多巴胺的能力。在P10，在SCN在含L-DOPA的培养基中孵育期间，在对照组（正常）和暴露于神经毒素后的动物中，均观察到多巴胺合成的增加，这表明仅在含单酶AAAD的神经元中合成了多巴胺。在P60的类似实验中，向培养液中添加L-DOPA也导致多巴胺的合成增加，但是，暴露于神经毒素的动物比对照组少。这意味着在成年动物中 多巴胺主要在含单酶AAAD的神经元中在SCN中合成，在较小程度上在单胺能结构中合成。因此，显示了SCN中的多巴胺是在由单酶TH的纤维分泌的L-DOPA中在单酶AAAD的神经元中合成的。