Fairman K, Giacobini E, Chiappinelli V
Brain Res. 1976 Feb 6;102(2):301-12. doi: 10.1016/0006-8993(76)90884-2.
The developmental variations of tyrosine hydroxylase (TH) and of acetylcholinesterase (AChE) were studied in embryonic and post-hatching chicken sympathetic ganglia. Different levels of TH activity were found in two different flocks of White Leghorn chicken, which are probably dependent on genetic differences. These enzymatic differences, however, do not become apparent before hatching and may indicate a combined effect of genetic variation and functional demands. During the period of incubation, TH activity is characterized by a pronounced and steady increase from the twelfth day of incubation up to day 2 after hatching. This corresponds to a period of intense maturation of the sympathetic neuron. In the period following hatching, the 'fourth day fall phenomenon' previously described by us for DOPA decarboxylase (DDC), dopamine-beta-hydroxylase (DBH), and monoamine oxidase (MAO) is not seen in the TH curve. Instead, TH activity tends to remain constant between days 2 and 14 after hatching (ah). Both ganglionic protein and weight remain constant in this period, indicating a phase of general pause in protein synthesis. AChE activity increases steadily from the eighth until the twenty-first day of incubation. A sudden and significant drop in AChE activity was found at day 2 ah followed by a period of rapid increase at day 3 ah and a levelling of activity up to day 30 ah. Comparing the present variations to those observed in our previous studies on DBH, a temporal relationship between TH and DBH activity is observed during the phases of synaptogenesis and maturation but not during the phase of intense functional activity. Our results strongly suggest that before hatching in chick embryo sympathetic ganglia, the cholinergic presynaptic terminals play a role in regulating the development of the adrenergic neurons. In the period following hatching, however, the DBH and TH levels in cell bodies seem to be principally regulated by the functional activity. This results in depletion of DBH, but not TH, through liberation along with the neurotransmitter at the periphery. Depletion of DBH at the terminals may result in increased transport and thereby depletion in the cell body. This mechanism is probably responsible for the difference in the profiles of activity of DBH and TH in the cell bodies observed in the first week after hatching.
研究了胚胎期和孵化后鸡交感神经节中酪氨酸羟化酶（TH）和乙酰胆碱酯酶（AChE）的发育变化。在两群不同的白来航鸡中发现了不同水平的TH活性，这可能取决于遗传差异。然而，这些酶活性差异在孵化前并不明显，可能表明遗传变异和功能需求的综合作用。在孵化期间，TH活性的特点是从孵化第12天到孵化后第2天有明显且稳定的增加。这与交感神经元强烈成熟的时期相对应。在孵化后的时期，我们之前描述的多巴脱羧酶（DDC）、多巴胺-β-羟化酶（DBH）和单胺氧化酶（MAO）的“第4天下降现象”在TH曲线中未出现。相反，TH活性在孵化后第2天到第14天趋于保持恒定。在此期间，神经节蛋白和重量均保持恒定，表明蛋白质合成处于总体暂停阶段。AChE活性从孵化第8天到第21天稳步增加。在孵化后第2天发现AChE活性突然显著下降，随后在孵化后第3天迅速增加，直到孵化后第30天活性趋于平稳。将目前的变化与我们之前对DBH的研究中观察到的变化进行比较，发现在突触形成和成熟阶段TH和DBH活性之间存在时间关系，但在强烈功能活动阶段则不存在。我们的结果强烈表明，在鸡胚交感神经节孵化前，胆碱能突触前终末在调节肾上腺素能神经元的发育中起作用。然而，在孵化后的时期，细胞体中的DBH和TH水平似乎主要受功能活动调节。这导致DBH而非TH通过与外周神经递质一起释放而耗竭。终末处DBH的耗竭可能导致转运增加，从而使细胞体中的DBH耗竭。这种机制可能是导致孵化后第一周观察到的细胞体中DBH和TH活性变化曲线差异的原因。
