Hida T, Arai R
Department of Anatomy, Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan.
Brain Res. 1998 Dec 14;814(1-2):209-12. doi: 10.1016/s0006-8993(98)00939-1.
The aim of the present study is to examine whether noradrenergic neurons of the locus coeruleus (LC) of the rat contain monoamine oxidase (MAO) activity. Sections were processed initially for MAO enzyme histochemistry using tyramine as a substrate, followed by fluorescence immunohistochemistry for tyrosine hydroxylase (TH). In the LC, virtually all TH-immunoreactive neurons (i.e., noradrenergic neurons) were also positive for MAO. No MAO activity was found in any TH-negative neurons. Neurons in the LC have previously been shown to form dopamine during noradrenaline biosynthesis and to produce serotonin from exogenously administered l-5-hydroxytryptophan. Moreover, dopamine- and serotonin-degrading MAO activity has also been found in LC neurons. Therefore, our results indicate that MAO activity is localized within noradrenergic neurons in the LC and is likely involved in the degradation of dopamine that is endogenously synthesized, and also in the elimination of serotonin that is produced from exogenous precursors.
本研究的目的是检测大鼠蓝斑（LC）中的去甲肾上腺素能神经元是否含有单胺氧化酶（MAO）活性。切片首先用酪胺作为底物进行MAO酶组织化学处理，然后进行酪氨酸羟化酶（TH）的荧光免疫组织化学检测。在LC中，几乎所有TH免疫反应性神经元（即去甲肾上腺素能神经元）的MAO也呈阳性。在任何TH阴性神经元中均未发现MAO活性。先前已证明LC中的神经元在去甲肾上腺素生物合成过程中会形成多巴胺，并能从外源性给予的L-5-羟色氨酸产生5-羟色胺。此外，在LC神经元中也发现了降解多巴胺和5-羟色胺的MAO活性。因此，我们的结果表明，MAO活性定位于LC中的去甲肾上腺素能神经元内，可能参与内源性合成多巴胺的降解，以及外源性前体产生的5-羟色胺的清除。
