Kummer W, Habeck J O
Institute for Anatomy and Cell Biology, University of Heidelberg, F.R.G.
Neuroscience. 1992;47(3):713-25. doi: 10.1016/0306-4522(92)90179-6.
Previous retrograde tracing studies on rat and guinea-pig showed a projection of sensory tyrosine hydroxylase-immunoreactive neurons to the region of the carotid bifurcation via the carotid sinus nerve. In the present study, focussing on the sensory innervation of the human carotid body, antisera to tyrosine hydroxylase and other catecholamine synthesizing enzymes were applied for an immunohistochemical investigation of carotid bodies obtained at autopsy. In addition, an array of antisera directed to non-enzyme antigens known to be present in viscero-afferent neurons were incorporated in the study. The glomic lobules consisting of glomus cells and sustentacular cells contained a variable number of enzyme-immunoreactive glomus cells. Arteries were supplied by nerve fibres displaying the full phenotype of sympathetic noradrenergic axons, i.e. immunoreactivity to tyrosine hydroxylase, aromatic-L-amino-acid-decarboxylase and dopamine-beta-hydroxylase. The glomic lobules, however, were densely innervated by tyrosine hydroxylase-immunoreactive axons lacking immunoreactivity to aromatic-L-amino-acid-decarboxylase and dopamine-beta-hydroxylase. These fibres reacted with neurofilament 160kD-antibody but were devoid of immunoreactivity to all neuropeptides tested (calcitonin gene-related peptide, somatostatin, substance P). Ultrastructurally, tyrosine hydroxylase/neurofilament 160kD-immunoreactive axons gave rise to large axonal swellings filled with mitochondria and vesicles, and established extensive contacts to glomus cells. Nerve bundles surrounded by a perineural sheath contained both myelinated (2.0-2.8 microns in diameter) and unmyelinated (0.14-3.0 microns) tyrosine hydroxylase-immunoreactive axons. Most of the unmyelinated immunoreactive axons were running singularly within a Schwann cell-sheath. Judged from the pattern of immunoreactivities as well as their preterminal and terminal ultrastructure, tyrosine hydroxylase-immunoreactive axons innervating glomus cells are of sensory origin. Although final proof by retrograde tracing cannot be presented in man, this conclusion is supported by experimental evidence in laboratory animals. The myelinated immunoreactive axons correspond to chemoreceptor A-fibres whereas the classification of the large unmyelinated immunoreactive axons has yet to be established. The lack of immunoreactivity to the dopamine-synthesizing enzyme, aromatic-L-amino-acid-decarboxylase, in this fibre type does not support the view of dopamine being the primary transmitter of chemoreceptor afferents.
以往对大鼠和豚鼠的逆行追踪研究表明，感觉性酪氨酸羟化酶免疫反应性神经元通过颈动脉窦神经投射至颈动脉分叉区域。在本研究中，聚焦于人类颈动脉体的感觉神经支配，应用针对酪氨酸羟化酶和其他儿茶酚胺合成酶的抗血清，对尸检获得的颈动脉体进行免疫组织化学研究。此外，一系列针对已知存在于内脏传入神经元中的非酶抗原的抗血清也纳入了本研究。由球细胞和支持细胞组成的球小叶含有数量不等的酶免疫反应性球细胞。动脉由显示交感去甲肾上腺素能轴突完整表型的神经纤维供应，即对酪氨酸羟化酶、芳香-L-氨基酸脱羧酶和多巴胺-β-羟化酶具有免疫反应性。然而，球小叶被缺乏对芳香-L-氨基酸脱羧酶和多巴胺-β-羟化酶免疫反应性的酪氨酸羟化酶免疫反应性轴突密集支配。这些纤维与神经丝160kD抗体反应，但对所有测试的神经肽（降钙素基因相关肽、生长抑素、P物质）均无免疫反应性。在超微结构上，酪氨酸羟化酶/神经丝160kD免疫反应性轴突产生充满线粒体和囊泡的大轴突肿胀，并与球细胞建立广泛联系。被神经束膜包围的神经束含有有髓（直径2.0 - 2.8微米）和无髓（0.14 - 3.0微米）的酪氨酸羟化酶免疫反应性轴突。大多数无髓免疫反应性轴突单独在施万细胞鞘内走行。从免疫反应模式及其终末前和终末超微结构判断，支配球细胞的酪氨酸羟化酶免疫反应性轴突起源于感觉神经。尽管在人类中无法通过逆行追踪提供最终证据，但这一结论得到了实验动物的实验证据支持。有髓免疫反应性轴突对应于化学感受器A纤维，而大的无髓免疫反应性轴突的分类尚待确定。这种纤维类型对多巴胺合成酶芳香-L-氨基酸脱羧酶缺乏免疫反应性，不支持多巴胺是化学感受器传入神经主要递质的观点。
