Massari V J, Shirahata M, Johnson T A, Gatti P J
Department of Pharmacology, Howard University, College of Medicine, Washington, DC 20059, USA.
J Neurocytol. 1996 Mar;25(3):197-208. doi: 10.1007/BF02284796.
Tyrosine hydroxylase immunoreactive sensory neurons in the petrosal ganglion selectively innervate the carotid body via the carotid sinus nerve. Central projections of the carotid sinus nerve were traced with horseradish peroxidase. The commissural nucleus of the tractus solitarius was examined by dual labelling light and electron microscopy. Dense bilateral labelling with horseradish peroxidase was found in the tractus solitarius and commissural nucleus of the tractus solitarius. Horseradish peroxidase was found in unmyelinated axons, myelinated axons, and nerve terminals. About 88% of horseradish peroxidase-labelled carotid sinus nerve axons were unmyelinated. Tyrosine hydroxylase immunoreactivity was identified in unmyelinated axons, myelinated axons, dendrites, perikarya, and nerve terminals. Most tyrosine hydroxylase immunoreactive axons (93%) in the commissural nucleus of the tractus solitarius were unmyelinated. Tyrosine hydroxylase immunoreactivity was simultaneously identified in carotid sinus nerve unmyelinated axons, myelinated axons, and nerve terminals. These double-labelled terminals comprised 28% of the number of tyrosine hydroxylase immunoreactive terminals in the commissural nucleus of the tractus solitarius, and 55% of transganglionically-labelled terminals. Therefore, there are both central and peripheral sources of tyrosine hydroxylase immunoreactive nerve terminals in the commissural nucleus of the tractus solitarius. These data support the hypothesis that peripheral tyrosine hydroxylase immunoreactive neurons are involved in the origination of the chemoreceptor reflex. Axo-axonic synapses between peripheral carotid sinus nerve afferent terminals and central terminals containing tyrosine hydroxylase immunoreactivity were observed in 22% of the axo-axonic synapses observed. Thus, central tyrosine hydroxylase immunoreactivity neurons are involved in the modulation of the chemo-and/or baroreceptor reflexes. Synaptic contacts were not observed between carotid sinus nerve afferents and tyrosine hydroxylase immunoreactive perikarya of dendrites. Catecholaminergic neurons are thus unlikely to be the second order neurons of either the chemo-or baroreceptor reflex in the commissural nucleus of the tractus solitarius.
岩神经节中酪氨酸羟化酶免疫反应性感觉神经元通过颈动脉窦神经选择性地支配颈动脉体。用辣根过氧化物酶追踪颈动脉窦神经的中枢投射。通过双重标记光镜和电镜检查孤束核的连合核。在孤束和孤束核的连合核中发现了辣根过氧化物酶的密集双侧标记。在无髓轴突、有髓轴突和神经末梢中发现了辣根过氧化物酶。约88%的辣根过氧化物酶标记的颈动脉窦神经轴突是无髓的。在无髓轴突、有髓轴突、树突、胞体和神经末梢中鉴定出酪氨酸羟化酶免疫反应性。孤束核连合核中大多数酪氨酸羟化酶免疫反应性轴突（93%）是无髓的。在颈动脉窦神经的无髓轴突、有髓轴突和神经末梢中同时鉴定出酪氨酸羟化酶免疫反应性。这些双重标记的终末占孤束核连合核中酪氨酸羟化酶免疫反应性终末数量的28%，以及经神经节标记终末的55%。因此，孤束核连合核中酪氨酸羟化酶免疫反应性神经终末既有中枢来源也有外周来源。这些数据支持外周酪氨酸羟化酶免疫反应性神经元参与化学感受器反射起源的假说。在观察到的轴-轴突触中，22%观察到外周颈动脉窦神经传入终末与含有酪氨酸羟化酶免疫反应性的中枢终末之间存在轴-轴突触。因此，中枢酪氨酸羟化酶免疫反应性神经元参与化学和/或压力感受器反射的调节。未观察到颈动脉窦神经传入与酪氨酸羟化酶免疫反应性树突胞体之间的突触联系。因此，儿茶酚胺能神经元不太可能是孤束核连合核中化学或压力感受器反射的二级神经元。
