Fritschy J M, Grzanna R
Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
J Comp Neurol. 1990 Jan 22;291(4):553-82. doi: 10.1002/cne.902910406.
The rat spinal cord receives noradrenergic (NA) projections from the locus coeruleus (LC) and the A5 and A7 groups. In contradiction to previous statements about the distribution of descending NA axons, we have recently proposed that in the rat LC neurons project primarily to the dorsal horn and intermediate zone, whereas A5 and A7 neurons project to somatic motoneurons and the intermediolateral cell column. The aim of the present study was to determine the funicular course and terminal distribution of descending NA axons from the LC and from the A5 and A7 groups. The organization of the coeruleospinal projection was analyzed by using the anterograde tracer Phaseolus vulgaris leucoagglutinin in combination with dopamine-beta-hydroxylase immunohistochemistry. The trajectory of A5 and A7 axons was studied in spinal cord sections of rats following ablation of the coeruleospinal projection with the neurotoxin DSP-4. To assess the relative contribution of the LC and the A5 and A7 groups to the NA innervation of the spinal cord, unilateral injections of the retrograde tracer True Blue were made at cervical, thoracic, and lumbar levels, and retrogradely labeled NA neurons were identified by dopamine-beta-hydroxylase immunofluorescence. The results of the anterograde tracing experiments confirm our previous findings that LC neurons project most heavily to the dorsal horn and intermediate zone. Analysis of horizontal sections revealed that LC axons descend the length of the spinal cord within layers I and II. In contrast to the intragriseal course of LC fibers, A5 and A7 axons travel in the ventral and dorsolateral funiculi and terminate in the ventral horn and the intermediolateral cell column. Retrograde transport studies indicate that the contribution of the A5 and A7 groups to the NA projection to the spinal cord is greater than that of the LC. We conclude that descending axons of the LC and A5 and A7 groups differ in their course and distribution within the spinal cord. The documentation of a definite topographic order in the bulbospinal NA projections suggests that the LC and the A5 and A7 groups have different functional capacities. The LC is in a position to influence the processing of sensory inputs, in particular nociceptive inputs, whereas A5 and A7 neurons are likely to influence motoneurons.
大鼠脊髓接受来自蓝斑（LC）以及A5和A7神经核群的去甲肾上腺素能（NA）投射。与先前关于下行NA轴突分布的说法相反，我们最近提出，在大鼠中，LC神经元主要投射至背角和中间带，而A5和A7神经元则投射至躯体运动神经元和中间外侧细胞柱。本研究的目的是确定来自LC以及A5和A7神经核群的下行NA轴突的纤维束行程和终末分布。通过使用顺行示踪剂菜豆白细胞凝集素结合多巴胺-β-羟化酶免疫组织化学来分析蓝斑脊髓投射的组织学结构。在用神经毒素DSP-4损毁蓝斑脊髓投射后，在大鼠脊髓切片中研究A5和A7轴突的行径。为评估LC以及A5和A7神经核群对脊髓NA神经支配的相对贡献，在颈、胸和腰段进行逆行示踪剂真蓝的单侧注射，并通过多巴胺-β-羟化酶免疫荧光鉴定逆行标记的NA神经元。顺行追踪实验结果证实了我们先前的发现，即LC神经元最主要地投射至背角和中间带。对水平切片的分析显示，LC轴突在脊髓全长的I层和II层内下行。与LC纤维在灰质内的行程不同，A5和A7轴突在腹侧和背外侧索中走行，并终止于腹角和中间外侧细胞柱。逆行运输研究表明，A5和A7神经核群对脊髓NA投射的贡献大于LC。我们得出结论，LC以及A5和A7神经核群的下行轴突在脊髓内的行程和分布不同。延髓脊髓NA投射中明确的拓扑顺序的记录表明，LC以及A5和A7神经核群具有不同的功能能力。LC能够影响感觉输入尤其是伤害性输入的处理，而A-5和A7神经元可能影响运动神经元。
