Taylor D G, Brody M J
Circ Res. 1976 Jun;38(6 Suppl 2):10-20. doi: 10.1161/01.res.38.6.10.
The role of descending spinal catecholamine (CA)-containing fibers in cardiovascular regulation was examined. Monoamine-containing fibers were visualized by fluorescence histochemical methods at the cervical, thoracic, and lumbar spinal segments. Two major groups of descending CA-containing axons were located in the lateral funiculus at the midcervical spinal level. At the thoracolumbar spinal segments CA-containing terminals were concentrated mostly around cells of the intermediolateral nucleus. In addition a distinct CA-containing fasciculus was observed at the level of the sympathetic nucleus which appeared to course toward the opposite site of the cord. To evaluate the role of the efferent CA-containing fibers, changes in heart rate, arterial pressure, femoral blood flow, and calculated peak vascular resistance were elicited by electrical stimulation of selected sites in the midcervical spinal cord. Although changes in femoral flow and arterial pressure were evoked from many midcervical sites, there was a distinct correlation between the magnitude of peak femoral resistance elevation and density of CA-containing axons activated. Furthermore, efferent spinal vasoconstrictor outflow to the hindlimbs crosses below the cervical level. This observation is in good agreement with fluorescence microscopy studies revealing CA-containing fibers which appear to decussate. Pharmacological studies also were undertaken to evaluate transmission in spinal vasopressor pathways. In these studies alpha-adrenergic receptor antagonists and agonists were perfused into the spinal subarachnoid space. Heart rate, arterial pressure, femoral flow, and femoral resistance responses elicited from efferent spinal pathways were significantly attenuated following superfusion of the spinal cord with the alpha-antagonists BE-2254 (HEAT) and phentolamine. It was shown that inhibition of the centrally evoked responses was due to actions of the alpha-antagonists at a spinal locus and not due to peripheral vascular alpha-receptor blockade. Spinal perfusion with the alpha-receptor agonist norepinephrine potentiated cardiovascular responses. Likewise, loading with the norepinephrine precursor 3,4-dihydroxy-L-phenylalanine (L-dopa) enhanced vasoconstrictor responses evoked in the cross-perfused hindlimb of p-chlorophenylalanine-pretreated cats. These observations support the idea that bulbospinal CA-containing fibers relay excitatory impulses to preganglionic vasoconstrictor neurons and that spinal alpha-adrenergic receptor activation is necessary for transmission of this information.
研究了下行含脊髓儿茶酚胺（CA）纤维在心血管调节中的作用。采用荧光组织化学方法在颈、胸和腰脊髓节段观察含单胺纤维。在颈髓中部水平，两组主要的下行含CA轴突位于外侧索。在胸腰脊髓节段，含CA终末主要集中在中间外侧核细胞周围。此外，在交感神经核水平观察到一条明显的含CA纤维束，它似乎向脊髓的对侧走行。为了评估传出含CA纤维的作用，通过电刺激颈髓中部的选定部位，引发心率、动脉压、股血流量和计算得出的峰值血管阻力变化。虽然许多颈髓中部部位都能引起股血流量和动脉压变化，但峰值股阻力升高的幅度与被激活的含CA轴突密度之间存在明显的相关性。此外，脊髓传出至后肢的血管收缩性传出纤维在颈髓水平以下交叉。这一观察结果与荧光显微镜研究结果一致，后者显示含CA纤维似乎发生了交叉。还进行了药理学研究以评估脊髓升压途径中的传递。在这些研究中，将α-肾上腺素能受体拮抗剂和激动剂注入脊髓蛛网膜下腔。在用α-拮抗剂BE-2254（HEAT）和酚妥拉明灌注脊髓后，脊髓传出途径引发的心率、动脉压、股血流量和股阻力反应明显减弱。结果表明，对中枢诱发反应的抑制是由于α-拮抗剂在脊髓部位的作用，而不是由于外周血管α-受体阻滞。用α-受体激动剂去甲肾上腺素灌注脊髓可增强心血管反应。同样，用去甲肾上腺素前体3,4-二羟基-L-苯丙氨酸（L-多巴）负荷可增强对氯苯丙氨酸预处理猫交叉灌注后肢中诱发的血管收缩反应。这些观察结果支持这样一种观点，即延髓脊髓含CA纤维将兴奋性冲动传递给节前血管收缩神经元，并且脊髓α-肾上腺素能受体激活对于该信息的传递是必要的。
