Qu L, Sherebrin R, Weaver L C
John P. Robarts Research Institute, University of Western Ontario, London, Canada.
Am J Physiol. 1988 Dec;255(6 Pt 2):R946-51. doi: 10.1152/ajpregu.1988.255.6.R946.
Although discharge of many sympathetic nerves decreases substantially on transection of the spinal cord in cats, firing of splenic and mesenteric postganglionic nerves continues unabated (R. L. Meckler and L. C. Weaver, Brain Res. 338: 123-135, 1985; R. D. Stein and L. C. Weaver. J. Physiol. Lond. 396: 155-172, 1988). Therefore, ongoing sympathetic outflow directed to the splanchnic circulation was proposed to be less dependent on supraspinal excitatory drive than that directed to other vascular beds. Blockade or transection of cervical spinal pathways in chloralose-anesthetized cats significantly decreased firing of gastric, hepatic, adrenal, and lumbar chain sympathetic nerves. Discharge of gastric and hepatic nerves decreased as much as that of adrenal and lumbar chain nerves; therefore, sustained discharge in the absence of bulbospinal excitation is not a characteristic of all sympathetic nerves innervating the splanchnic circulation. In contrast, discharge of the preganglionic greater splanchnic nerves was not decreased after spinal transection, although it changed from a rhythmic to an asynchronous pattern. This provocative finding suggests that rhythmicity of preganglionic discharge may be important for effective synaptic transmission to some postganglionic neurons, since postganglionic gastric, hepatic, and adrenal nerve firing decreased in the presence of sustained but asynchronous preganglionic input.
尽管在猫脊髓横断后，许多交感神经的放电活动大幅减少，但脾神经和肠系膜神经节后神经的放电仍未减弱（R. L. 梅克勒和L. C. 韦弗，《脑研究》338: 123 - 135, 1985；R. D. 斯坦和L. C. 韦弗，《伦敦生理学杂志》396: 155 - 172, 1988）。因此，有人提出，内脏循环的持续交感神经输出比其他血管床的交感神经输出对脊髓上兴奋性驱动的依赖性更小。在水合氯醛麻醉的猫中，阻断或横断颈脊髓通路会显著降低胃、肝、肾上腺和腰链交感神经的放电。胃神经和肝神经的放电减少程度与肾上腺神经和腰链神经相同；因此，在没有延髓脊髓兴奋的情况下持续放电并非所有支配内脏循环的交感神经的特征。相比之下，脊髓横断后，内脏大神经节前神经的放电并未减少，尽管其从节律性模式转变为非同步模式。这一引人注目的发现表明，节前放电的节律性可能对有效地向某些节后神经元进行突触传递很重要，因为在存在持续但非同步的节前输入时，节后胃神经、肝神经和肾上腺神经的放电会减少。
