Leem J W, Gwak Y S, Nam T S, Paik K S
Department of Physiology, Yonsei University College of Medicine, Seoul, South Korea.
Neurosci Lett. 1997 Sep 26;234(1):39-42. doi: 10.1016/s0304-3940(97)00658-7.
The present study examined the effects of sympathetic stimulation on the activity of primary afferent neurons that had peripheral axons being injured previously by a spinal nerve ligation. About 22% of afferents with injured fibers that showed spontaneous discharge were excited by sympathetic stimulation or systemic injection of adrenaline. Most sympathetically-excited afferent neurons had axons that conducted in the A-fiber range. This sympathetically-evoked afferent excitation was not affected by cutting the spinal nerve at a place close to the dorsal root ganglion (DRG). Yohimbine, alpha2-antagonist, suppressed sympathetically-evoked afferent excitation which was not affected by alpha1-antagonist prazosin. Clonidine, alpha2-agonist, exerted an excitatory effect, whereas alpha1-agonist phenylephrine had no effect on the activity of afferents with injured fibers. No afferent fibers in control preparations responded to sympathetic stimulation. The results suggest that after a spinal nerve ligation, injured DRG neurons with fast-conducting fibers become sensitive to sympathetic activity via activation of alpha2-adrenoceptors.
本研究考察了交感神经刺激对初级传入神经元活动的影响，这些初级传入神经元的外周轴突先前已被脊神经结扎损伤。约22%有损伤纤维且表现出自发放电的传入神经被交感神经刺激或全身注射肾上腺素所兴奋。大多数交感神经兴奋的传入神经元具有在A纤维范围内传导的轴突。这种交感神经诱发的传入兴奋不受在靠近背根神经节（DRG）处切断脊神经的影响。α2拮抗剂育亨宾抑制交感神经诱发的传入兴奋，而α1拮抗剂哌唑嗪对此无影响。α2激动剂可乐定产生兴奋作用，而α1激动剂去氧肾上腺素对有损伤纤维的传入神经活动无影响。对照制剂中的传入纤维对交感神经刺激无反应。结果表明，脊神经结扎后，具有快速传导纤维的损伤DRG神经元通过α2肾上腺素能受体的激活而对交感神经活动变得敏感。
