Department of Dentistry, National Taiwan University Hospital, 1 Chang-Te Street, Taipei, Taiwan.
J Formos Med Assoc. 2011 Feb;110(2):93-9. doi: 10.1016/S0929-6646(11)60015-6.
BACKGROUND/PURPOSE: Mercury is a well-known neurotoxin but the susceptibility of autonomic nerves to mercury poisoning in vivo has seldom been studied. Our previous studies have shown that the hypoglossal nerve in hamsters contains somatic motor and postganglionic sympathetic fibers. The aim of this study was to investigate the ultrastructural changes in the nervous system following intraneural injection of mercuric chloride into the hypoglossal nerve in hamsters.
Six adult hamsters were used in this study. After anesthesia, the digastric muscle on the right side was removed and the trunk of the hypoglossal nerve was exposed. Two microliters of mercuric chloride aqueous solution was injected into the main trunk of the hypoglossal nerve at the bifurcation. The contralateral hypoglossal nerve was kept intact and used as the normal control. Animals were allowed to survive for 1 or 3 days and were prepared for ammonium sulfide histochemistry and electron microscopy.
Three days after injection of mercuric chloride solution, almost all unmyelinated sympathetic fibers in the hypoglossal nerve trunk were lost, whereas myelinated somatic axons were spared. Although mercury deposition in the myelin sheaths of neuronal processes was observed in the hypoglossal nucleus, the neuronal somas were intact. By contrast, degenerated neuronal processes and mercury deposition in neuronal somas were frequently found in the superior cervical ganglia.
This study demonstrated an undue susceptibility of sympathetic fibers to mercury intoxication. The mechanisms that underlie the selective reaction of sympathetic fibers to mercury warrant further investigation.
背景/目的：汞是一种众所周知的神经毒素，但体内自主神经对汞中毒的敏感性很少被研究。我们之前的研究表明，仓鼠舌下神经中含有躯体运动和节后交感神经纤维。本研究旨在探讨氯化汞注入仓鼠舌下神经后神经系统的超微结构变化。
本研究使用了 6 只成年仓鼠。麻醉后，取下右侧二腹肌，暴露舌下神经干。在舌下神经干分叉处将 2 微升氯化汞水溶液注入主干。对侧舌下神经保持完整，作为正常对照。动物存活 1 或 3 天后，进行硫化铵组织化学和电子显微镜检查。
氯化汞溶液注射后 3 天，舌下神经干中的几乎所有无髓交感纤维都消失了，而有髓体轴突则幸免。虽然在舌下神经核中观察到神经元突起的髓鞘中有汞沉积，但神经元体是完整的。相比之下，在颈上神经节中经常发现退行性神经元突起和汞在神经元体中的沉积。
本研究表明交感纤维对汞中毒具有过度的敏感性。交感纤维对汞选择性反应的机制值得进一步研究。
