Finley Dana B, Wang Xiaochun, Graff Jaimie E, Herr David W
Toxicology Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
J Pharmacol Toxicol Methods. 2009 Mar-Apr;59(2):108-19. doi: 10.1016/j.vascn.2009.02.001.
Exposure to irreversible cholinesterase (ChE)-inhibiting compounds, such as organophosphates may produce neuromuscular dysfunction. However, less is known about changes in neuromuscular transmission after treatment with reversible ChE-inhibitors. These studies adapted single fiber electromyography (SFEMG) techniques to quantify neuromuscular jitter in adult and juvenile rats after treatment with agents that alter cholinergic neurotransmission.
Anesthetized adult and juvenile rats were tested using stimulation SFEMG, recorded in the gastrocnemius muscle, after stimulation in the sciatic notch region. The influence of electrode placement, treatment with decamethonium (to disrupt neuromuscular transmission) or physostigmine (reversible ChE inhibitor), and the impact of varied stimulation frequency were quantified.
No significant effects of needle placement or criterion amplitude were observed when calculating the mean consecutive difference (MCD). Treatment with decamethonium did not alter MCD values in adult or juvenile rats. However, decamethonium produced an increased blocking of muscle action potentials (MAP) in juveniles. Also, when stimulated at 9.09 Hz, both adult and juvenile animals had a greater decrease in MAP amplitude between the first and fourth responses (T(1)-T(4) decrement) after treatment with decamethonium. Prior to treatment with decamethonium, the T(1)-T(4) decrement averaged about 3 fold greater in juveniles than adults, and was larger at 3.03 and 9.09 Hz than with 0.91 Hz stimulation. Treatment with physostigmine resulted in at least 50% inhibition of muscle ChE activity, but produced minimal changes in the MCD values in adults or juveniles. Combined over treatments and stimulation frequencies, the median MCD for juveniles (11.6 micros) was less than that for of adults (18.8 micros). In juveniles, the median MCD increased from 9.3 micros to 13.9 micros as the stimulation rate was increased from 0.91 to 9.09 Hz. This stimulus-dependent change was more evident in juveniles than in adults.
A technique was developed to record stimulation SFEMG and neuromuscular jitter, in vivo, in adult and juvenile rats. The method was sufficiently sensitive to detect age-related differences, potentially allowing developmental processes to be examined. Based on the literature and the current data, the technique appears to be more sensitive to prolonged inhibition of ChE enzymes than the reversible inhibition produced by physostigmine.
接触不可逆胆碱酯酶（ChE）抑制化合物，如有机磷酸酯，可能会导致神经肌肉功能障碍。然而，关于用可逆性ChE抑制剂治疗后神经肌肉传递的变化，人们了解得较少。这些研究采用单纤维肌电图（SFEMG）技术，对用改变胆碱能神经传递的药物治疗后的成年和幼年大鼠的神经肌肉抖动进行量化。
对麻醉的成年和幼年大鼠进行刺激SFEMG测试，在坐骨切迹区域刺激后，记录腓肠肌的情况。量化电极放置、用十烃季铵（以破坏神经肌肉传递）或毒扁豆碱（可逆性ChE抑制剂）治疗的影响，以及不同刺激频率的影响。
计算平均连续差值（MCD）时，未观察到针放置或标准幅度的显著影响。用十烃季铵治疗未改变成年或幼年大鼠的MCD值。然而，十烃季铵使幼年大鼠的肌肉动作电位（MAP）阻滞增加。此外，当以9.09 Hz刺激时，用十烃季铵治疗后，成年和幼年动物在第一个和第四个反应之间的MAP幅度下降更大（T(1)-T(4) 递减）。在用十烃季铵治疗之前，幼年大鼠的T(1)-T(4) 递减平均比成年大鼠大3倍左右，并且在3.03和9.09 Hz时比0.91 Hz刺激时更大。用毒扁豆碱治疗导致肌肉ChE活性至少50%受到抑制，但在成年或幼年大鼠中MCD值变化最小。综合各种治疗和刺激频率，幼年大鼠的MCD中位数（11.6微秒）低于成年大鼠（18.8微秒）。在幼年大鼠中，随着刺激率从0.91 Hz增加到9.09 Hz，MCD中位数从9.3微秒增加到13.9微秒。这种刺激依赖性变化在幼年大鼠中比在成年大鼠中更明显。
开发了一种在成年和幼年大鼠体内记录刺激SFEMG和神经肌肉抖动的技术。该方法足够灵敏，能够检测与年龄相关的差异，有可能用于研究发育过程。根据文献和当前数据，该技术似乎对ChE酶的长期抑制比对毒扁豆碱产生的可逆抑制更敏感。
