Mann Mandeep K, Dong Xu-Dong, Svensson Peter, Cairns Brian E
Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, Canada.
J Orofac Pain. 2006 Fall;20(4):325-36.
To investigate whether local administration of nerve growth factor (NGF) decreases the mechanical threshold (MT) of putative nociceptive masseter afferent fibers as part of its mechanism of mechanical sensitization.
Electrophysiologic recordings were made from masseter afferents and a randomized, blinded approach was used to test the effects of intramuscular injection of NGF (2.5 or 25 microg/mL) into the rat masseter muscle on the MT of masseter afferents (n=65) and plasma protein extravasation.
The plasma protein extravasation data and electrophysiological recordings indicated that rat NGF injection was not inflammatory and did not evoke afferent discharge or induce mechanical sensitization (as reflected in a decreased MT) in masseter afferents in either male or female rats. To investigate whether the lack of effect of NGF injection might be due to differences between human and rat NGF, additional experiments with human NGF injection (25 microg/mL) were undertaken. Intramuscular injection of human NGF into the rat masseter muscle also failed to evoke afferent discharges; however, it did decrease the MT of masseter afferent fibers.
The finding that neither rat nor human NGF excited putative nociceptive masseter afferent fibers is consistent with a previous report that intramuscular NGF injections are not acutely painful in human subjects. The ability of human NGF injection into the rat masseter muscle to induce afferent mechanical sensitization suggests that this experimental approach may be useful for the study of peripheral mechanisms of myofascial pain and tenderness associated with temporomandibular disorders.
研究局部给予神经生长因子（NGF）是否会降低假定的伤害性咬肌传入纤维的机械阈值（MT），这是其机械致敏机制的一部分。
对咬肌传入纤维进行电生理记录，并采用随机、盲法来测试向大鼠咬肌内肌肉注射NGF（2.5或25微克/毫升）对咬肌传入纤维MT（n = 65）和血浆蛋白外渗的影响。
血浆蛋白外渗数据和电生理记录表明，注射大鼠NGF并无炎症反应，在雄性或雌性大鼠的咬肌传入纤维中均未引发传入放电或诱导机械致敏（表现为MT降低）。为研究注射NGF无效是否可能是由于人源和大鼠源NGF之间存在差异，进行了额外的人源NGF注射（25微克/毫升）实验。向大鼠咬肌内肌肉注射人源NGF也未能引发传入放电；然而，它确实降低了咬肌传入纤维的MT。
大鼠和人源NGF均未激发假定的伤害性咬肌传入纤维这一发现，与先前关于肌肉注射NGF对人类受试者不会产生急性疼痛的报告一致。向大鼠咬肌内肌肉注射人源NGF可诱导传入机械致敏，这表明该实验方法可能有助于研究与颞下颌关节紊乱相关的肌筋膜疼痛和压痛的外周机制。
