Department of Physiological Sciences, Piracicaba Dental School, University of Campinas, Piracicaba, Brazil.
Section of Orofacial Pain and Jaw Function, Department of Dentistry and Oral Health, Aarhus University, Aarhus, Denmark.
Eur J Pain. 2019 Oct;23(9):1619-1630. doi: 10.1002/ejp.1438. Epub 2019 Jul 16.
Quantification of motor-evoked potentials (MEPs) can contribute to better elucidate the central modulation of motor pathways in response to nociceptive inputs. The primary aim of this study was to assess the modulatory effects of nerve growth factor (NGF) injection on masseter corticomotor excitability.
The healthy participants of this randomized, double blind placebo-controlled experiment were assigned to have injected into the right masseter muscle either NGF (n = 25) or isotonic saline (IS, n = 17). The following variables were assessed at baseline and 48 hr after the injection: right masseter MEP amplitude and corticomotor mapping and clinical assessment of jaw pain intensity and function. Repeated Measures ANOVA was applied to the data.
NGF caused jaw pain and increased jaw functional disability after the injection (p < 0.050). Also, the participants in the NGF group decreased the MEP amplitude (p < 0.001) but the IS group did not present any significant modulation after the injection (p > 0.050). Likewise, the participants in the NGF group reduced corticomotor map area and volume (p < 0.001), but the IS group did not show any significant corticomotor mapping changes after the injection (p > 0.050). Finally, there was a significant correlation between the magnitude of decreased corticomotor excitability and jaw pain intensity on chewing 48 hr after the NGF injection (r = -0.51, p = 0.009).
NGF-induced masseter muscle soreness can significantly reduce jaw muscle corticomotor excitability, which in turn is associated with lower jaw pain intensity and substantiates the occurrence of central changes that most likely aim to protect the musculoskeletal orofacial structures.
Intramuscular administration of nerve growth factor into masseter muscle causes inhibitory corticomotor plasticity, which likely occurs to prevent further damage and seems associated with lower pain intensity on function.
运动诱发电位（MEPs）的量化有助于更好地阐明感觉传入刺激下运动通路的中枢调节。本研究的主要目的是评估神经生长因子（NGF）注射对咬肌皮质运动兴奋性的调制作用。
这项随机、双盲、安慰剂对照实验的健康参与者被分配到右侧咬肌注射 NGF（n=25）或等渗盐水（IS，n=17）。在基线和注射后 48 小时评估以下变量：右侧咬肌 MEP 幅度和皮质运动图以及咀嚼时的颌痛强度和功能的临床评估。对数据进行重复测量方差分析。
NGF 注射后引起颌痛和咀嚼功能障碍增加（p<0.050）。此外，NGF 组的参与者 MEP 幅度降低（p<0.001），而 IS 组注射后没有出现明显的调制（p>0.050）。同样，NGF 组的参与者皮质运动图面积和体积减少（p<0.001），而 IS 组注射后皮质运动图没有发生明显变化（p>0.050）。最后，NGF 注射后 48 小时，皮质运动兴奋性降低的幅度与咀嚼时颌痛强度之间存在显著相关性（r=-0.51，p=0.009）。
NGF 诱导的咬肌酸痛可显著降低咀嚼肌皮质运动兴奋性，这反过来与颌痛强度降低有关，证实了中枢变化的发生，这很可能旨在保护肌肉骨骼或颌面结构。
NGF 注射到咬肌可引起抑制性皮质运动可塑性，这可能是为了防止进一步的损伤，并且似乎与功能时的低疼痛强度有关。
