Morphological and functional changes in regenerated primary afferent fibres following mental and inferior alveolar nerve transection
Morphological and functional changes in regenerated primary afferent fibres following mental and inferior alveolar nerve transection
复制标题
颏神经和下牙槽神经横断后再生初级传入纤维的形态和功能变化
作者：
Tsuboi Y;Honda K;Bae YC;Shinoda M;Kondo M;Katagiri A;Echizenya S;Kamakura S;Lee J;Iwata K.
研究背景了解下牙槽神经（inferior alveolar nerve，IAN）再生引起的疼痛异常的机制，对于发展口面神经病理性疼痛的治疗方法具有重要意义。然而，IAN再生后口面疼痛异常的外周机制尚未完全了解。方法头退缩阈值（HWT），下颌开放反射（JOR）阈值，再生的颏神经（MN）纤维的单纤维记录，降钙素基因相关肽（CGRP），isolectin B4（IB 4），外周蛋白，三叉神经节（TG）细胞中的神经丝-200（NF-200）和瞬时受体电位香草素1（TRPV 1）表达，并在MN-和IAN-横切（M-IANX）中研究了再生MN纤维的电子显微镜（EM）观察结果与假手术大鼠相比，M-IANX大鼠对颏部皮肤的机械或热刺激的HWT显著降低。与假手术大鼠相比，M-IANX大鼠中从MN纤维（n= 124）记录的动作电位的平均传导速度显著较慢。与假手术大鼠相比，M-IANX大鼠中Fluoro-Gold（FG）标记的CGRP-、peripherin-或TRPV 1-免疫反应（IR）细胞的百分比显著更大，而与假手术大鼠相比，M-IANX大鼠中FG标记的IB-4-和NF-200-IR细胞的百分比显著更小。在M-IANX大鼠中很少观察到大尺寸的有髓神经纤维，而经常观察到大尺寸的无髓神经纤维，并在再生axons.ConclusionsThese研究结果表明，MN纤维再生后脱髓鞘可能参与外周敏化，导致三叉神经损伤相关的口面神经病理性疼痛。
BackgroundIt is important to know the mechanisms underlying pain abnormalities associated with inferior alveolar nerve (IAN) regeneration in order to develop the appropriate treatment for orofacial neuropathic pain patients. However, peripheral mechanisms underlying orofacial pain abnormalities following IAN regeneration are not fully understood.MethodsHead withdrawal threshold (HWT), jaw opening reflex (JOR) thresholds, single‐fibre recordings of the regenerated mental nerve (MN) fibres, calcitonin gene‐related peptide (CGRP), isolectin B4 (IB4), peripherin, neurofilament‐200 (NF‐200) and transient receptor potential vanilloid 1 (TRPV1) expression in trigeminal ganglion (TG) cells, and electron microscopic (EM) observations of the regenerated MN fibres were studied in MN‐ and IAN‐transected (M‐IANX) rats.ResultsHWT to mechanical or heat stimulation of the mental skin was significantly lower in M‐IANX rats compared with sham rats. Mean conduction velocity of action potentials recorded from MN fibres (n= 124) was significantly slower in M‐IANX rats compared with sham rats. The percentage of Fluoro‐Gold (FG)‐labelled CGRP‐, peripherin‐ or TRPV1‐immunoreactive (IR) cells was significantly larger in M‐IANX rats compared with that of sham rats, whereas that of FG‐labelled IB4‐ and NF‐200‐IR cells was significantly smaller in M‐IANX rats compared with sham rats. Large‐sized myelinated nerve fibres were rarely observed in M‐IANX rats, whereas large‐sized unmyelinated nerve fibres were frequently observed and were aggregated in the bundles at the distal portion of regenerated axons.ConclusionsThese findings suggest that the demyelination of MN fibres following regeneration may be involved in peripheral sensitization, resulting in the orofacial neuropathic pain associated with trigeminal nerve injury.