Kitamura Y, Matsuka Y, Spigelman I, Ishihara Y, Yamamoto Y, Sonoyama W, Kamioka H, Yamashiro T, Kuboki T, Oguma K
Department of Oral Rehabilitation and Regenerative Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
Neuroscience. 2009 Apr 10;159(4):1422-9. doi: 10.1016/j.neuroscience.2009.01.066. Epub 2009 Feb 3.
Many patients with trigeminal neuropathies suffer severe chronic pain which is inadequately alleviated with centrally-acting drugs. These drugs also possess severe side effects making compliance difficult. One strategy is to develop new treatments without central side effects by targeting peripheral sensory neurons, since sensory neuron excitability and neurotransmitter release increase in chronic pain states. Such treatments may include the highly purified botulinum toxin type A 150 kDa (BoNT/A) which reportedly blocks vesicular neurotransmitter release. We set out to determine if experimental trigeminal neuropathy induced by infraorbital nerve constriction (IoNC) in rats could alter neurotransmitter release from somata of trigeminal sensory neurons and if it could be attenuated by BoNT/A. Thus, we monitored the secretory activity of acutely dissociated trigeminal ganglion (TRG) neurons from naïve and IoNC rats by measuring the fluorescence intensity of the membrane-uptake marker (N-(3-triethylammoniumpropyl)-4-(6-(4-(diethylamino)phenyl)hexatrienyl)pyridinium dibromide (FM4-64). FM4-64 staining showed that neurons possess a pool of recycled vesicles which could be released by high KCl (75 mM) application. BoNT/A pre-treatment of acutely dissociated TRG neurons from naïve rats significantly reduced the rate of FM4-64 dye release. Neurons isolated from TRG ipsilateral to IoNC exhibited significantly faster onset of FM4-64 release than neurons contralateral to IoNC (sham surgery). IoNC also produced long-lasting ipsilateral tactile allodynia, measured as large decreases of withdrawal thresholds to mechanical stimulation. Intradermal injection of BoNT/A in the area of infraorbital branch of the trigeminal nerve (IoN) innervation alleviated IoNC-induced mechanical allodynia and reduced the exaggerated FM4-64 release in TRG neurons from these rats. Our results suggest that BoNT/A decreases neuropathic pain behaviors by decreasing the exaggerated neurotransmitter release from TRG sensory neurons.
许多三叉神经病变患者遭受严重的慢性疼痛，而中枢作用药物并不能充分缓解这种疼痛。这些药物还具有严重的副作用，使得患者难以坚持服药。一种策略是通过靶向外周感觉神经元来开发无中枢副作用的新治疗方法，因为在慢性疼痛状态下感觉神经元的兴奋性和神经递质释放会增加。此类治疗方法可能包括高度纯化的150 kDa A型肉毒杆菌毒素（BoNT/A），据报道它能阻断囊泡神经递质的释放。我们着手确定大鼠眶下神经缩窄（IoNC）诱导的实验性三叉神经病变是否会改变三叉神经感觉神经元胞体的神经递质释放，以及它是否能被BoNT/A减弱。因此，我们通过测量膜摄取标记物（N-(3-三乙铵丙基)-4-(6-(4-(二乙氨基)苯基)己三烯基)吡啶二溴化物（FM4-64））的荧光强度，监测了来自未处理大鼠和IoNC大鼠的急性解离三叉神经节（TRG）神经元的分泌活性。FM4-64染色显示神经元拥有一组可循环利用的囊泡，高钾（75 mM）应用可使其释放。对来自未处理大鼠的急性解离TRG神经元进行BoNT/A预处理可显著降低FM4-64染料的释放速率。与IoNC对侧（假手术）的神经元相比，从IoNC同侧TRG分离出的神经元表现出FM4-64释放的起始明显更快。IoNC还产生了持久的同侧触觉异常性疼痛，表现为对机械刺激的撤换阈值大幅降低。在三叉神经眶下支（IoN）支配区域皮内注射BoNT/A可减轻IoNC诱导的机械性异常性疼痛，并减少这些大鼠TRG神经元中过度的FM4-64释放。我们的结果表明，BoNT/A通过减少TRG感觉神经元过度的神经递质释放来减轻神经性疼痛行为。
