Zakharov A, Vitale C, Kilinc E, Koroleva K, Fayuk D, Shelukhina I, Naumenko N, Skorinkin A, Khazipov R, Giniatullin R
Laboratory of Neurobiology, Kazan Federal University Kazan, Russia ; Department of Physiology, Kazan State Medical University Kazan, Russia.
Department of Neurobiology, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland Kuopio, Finland.
Front Cell Neurosci. 2015 Jul 28;9:287. doi: 10.3389/fncel.2015.00287. eCollection 2015.
Trigeminal nerves in meninges are implicated in generation of nociceptive firing underlying migraine pain. However, the neurochemical mechanisms of nociceptive firing in meningeal trigeminal nerves are little understood. In this study, using suction electrode recordings from peripheral branches of the trigeminal nerve in isolated rat meninges, we analyzed spontaneous and capsaicin-induced orthodromic spiking activity. In control, biphasic single spikes with variable amplitude and shapes were observed. Application of the transient receptor potential vanilloid 1 (TRPV1) agonist capsaicin to meninges dramatically increased firing whereas the amplitudes and shapes of spikes remained essentially unchanged. This effect was antagonized by the specific TRPV1 antagonist capsazepine. Using the clustering approach, several groups of uniform spikes (clusters) were identified. The clustering approach combined with capsaicin application allowed us to detect and to distinguish "responder" (65%) from "non-responder" clusters (35%). Notably, responders fired spikes at frequencies exceeding 10 Hz, high enough to provide postsynaptic temporal summation of excitation at brainstem and spinal cord level. Almost all spikes were suppressed by tetrodotoxin (TTX) suggesting an involvement of the TTX-sensitive sodium channels in nociceptive signaling at the peripheral branches of trigeminal neurons. Our analysis also identified transient (desensitizing) and long-lasting (slowly desensitizing) responses to the continuous application of capsaicin. Thus, the persistent activation of nociceptors in capsaicin-sensitive nerve fibers shown here may be involved in trigeminal pain signaling and plasticity along with the release of migraine-related neuropeptides from TRPV1 positive neurons. Furthermore, cluster analysis could be widely used to characterize the temporal and neurochemical profiles of other pain transducers likely implicated in migraine.
脑膜中的三叉神经与偏头痛疼痛背后的伤害性放电产生有关。然而,脑膜三叉神经中伤害性放电的神经化学机制却鲜为人知。在本研究中,我们使用从分离的大鼠脑膜中三叉神经外周分支进行的吸力电极记录,分析了自发的和辣椒素诱导的顺向尖峰活动。在对照组中,观察到具有可变幅度和形状的双相单峰。将瞬时受体电位香草酸受体1(TRPV1)激动剂辣椒素应用于脑膜可显著增加放电,而尖峰的幅度和形状基本保持不变。这种效应被特异性TRPV1拮抗剂辣椒平所拮抗。使用聚类方法,识别出了几组均匀的尖峰(簇)。聚类方法与辣椒素应用相结合,使我们能够检测并区分“反应者”(65%)和“非反应者”簇(35%)。值得注意的是,反应者以超过10Hz的频率发放尖峰,这一频率足以在脑干和脊髓水平提供突触后兴奋的时间总和。几乎所有尖峰都被河豚毒素(TTX)抑制,这表明TTX敏感的钠通道参与了三叉神经元外周分支的伤害性信号传导。我们的分析还确定了对持续应用辣椒素的瞬时(脱敏)和持久(缓慢脱敏)反应。因此,此处显示的辣椒素敏感神经纤维中伤害感受器的持续激活可能与三叉神经疼痛信号传导和可塑性有关,同时也与TRPV1阳性神经元释放偏头痛相关神经肽有关。此外,聚类分析可广泛用于表征可能与偏头痛有关的其他疼痛感受器的时间和神经化学特征。