Spicarova Diana, Adamek Pavel, Kalynovska Nataliia, Mrozkova Petra, Palecek Jiri
Department of Functional Morphology, Institute of Physiology vvi, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague 4, Czech Republic.
Neuropharmacology. 2014 Jun;81:75-84. doi: 10.1016/j.neuropharm.2014.01.041. Epub 2014 Feb 1.
Modulation of nociceptive synaptic transmission in the spinal cord is implicated in the development and maintenance of several pathological pain states. The chemokine CCL2 (C-C motif ligand 2) was shown to be an important factor in the development of neuropathic pain after peripheral nerve injury. In our experiments we have studied the effect of CCL2 application and TRPV1 (transient receptor potential vanilloid 1) receptor activation on nociceptive signaling and the modulation of synaptic transmission. Intrathecal drug application in behavioral experiments and patch-clamp recordings of spontaneous, miniature and dorsal root stimulation-evoked excitatory postsynaptic currents (sEPSCs, mEPSCs, eEPSCs) from superficial dorsal horn neurons in acute rat spinal cord slices were used. The intrathecal application of CCL2 induced thermal hyperalgesia and mechanical allodynia, while pretreatment with the TRPV1 receptor antagonist SB366791 diminished the thermal but not the mechanical hypersensitivity. Patch-clamp experiments showed an increase of sEPSC and mEPSC (124.5 ± 12.8% and 161.2 ± 17.3%, respectively) frequency in dorsal horn neurons after acute CCL2 application. This CCL2-induced increase was prevented by SB366791 pretreatment (89.4 ± 6.0%, 107.5 ± 14.2%). CCL2 application increased the amplitude of eEPSCs (188.1 ± 32.1%); this increase was significantly lower in experiments with SB366791 pretreatment (120.8 ± 17.2%). Our results demonstrate that the activation of spinal TRPV1 receptors plays an important role in the modulation of nociceptive signaling induced by CCL2 application. The mechanisms of cooperation between the CCL2 activated receptors and TRPV1 receptors on the central branches of primary afferent fibers may be especially important during different pathological pain states and need to be further investigated.
脊髓中伤害性突触传递的调制与几种病理性疼痛状态的发生和维持有关。趋化因子CCL2（C-C基序配体2）被证明是外周神经损伤后神经性疼痛发生的一个重要因素。在我们的实验中，我们研究了应用CCL2和激活TRPV1（瞬时受体电位香草酸亚型1）受体对伤害性信号传导和突触传递调制的影响。在行为实验中进行鞘内给药，并对急性大鼠脊髓切片中浅表背角神经元的自发、微小和背根刺激诱发的兴奋性突触后电流（sEPSCs、mEPSCs、eEPSCs）进行膜片钳记录。鞘内应用CCL2可诱发热痛觉过敏和机械性异常性疼痛，而用TRPV1受体拮抗剂SB366791预处理可减轻热敏感性，但不能减轻机械性超敏反应。膜片钳实验显示，急性应用CCL2后，背角神经元中sEPSC和mEPSC的频率增加（分别为124.5±12.8%和161.2±17.3%）。SB366791预处理可防止CCL2诱导的这种增加（89.4±6.0%，107.5±14.2%）。应用CCL2可增加eEPSCs的幅度（188.1±32.1%）；在SB366791预处理的实验中，这种增加明显较低（120.8±17.2%）。我们的结果表明，脊髓TRPV1受体的激活在CCL2应用诱导的伤害性信号传导调制中起重要作用。在不同的病理性疼痛状态下，CCL2激活的受体与初级传入纤维中枢支上的TRPV1受体之间的协同机制可能尤为重要，需要进一步研究。
