Modulation of synaptic transmission as the therapeutic strategies for chronic pain

1.为了阐明加巴喷丁的脊髓上作用机制，采用全细胞膜片钳技术记录了周围神经损伤小鼠和假手术小鼠的脑干切片中蓝斑（LC）神经元，并研究了加巴喷丁对突触传递的影响。加巴喷丁（10-100 μM）浓度依赖性地减少部分神经结扎小鼠切片中GABA A受体介导的IPSC（Seltzer模式），而谷氨酸介导的EPSC几乎不受影响。相比之下，加巴喷丁并没有减少取自假手术小鼠的切片中的IPSC。由于加巴喷丁减少IPSC，同时增加配对脉冲比，因此它作用于LC中的突触前GABA能神经末梢。此外，蛋白激酶A抑制剂11-89而不是蛋白激酶C抑制剂白屈菜红碱消除了加巴喷丁对IPSC的抑制作用，这表明PICA介导的磷酸化似乎是IPSC的重要机制。 ...更多信息 加巴喷丁共同产生GABA能突触传递的PICA依赖性突触前抑制，从而消除仅在神经病理性疼痛状态下对LC神经元的抑制影响（去甲肾上腺素能下行系统的去抑制）.我们解决了增加脊髓甘氨酸外源性应用或通过使用其选择性抑制剂肌氨酸和NFPS对小鼠神经性和炎症性疼痛的甘氨酸转运蛋白1（GlyT 1）的封锁的治疗影响。甘氨酸、肌氨酸和NFPS可改善Seltzer模型小鼠的热和机械超敏反应，并降低STZ注射糖尿病小鼠的机械超敏反应。此外，它们选择性地抑制福尔马林诱发的舔/咬行为的第二阶段。从Seltzer模型小鼠制备的海马切片中，LTP维持在显著低于假治疗小鼠的水平。这种损害的LTP从未观察到时，它是在NFPS的存在下诱导。总之，通过GlyT 1阻断增加内源性甘氨酸不仅导致对脊髓水平疼痛传递的净抑制作用，而且还在脊髓上缓解了可能与慢性疼痛住院患者经常描述的认知障碍相关的突触功效降低。在与初级传入纤维和浅背角神经元之间的疼痛传递相关的药理学和生理学研究中，已经使用了从大鼠制备的具有附着背根的脊髓切片。然而，突触传递使用小鼠脊髓切片连接背根几乎没有评价。我们将这种大鼠脊髓切片制备物用于成年小鼠，并探讨周围神经损伤后HCN通道是否有助于Aδ和C纤维介导的EPSC。与我们的行为研究一致，表明鞘内注射HCN通道阻断剂ZD 7288可降低Seltzer模型小鼠的热和机械超敏反应，7288可降低Aδ和C纤维介导的EPSC。少

1. To clarify the supraspinal mechanism of action of gabapentin, whole-cell patch-clamp recordings were performed on locus coeruleus (LC) neurons in brainstem slices prepared from mice after peripheral nerve injury or mice subjected to a sham operation, and the effects of gabapentin on synaptic transmission were studied. Gabapentin (10-100 μM) concentration-dependently reduced the GABAAreceptor-mediated IPSCs in slices prepared from partial nerve-ligated mice (the Seltzer mode)), whereas glutamate-mediated EPSCs were hardly affected. By contrast, gabapentin did not reduce IPSCs in slices taken from mice given a sham operation. Since gabapentin reducedIPSCs together with an increase in the paired-pulse ratio, it acts on the presynaptic GABAergic nerve terminals in the LC. Moreover, the protein kinase A inhibitor 11-89 but not the protein kinase C inhibitor chelerythrine abolished the inhibitory action of gabapentin on IPSCs, suggesting that PICA-mediated phosphorylation seems to be impo … More rtant for supraspinal gabapentin responsiveness in neuropathic conditions.Together, gabapentin generates PICA-dependent presynaptic inhibition of GABAergic synaptic transmission, and thereby removes the inhibitory influence on LC neurons (disinhibition of the descending noradrenergic system) only under neuropathic pain states.2. We addressed the therapeutic impact of increasing spinal glycine applied exogenously or via blockade of glycine transporter 1 (GlyT1) using its selective inhibitors sarcosine and NFPS on neuropathic and inflammatory pain in mice. Glycine, sarcosine and NFPS ameliorated thermal and mechanical hypersensitivity in Seltzer model mice, and reduced mechanical hypersensitivity in STZ injected diabetic mice. Moreover, they selectively inhibited the second phase of formalin evoked licking/biting behavior. In hippocampal slices prepared from Seltzer model mice, LTP was maintained at a significantly lower level than that in sham-treated mice. Such impairment of LTP was never observed when it was induced in the presence of NFPS. Together, an increase in endogenous glycine via GlyT1 blockade not only results in a net inhibitory influence on pain transmission at the spinal level but also supraspinally relieves decreased synaptic efficacy presumably related to cognitive disturbance often described inpatients with chronic pain.3. In the pharmacological and physiological studies related with pain transmission between primary afferent fibers and superficial dorsal horn neurons, spinal cord slices with attached dorsal roots prepared from rats have been used. However, synaptic transmission using mice spinal cord slices attached dorsal roots is hardly evaluated. We adapted this rat spinal slice preparation to adult mice, and addressed whether HCN channels contribute to Aδ-and C-fiber-mediated EPSCs after peripheral nerve injury. Consistent with our behavioral study demonstrating that intrathecal injection of the HCN channel blocker ZD7288 reduced thermal and machanical hypersensitivity in Seltzer model mice, 7288 reduced Aδ-and C-fiber-mediated EPSCs. Less