Reversal of pain by group II metabotropic glutamate receptors

描述(申请人提供)：炎症或损伤可以使伤害性神经元变得敏感，由此产生的过度兴奋被认为是导致痛觉增加的媒介。虽然疼痛通常会随着时间的推移而缓解，但促使患者回到g医生身边的机制却鲜为人知。这种机制的功能障碍可能导致慢性疼痛的持续，而激活则可以缓解疼痛。这一建议的中心假设是，外周II组代谢性谷氨酸受体(MGluRs)调节伤害性感受器敏化和痛敏的逆转。这一假设将通过解剖学、神经生理学和行为学方法的组合进行验证。存在第二组mGluR的两个亚型，mGluR2和mGluR3。每个亚型在背根神经节(DRG)中的特定表达将被描述。然后，我们将使用mGluR2和mGluR3基因敲除小鼠来确定mGluR2或mGluR3对于炎症性和神经病理性疼痛的正常恢复是必要的。我们认为II组mGluRs可以逆转伤害性感受器敏化。为了测试这一点，膜片钳技术将被用来测量致敏的DRG神经元的神经元兴奋性。在对II组进行药物处理后，将重新评估mGluRs的兴奋性。膜的兴奋性由通过离子通道的电流决定，但尚不清楚第二组mGluRs是否调节参与敏化的电流。两种候选电流，河豚毒素抗性的Na+和T型钙电流，将被致敏的DRG神经元上的II组mGluRs调制的能力测试。我们假设II组mGluRs参与了痛觉过敏的内源性恢复。为了测试这一点，我们将确定II组mGluRs的正变构调节剂是否加速炎性痛觉过敏的恢复。最后，我们将确定第二组mGluRs是否能够使用操作性条件反射范式来缓解持续的神经病理性疼痛。

DESCRIPTION (provided by applicant): Inflammation or injury can sensitize nociceptive neurons and the resulting hyperexcitability is thought to mediate increased pain sensation. Although pain typically resolves with time, the mechanisms that promote the return to Dr. g are poorly understood. Dysfunction of such a mechanism could contribute to the persistence of chronic pain, while activation could provide relief from pain. The central hypothesis of this proposal is that peripheral group II metabotropic glutamate receptors (mGluRs) regulate the reversal of nociceptor sensitization and hyperalgesia. This hypothesis will be tested with a combination of anatomical, neurophysiological, and behavioral methods. Two subtypes of group II mGluRs exist, mGluR2 and mGluR3. The specific expression of each subtype within dorsal root ganglia (DRG) will be characterized. We will then determine whether mGluR2 or mGluR3 is necessary for the normal recovery from inflammatory and neuropathic pain using mGluR2 and mGluR3 knockout mice. We propose that group II mGluRs can reverse nociceptor sensitization. To test this, patch-clamp techniques will be used to measure neuronal excitability in sensitized DRG neurons. After pharmacological manipulation of group II mGluRs excitability will be reassessed. Membrane excitability is determined by current flux through ion channels, but it is not clear whether group II mGluRs regulate currents involved in sensitization. Two candidate currents, the tetrodotoxin- resistant Na+ and T-type Ca2+ current will be tested for their ability to be modulated by group II mGluRs in sensitized DRG neurons. We hypothesize that group II mGluRs are involved in the endogenous recovery from hyperalgesia. To test this, we will determine whether positive allosteric modulators of group II mGluRs accelerate the recovery from inflammatory hyperalgesia. Finally, we will determine whether group II mGluRs are capable of relieving ongoing neuropathic pain using an operant conditioning paradigm.