基于Orexin调控的前额皮层谷氨酸能系统在针刺缓解慢性痛奖赏效应中的作用

Relief of pain often promotes a positive emotional state. Thus, relief of the chronic pain stimulus, as the negative reinforcement from pain, has been appropriately described as a reward. Primary rewards are encoded in brain reward/motivational circuits. Rewarding features of pain relief are likely to facilitate learning during the healing process about actions leading to relief. The neural mechanisms within reward circuits underlying reward from pain relief may therefore drive decisions promoting pain relief-motivated behavior that accelerate recovery. The glutamatergic pyramidal neurons in the prefrontal cortex and orexin-A regulation in the lateral hypothalamus, as two important brain regions in brain reward network, are not only involved in reward but also in chronic pain. However, little was known about the effects of acupuncture on reward from chronic pain relief and the mechanisms of acupuncture analgesia implicated in brain reward/motivational circuits. We observed previously that acupuncture relieved nerve injury evoked hypersensitivity and produced conditioned place preference (CPP). In our pilot study, we found that acupuncture analgesia induced c-fos expression in the infralimbic prefrontal cortex. Here, we will conduct systematic experiments on effectiveness during a given period of time for acupuncture on acupuncture-induced reward from chronic pain relief. We will also point out possible mechanisms of acupuncture analgesia involved in glutamatergic pyramidal neurons in the prefrontal cortex by PKC-NMDA receptor pathway. In addition, we will also investigate the modulatory effects of acupuncture and orexin neurons in the lateral hypothalamus on glutamate receptor function and activity in glutamatergic pyramidal neurons from rat prefrontal cortex. The techniques such as the multi-electrode array recording in freely moving rats, optogenetics, immunohistochemistry, and molecular biotechnology will be used in present study. This study will be helpful to further explore the core mechanisms of acupuncture analgesia.

慢性痛的缓解作为疼痛的负性强化，被认为是一种奖赏，激活大脑奖赏系统。前额皮层谷氨酸能系统及下丘脑外侧区Orexin调控作为脑奖赏网络的重要节点，不仅涉及奖赏而且参与疼痛过程。目前针刺缓解慢性痛的奖赏效应和脑内奖赏系统参与针刺镇痛的机制研究尚不充分。申请人已观察到电针能有效缓解神经病理痛并产生了条件性位置偏爱（CPP）。预实验发现针刺镇痛前额皮层边缘下区c-fos基因表达明显增加，提示针刺镇痛激活前额皮层神经元活动。考虑到我们前期工作发现Orexin对前额皮层神经元的调制作用。本研究拟采用CPP范式明确针刺缓解慢性痛奖赏的时效特点；采用微阵列电生理、光基因技术、免疫组化和分子生物学技术，探索前额皮层PKC-NMDA谷氨酸受体通路以及谷氨酸能锥体神经元参与针刺镇痛和奖赏；观察下丘脑外侧区Orexin对针刺镇痛前额皮层谷氨酸能神经元的调控作用，为进一步阐明针刺镇痛的神经生物学机制提供新思路。

慢性痛的缓解作为疼痛的负性强化，被认为是一种奖赏，激活大脑奖赏系统。前额皮层谷氨酸能系统及下丘脑外侧区Orexin调控作为脑奖赏网络的重要节点，不仅涉及奖赏而且参与疼痛过程。目前针刺缓解慢性痛的奖赏效应和脑内奖赏系统参与针刺镇痛的机制研究尚不充分。本研究采用条件性位置偏爱范式明确针刺缓解慢性痛奖赏的时效特点；采用微阵列电生理、光基因技术、免疫组化和分子生物学技术，探索前额皮层谷氨酸能锥体神经元和下丘脑外侧区Orexin在针刺镇痛奖赏中的作用。结果发现，在不同的动物模型上（急性痛、炎性痛和神经病理性疼痛动物模型），针刺镇痛能诱导条件性位置偏爱，而假手术大鼠电针不产生条件性位置偏爱；刺激非穴位不产生条件性位置偏爱。针刺镇痛效应产生的时效特点表现为慢性痛早期而不是后期。针刺只能在慢性痛的早期诱导条件性位置偏爱，提示了神经元的可塑性在针刺奖赏中的影响。本研究进一步发现针刺镇痛奖赏激活前额皮层边缘下区神经元；药理学方法抑制前额皮层边缘下区神经元能阻断针刺镇痛奖赏效应；采用Fos/VGlut2免疫荧光双标发现，针刺镇痛激活前额皮层边缘下区谷氨酸能神经元。针刺镇痛及诱导的条件性位置偏爱增加前额皮层边缘下区谷氨酸能神经元放电活动。采用光遗传技术，激活CamK‖-Cre小鼠前额皮层边缘下区谷氨酸能神经元能模拟针刺镇痛及奖赏效应，抑制前额皮层边缘下区谷氨酸能神经元逆转针刺镇痛及奖赏效应；免疫组化Fos表达全脑图谱发现，针刺奖赏激活的脑区集中在大脑奖赏系统，包括前额皮层，伏隔核和下丘脑外侧区。研究进一步发现，针刺镇痛奖赏激活下丘脑外侧区Orexin阳性神经元的表达，下丘脑外侧区微注射orexin拮抗剂能显著减轻SNI疼痛模型大鼠条件性位置偏爱。采用荧光示踪技术，观察到针刺镇痛奖赏激活下丘脑外侧区Orexin神经元到前额皮层谷氨酸环路的神经环路。针刺联合注射小剂量的Orexin能产生协同镇痛效应，本研究为进一步阐明针刺镇痛的神经生物学机制提供新思路和新视角。