从离子通道及突触传递角度探讨中药青风藤镇痛的脊髓机制

Chronic pain can cause serious physical as well as emotional harm to the patients. The analgesics currently commonly used in clinic have their limitations because of the side effects. The Traditional Chinese Medicines have their own characteristics and advantages in the treatment of pain, however, most of their underlying mechanisms are unclear and the majority of the researches mainly focused on the peripheral analgesic mechanisms. According to the pharmaceutical characteristics of Caulis Sinomenii and sinomenine, the most important effective ingredient of Caulis Sinomenii in pain treatment, and the physiological and pathological characteristics of the nociceptive transmission and modulation, in this project we brought forward the view that, sinomenine could play roles in the central nervous system and the possible central analgesic mechanisms underlying the analgesic effects of sinomenine should be addressed. In this project, firstly, we planned to study the different effects of sinomenine on pain transmission in the dorsal horn of the spinal cord in different chronic pain models by using in vivo research method; secondly, we will study the effects of sinomenine on various subtypes of ion channels in the dorsal root ganglion neurons and the ion channels respectively heterologously expressed in the HEK293 cells in order to clarify the characteristics of the roles of sinomenine on the ion channels involved in nociceptive transmission and modulation; finally, we will study the effects of sinomenine on the functions of NMDA and AMPA receptors in alive spinal cord slices in order to explore the mechanisms underlying the impacts of sinomenine on the central sensitization in spinal cord in different chronic pain models. The above researches may clarify the ion channel and synaptic transmission mechanisms underlying the analgesic effects of Caulis Sinomenii and sinomenine in the spinal cord, which may provide us the theoretical basis for Caulis Sinomenii and sinomenine treatment of pain in clinic and for further development of them, which may also offer us useful references for the further studies of the central analgesic mechanisms underlying the analgesic effects of other Traditional Chinese Medicines and their effective constituents.

慢性疼痛严重危害患者身心健康，目前临床常用的镇痛药均有其局限性。中医药治疗疼痛有其特色和优势，但大多机制不明且多为外周镇痛机制的研究。基于对青风藤及其镇痛有效成分青藤碱的药学特性以及痛觉传递及调控的生理病理特点的认识，本项目提出青风藤及青藤碱的镇痛作用可能存在中枢机制。计划首先采用在体研究方法，阐明青藤碱对不同性质疼痛模型脊髓背角痛觉传递的不同影响；进而在背根节神经元和异源表达各亚型离子通道的HEK293细胞上，阐明青藤碱对参与痛觉传递与调控的各种离子通道的作用特点；然后在活体脊髓片上，从NMDA及AMPA受体功能角度探索青藤碱对慢性痛脊髓敏化机制的影响。上述研究，可能从离子通道和痛觉突触传递角度阐明青风藤及青藤碱镇痛的脊髓机制，为青风藤及青藤碱临床治疗疼痛和进一步开发它们的药用价值提供理论依据，也为其他中药及有效成分镇痛的中枢机制研究提供借鉴。

本项目基于青风藤及其镇痛有效成分青藤碱的药学特性以及痛觉传递及调控的生理病理特点，从痛觉通路离子通道及突触传递角度探索了青藤碱镇痛的脊髓机制。首先采用在体研究方法，研究了青藤碱对不同病理痛模型大鼠脊髓背角痛觉传递的不同影响；进而在背根节神经元和异源表达各亚型离子通道的HEK293细胞上，研究了青藤碱对参与痛觉传递与调控的各种离子通道的作用特点；然后在活体脊髓片上，从NMDA及AMPA受体功能等突触功能角度探索了青藤碱对慢性痛脊髓敏化机制的影响。结果表明，持续脊髓鞘内给予青藤碱对脊神经结扎神经病理痛模型具有明确的镇痛作用，且其镇痛作用不具有耐受性，而慢性给予吗啡产生明显耐受性。持续脊髓鞘内给予青藤碱，对角叉菜胶致炎性痛模型大鼠的疼痛行为亦具有明显抑制作用。青藤碱对正常大鼠生理性测痛模型及两种不同性质的病理痛模型大鼠脊髓背角WDR神经元诱发放电均具有明显抑制作用。青藤碱对背根节小细胞高电压激活的钙电流，特别是N、P/Q型钙电流具有明确的抑制作用。与正常大鼠比较，病理痛模型大鼠脊髓背角胶状质神经元的NMDA受体电流明显增大，慢性给予青藤碱对NMDA受体电流具有明显的抑制作用，提示青藤碱可能通过抑制NMDA受体功能发挥对慢性痛痛觉过敏的抑制。另外研究表明，CDK5及Calpain通路可能参与了慢性痛时青藤碱对NMDA受体功能和痛觉过敏的调制。上述研究从离子通道及突触传递角度对青风藤及青藤碱镇痛作用的脊髓机制进行了探讨，为青风藤及青藤碱临床治疗疼痛和进一步开发它们的药用价值提供了理论依据。