神经元性一氧化氮合酶在强啡肽致瘫和镇痛中的作用

Role of neuronal nitric oxide synthase in dynorphin spinal neurotoxicity and analgesia in rats

目的探讨神经元性原生型一氧化氮合酶（ｎｃＮＯＳ）在强啡肽（Ｄｙｎ）Ａ（１１７）致瘫和镇痛中的不同作用。方法采用ｎｃＮＯＳ免疫组织化学和３Ｈ左旋精氨酸转化技术，观测Ｄｙｎ致瘫和镇痛过程中ｎｃＮＯＳ活性和免疫活性（ＩＲ）变化，并探讨ｎｃＮＯＳ选择性抑制剂７硝基吲唑对Ｄｙｎ致瘫和镇痛作用的影响。结果ＤｙｎＡ（１１７）蛛网膜下腔注射引起剂量相关性后肢和尾部瘫痪及甩尾甩足抑制；ＤｙｎＡ（１１７）１０ｎｍｏｌ明显抑制背角浅层ｎｃＮＯＳＩＲ，而腹角的ｎｃＮＯＳＩＲ与蛛网膜下腔注射对照无明显差异；ＤｙｎＡ（１１７）２０ｎｍｏｌ明显诱导腹角细胞表达ｎｃＮＯＳＩＲ而抑制背角浅层ｎｃＮＯＳＩＲ，显著升高腹侧脊髓ｃＮＯＳ活性而不影响背侧脊髓ｃＮＯＳ活性。７硝基吲唑可显著对抗ＤｙｎＡ（１１７）２０ｎｍｏｌ致瘫，而甩尾甩足抑制仍然存在；可显著对抗ＤｙｎＡ（１１７）２０ｎｍｏｌ／Ｌ引起的伤后４小时腹侧脊髓ｃＮＯＳ活性增加和ｎｃＮＯＳＩＲ增强，但不影响甚至加强ＤｙｎＡ（１１７）２０ｎｍｏｌ／Ｌ对背侧脊髓ｃＮＯＳ活性和ｎｃＮＯＳＩＲ的抑制作用。结论腹侧脊髓ｎｃＮＯＳ过度激活与Ｄｙｎ致脊髓损伤有关，背侧脊髓ｎｃ?

Objective To investigate the different role of neuronal constitutive nitric oxide synthase (ncNOS) in dynorphin (Dyn) A(1 17) spinal neurotoxicity and analgesia.Methods The cNOS activity in ventral and dorsal spinal cord in rats was measured with 3H L arginine conversion, and ncNOS immunoreactivity(IR) was observed with strepavidin peroxidase immunohisto chemistry.Results Intrathecal administration of Dyn A(1 17) produced dose dependent paralysis of hindlimbs and tail as well as inhibition of tail flick (TF) and foot flinch (FF) reflexes. Dyn A(1 17) 10 nmol induced only transient paralysis and apparently reduced the ncNOS IR in the superficial dorsal horn but did not induce any change of ncNOS IR in the ventral horn cells as compared with saline control. Dyn A(1 17) 20 nmol produced permanent paraplegia with irreversible spinal cord damage, characterized by central and progressive necrosis. Dyn A(1 17) 20 nmol remarkedly induced the expression of ncNOS IR in the ventral horn cells whereas inhibited ncNOS IR in the superficial dorsal horn. Dyn A(1 17) 20 nmol also significantly increased the activities of cNOS in the ventral spinal cord but did not affect cNOS activities in the dorsal spinal cord. Intrathecal pretreatment with 7 nitroindazole (7 NI) 1 μmol, a selective ncNOS inhibitor 10 min prior to i.t. Dyn A(1 17) 20 nmol significantly ameliorated Dyn induced neurological outcome, but TF and FF remained inhibited. 7 nitroindazole also significantly antagonized the increases of cNOS activities and ncNOS IR in the ventral spinal cord at 4 h after i.t. Dyn A(1 17) 20 nmol, but did not affect or even potentiated Dyn induced inhibition of cNOS activity and ncNOS IR in the dorsal spinal cord.Conclusions Over expression or over activation of ncNOS in the ventral spinal cord may be involved in Dyn spinal neurotoxicity, whereas as the reduction of ncNOS activities in the dorsal spinal cord might reflect Dyn spinal analgeisia or pain modulation.