Li F, Hu W, Liu N
Research Institute of Surgery, Daping Hospital, Third Military Medical University, Chongquing 400042.
Zhonghua Yi Xue Za Zhi. 1999 Mar;79(3):217-20.
To investigate the different role of neuronal constitutive nitric oxide synthase (nc-NOS) in dynorphin (Dyn) A(1-17) spinal neurotoxicity and analgesia.
The cNOS activity in ventral and dorsal spinal cord in rats was measured with H-L-arginine conversion, and ncNOS immunoreactivity(IR) was observed with strepavidin-peroxidase immunohisto-chemistry.
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 mumol, 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.
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.
探讨神经元型一氧化氮合酶（nc-NOS）在强啡肽（Dyn）A（1-17）脊髓神经毒性和镇痛作用中的不同作用。
采用H-L-精氨酸转化法测定大鼠脊髓腹侧和背侧的cNOS活性，并用链霉亲和素-过氧化物酶免疫组织化学法观察ncNOS免疫反应性（IR）。
鞘内注射Dyn A（1-17）可产生剂量依赖性的后肢和尾部麻痹以及抑制甩尾（TF）和足趾退缩（FF）反射。与生理盐水对照组相比，10 nmol的Dyn A（1-17）仅引起短暂性麻痹，并明显降低背角浅层的ncNOS-IR，但未引起腹角细胞ncNOS-IR的任何变化。20 nmol的Dyn A（1-17）导致永久性截瘫和不可逆的脊髓损伤，其特征为中央性进行性坏死。20 nmol的Dyn A（1-17）显著诱导腹角细胞中ncNOS-IR的表达，而抑制背角浅层的ncNOS-IR。20 nmol的Dyn A（1-17）还显著增加脊髓腹侧的cNOS活性，但不影响脊髓背侧的cNOS活性。在鞘内注射20 nmol Dyn A（1-17）前10分钟，用1 μmol的选择性ncNOS抑制剂7-硝基吲唑（7-NI）进行鞘内预处理，可显著改善Dyn诱导的神经学结局，但TF和FF仍受抑制。7-硝基吲唑还显著拮抗鞘内注射20 nmol Dyn A（1-17）后4小时脊髓腹侧cNOS活性和ncNOS-IR的增加，但不影响甚至增强Dyn诱导的脊髓背侧cNOS活性和ncNOS-IR的抑制。
脊髓腹侧ncNOS的过度表达或过度激活可能与Dyn脊髓神经毒性有关，而脊髓背侧ncNOS活性的降低可能反映Dyn脊髓镇痛或疼痛调节作用。
