Department of Morphology, Physiology and Pathology, School of Odontology, University of São Paulo, Campus Ribeirão Preto, Av. Café S/N, Ribeirão Preto, SP, 14040-904, Brazil,
Neurotox Res. 2014 Jan;25(1):33-44. doi: 10.1007/s12640-013-9406-3. Epub 2013 Jun 27.
Nitric oxide synthase inhibitors reduce L-3, (Del-Bel et al., Cell Mol Neurobiol 25(2):371-392, 2005) 4-dihydroxyphenylalanine (L-DOPA)-induced abnormal motor effects subsequent to depletion of dopaminergic neurons in rodents and non-human primates. The present study used quantitative high-performance liquid chromatography to analyze, for the first time, dopamine metabolism in striatum of rats in order to elucidate the mechanism of action of the nitric oxide synthase inhibitors. Adult male Wistar rats received unilateral microinjection of saline (sham) or 6-hydroxydopamine (6-OHDA-lesioned) in the medial forebrain bundle. Past 3 weeks, rats were treated during 21 days with L-DOPA/benserazide (30 mg/kg/7.5 mg/kg, respectively, daily). On the 22nd day rats received an intraperitoneal (i.p.) injection of either vehicle or 7-nitroindazole, a preferential neuronal nitric oxide synthase inhibitor before L-DOPA. Abnormal involuntary movements and rotarod test were assessed as behavioral correlate of motor responses. Lesion intensity was evaluated through tyrosine hydroxylase immunohystochemical reaction. Dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), and an extent of dopamine striatal tissue levels/dopamine metabolism were measured in the striatum. Lesion with 6-OHDA decreased dopamine, DOPAC, and DOPAC/dopamine ratio in the lesioned striatum. L-DOPA treatment induced abnormal involuntary movements and increased DOPAC/dopamine ratio (nearly five times) in the lesioned striatum. L-DOPA-induced dyskinesia was mitigated by 7-nitroindazole, which also decreased dopamine turnover, dopamine and DOPAC levels. Our results revealed an almost two times increase in dopamine content in the non-lesioned striatum of 6-OHDA-lesioned rats. Reduction of striatal DOPAC/dopamine ratio in dyskinetic rats may suggest an increase in the dopamine availability. Our data confirm contribution of nitrergic transmission in the pathogenesis of L-DOPA-induced dyskinesia with potential utilization of nitric oxide synthase inhibitors for treatment.
一氧化氮合酶抑制剂可降低 L-3,（Del-Bel 等人，细胞分子神经生物学 25(2):371-392, 2005）4-二羟基苯丙氨酸（L-DOPA）诱导的啮齿动物和非人类灵长类动物中多巴胺能神经元耗竭后的异常运动效应。本研究首次使用定量高效液相色谱法分析大鼠纹状体中的多巴胺代谢，以阐明一氧化氮合酶抑制剂的作用机制。成年雄性 Wistar 大鼠接受内侧前脑束中盐水（假手术）或 6-羟多巴胺（6-OHDA 损伤）的单侧微注射。过去 3 周，大鼠接受 L-DOPA/苯甲酰拉明（30mg/kg/7.5mg/kg，每日）治疗 21 天。在第 22 天，大鼠接受腹腔（i.p.）注射载体或 7-硝基吲唑，这是一种优先的神经元一氧化氮合酶抑制剂，然后给予 L-DOPA。异常不自主运动和旋转棒测试作为运动反应的行为相关性进行评估。通过酪氨酸羟化酶免疫组织化学反应评估损伤强度。在纹状体中测量多巴胺、3,4-二羟基苯乙酸（DOPAC）和多巴胺纹状体组织水平/多巴胺代谢的程度。6-OHDA 损伤降低了损伤纹状体中的多巴胺、DOPAC 和 DOPAC/多巴胺比值。L-DOPA 治疗诱导异常不自主运动并增加损伤纹状体中的 DOPAC/多巴胺比值（近五倍）。7-硝基吲唑减轻了 L-DOPA 诱导的运动障碍，同时还降低了多巴胺周转率、多巴胺和 DOPAC 水平。我们的结果显示，6-OHDA 损伤大鼠的非损伤纹状体中多巴胺含量增加了近两倍。运动障碍大鼠纹状体 DOPAC/多巴胺比值降低可能表明多巴胺可用性增加。我们的数据证实了氮能传递在 L-DOPA 诱导的运动障碍发病机制中的作用，并可能利用一氧化氮合酶抑制剂进行治疗。
