Lagos P, Ballejo G
Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto-São Paulo, Brazil.
Neuroscience. 2004;125(3):663-70. doi: 10.1016/j.neuroscience.2003.10.048.
The aim of this study was to examine the participation of nitrergic neurotransmission in the initiation of micturition hyperreflexia associated to cyclophosphamide (CP)-induced cystitis in rats. Micturition threshold volume was significantly reduced 4 h after CP administration (100 mg/kg, i.p.); this reduction was attenuated by intra-arterially injected N(G)-nitro-l-arginine-methyl ester (l-NAME), a non selective nitric oxide synthase (NOS) inhibitor, but not by intravesical infusion of S-methyl-l-thiocitrulline (l-SMTC), another structurally different NOS inhibitor. Interestingly, l-NAME failed to affect micturition threshold volume in normal rats. The magnitude of isolated detrusor strips contractions elicited by either carbachol or nerve activation was significantly reduced in CP-treated rats but was unaffected by the addition of N(G)-nitro-l-arginine (l-NOARG), a nonselective NOS inhibitor. In contrast, intrathecal l-NAME and l-SMTC but not N(G)-nitro-d-arginine-methyl ester (d-NAME) administration augmented the micturition threshold volume in CP-treated rats in an l-arginine preventable manner. As with the systemic injection, intrathecal l-NAME also did not affect the micturition threshold volume in normal rats. Four hours after CP injection, the number of neuronal NOS immunoreactive or nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) positive neurons in spinal lumbosacral segments (L6-S2) was not altered whereas the number of c-Fos immunoreactive neurons increased significantly in the dorsal gray commissural nucleus (DGC), the parasympathetic sacral nucleus (PSN) and lamina X of these segments. Ca(2+)-dependent, but not Ca(2+)-independent NOS activity increased significantly in spinal L6-S2 segments but not in thoracic segments of CP-treated rats. These data indicate that the micturition hyperreflexia observed in the initial hours of CP-induced cystitis is associated with an increase in Ca(2+)-dependent NOS activity in spinal L6-S2 segments suggesting an increased production of nitric oxide (NO). The increased production of NO in these spinal segments appears to be necessary for the initiation of the micturition hyperreflexia.
本研究旨在探讨一氧化氮能神经传递在大鼠环磷酰胺（CP）诱导的膀胱炎相关的排尿反射亢进起始过程中的作用。腹腔注射CP（100 mg/kg）4小时后，排尿阈值体积显著降低；动脉内注射非选择性一氧化氮合酶（NOS）抑制剂N(G)-硝基-L-精氨酸甲酯（L-NAME）可减弱这种降低，但膀胱内灌注另一种结构不同的NOS抑制剂S-甲基-L-硫代瓜氨酸（L-SMTC）则无此作用。有趣的是，L-NAME对正常大鼠的排尿阈值体积没有影响。在CP处理的大鼠中，由卡巴胆碱或神经激活引起的离体逼尿肌条收缩幅度显著降低，但添加非选择性NOS抑制剂N(G)-硝基-L-精氨酸（L-NOARG）对其无影响。相反，鞘内注射L-NAME和L-SMTC，但不是N(G)-硝基-D-精氨酸甲酯（D-NAME），以L-精氨酸可预防的方式增加了CP处理大鼠的排尿阈值体积。与全身注射一样，鞘内注射L-NAME对正常大鼠的排尿阈值体积也没有影响。CP注射4小时后，腰骶段脊髓（L6-S2）中神经元型NOS免疫反应性或烟酰胺腺嘌呤二核苷酸磷酸黄递酶（NADPH-d）阳性神经元的数量没有改变，而这些节段的背侧灰质连合核（DGC）、骶副交感核（PSN）和X层中c-Fos免疫反应性神经元的数量显著增加。在CP处理的大鼠中，脊髓L6-S2节段中钙依赖性而非钙非依赖性NOS活性显著增加，但胸段则无此现象。这些数据表明，在CP诱导的膀胱炎最初几小时观察到的排尿反射亢进与脊髓L6-S2节段中钙依赖性NOS活性增加有关，提示一氧化氮（NO）产生增加。这些脊髓节段中NO产生的增加似乎是排尿反射亢进起始所必需的。
