Acute oral toxicity test and assessment of rhynchophylline in mice

As the main alkaloid constituent of Uncaria species, rhynchophylline has drawn extensive attention in recent years for its antihypertensive and neuroprotective activities. However, toxicity study of the rhynchophylline is still lacking. In the present study, oral acute toxicity of rhynchophylline was conducted in Kunming mice. The mice were orally treated with 520.00, 442.00, 375.70, 319.34 and 271.44 mg/kg of rhynchophylline for 14 d. The general behavior, body weight changes, toxic reaction, and death were recorded, and histopathological analyses were performed. The acute toxicity was evaluated by the assessment of the median lethal dose (LD₅₀). The acute toxicity study showed that no significant difference was found in the body weight of the mice in the control group and those in the drug group. However, the mice treated with rhynchophylline showed obvious abnormal symptoms and mortality. The median lethal dose (LD₅₀) of orally administered rhynchophylline was 308.08 mg/kg. The histopathological results showed that the mice in the high-dose rhynchophylline group displayed toxic effects in the brain, liver, lung, and kidney. The results of the current study indicated that rhynchophylline could not be taken at a high dose. Collectively, our current findings provided a strong basis for further clinical investigation.     

Effects of Rhynchophyline on L-type Calcium Channels in Isolated Rat Cortical Neurons During Acute Hypoxia

目的：研究钩藤碱对急性分离的Ｗｉｓｔａｒ大鼠大脑皮层神经元低氧状态下Ｌ型钙通道的作用。方法：细胞贴附膜片钳技术，从－４０ｍＶ去极化至０ｍＶ激活Ｌ型钙通道。结果：低氧可激活皮层神经元Ｌ型钙通道开放，使平均开放时间延长，平均关闭时间缩短，开放概率增加。钩藤碱（１５和３０μｍｏｌ·Ｌ－１）可浓度依赖性抑制低氧状态下此钙通道的激活，缩短其平均开放时间（从８８７ｍｓ缩至３０３ｍｓ和２２３ｍｓ，Ｐ＜０００１），延长其平均关闭时间（从９２３ｍｓ延至３８８４和５４４３ｍｓ，Ｐ＜０００１）并降低其开放概率（从０１４２降至００３１和００２５，Ｐ＜０００１）此作用与维拉帕米（１５μｍｏｌ·Ｌ－１）相似，但稍弱。结论：钩藤碱对低氧大鼠大脑皮层神经元Ｌ型钙通道有阻滞作用，从而降低细胞内钙超载，此为钩藤碱改善低氧性脑代谢紊乱的机制之一     

Rhynchophylline and isorhynchophylline inhibit NMDA receptors expressed in Xenopus oocytes

Rhynchophylline and isorhynchophylline are major tetracyclic oxindole alkaloid components of Uncaira species, which have been long used as medicinal plants. In this study, the effects of rhynchophylline and isorhynchophylline on the ionotropic and metabotropic glutamate receptor-mediated current responses were examined using Xenopus oocytes injected with total RNA prepared from rat cortices or cerebelli. Rhynchophylline and isorhynchophylline (1-100 microM) per se failed to induce membrane current, but these alkaloids reversibly reduced N-methyl-D-aspartate (NMDA)-induced current in a concentration-dependent but voltage-independent manner. The IC(50) values of rhynchophylline and isorhynchophylline were 43.2 and 48.3 microM, respectively. Substitution of Ba(2+) for Ca(2+) in the recording medium did not alter the extent of rhynchophylline- and isorhynchophylline-induced suppression of NMDA currents. In contrast, neither alkaloid had an effect on the currents mediated by ionotropic kainic acid-type and (+/-)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors or by the metabotropic glutamate receptor(1 and 5) (mGlu(1/5)). Rhynchophylline and isorhynchophylline (30 microM) significantly reduced the maximal current responses evoked by NMDA and glycine (a co-agonist of NMDA receptor), but had no effect on the EC(50) values and Hill coefficients of NMDA and glycine for inducing currents. These alkaloids showed no interaction with the polyamine binding site, the Zn(2+) site, proton site or redox modulatory site on the NMDA receptor. These results suggest that rhynchophylline and isorhynchophylline act as noncompetitive antagonists of the NMDA receptor and that this property may contribute to the neuroprotective and anticonvulsant activity of the Uncaira species plant extracts.     

钩藤碱对甲基苯丙胺条件性位置偏爱大鼠AMPA受体蛋白改变的影响

目的 观察甲基苯丙胺成瘾大鼠伏隔核及下丘脑中AMPA受体表达的改变及钩藤碱对其的干预作用.方法 SPF级雄性SD大鼠分为空白对照组、甲基苯丙胺模型组、钩藤碱低剂量组及钩藤碱高剂量组,每组8只.采用条件性位置偏爱(CPP)实验建立甲基苯丙胺成瘾大鼠模型,采用蛋白免疫印迹(Western blotting)方法观察大鼠伏隔核及下丘脑中GluR2/3亚基表达的改变.各组大鼠在伴药箱中的停留时间采用独立样本t检验,蛋白条带光密度分析采用单因素方差分析.结果 与空白对照组[给药后伴药箱中停留时间为(383.00±38.20)s]比较,甲基苯丙胺能引起大鼠位置偏爱[给药后伴药箱中停留时间为(536.20±57.49)s],低剂量(30mg/kg)及高剂量(60mg/kg)钩藤碱[给药后伴药箱中停留时间分别为(299.80±15.96)s、(189.40±59.02)s]均能消除甲基苯丙胺诱导的大鼠位置偏爱.与空白对照组[平均灰度值的比值分别为(0.54±0.04)INT·mm~2、(0.70±0.04)INT·mm~2]比较,甲基苯丙胺模型组[平均灰度值的比值为(0.89±0.03)INT·mm~2]及钩藤碱低剂量组[平均灰度值的比值为(0.93±0.03)INT·mm~2]大鼠伏隔核内GluR2/3亚基蛋白表达显著上调(P<0.01),下丘脑内GluR2/3亚基蛋白[平均灰度值的比值分别为(0.53±0.03)INT·mm~2、(0.52±0.04)INT·mm~2]表达则显著下调(P<0.01).钩藤碱高剂量组大鼠伏隔核及下丘脑内GluR2/3亚基蛋白[平均灰度值的比值分别为(0.57±0.06)INT·mm~2、(0.65±0.01)INT·mm~2]表达与空白对照组无差异(P>0.05).结论 甲基苯丙胺CPP大鼠伏隔核内GluR2/3亚基蛋白表达蹭多,下丘脑内CluR2/3亚基蛋白表达减低,高剂量钩藤喊可将上述改变恢复至正常水平.     

钩藤碱治疗膀胱过度活动的实验研究

目的:探讨钩藤碱对膀胱过度活动(overactive bladder,OAB)的治疗作用。方法:将60只SD大鼠随机分为4组,每组15只。假手术组不予任何处理;OAB组:给予手术处理,制备大鼠OAB模型;钩藤碱干预组:对OAB大鼠给予腹腔注射钩藤碱(5 ml.kg-1);生理盐水干预组:对OAB大鼠给予腹腔注射生理盐水(5 ml.kg-1)。各组分别进行尿流动力学检测和逼尿肌肌条的电生理学指标测定。结果:与OAB组和生理盐水干预组对比,钩藤碱干预组膀胱最大容量、膀胱充盈压和漏尿点压减小,收缩频率和动力指数(MI)降低,差异均有统计学意义(P<0.01)。结论:钩藤碱对OAB有治疗作用。