不同干燥加工方法对知母化学成分含量的影响

目的:揭示各种干燥加工方法对知母有效成分含量的影响。方法:分别采用晒干、阴干、烘干、远红外干燥、微波干燥的方法对知母进行干燥加工,以菝葜皂苷元、知母皂苷AⅢ、芒果苷、新芒果苷为指标,通过高效液相色谱法(HPLC),分析各种干燥加工条件下知母中各类指标成分的含量变化情况。其中菝葜皂苷元、知母皂苷AⅢ采用高效液相蒸发光散射检测法(HPLC-ELSD)进行检测,用外标两点法对数方程计算含量,芒果苷、新芒果苷采用高效液相紫外检测法(HPLC-UV)检测。结果:采用烘干、远红外干燥、微波干燥方法加工后,知母菝葜皂苷元、知母皂苷AⅢ、芒果苷含量与晒干、阴干相比均有不同程度上升,新芒果苷含量与晒干、阴干相比有所下降。结论:从有效成分保存方面考虑,不同干燥方法的优劣顺序为微波干燥>远红外干燥>烘干>晒干≈阴干。     

HPLC-CAD同时测定知母中芒果苷和知母皂苷BⅡ的含量

目的:建立HPLC-CAD方法同时测定知母中芒果苷和知母皂苷BⅡ的含量。方法:采用Acclaim-C₁₈色谱柱(150 mm×4.6 mm,3μm),以乙腈(A)-0.2%醋酸水溶液(B)为流动相,梯度洗脱(0~10 min,15%A→21%A;10~12 min,21%A→23%A,12~30 min,23%A→25%A),流速1.0 mL·min^-1,柱温30℃;电雾式检测器(CAD)参数:采集频率10 Hz,雾化温度55℃,滤波为5 s。结果:知母中芒果苷和知母皂苷BⅡ均具有良好的线性关系(r>0.999),LOD分别为0.43 ng和1.20 ng,LOQ分别为1.28 ng和4.80 ng,精密度、重复性、24 h稳定性试验的RSD均小于3.0%,平均加样回收率分别为102.3%和95.2%。11批样品中芒果苷和知母皂苷BⅡ的含量范围分别为0.54%~1.69%和3.27%~5.57%。结论:建立的HPLC-CAD法可同时对知母中芒果苷和知母皂苷BⅡ进行含量测定,为知母药材和饮片的检测分析和质量控制提供了新的方法。     

知母活性成分对脓毒症性心肌损伤模型小鼠的改善作用

目的 为阐明知母改善脓毒症性心肌损伤的作用及可能的活性物质基础提供实验参考。方法 采用热回流法制备知母水提物,大孔吸附树脂法分离知母总双苯吡酮和总皂苷。采用腹腔注射脂多糖建立脓毒症性心肌损伤小鼠模型,考察知母3个提取部位及知母单体成分芒果苷、知母皂苷AⅢ、知母皂苷BⅡ对模型小鼠存活率的影响;HE染色法观察知母单体成分芒果苷、知母皂苷AⅢ、知母皂苷BⅡ对模型小鼠心肌组织形态的影响;检测芒果苷对模型小鼠心肌组织中炎症因子[白细胞介素6(IL-6)、IL-1β和肿瘤坏死因子α(TNF-α)] mRNA表达及活性氧（ROS）水平的影响。结果 知母总双苯吡酮、总皂苷、水提物干预组小鼠存活率较模型组均不同程度升高,其中以知母总双苯吡酮部位效果较佳;芒果苷、知母皂苷AⅢ和知母皂苷BⅡ均可改善模型小鼠心肌细胞肿胀、肌束排列紊乱程度,且以芒果苷的效果更为明显。芒果苷干预后小鼠心肌组织中IL-6、IL-1β、TNF-α mRNA表达水平及ROS水平较模型组不同程度降低。结论 知母不同提取部位均可提高脓毒症性心肌损伤小鼠的存活率,其中以知母总双苯吡酮部位效果较佳。3个知母单体成分中以芒果苷改善脓毒症性心肌损...     

知母盐制后增量成分对HepG-2细胞葡萄糖消耗的影响

目的：通过探讨知母盐制后增量成分知母皂苷AⅢ、知母皂苷BⅢ、芒果苷对HepG-2细胞葡萄糖消耗的影响,进一步验证知母盐炙后降糖作用增强的炮制原理。方法：将HepG-2细胞分为空白对照组、知母皂苷AⅢ组、知母皂苷BⅢ组、芒果苷组、二甲双胍组,在5% CO₂培养箱中培养24 h,饥饿12 h,再加入不同浓度相应的含药或不含药血清培养基,采用葡萄糖试剂盒检测培养液中的葡萄糖含量,葡萄糖消耗实验之后,加入cck-8试剂培养2 h,用酶标仪测定吸光度（OD）;采用胰岛素诱导建立胰岛素抵抗HepG-2细胞模型,同上法比较知母皂苷AⅢ、知母皂苷BⅢ以及芒果苷对胰岛素抵抗HepG-2细胞葡萄糖消耗的影响。结果：知母皂苷AⅢ、知母皂苷BⅢ、芒果苷对正常组和胰岛素抵抗HepG-2细胞的葡萄糖消耗量和细胞增殖均有显著增加（P<0.05）。结论：知母皂苷AⅢ、知母皂苷BⅢ、芒果苷均具有降糖活性,尤其对胰岛素抵抗的HpeG-2细胞作用明显,是盐知母降糖作用的物质基础。     

知母栽培品和野生品的指纹图谱建立及差异性成分确认

目的建立知母栽培品和野生品的指纹图谱,确认两者的差异性成分。方法采用蒸发光散射检测器,以高效液相色谱法结合《中药色谱指纹图谱相似度评价系统(2012版)》建立14批知母栽培品和14批知母野生品的指纹图谱,并进行相似度评价,通过与混合对照品色谱图比对指认共有峰。同法测定知母栽培品和野生品中指认共有峰对应成分的含量,通过主成分分析和正交偏最小二乘法-判别分析确认两者的差异性成分,并比较其含量。结果在28批知母药材中共有10个共有峰,指认出新芒果苷(峰1)、芒果苷(峰2)、异芒果苷(峰3)、知母皂苷BⅡ(峰7)、知母皂苷BⅢ(峰8)、知母皂苷Ⅰ(峰9)、知母皂苷AⅢ(峰10)7个成分;各样品指纹图谱与对照指纹图谱的相似度均不低于0.963。知母栽培品与野生品中7个成分的平均总含量分别为74.18、84.72 mg/g,二者比较差异有统计学意义(P<0.05)。知母栽培品与野生品可被分为两类,差异性成分为新芒果苷、芒果苷、知母皂苷BⅡ、知母皂苷AⅢ(变量投影重要性值均大于1)。知母栽培品中新芒果苷含量明显高于野生品(P<0.05),芒果苷、知母皂苷BⅡ和知母皂苷AⅢ含量均明显低于野生品(P<0.05)。结论成功建立了知母的指纹图谱,并初步确认了知母栽培品和野生品的差异性成分。     

不同产地知母药材的含量测定及指纹图谱研究

目的收集不同产地的知母药材,测定其芒果苷和知母皂苷BⅡ的含量,建立知母药材的HPLC-UV-ELSD指纹图谱测定方法。方法采用HPLC-UV-ELSD法测定3个不同产地的15批知母药材。色谱条件:Agilent ZORBAX SB-C_(18)色谱柱(250 mm×4.6 mm,5μm)。乙腈(A)-1 mL·L~(-1)乙酸(B)梯度洗脱,梯度为:0～5 min,2%A→5%A;5～12 min,5%A→20%A;12～18 min,20%A→25%A;18～23 min,25%A;23～40 min,25%A→100%A;40～45 min,100%A。柱温:30℃;流速:1.0 mL·min~(-1);波长:258 nm。ELSD参数:漂移管温度:105℃;氮气流速:2.6 L·min~(-1)。结果 15批知母药材中芒果苷的含量为0.803%～1.687%,知母皂苷BⅡ的含量为3.253%～7.332%。建立了知母药材的指纹图谱,包含11个共有峰,通过对照品指认了芒果苷和知母皂苷BⅡ2个峰,对15批知母药材指纹图谱的相似度进行评价,其相似度均大于0.9。结论该方法操作简便、快捷,可用于知母药材的质量研究。     

翻转肠囊法研究芒果苷在大鼠的肠吸收动力学

目的考察芒果苷在大鼠不同肠段的吸收特性及知母、知母-黄柏、P-糖蛋白抑制剂对芒果苷肠吸收的影响。方法采用大鼠肠外翻模型,UPLC法测定不同时间点肠囊内芒果苷浓度,寻找芒果苷在肠中吸收的最佳部位;观察知母、知母-黄柏及P-糖蛋白抑制剂对芒果苷吸收的影响。结果芒果苷在小肠的吸收为回肠>空肠>结肠;在回肠段知母水煎液中芒果苷90 min累积吸收量(Q90)、转运速率(Vt)和表观渗透系数(Paap)均大于芒果苷单体组和知母-黄柏水煎液组(P<0.05);环孢素A提高芒果苷在回肠K氏液中的浓度(P<0.05)。结论芒果苷在不同肠段的吸收有差异;知母促进了芒果苷的肠吸收;芒果苷可能是P-gp底物。     

基于指纹图谱-网络药理学-分子对接技术的知母质量标志物预测分析

摘要：目的:预测知母的质量标志物(Q-Marker)。方法:采用高效液相色谱-蒸发光散射检测(HPLC-ELSD)法建立不同产地知母指纹图谱特征,色谱柱：InertSustain C18(250 mm×4.6 mm, 5μm);流动相：乙腈-水,梯度洗脱;流速：1.0 ml·min-1;柱温：30℃;进样量：10μl; N2流速：3 L·min-1;漂移管温度：100℃。采用《中药色谱指纹图谱相似度评价系统(2012版)》,设定时间为平均值±0.5 min,采用Mark峰匹配,建立其HPLC指纹图谱,并进行相似度评价筛选出Q-Marker候选成分;然后对筛选出的Q-Marker候选成分进行网络药理学分析,构建“知母Q-Marker候选成分-靶点-通路”网络,预测知母的皂苷类Q-marker,再采用分子对接方法验证其Q-Marker生物活性。结果:10批不同产地的知母饮片中共筛选出6个Q-Marker活性成分,分别为芒果苷、知母皂苷E、知母皂苷B-Ⅱ、知母皂苷B-Ⅲ、知母皂苷A2、知母皂苷A3,进一步网络药理学分析显示知母皂苷B-Ⅲ、知母皂苷B-Ⅱ、知母皂苷A2为知母皂苷类成分的Q-Marker,“活性成分-作用靶点-通路”网络构建结果表明关键作用靶点为丝裂原活化蛋白激酶(MAPK)10、MAPK1、MAPK8,分子对接结果表明核心化学成分知母皂苷A2与MAPK10以及知母皂苷A2与MAPK1有较高的结合活性。结论:建立的知母指纹图谱分析方法简便可行,结合网络药理学-分子对接技术发现知母3个活性成分与其功效属性密切相关,为知母饮片的质量控制提供参考,同时也为知母抗炎作用机制的探索奠定了基础。     

用HPLC-ELSD法同时测定不同产地知母饮片中芒果苷、新芒果苷和知母皂苷BⅡ的含量

目的:建立测定知母药材中芒果苷、新芒果苷和知母皂苷BⅡ含量的HPLC-ELSD方法。方法:色谱柱为Agilent Zorbax SB-C18色谱柱(250 mm×4.6 mm,5μm);流动相为乙腈(A相)-水(用冰醋酸调节至pH3.3)(B相);梯度洗脱:0~15 min,5%~22%A相;15~24 min,22%~23%A相;24~45 min,23%~50%A相。检测波长:254 nm;流速:1.0 ml/min;柱温:25℃;进样量20μl。ELSD条件为:漂移管温度40℃,载气(空气)压力350 kPa,增益值7,气体流量9 L/min。结果:芒果苷、新芒果苷和知母皂苷BⅡ分别在81.1~486.6μg/ml(r=0.999 8)、81.6~489.6μg/ml(r=0.999 9)和192.2~1 153.0μg/ml(r=0.999 7)范围内线性关系良好;平均回收率分别为98.75%、101.83%和99.14%;RSD分别为2.03%、2.87%和1.77%。结论:该方法简便、准确,重复性好,适用于知母药材饮片的质量控制。     

知母酒炙前后指纹图谱的比较及对α-葡萄糖苷酶抑制作用的比较研究

目的 建立知母酒炙前后的指纹图谱,比较知母酒炙前后指纹图谱的变化;比较知母酒炙前后对α-葡萄糖苷酶活性抑制作用的变化.方法 采用高效液相色谱实验条件为:phenomenex色谱柱,乙腈:0.2％乙酸水梯度洗脱,紫外检测器(UV)与蒸发光散射检测器(ELSD)联用,获得10批不同产地知母酒炙前后的指纹图谱,比较知母酒炙前后指纹图谱的变化;以对-硝基苯基-α-吡喃葡萄糖苷(PNPG)为底物,分别测定生品知母和酒炙知母对α-葡萄糖苷酶活性的抑制率.结果 知母酒炙后指纹图谱中的主要色谱峰发生了明显变化:芒果苷、知母皂苷N、知母皂苷BⅡ的峰面积明显减小,而新芒果苷和知母皂苷B的峰面积明显增加;酒炙后知母的指纹图谱多了1号峰、12号峰2个新峰,而15号峰消失.酒炙后知母对α-葡萄糖苷酶活性的抑制率明显降低.结论 本研究建立了条件适中、重现性好的HPLC指纹图谱制备方法,可用于知母及其酒炙品的质量控制.知母酒炙后,指纹图谱发生了明显变化,对α-葡萄糖苷酶活性的抑制作用也明显减弱.     

Synthesis and evaluation of 2,6-piperidinedione derivatives as potentially novel compounds with analgesic and other CNS activities

New 2,6-piperidinediones 2_a–g and 4_a–d were prepared by initial condensation of aromatic aldehydes or cycloalkanones with cyanoacetamide to give α-cyanocinnamides l_a–g or cycloalkylidenes 3_a,b which underwent Michae1 addition with ethyl cyanoacetate or diethylmalonate. Compounds 4_a–d were alkylated by various alkyl halides to produce the N-alkylated 2,6-piperidinedione derivatives 5_a–m. Some new selected compounds 2_a–c,f, 4_a–d & 5_e,h,j were pharmacologically evaluated for potential anticonvulsant, sedative and analgesic activities. These compounds exhibited significant anticonvulsant and analgesic effects after a single I.P. administration 100 mg/kg b.wt. . On the other hand all the investigated compounds induced hypnotic activity and prolonged the phenobarbital sodium- induced sleep as compared with the control group and the most potent compound was found to be 2_f.     

NEURAMIDE STIMULATES ADRENOCORTICOTROPIN BUT NOT PROLACTIN RELEASE FROM RAT PITUITARY

Neuramide (NMD), a substance found in crude preparations of porcine stomach extract, is a viral inhibitor that also has putative immunostimulatory effects. The effects of NMD on stress-hormone (ACTH and prolactin—PRL) release were assessed inin vivoandin vitrostudies. In the former, blood levels of corticosterone and PRL were measured in NMD-treated male rats.In vitroexperiments were performed to evaluate the effects of NMD and three of its fractions (obtained with high performance liquid chromatography) on ACTH and PRL release from perfused rat pituitary slices. NMD increased plasma corticosterone levelsin vivoand produced dose-dependent increases inin vitropituitary release of ACTH. No effects on PRL secretion were observedin vivoorin vitro. The stimulatory effects on ACTH release were caused by the NMD fraction with a molecular weight of >5000<10000Da.     

EFFECT OF POLICOSANOL SUCCESSIVE DOSE INCREASES ON PLATELET AGGREGATION IN HEALTHY VOLUNTEERS

Policosanol is a cholesterol-lowering drug with hypocholesterolemic effects demonstrated in experimental models, healthy volunteers and type II hypercholesterolemic patients. In addition, antiplatelet effects of policosanol have been shown in experimental models and healthy volunteers. The effect of successively increasing doses of policosanol on platelet aggregation was investigated in a randomized, placebo-controlled, double-blind study conducted in 37 healthy volunteers. The volunteers were on a placebo-baseline period (two tablets per day) for 7 days and thereafter they received randomly, under double-blind conditions, placebo or policosanol (10mgday⁻¹) for 7 days. After this period dosage was doubled to 20mgday⁻¹for the next 7 days and then again doubled to 40mgday⁻¹, while the control group received placebo tablets all the time. Platelet aggregation as well as coagulation time was measured at baseline and after each dosing step. Results showed that antiplatelet effects of policosanol were successfully enhanced throughout the study, thus suggesting a dose-dependent relationship. No significant effect was reached during the first dosing period, but significant reductions of epinephrine and ADP-induced platelet aggregation were observed after the second one. Finally, a significant inhibition of platelet aggregation induced by all the agonists was observed at the last dosing step. Coagulation time remained unchanged during the trial.     

INDIRECT PARASYMPATHOMIMETIC ACTIVITY OF THE CLASS III ANTIARRHYTHMIC SUBSTANCE / -SOTALOLIN VITRO: REVERSIBLE INHIBITION OF CHOLINESTERASE ISOENZYMES FROM BLOOD AND THE HUMAN CENTRAL NERVOUS SYSTEM

Inhibitory effects of the class III antiarrhythmic compound / -sotalol on acetylcholinesterase (AChE; EC 3.1.1.7) isoenzymes of both erythrocytes and the human caudate nucleus and on serum cholinesterase (ChE; EC 3.1.1.8) were studiedin vitrousing a spectrophotometric kinetic assay with acetylthiocholine (ASCh) as substrate. Sotalol concentrations in the assays varied from 0.32 to 3.2m . All isoenzymes studied were inhibited by / -sotalol in a reversible and concentration-dependent manner. Double reciprocal plots of the reaction velocity against varying ASCh concentrations revealed that / -sotalol reduced substrate affinity (apparent Michaelis constant, KM, increased) of serum ChE, but did not change the enzyme's maximal rate of ASCh hydrolysis (V_max). Thus, / -sotalol inhibition of serum ChE was of the competitive type (rate constant for reversible competitive inhibition: K_i=0.51m ). In contrast, / sotalol reduced the maximal reaction velocity of the AChE isoenzyme from the central nervous system (caudate nucleus), but had no influence on substrate affinity of the enzyme (K_Mwith ASCh unchanged) indicating purely non-competitive inhibition kinetics (rate constant of reversible non-competitive inhibition: K_i′=0.44m ). / -sotalol inhibition of erythrocyte AChE was of mixed competitive/non-competitive type (K_i=0.31m , K_i′=0.49m ). Non-competitive / -sotalol inhibition of caudate nucleus AChE and the non-competitive component of erythrocyte AChE inhibition cannot be overcome by increased concentrations of the cholinergic transmitter acetylcholine (ACh). Peak / -sotalol plasma levels as described in the literature for both humans (15μ ) and experimental animals (dogs: 18μ ; rats: 260μ ) as well as maximal myocardial concentrations of the substance (dogs: 46μ ; rats: 478μ ) are in the range of about 2% to 100% of the sotalol inhibition rate constants determined in the present paper for cholinesterase isoenzymesin vitro. Thus, / -sotalol inhibition of ACh hydrolysisin vivomay contribute to both the well known antiarrhythmic potential and proarrhythmic side effects of the compound.     

鼻渊净胶囊的HPLC指纹图谱研究

目的 建立鼻渊净胶囊的高效液相色谱（HPLC）指纹图谱。方法 采用Agilent SB-C₁₈（4.6 mm×250 mm,5 μm）色谱柱,乙腈-水为流动相、以1.0 ml/min流速行梯度洗脱,检测波长210 nm,柱温30 ℃,洗脱时间为80 min。采用中药色谱指纹图谱相似度评价系统（2004A版）对检测出色谱进行指纹图谱相似度评价。结果 建立了鼻渊净胶囊的HPLC指纹图谱,确定了20个共有峰,15个峰归属到各药材,其中5个峰确认了化学成分;10批样品的指纹图谱的整体相似度与对照图谱比较,均在90%以上。结论 所建立的鼻渊净胶囊指纹图谱有助于从整体上控制该制剂的质量。     

Investigation of the prevalence of tetQ, tetX and tetX1 genes in Bacteroides strains with elevated tigecycline minimum inhibitory concentrations

In this study, the antibiotic susceptibilities to tigecycline and tetracycline of 35 selected Bacteroides fragilis group strains were determined by Etest, and the presence of tetQ, tetX, tetX1 and ermF genes was investigated by polymerase chain reaction (PCR). tetQ was detected in all 12 B. fragilis group isolates (100%) exhibiting elevated tigecycline minimum inhibitory concentrations (MICs) (≥8 μg/mL) as well as the 8 strains (100%) with a tigecycline MIC of 4 μg/mL, whilst tetX and tetX1 were present in 15% and 75% of these strains, respectively. All of these strains were fully resistant to tetracycline (MIC ≥ 16 μg/mL). On the other hand, amongst the group of strains with tigecycline MICs < 4 μg/mL (15 isolates), tetQ, tetX and tetX1 were found less frequently (73.3%, 13.3% and 46.7%, respectively). All but two strains harbouring the tetQ gene in this group were non-susceptible to tetracycline, with a MIC > 4 μg/mL. These data suggest that in most cases tigecycline overcomes the tetracycline resistance mechanisms frequently observed in Bacteroides strains. However, the presence of tetX and tetX1 genes in some of the strains exhibiting elevated MICs for tigecycline draws attention to the possible development and spread of resistance to this antibiotic agent amongst Bacteroides strains. The common occurrence of ermF, tetX, tetX1 and tetQ genes together predicted the presence of the CTnDOT-like Bacteroides conjugative transposon in this collection of Bacteroides strains.     

AMELIORIATION OF CHEMICALLY-INDUCED HEPATOCYTE INJURY BY CYCLOSPORINE A

Cyclosporine A, beside its current applications, possesses potential hepatoprotective effects. This study was directed to investigate the effect of Cyclosporine A pretreatment on hepatic injury due to carbon tetrachloride (CCl₄) and -galactosamine. Rats were injected by two successive doses of Cyclosporine A (5mgkg⁻¹day⁻¹). Six hours after the second dose, 1mlkg⁻¹of CCl₄was administered i.p. Effects associated with Cyclosporine A pretreatment were examined by using isolated hepatocytes and hepatocytes that were immobilized and continuously perfused. -Galactosamine (5m ) was added directly to the perfusion medium. After isolation, hepatocytes were examined histologically by light and electron microscopy, immobilized and perfused for further metabolic functional activity evaluation. Cyclosporine A pretreatmentin vivoproduced hepatoameliorative effects of various degrees which were statistically significant as manifested by: (1) an increased trypan blue exclusion after CCl₄; (2) an improved ureagenesis after CCl₄; (3) a reduction in the lipid droplets accumulation in the cytoplasm produced by CCl₄administration; (4) well preserved cytoplasmic organelles as mitochondria, endoplasmic reticulum ER, nuclear chromatin structures that were altered by CCl₄; and (5) an increased hepatocytes survival in the agarose gel matrix, reduction of LD leakage and improvement of ureagenesis after -galactosamine addition to the perfusion medium. The beneficial effect of Cyclosporine A pretreatment in modifying hepatotoxicity of chemical insults merits further studies.     

喙果黑面神化学成分研究

目的研究大戟科植物喙果黑面神(Breynia rostrata Merr.)的化学成分。方法利用硅胶、凝胶等色谱技术分离纯化化学成分,根据化合物的理化性质和光谱数据进行结构鉴定。结果从喙果黑面神的正丁醇萃取部分分离得到4个化合物,分别鉴定为6-O-甲基丙酰基-α-D-吡喃葡糖(6-O-methylpropanoyl-α-D-glucopyranose,1);4″-苯酚基-6-O-甲基丙酰基-β-D-吡喃葡糖苷(4″-phenolic-6-O-methylpropanoyl-β-D-glucopyranoside,2);1-O-没食子酰基-β-D-吡喃葡糖苷(1-O-galloyl-β-D-glucopyranoside,3);熊果苷(arbutin,4)。结论化合物1和2为新化合物,3和4均为首次从该种植物分离得到。     

EFFECTS OF 2-GUANIDINE-4-METHYLQUINAZOLINE ON GASTRIC ACID SECRETION IN RATS

In this study 2-guanidine-4-methylquinazoline (2-GMQ) appeared to decrease basal and stimulated gastric acid secretion, while structurally related compounds as dimethyl- biguanide, cyanoguanidine and 2-cyanoamino-4-methylpyrymidine did not. Thus, there is an antisecretory effect when the biguanide group is associated with a lipophilic structure. The antisecretive effects exerted by 2-GMQ are associated with anti H₂-histamine activity.The anti H₂-histamine nature of the effects of 2-GMQ was confirmed by the capacity of this compound of depressing the chronotropic activity of the isolated guinea pig auricle increased by histamine, as well as relaxant activity in rat uterus contracted by histamine, since both preparations are rich in H₂-histamine receptors.     

Effect of bay K 8644, a calcium channel agonist,on dog cardiac muscarinic receptors

To investigate further whether the effects of the dihydropyridine (DHP) drugs on calcium channels are related to those of these drugs on muscarinic receptors, the binding characteristics of the DHP calcium channel agonist, Bay K 8644, on muscarinic receptors and calcium channels were compared to those of the DHP calcium channel antagonists, nicardipine and nimodipine in the dog cardiac sarcolemma. Bay K 8644, nicardipine and nimodipine inhibited the specific [³H]QNB binding with K _i values of 16.7μM, 3.5μM and 15.5μM respectively. Saturation data of [³H]QNB binding in the presence of these DHP drugs showed this inhibition to be competitive. Bay K 8644, like nicardipine and nimodipine, blocked the binding of [³H]nitrendipine to the high affinity DHP binding sites, but atropine did not, indicating that the muscarinic receptors and the DHP binding sites on calcium channels are distinct. The K _i value of Bay K 8644 for the DHP binding sites was 4 nM. Nicardipine and nimodipine (K _i :0.1–0.2 nM) were at least 20 times more potent than Bay K 8644 in inhibiting [³H]nitrendipine binding. Thus, the muscarinic receptors were about 4000 times less sensitive than these high affinity DHP binding sites to Bay K 8644. These results suggest that the DHP calcium agonist Bay K 8644 binds directly to the muscarinic receptors but its interaction with the muscarinic receptors is not related to its binding to the DHP binding sites on calcium channels.