A型肉毒毒素抑制大鼠离体食管下括约肌收缩的实验研究

目的:研究A型肉毒毒素(BTX-A)对大鼠食管下括约肌(LES)离体肌条自发性收缩的影响,并观察BTX-A对电场刺激(EFS)引发的肌条收缩是否存在抑制作用。方法:成年SD大鼠叩击头部致昏后取食管下括约肌制备肌条,随机分为对照(control)组、BTX-A组、EFS组、EFS+BTX-A组,采用Biolap420E生物机能实验系统记录下括约肌肌条收缩实验数据。结果:①BTX-A降低食管下括约肌肌条自发性收缩张力及振幅(P<0.05);②EFS增强食管下括约肌肌条张力及振幅(P<0.01);③BTX-A抑制EFS对食管下括约肌肌条张力增强效应(P<0.01)及振幅增大效应(P<0.01)。结论:①BTX-A可抑制食管下括约肌肌条自发性收缩;②EFS可增强食管下括约肌肌条收缩能力;③BTX-A可抑制EFS引发的食管下括约肌肌条收缩能力的增强。     

一氧化氮在失血性休克大鼠肠运动功能障碍中的作用

目的 探讨一氧化氮(NO)在失血性休克(HS)大鼠肠运动功能障碍中的作用.方法 16只雄性Wistar大鼠按随机数字表法分组.经股动脉放血复制HS模型;制模后留取十二指肠,分别加入不同诱导物,检测肠管对乙酰胆碱(ACh)的收缩反应,以及肠组织中诱导型一氧化氮合酶(iNOS)活性和NO含量,并进行形态学观察.结果 HS 180 min大鼠肠平滑肌条自发性收缩性和ACh诱发的收缩性均明显降低,与对照组比较,HS组肠平滑肌对ACh的收缩反应降低了近60％ (g· mm-2·s-1:0.40±0.11比1.00±0.20,P＜0.01);iNOS抑制剂NG-硝基-L-精氨酸甲基酯(L-NAME)可明显逆转HS对十二指肠平滑肌收缩反应的抑制效应(0.97±0.25比0.40±0.11,P＜0.01),而且,可溶性鸟苷酸环化酶(sGC)抑制剂1H-[1,2,4]恶二唑[4,3-a]喹喔啉-1-酮(ODQ)也可显著改善HS对十二指肠平滑肌条的收缩反应(0.79±0.17比0.40±0.11,P＜0.01);但ATP敏感性钾通道(KATP)阻断剂格列本脲(Gli)对HS十二指肠平滑肌收缩反应无明显影响(0.47±0.14比0.40±0.11,P＞0.05).与对照组比较,HS组肠组织iNOS活性(U/g:2.295±0.310比1.319±0.322)和NO含量(μmol/g:2.880±0.353比1.505±0.387)显著升高(均P＜0.01).光镜下观察HS大鼠十二指肠组织最具特征性的组织形态学改变为炎细胞浸润明显.结论 HS诱导表达的iNOS产生大量NO,通过环磷酸鸟苷酸(cGMP)机制参与了大鼠肠运动功能障碍的发生;而且NO介导的炎细胞浸润也可能参与了HS肠运动功能障碍的发展.     

氟虫腈对小鼠离体胃平滑肌的作用及甲氧氯普胺对其的影响

目的:观察氟虫腈对小鼠离体胃平滑肌的作用及甲氧氯普胺对其的影响.方法:取小鼠离体胃平滑肌,将其置于50 mL恒温(37℃)灌流肌槽中,记录5个剂量组氟虫腈(1.020、1.275、1.594、1.992、2.490 g/L)作用下肌条的收缩活动;小鼠离体胃平滑肌经氟虫腈(1.594 g/L)预作用后3min加入5个剂量组甲氧氯普胺(0.02、0.04、0.08、0.14、0.24 g/L),观察其对胃肌条收缩活动的影响.结果:急性中毒小鼠胃平滑肌收缩活动与对照组相比肌张力及收缩幅度均下降(P＜0.05或P＜0.01),该作用经甲氧氯普胺干预后无明显变化(P＞0.05).结论:氟虫腈可抑制小鼠离体胃平滑肌收缩活动,急性中毒小鼠经甲氧氯普胺干预后胃平滑肌收缩活动未受影响.     

低强度超声影响大鼠肠管平滑肌收缩的量效关系研究

目的 研究低强度超声对大鼠肠管平滑肌收缩的影响,找出超声引起肠管平滑肌收缩的适宜辐照参数.方法 采用频率固定、声强可进行选择的低强度超声(频率600 kHz,声强为10.8、14、18W/Cm2)分别辐照离体和活体的大鼠肠管,采用BL410生物机能实验系统记录离体肠管平滑肌的收缩情况,用亚甲监推进实验来观察大鼠活体肠管的收缩变化.结果 离体实验表明超声辐照大鼠肠管的收缩频率、幅度、张力及活动力均明显高于辐照前(P＜0.05),辐照停止1 2 min左右,肠管收缩与辐射前状态基本保持一致;在l 4 W/cm2,辐照7 min时,肠道收缩的频率、幅度、活动力达到最大(P＜(0.05).活体实验表明辐照后各组大鼠肠管内亚甲蓝移动率明显高于对照组(P＜0.05);在14 W/cm2,辐照7 min时亚甲蓝移动率较对照组的差异明显高于其余各组(P＜0.05).结论 低强度超声对大鼠肠管平滑肌收缩有一定影响,在频率为600 kHz时,14 W/cm2,辐照7 min是适宜的辐照参数.     

延胡索对未孕大鼠离体子宫平滑肌运动的抑制作用

目的:观察延胡索乙素对未孕大鼠离体子宫平滑肌条运动的抑制作用。方法:实验于2003-11/2004-03在兰州大学医学院生理学教研室进行。①成年未孕Wistar大鼠90只,于实验前72h皮下注射乙烯雌酚0.5mg/kg,造成人工动情期以提高子宫对药物的敏感性。②猛击大鼠头部致昏,取卵巢及子宫分叉处之间的中段子宫,制成8mm×2mm的肌条,将肌条安置在恒温平滑肌肌槽中,每个肌槽中分别盛有5mL37℃Krebs液。③肌条在1g的前负荷下温育,每20min更换一次5mL新鲜的Krebs液(37℃),待肌条的自发活动平稳后加入不同剂量的延胡索乙素(2×10-5,2×10-4,4×10-4,8×10-4,1.6×10-3kg/L),观察延胡索乙素对大鼠离体子宫平滑肌条收缩活动的影响。④分别加入不同的受体拮抗剂5min后(2×10-6mol/L酚妥拉明,2×10-7mol/L异搏定,2×10-5mol/吲哚美辛和2×10-6mol/L苯海拉明),再加入8×10-4延胡索乙素,观察使用拮抗剂后延胡索乙素对大鼠离体子宫平滑肌条作用的影响。⑤计算给药前5min和给药后5min子宫平滑肌条的收缩波的频率、平均振幅和收缩波间隔平均持续时间。结果:①不同浓度的延胡索乙素均能抑制子宫平滑肌收缩运动,可使子宫平滑肌收缩波的频率减慢,在延胡索乙素浓度8×10-4kg/L,1.6×10-3kg/L时为其抑制作用差异具有显著性(P<0.01);延胡索乙素各浓度虽可以降低子宫平滑肌收缩波的振幅但差异无显著性(P>0.05);而当延胡索乙素浓度为4×10-4,8×10-4,1.6×10-3kg/L时,可显著延长收缩波的间歇时间(P<0.01)。②在加入H1受体阻断剂苯海拉明后延胡索乙素使子宫平滑肌的收缩频率降低(P<0.05),收缩波间隔的持续时间延长(P<0.05),而收缩振幅增高(P<0.05);在加入α受体阻断剂酚妥拉明后,延胡索乙素抑制子宫平滑肌的作用与单独使用延胡索乙素组相比差异无显著性(P>0.05);在加入吲哚美辛抑制前列腺素合成酶合成和释放后,延胡索乙素抑制子宫平滑肌的作用与延胡索乙素组相比仍然可以使收缩波的频率降低(P<0.05),振幅减小(P<0.05),收缩波间隔持续时间延长(P<0.05)。加入L型Ca2 通道阻断剂异搏定后延胡索乙素对未孕大鼠离体子宫平滑肌的运动有抑制作用,收缩间隔时间延长(P<0.05),但振幅不变(P<0.05)。结论:延胡索乙素抑制大鼠子宫平滑肌收缩运动的部分作用可能与L型电压依从性Ca2 通道使平滑肌细胞内Ca2 浓度降低有关,也可能与前列腺素的合成与释放有关。     

中药对豚鼠胆囊肌条运动影响的实验研究

目的观察乌梅、芫花、巴豆对豚鼠胆囊肌条运动的影响. 方法用 8个灌流肌槽同时记录实验动物胆囊肌条的自发收缩活动. 结果①低浓度的乌梅对胆囊肌条的收缩活动具有抑制作用( P< 0.01,t=3.918),而高浓度的乌梅对胆囊肌条张力的影响则呈现先降低后增高的双向性反应 (P< 0.05,t=2.297).普萘洛尔、吲哚美辛、雷尼替丁、六烃季胺、 L-NNA均末阻断乌梅对肌条的作用 (P >0.05).②芫花和巴豆均可增高离体胆囊肌条的张力 (P< 0.01,t=16; t=11.79)、加快收缩频率 (P< 0.01,t=5.47; t=4.00)、减小收缩波平均振幅 (P< 0.01,t=12.37; t=10.5).③酚妥拉明、苯海拉明、吲哚美辛可部分阻断芫花和巴豆对胆囊肌条的作用.另外,六烃季胺可部分阻断巴豆的作用. 结论①乌梅对豚鼠胆囊肌条的作用可能是直接作用于平滑肌.②芫花和巴豆对胆囊肌条的作用与肾上腺能α受体、组胺 H1受体、前列腺素合成酶有关.而巴豆还与胆碱能 N受体有关.     

脊髓损伤后早期小鼠肠道功能的变化

目的探讨脊髓损伤后短期内小鼠肠道功能的变化。方法将105只昆明种小鼠随机分为正常组(A组,n=30)、假手术组(B组,n=30)和模型组(C组,n=45)。A组不作处理,B组仅暴露脊髓,不夹持。C组采用动脉瘤夹夹持T10处脊髓,复制脊髓损伤模型。分别于术后12 h、24 h、48 h测定小鼠回肠肌电慢波及平滑肌收缩力,并做回肠HE染色。结果脊髓损伤后12 h、24h、48 h,C组小鼠肌电频率和振幅低于A组和B组(P0.05),收缩力振幅低于A组和B组(P0.05),但24 h、48 h后收缩力频率高于A组和B组(P0.05)。C组各时间点肠黏膜评分均较A组和B组高(P0.05)。结论小鼠脊髓损伤后早期,肠道平滑肌肌电活动减弱,收缩力减小,肠黏膜轻度损伤。     

乙酰胆碱及其M受体在吗啡成瘾大鼠蓝斑核痛觉调制的作用

目的:研究蓝斑核(LC)在吗啡成瘾大鼠痛觉调制中的作用及其与乙酰胆碱(ACh)受体的关系.方法:采用侧脑室(icv)注射给药的方法,以电脉冲刺激坐骨神经作为伤害性痛刺激.用玻璃微电极细胞外记录方式观察LC中痛反应神经元的电活动,并观察ACh、阿托品或毛果芸香碱对吗啡成瘾大鼠LC中痛反应神经元电活动的影响.结果:(1)icv注入ACh能使吗啡成瘾大鼠LC中痛兴奋神经元(PEN)痛诱发放电频率增加、潜伏期缩短,痛抑制神经元(PIN)痛诱发放电频率减少、完全抑制时程延长;(2)icv注入ACh的M受体拮抗剂阿托品能够阻断ACh的上述效应;(3)icv注入ACh的M受体激动剂毛果芸香碱可使PEN和PIN产生与ACh作用相似的效应.结论:(1)外源性ACh或毛果芸香碱可使吗啡成瘾大鼠LC中痛反应神经元对伤害性刺激的反应增强,表现为致痛效应;(2)阿托品能使吗啡成瘾大鼠LC中痛反应神经元对伤害性刺激的反应减弱,表现为镇痛效应.上述结果提示,LC在吗啡成瘾大鼠痛觉调制中起重要作用可能是通过M受体介导而实现的.     

苦豆子对豚鼠内脏平滑肌收缩活动的干预

目的:观察苦豆子水煎剂对豚鼠离体内脏平滑肌作用的影响,分析其发挥作用途径。方法:实验于2004-12在宁夏医学院基础学院生理实验室完成。①选用健康成年三色毛豚鼠24只,雌雄不拘。②苦豆子(由银川市中医院提供,由该院检定)被制备成1kg/L的水煎剂,实验的系列质量浓度为1×10-4,3×10-4,1×10-3,3×10-3,1×10-2,2×10-2kg/L。③实验方法:实验时分别取出豚鼠胆囊、胃、小肠及膀胱。每个胆囊制备3条平滑肌肌条,共72条;胃、小肠及膀胱各制备12条平滑肌肌条。累积于置胆囊、胃、小肠及膀胱平滑肌肌条各12条的肌槽中加入1×10-4,3×10-4,1×10-3,3×10-3,1×10-2,2×10-2kg/L苦豆子水煎剂,加药间隔2min,容量50μL。④按随机抽签法将其余60条胆囊肌条分为5组:阿托品 苦豆子组、酚妥拉明 苦豆子组、维拉帕米 苦豆子组、苯海拉明 苦豆子组、吲哚美辛 苦豆子组,每组12条。上述5组分别加入拮抗剂阿托品(胆碱能M受体阻断剂)1×10-6mol/L,酚妥拉明(肾上腺素能α受体阻断剂)1×10-6mol/L,维拉帕米(Ca2 拮抗剂)1×10-7mol/L,苯海拉明(组织胺H1受体阻断剂)1×10-6mol/L,吲哚美辛(前列腺素受体阻断剂)1×10-6mol/L后2min再依次加入前述“累积加药”中各质量浓度苦豆子。⑤通过JH-2肌肉张力换能器将信号输出BL-410生物机能实验系统读出标本的张力、收缩波平均振幅及收缩频率的变化值。⑥数据间差异性比较采用均数t检验。结果:①累积加入苦豆子水煎剂1×10-4,3×10-4,1×10-3,3×10-3,1×10-2,2×10-2kg/L后,胆囊肌条张力逐渐增高、收缩频率逐渐加快、收缩波平均振幅逐渐减小。②当苦豆子水煎剂累积质量浓度为2×10-2kg/L时,酚妥拉明 苦豆子组离体胆囊肌条张力和收缩频率明显低于或慢于苦豆子组(t=2.3401,2.1404,P<0.05),而收缩波平均振幅明显高于苦豆子组(t=2.8256,P<0.05)。维拉帕米 苦豆子组离体胆囊肌条张力明显低于苦豆子组(t=2.3464,P<0.05)。③当苦豆子水煎剂累积质量浓度为1×10-2kg/L时,酚妥拉明 苦豆子组离体胆囊肌条张力明显低于苦豆子组(t=2.430,P<0.05),而收缩波平均振幅明显高于苦豆子组(t=2.2279,P<0.05)。维拉帕米 苦豆子组离体胆囊肌条张力明显低于苦豆子组(t=2.6576,P<0.05)。④累积加入不同质量浓度苦豆子水煎剂后对豚鼠胃、小肠及膀胱肌条的张力、收缩波平均振幅及收缩频率无明显影响(P>0.05)。结论:①苦豆子水煎剂可呈剂量依赖性增高胆囊平滑肌肌条的张力、加快收缩频率、减小收缩波平均振幅,其作用可被酚妥拉明及维拉帕米部分阻断,且该种作用可能与胆囊平滑肌细胞膜上的肾上腺素能α受体和细胞膜上的Ca2 通道有关。②苦豆子水煎剂对豚鼠胃、小肠及膀胱平滑肌的收缩活动无明显影响。     

血管生成素-1对脓毒症小鼠肺血管通透性的影响

目的 探讨外源性血管生成素-1(Ang-1)对脓毒症小鼠肺血管通透性的影响.方法 腹腔注射脂多糖(LPS)制作脓毒症小鼠模型.64只BALB/c小鼠随机分为NS组、Ang-1组、LPS组和LPS+ Ang-1组(n=16).各组经处理12 h后,分别收集血浆、肺泡灌洗液及肺组织标本.ELISA法测定血浆Ang-1、Ang-2浓度并计算Ang-2/Ang-1比值,测定血浆、肺泡灌洗液的总蛋白浓度并计算肺通透指数(LPI),测定肺组织湿干比及观察肺组织病理变化.结果 Ang-1组血浆Ang-1浓度较NS组明显升高(P＜0.05).LPS组和LPS+ Ang-1组血浆Ang-1浓度较NS组均明显降低(P＜0.01),而血浆Ang-2浓度及Ang-2/Ang-1比值较NS组均明显升高(P＜0.01).LPS+ Ang-1组血浆Ang-1浓度较LPS组明显升高(P＜0.01),且血浆Ang-2浓度及Ang-2/Ang-1比值较LPS组明显降低(P＜0.01).Ang-2/Ang-1比值与小鼠肺湿干比呈明显正相关(r=0.76,P＜0.01).LPS组肺湿干比、肺通透指数较NS组明显升高(P＜0.01),LPS+ Ang-1组肺湿干比、肺通透指数较LPS组明显降低(P＜0.01),且肺组织病理渗出水肿较LPS组明显好转.结论 外源性Ang-1通过调节脓毒症小鼠Ang-2/Ang-1失平衡而发挥降低肺血管通透性及改善肺水肿作用.     

Prolonged consumption of moderate doses of alcohol and in vitro gastro-duodenal and ileal contractility in the rat

Abstract. The effects of chronic feeding with moderate doses of ethanol (3% vol/vol in drinking water for 8 weeks), which do not induce tolerance, dependence and withdrawal, on the contractility of gastric, duodenal and ileal strips from rats were investigated. Only 50% of ethanol-treated specimens (as compared to 100% of saccharose-fed controls) exhibited antral phasic contractions (frequency decreased by 31% and 27% in the antrum and duodenum, respectively; P < 0.03 vs. controls). The depolarizing agent potassium chloride (KG, 80 mm) produced less peak active tension in the fundus of ethanol-fed rats ( P < 0.01). In alcoholic rats the sensitivity of the antrum to acetyl-choline was fourfold less than that of control specimens. It is concluded that, in the rat, moderate doses of ethanol given chronically impair both spontaneous and tonic contractility of the stomach and duodenal muscle without affecting ileal contraction. It is possible that motility defects in the gut exposed to ethanol concentrations which do not cause tolerance, dependence or withdrawal in the rat may be due to a local rather than a systemic effect on the smooth muscle.     

Melatonin treatment reverts age-related changes in Guinea pig gallbladder neuromuscular transmission and contractility

The incidence of gallbladder illness increases with age, but the altered mechanisms leading to gallbladder dysfunction are poorly understood. Here we determine the age-related alterations in gallbladder contractility and the impact of melatonin treatment. Isometric tension changes in response to electrical field stimulation and to agonists were recorded from guinea pig gallbladder muscle strips. [Ca(2+)](i) was determined by epifluorescence microscopy in fura-2 loaded isolated gallbladder smooth muscle cells, and F-actin content was quantified by confocal microscopy. Aging reduced neurogenic contractions, which was associated with the impairment of nitrergic innervation and with increased responsiveness of capsaicin-sensitive relaxant nerves, possibly involving calcitonin gene-related peptide. Melatonin treatment for 4 weeks restored neurogenic responses to normal values, with an associated recovery of nitrergic function and the disappearance of the capsaicin-sensitive component. Aging also reduced the contractile responses to cholecystokinin and Ca(2+) influx. The impaired contractility only correlated with diminished Ca(2+) mobilization in response to activation of Ca(2+) influx. Melatonin improved contractility and increased smooth muscle F-actin content without changing Ca(2+) homeostasis. In conclusion, aging impairs gallbladder function as the result of changes in the inhibitory neuromodulation of smooth muscle contractility and the reduction in the myogenic response to contractile agonists. Impaired contractility seems to be related to decreased Ca(2+) influx and damage of contractile proteins. Melatonin significantly ameliorated these age-related changes.     

Colitis-induced alterations in adrenergic control of circular smooth muscle in vitro in rats

The present study investigated inflammation-induced changes in adrenergic regulation of smooth muscle. Colitis was induced in rats by intrarectal administration of trinitrobenzenesulfonic acid in ethanol. After 4 h (acute) or 7 days (chronic), in vitro isometric tension was measured in strips of circular smooth muscle taken from the distal colon. In controls, the major inhibitory control of smooth muscle responses to nerve stimulation was mediated by nitric oxide and beta adrenergic receptors. There was less evidence of alpha adrenergic control. Studies with the beta3 receptor antagonist cyanopindolol and the beta3 receptor agonist BRL37344 revealed that beta adrenergic regulation of spontaneous contractions and responses to nerve stimulation were mediated primarily by the beta3 adrenoreceptor. Both acute and chronic colitis significantly increased responses to electrical field stimulation. This effect was attributed to a loss of inhibitory nitrergic regulation as well as to selective changes in the beta adrenergic control of colonic circular smooth muscle. Inflammation did not alter alpha adrenergic control. Chronic colitis also decreased the sensitivity to nerve stimulation and pharmacological contractile agents. Acute and chronic inflammation reduced the ability of BRL37344 to inhibit contractions in response to nerve stimulation. In addition, in inflamed colon, BRL37344 was less effective in relaxing carbachol-induced precontractions. Finally, inflammation resulted in a loss of the ability of the cyanopindolol to increase the amplitude of both spontaneous contractions and contractions in response to nerve stimulation. These effects indicated that colitis induced a down-regulation of inhibitory beta3 adrenergic control of colonic smooth muscle function. This loss of adrenergic regulation may contribute to the diarrhea in inflammatory bowel disease.     

Modulation of cholinergic neural bronchoconstriction by endogenous nitric oxide and vasoactive intestinal peptide in human airways in vitro.

Human airway smooth muscle possesses an inhibitory nonadrenergic noncholinergic neural bronchodilator response mediated by nitric oxide (NO). In guinea pig trachea both endogenous NO and vasoactive intestinal peptide (VIP) modulate cholinergic neural contractile responses. To identify whether endogenous NO or VIP can modulate cholinergic contractile responses in human airways in vitro, we studied the effects of specific NO synthase inhibitors and the peptidase alpha-chymotrypsin on contractile responses evoked by electrical field stimulation (EFS) at three airway levels. Endogenous NO, but not VIP, was shown to inhibit cholinergic contractile responses at all airway levels but this inhibition was predominantly in trachea and main bronchus and less marked in segmental and subsegmental bronchi. To elucidate the mechanism of this modulation we then studied the effects of endogenous NO on acetylcholine (ACh) release evoked by EFS from tracheal smooth muscle strips. We confirmed that release was neural in origin, frequency dependent, and that endogenous NO did not affect ACh release. These findings show that endogenous NO, but not VIP, evoked by EFS can inhibit cholinergic neural responses via functional antagonism of ACh at the airway smooth muscle and that the contribution of this modulation is less marked in lower airways.     

平滑肌BKCa通道在运动改变大鼠胸主动脉舒缩特性中的作用

背景:大电导钙激活钾通道(BKCa)是调节细胞兴奋性和血管张力的重要离子通道,有关大动脉平滑肌BKCa通道的作用机制鲜有报道。目的:观察有氧运动对大鼠胸主动脉舒缩特性的影响,并探讨平滑肌BKCa通道在其中的作用。方法:将20只Wistar大鼠随机分为安静对照组和有氧运动组,运动组进行12周跑台运动,坡度0°,20m/min,60min/d,5d/周。之后每组5只大鼠行股动静脉插管术。恢复1d后,于在体、清醒状态下进行心血管功能监测。另各组5只大鼠,取胸主动脉制备去内皮血管环,进行体外血管收缩特性检测。结果与结论:①有氧运动后静脉注射去甲肾上腺素引起的升压反应幅度下降。②静脉注射BKCa通道阻断剂Iberiotoxin可诱发升压反应,且运动组更显著。③120mmol/LKCl在两组胸主动脉血管环均可诱发收缩,最大张力差异无显著性意义。④去甲肾上腺素(10-9～10-5mol/L)诱发的血管收缩呈浓度依赖性,但运动组的最大张力显著低于安静组。⑤Iberiotoxin(3×10-8mol/L)预处理血管后,可增强去甲肾上腺素(10-5mol/L)诱发的张力增加,且运动组增加幅度显著大于安静组。⑥BKCa通道开放剂NS1619(10-10～10-6mol/L)可引起去甲肾上腺素诱发的血管收缩张力下降,且运动组对其敏感性(pD2)增加。提示,有氧运动可诱导大鼠心血管反应性和胸主动脉舒缩特性改变,其中平滑肌BKCa通道起着重要作用。     

Chemical oxidant potentiates electrically and acetylcholine-induced contraction in rat trachea: possible involvement of cholinesterase inhibition

To determine the roles of oxidants in airway responsiveness, we studied the effects of the chemical oxidant N-chlorosuccinimide (NCS) on the contractile responses to electrical field stimulation (EFS) and acetylcholine (ACh) in isolated rat tracheal smooth muscle segments. Effects of NCS on the contractile response to EFS (5 Hz, 20 sec of duration, 50 V) reached the maximum with a 60-min incubation time. NCS potentiated the contractile response to EFS, with a maximum effect at 3 x 10(-7) M and to ACh, with a maximum effect at 3 x 10(-6) M. Thus, at a concentration of 3 x 10(-6) M, NCS significantly decreased log ED50 concentration of ACh from a control value of -5.56 +/- 0.05 to -6.24 +/- 0.06. Physostigmine (10(-7) M), at a concentration that did not alter resting tension, mimicked NCS-induced effects on contractile responses to ACh and EFS with the greater degree of shift in the respective dose-response curves. However, NCS failed to alter dose-response curves to carbachol. Removal of the epithelium shifted the dose-response curves to ACh to lower concentrations, but NCS showed similar effects on dose-response curves to ACh with and without the epithelium. Active staining showed that both acetylcholinesterase (EC 3.1.1.7) and butyrylcholinesterase (EC 3.1.1.8) activities were found in the smooth muscle of the rat trachea. NCS inhibited both enzyme activities from rat tracheal homogenates in a concentration-dependent fashion. These results suggest that NCS potentiates cholinergically induced contraction by decreasing cholinesterase activity and that the oxidation of cholinesterase may cause hyperresponsiveness of airway smooth muscle by inhibition of the enzyme activity.     

Inhibitory effect of methylmercuric chloride on the contraction mediated by muscarinic receptor of intestinal smooth muscle of the guinea-pig

Effects of methylmercuric chloride (MMC) on the contractile responses to nerve and drug stimulation in the guinea-pig taenia coli were examined. MMC (25-50 microM) severely reduced both responses to electrical and pharmacological (nicotine) stimulation of cholinergic nerves without affecting the responses to direct stimulation of muscles. MMC also suppressed markedly the response to acetylcholine (ACh), but did not change the maximum response to ACh. Dose-inhibition curve for MMC on the response to nerve stimulation was quite similar to that on the response to externally applied ACh. MMC only at a high concentration slightly reduced the response to histamine. MMC depolarized the membrane of the smooth muscle by about 8 mV with the sucrose-gap method. However, conditioning depolarization of the muscle strip by a 25 mM-K solution did not suppress the response to ACh. It was suggested that MMC-induced inhibition of the responses of the guinea-pig taenia coli to cholinergic nerve stimulation resulted from the inactivation of the muscarinic receptor of the smooth muscle.     

不同浓度的神经安定类药物对离体兔气管平滑肌的松弛效应比较

背景神经安定类药物广泛应用于临床,但各药对气道平滑肌的松弛效应尚无比较研究.目的为了对气道高反应性患者筛选最佳神经安定药物,对不同浓度的安定、氟哌利多、氯丙嗪及异丙嗪对离体兔气管平滑肌的松弛效应进行了比较研究.设计自身对照实验研究.地点和对象实验在南京医科大学第一附属医院麻醉科完成,成年健康兔24只,雌雄各12只,体质量(2.5±0.5)kg,由南京医科大学实验动物研究中心提供.干预将兔随机分为4组.将离体兔气管平滑肌标本浸于35,140 μmol/L安定,2.6,10.4 μmol/L氟哌利多,28,112 μmol/L氯丙嗪及31,124 μumol/L异丙嗪中,用电场刺激测定离体兔气管平滑肌张力.自身用药前后比较采用t检验.主要观察指标安定、氟哌利多、氯丙嗪及异丙嗪对电场刺激引起的兔气管平滑肌张力变化.结果4种药物均使兔气管平滑肌张力呈浓度依赖性减弱,但低浓度安定时无显著统计学意义(t=2.568,P＞0.05),高浓度安定用药前后平滑肌张力分别为(430±264)和(297±212)mg,有显著的统计学意义(t=2.821,P＜0.05);高、低浓度氟哌利多、氯丙嗪及异丙嗪均有显著或非常显著统计学意义(t＞2.921,P＜0.05,或t＞4.125,P＜0.01).等效镇静剂量,各药降低气管平滑肌收缩强度依次为异丙嗪＞氯丙嗪＞氟哌利多＞安定.结论气道高反应性患者,此4种药物均可应用,以异丙嗪为最优;在哮喘发作或术中发生支气管痉挛时,可试用异丙嗪、氯丙嗪或氟哌利多处理.     

Effects of pH on vascular smooth muscle contraction]

Effects of pH on vascular smooth muscle contractility were reviewed. Basic effect of acidosis seems to be the inhibition of K channels and L-type Ca channels. Inhibition of K channels results in a membrane depolarization, opening of L-type Ca channels, increase in Ca influx and muscle contraction. Inhibition of Ca channels results in an opposit effect. Thus, the effect of acidosis is determined by the relative potency of these two contradictory effects. This may be the reason why acidosis induces contraction in polarized muscle whereas it slightly inhibits contraction in depolarized muscle. In addition, measurements of cytosolic Ca level simultaneously with muscle tension suggest that acidosis increases Ca sensitivity of contractile elements, and this effect also helps acidosis to induce contraction in vascular smooth muscle.