生长激素释放肽ghrelin对小鼠结肠动力的影响

目的 探讨生长激素促分泌素受体(growth hormone secretagogue receptor,GHSR)内源性激动剂生长激素释放肽ghrelin对小鼠结肠动力的影响.方法 小鼠按随机数字法分组后,分别注射生理盐水和不同剂量ghrelin(20,50,100,200 ng/g),用炭末推进实验的方法观察ghrelin对小鼠结肠推进的影响,研究阿托品、NG-硝基精氨酸甲酯和D-Lys3-GHRP-6(GHSR阻断剂)对ghrelin(100 ng/g)引起的小鼠结肠推进改变的影响.将小鼠近端结肠环形平滑肌条安置在恒温灌流肌槽中并用SMUP-E生物信号处理系统记录肌条的自发收缩活动,观察不同浓度的ghrelin(0.01、0.1、1和10 μmol/L)对肌条自发收缩幅度的影响.结果 ghrelin能显著提高小鼠的结肠推进速度,有明显的量效关系.阿托品、NG-硝基精氨酸甲酯、D-lys3-GHRP-6均能显著抑制ghrelin促进结肠推进的作用(t=10.230,12.560,11.590,P＜0.05).ghrelin能显著增加小鼠近端结肠环形平滑肌的自发收缩幅度,河豚毒素预处理肌条后ghrelin不能显著增加肌条的自发收缩幅度.结论 ghrelin可以显著增加小鼠结肠的推进,可能是通过结肠肌间神经丛的硝基能神经和胆碱能神经上的GHSR而起作用.     

Ghrelin及其合成肽生长激素释放肽6对小鼠胃动力的影响和机制

目的探讨生长激素促分泌素受体（GHS-R）内源性激动剂ghrelin及其合成肽生长激素释放肽6（GHRP．6）对小鼠胃动力影响及机制。方法小鼠随机分组后，分别注射生理盐水、ghrelin（20、50、100和200μg／kg）及GHRP-6（20、50、100和200μg／kg），用灌食酚红的方法研究ghrelin和GHRP-6对小鼠胃排空的影响，并研究阿托品、一氧化氮合成酶抑制剂左旋．硝基精氨酸甲基酯（L-NAME）和GHS．R阻断剂D．lys3-GHRP-6对ghrelin和GHRP-6引起小鼠胃排空改变的影响。小鼠胃底环形平滑肌条安置在恒温灌流肌槽中，并用SMUP-E生物信号处理系统记录肌条的自发收缩活动，观察不同浓度的ghrelin（0．01、0.1．0和10．0μmol／L）和GHRP-6（0．01、0．1、1．0和10．0μmol／L）对肌条自发收缩活动的影响。结果GHRP-6和ghrelin注射剂量在50、100和200μg／kg时，均能显著提高小鼠的胃排空（P〈0．05）。阿托品、L-NAME和D-lys3-GHRP-6均能显著抑制GHRP-6或ghrelin促进胃排空的作用（P〈0．05）。GHRP-6和ghrelin浓度在0．1、1．0和10．0μmol／L时，均能显著增加小鼠胃底环形平滑肌条的自发收缩幅度（P〈0．05）；在河豚毒素同时存在的情况下，GHRP-6或ghrelin均不能显著增加肌条的自发收缩幅度（P〉0．05）。结论GHRP-6和ghrelin均可显著增加小鼠的胃排空．其机制可能是通过肌间丛神经系统的硝基能神经和胆碱能神经上的受体而起作用。     

Ghrelin对糖尿病小鼠结肠动力的影响及机制

目的：探讨生长激素促分泌素受体（GHS-R）内源性激动剂Ghrelin对糖尿病小鼠结肠动力的影响,进一步探讨其作用机制。方法：建立糖尿病小鼠模型,用炭末推进实验测定正常小鼠和糖尿病小鼠的结肠推进率,分析Ghrelin、阿托品、L-NAME和D-lys3-GHRP-6对糖尿病小鼠结肠转运的影响,并观察Ghrelin和河豚毒素（TTX）在体外对糖尿病小鼠近端环形平滑肌条自发收缩活动的影响。结果：糖尿病小鼠的结肠推进率为（34.70±1.42）%,正常小鼠的结肠推进率为（39.70±1.78）%,二者差异有统计学意义（P〈0.05）。Ghrelin注射剂量为50、100、200μg/kg时糖尿病小鼠结肠推进率均显著提高,分别为（40.10±1.23）%、45.30±2.32）%、56.40±2.81）%,有明显的量效关系（P〈0.05）。而阿托品、（（L-NAME和D-lys3-GHRP-6均能抑制Ghrelin增加糖尿病小鼠结肠推进率的效应。在体外,Ghrelin浓度在0.1、1和10μmol/L时均可显著增加肌条的自发收缩幅度,分别增加至不加药情况下的（1.12±0.04）、1.23±0.03）和（1.35±0.04）倍,有明显的量效关系（P〈0.05）,能阻断该效应。结论：Ghrelin（TTX能提高糖尿病小鼠的结肠动力,其作用机制可能是通过肌间神经丛系统的硝基能神经和胆碱能神经上的受体而起作用。     

ghrelin/ghrelin受体途径参与大鼠小肠动力的外周作用

目的 探讨ghrelin对大鼠小肠动力的外周作用机制.方法 观察不同浓度ghrelin(0、20、40、80 μg/kg)对大鼠小肠转运的影响,ghrelin(0.1、0.5、1.0μmol/L)对体外大鼠小肠平滑肌肌条收缩的影响,免疫荧光方法检测ghrelin受体(GHS-R1a)在小肠肌层中的分布.结果 ghrelin 能够剂量依赖性地增加小肠转运率(42.73±0.57)％、(47.13 ±0.84)％、(56.88±1.67)％、(69.04±1.79)％,增强卡巴胆碱引起的肌条收缩(152±3)％、(182±4)％、(218±3)％,ghrelin受体主要分布在肠内肌层中的神经细胞膜上.结论 ghrelin可通过作用于小肠肌层中的神经细胞而增强小肠平滑肌的收缩.     

芫花素对大鼠离体子宫收缩作用的研究

目的研究芫花素(益母草中的活性物质)对大鼠离体子宫收缩的影响及其作用机制。方法制作大鼠子宫肌条,观察芫花素(10~(-7)～10~(-4) mol/L)和缩宫素(10~(-7)～10~(-4) mol/L)对大鼠离体子宫平滑肌条自发收缩振幅的影响。建立大鼠离体子宫平滑肌收缩模型,分为缩宫素0.002U/ml、芫花素1.5μg/ml(小剂量)、芫花素3μg/ml(中剂量)、芫花素6μg/ml(大剂量)组,观察给药前后子宫平滑肌收缩幅度及舒张幅度变化。结果芫花素和缩宫素均有效地诱导子宫平滑肌条的收缩,且两组效果无显著性差异(P0.05);芫花素各组对大鼠离体子宫平滑肌的收缩值和舒张值均有显著的增强作用(P0.01),并且发现其对子宫平滑肌条的收缩作用与缩宫素相当(P0.05)。结论芫花素对大鼠离体子宫平滑肌具有显著的收缩作用,为芫花素用于产后出血等疾病的临床应用提供药理实验依据。     

BKCa和PKG在氯胺酮舒张哮喘大鼠离体气管平滑肌中的作用

目的 评价大电导钙激活钾通道(BKCa)和蛋白激酶G(PKG)在氯胺酮舒张哮喘大鼠离体气管平滑肌中的作用.方法 健康SD大鼠,体重250 ～ 300 g,采用卵蛋白致敏法建立哮喘模型,取哮喘大鼠15只,每只大鼠制备2～3条离体气管环.取哮喘大鼠离体气管环36条,采用随机数字表法,将其分为3组(n=12):氯胺酮处理组(AK组)、BKCa阻断剂IBTX+氯胺酮处理组(AKI组)和PKG抑制剂KT-58232+氯胺酮处理组(AKK组);AK组采用0.1 mmol/L乙酰胆碱预收缩大鼠气管环达稳态后,用0.4 g/L氯胺酮孵育15 min; AKI组用乙酰胆碱和氯胺酮孵育前,用3 μmol/L IBTX孵育30 min;AKK组用入乙酰胆碱和氯胺酮孵育前,用2μmol/L KT-5823孵育30 min;采用气管环相连的力-位移换能器测定气管环舒张幅度.结果 与AK组比较,AKI组和AKK组大鼠离体气管平滑肌舒张幅度降低(P＜0.05).结论 氯胺酮可通过激活BKCa和PKG信号通路舒张哮喘大鼠离体气管平滑肌.     

三磷酸肌醇对大鼠离体逼尿肌肌条自发收缩作用的影响

目的:观察三磷酸肌醇(IP3)对大鼠逼尿肌肌条自发收缩频率及收缩幅度的作用。方法:建立逼尿肌不稳定(DI)大鼠模型,制作大鼠离体逼尿肌肌条,比较同等张力下DI及逼尿肌稳定(detrusorstability,DS)组逼尿肌肌条自发收缩频率和收缩幅度的变化,观察不同浓度IP3及其抑制剂肝素对二组肌条自发收缩频率和收缩幅度的影响。结果:大鼠膀胱下尿路梗阻6周后DI发生率为57.4%。同等张力下,DI组肌条自发收缩频率显著高于DS组(P<0.01),收缩幅度显著低于DS组(P<0.01)。IP3能显著增加DI、DS大鼠逼尿肌肌条自发收缩频率及收缩幅度(P<0.01),肝素能显著抑制DI鼠逼尿肌肌条的自发收缩频率(P<0.05),但对其收缩幅度没有显著影响(P<0.05)。结论:IP3能显著提高大鼠逼尿肌肌条自发收缩频率和收缩幅度,DI逼尿肌自发兴奋性升高可能与IP/Ca2 信号通路的改变有密切联系。     

内源性一氧化碳对离体犬阴茎海绵体平滑肌的作用

目的:探讨内源性一氧化碳(CO)对离体犬阴茎海绵体平滑肌作用的影响。方法:利用水浴条件下阴茎海绵体肌条的张力测定技术,用CO合成的关键酶血红素氧合酶(HO)的诱导剂———氯高铁血红素诱导海绵体平滑肌生成内源性CO,观察CO对去氧肾上腺素(PE)诱导收缩的阴茎海绵体肌条作用的影响。结果:氯高铁血红素对10μmol/L PE诱导的肌条收缩具有浓度依赖性的松弛作用,10~100μmol/L氯高铁血红素对平滑肌肌条的松弛效应与空白对照相比明显升高(P<0.01)。用锌原卟啉-Ⅸ(ZnPP-Ⅸ)或亚甲蓝孵育处理后的肌条,氯高铁血红素的舒张作用明显减弱(P<0.01)。结论:内源性CO具有浓度依赖性松弛阴茎海绵体平滑肌的作用,其机制可能是通过CO环磷酸鸟苷途径作用所致。     

粉防己碱舒张离体新西兰白兔阴茎海绵体平滑肌的机制研究

目的观察粉防己碱(tetrandrine,Tet)对阴茎海绵体平滑肌胞内钙释放和胞外钙内流的影响,初步探讨其舒张作用的机制。方法采用离体阴茎海绵体平滑肌肌条张力记录法,观察Tet对去氧肾上腺素(phenylephrine,PE)和氯化钾(KCI)诱导收缩的肌条的影响；采用无Ca~(2 )-复Ca~(2 )实验法,观察Tet对PE诱导的依赖细胞内钙和细胞外钙的肌条收缩反应的影响。结果Tet对PE或kcl诱导的肌条收缩均具有浓度依赖性的抑制作用。100μmol/L Tet可抑制20μmol/L PE引起的依赖细胞内钙和细胞外钙的肌条收缩(P＜0．05)；结论Tet可通过阻滞电压依赖性钙通道、受体依赖性钙通道和抑制细胞内钙库释放,从而介导其对海绵体平滑肌的舒张作用。     

17β-雌二醇对豚鼠胆囊平滑肌收缩的影响

目的 观察17p-雌二醇对豚鼠胆囊平滑肌的基因组和非基因组效应,初步探究其机制。方法 构建去卵巢豚鼠动物模型,皮下注射17β-雌二醇,检测各组豚鼠血清雌二醇和八肽胆囊收缩素(CCK-8)含量;采用张力换能器观察17p-雌二醇对胆囊离体肌条收缩的影响。观察17β-雌二醇对豚鼠胆囊平滑肌肌条的急性效应及可能机制。结果 与假手术组相比,去卵巢组豚鼠血清雌二醇和CCK-8含量降低(P＜0.05),离体胆囊肌条对CCK-8以及乙酰胆碱的敏感性升高(P＜0.05)。随着皮下注射17β-雌二醇时间（1、3和7 d）的延长,二者含量升高(P＜0.05),离体胆囊肌条对CCK-8和乙酰胆碱的敏感性下降(P＜0.05)。10-9～10-7 mol/L的17β-雌二醇对正常豚鼠离体胆囊肌条收缩无明显影响(P＞0.05),10 6～10 5mol/L的17β-雌二醇可以抑制胆囊肌条收缩(P＜0.05),这种抑制效应可以被尼莫地平、阿托品、地伐西匹、ICI 182,780和Y-27632等阻断剂阻断。结论 17β-雌二醇与胆囊动力相关,可以通过基因组和非基因组机制影响胆囊平滑肌的收缩。     

Effect of vasoactive intestinal peptide on the motility of guinea-pig colon in vitro

The effects of vasoactive intestinal peptide (VIP) on longitudinal and circular muscle strips of guinea-pig proximal and distal colons, and on propulsive activity of guinea-pig distal colon were investigated in vitro. VIP (10(-9)-10(-6) M) produced relaxations of longitudinal and circular muscle strips in proximal colon and of circular muscle strip in distal colon, but produced a contraction of longitudinal muscle strip in distal colon. VIP-induced responses of the muscle strips were not influenced by indomethacin (10(-6) M). Tetrodotoxin (10(-6) M) and atropine (10(-6) M) converted VIP-induced contraction into relaxation in longitudinal muscle strip of distal colon, although these nerve blockers did not influence VIP-induced relaxations of longitudinal and circular muscle strips in proximal colon and of circular muscle strip in distal colon. VIP (10(-6) M) inhibited spontaneous and carbachol (10(-8) M)-stimulated propulsive activities of the isolated segment in distal colon. These results suggest that VIP may directly relax colonic smooth muscle cells and may indirectly contract longitudinal muscle strip of distal colon, mainly via stimulation of cholinergic neurones in the myenteric plexus of the muscle strip. It is also suggested that VIP-induced watery diarrhea in WDHA syndrome may not due to a direct stimulation of colonic motility.     

The effect of propofol on human gastric and colonic muscle contractions.

Although propofol is widely used for sedation in the intensive care unit, there are limited data on its effects on gastrointestinal motility. For that reason, we studied the in vitro effects of propofol on human gastric and colonic smooth muscle. Grossly normal human gastric and colonic muscle strips were mounted in an organ bath set-up for isometric contraction and stimulated by acetylcholine (Ach), using a cumulative dose schedule in the absence or presence of different concentrations of propofol [1.7 x 10(-6) M (0.3 microg/mL) to 4.4 x 10(-4) M (78 microg/mL)]. Ach led to concentration-dependent contraction of both gastric and colonic muscle strips, whereas propofol, at a concentration 6.7 x 10(-6) M (1.2 microg/mL) and above, significantly depressed Ach-induced contraction in a concentration-dependent manner for both smooth muscle preparations. In addition, propofol, at a concentration 2.7 x 10(-5)M (4.8 microg/mL) and above, depressed spontaneous contractile activity of both smooth muscle preparations. Fat emulsion 10% (Intralipid), the solvent for propofol, had no effect on either the spontaneous activity or the Ach-induced contraction of gastric and colonic smooth muscles. IMPLICATIONS: The success of enteral feeding requires a normal gastrointestinal motility. We found that, at clinically relevant concentrations, propofol impaired gastrointestinal contractile activity. Further investigations are required to determine the clinical significance of this change.     

Differential effect of nitric oxide synthase inhibition on sigmoid colon longitudinal and circular muscle responses to nicotine and nerve stimulation in vitro

BACKGROUND: Nicotine has been shown to release nitric oxide from nerves in human sigmoid colon. This effect has been used to investigate the innervation and functional relationship of the longitudinal and circular muscle layers. METHODS: Strips of longitudinal and circular muscle were obtained from 19 patients with colorectal cancer. The strips from ten patients were subjected to electrical field stimulation (EFS) in vitro using stimulus parameters for selective stimulation of nerves. The effect of nicotine 1-10 micromol/l on EFS responses was then measured in the presence and absence of a nitric oxide synthase inhibitor, nitro-L-arginine methyl ester (L-NAME) 200 micromol/l. The effect of nicotine on spontaneous activity was investigated in the muscle strips from the other nine patients. RESULTS: Both longitudinal and circular strips responded to EFS with contraction. The time to achieve a peak contractile response (time to peak; TTP) was significantly longer (P<0.001) in circular strips. L-NAME reduced the mean(s.e.m.) TTP in circular muscle from 23.3(2.0) to 17.2(1.5) s (P=0.007) and altered its pattern of response to resemble that of longitudinal muscle. Nicotine 10 micromol/l reduced the contraction to EFS in circular (P<0.001) but not in longitudinal (P=0.347) muscle. The nicotine-induced reduction in circular muscle contraction was blocked by L-NAME 200 micromol/l (P=0.005). CONCLUSION: These findings suggest that nitric oxide release on neural stimulation is greater in circular than in longitudinal muscle.     

Mechanism mediating nitric oxide-induced inhibition in human jejunal longitudinal smooth muscle

BACKGROUND: Enteric neurotransmission is a complex process involving multiple neurotransmitters, including nitric oxide (NO). Our aim was to evaluate the role and mechanism(s) of action of NO in normal human jejunal longitudinal smooth muscle. METHODS: Transmural strips of normal human jejunum obtained from subjects undergoing gastric bypass were studied in organ chambers. Effects of exogenous NO (7 x 10(-6) mol/L to 7 x 10(-5) mol/L) and electrical field stimulation (nonspecific release of endogenous neurotransmitters) on spontaneous contractile activity and on precontracted muscle strips (substance P, 10(-5) mol/L) were evaluated in the presence and absence of the competitive NO synthase inhibitor N(G)-amino-L-arginine (L-NNA, 10(-3) mol/L) and the specific soluble guanylyl cyclase inhibitor 1H-[1,2,4]-oxadiazaolo-[4,3-a]-quinoxalin-1-one (ODQ, 10(-5) mol/L and 10(-4) mol/L). RESULTS: Exogenous NO dose-dependently inhibited spontaneous contractility and relaxed precontracted smooth muscle strips. The effects of NO were markedly attenuated or completely inhibited in the presence of ODQ. Electric field stimulation under nonadrenergic, noncholinergic conditions also inhibited spontaneous contractility and relaxed precontracted smooth muscle strips; both of these effects were attenuated, but not completely inhibited, in the presence of both ODQ and L-NNA. CONCLUSIONS: NO is an endogenous inhibitory neurotransmitter in human jejunal longitudinal smooth muscle, acting at least in part via a mechanism mediated by guanylyl cyclase. Other (non-nitrergic) nonadrenergic, noncholinergic inhibitory neurotransmitters are likely active in this portion of the human gut.     

生长激素促分泌素参与大鼠小肠平滑肌运动的双相调节

目的探讨生长激素促分泌素（ghrelin）对大鼠小肠平滑肌舒缩活动的影响及其机制。方法制备迷走神经切断大鼠模型,腹腔注射不同浓度ghrelin（0、20、40和80μg／kg）,每种浓度6只大鼠,观察其对小肠转运的影响。体外实验观察在50nmol／L卡巴胆碱（Cch）存在时,不同浓度的ghrelin（0．01、0．1、0．5、1．0μmol／L）对肌条舒缩活动的影响,免疫荧光方法检测ghrelin受体（GHS．R1a）在小肠肌层中不同类型细胞的分布。结果0、20、40和80Ixg／kg4种浓度的ghrelin能够剂量依赖性地增加小肠转运率,分别为（25．4±1．0）％、（33．7±1．9）％、（39．3±2．4）％和（44．7±2．1）％,组间比较差异有统计学意义（P〈0．05）。体外应用0．01、0．1、0．5和1．0μmol／L4种浓度的ghrelin能剂量依赖增强Cch引起的肌条收缩[（67．0±2．4）％、（149．5±3．3）％、（187．1±4．7）％、（213．5±3．4）％]和舒张[（35．3±1．1）％、（62．9±3．8）％、（79．6±2．7）％、（94．6±2．2）％]效应,组问比较差异均有统计学意义（均P〈0．05）。免疫荧光检测显示,ghrelin受体主要分布在肠内肌层中的神经细胞膜上,平滑肌细胞膜上无分布。结论ghrelin可通过直接作用于小肠肌层神经丛中的神经细胞而增强胆碱能神经递质引起的小肠平滑肌的舒缩活动。     

Ghrelin受体表达对大鼠胃肠手术后小肠动力不足的影响

目的探讨ghrelin受体变化对大鼠术后小肠动力不足的影响。方法采用体外肌条实验观察在卡巴胆碱（10nmol／L）存在和缺乏时,不同浓度的ghrelin（0、0．01、0．1、0．5、1．0μmol／L）对肌条收缩力的影响。采用免疫组织化学方法和Westemblot技术检测行端侧肠吻合的实验组大鼠和行假手术的对照组大鼠小肠肌层ghrelin受体（GHS—R1a）的表达情况。结果在体外,卡巴胆碱存在时,ghrelin能够增强小肠平滑肌肌条的收缩,不同浓度的ghrelin（0．1、0．5、1．0la,mol／L）引起的收缩力差异具有统计学意义[（223±18）％、（245±22）％、（264±25）％,P〈0．01]。免疫组化染色显示．GHS—R1a主要分布于小肠肌层．实验组大鼠小肠环形肌和纵行肌中GHS—R1a表达均弱于对照组。Westernblot结果显示,实验组小肠ghrelin受体表达量（0．51±0．02）明显低于对照组（0．71±0．01,P〈0．01）。结论术后小肠肌层ghrelin受体表达下调所导致的ghrelin效应减弱可能参与术后小肠动力不足的发生。     

Calcitonin gene-related peptide inhibits gallbladder contractility

Calcitonin gene-related peptide (CGRP), a 37-amino acid peptide, is widely distributed in the gastrointestinal tract where it is colocalized with substance P. The effect of CGRP on gallbladder motility is unknown. The objective of this study was to examine the effect of CGRP on cholecystokinin-octapeptide (CCK-8) and substance P-stimulated gallbladder contraction in vivo and in vitro. In in vivo studies intragallbladder pressure was measured in response to bolus administration of CCK-8 (10(-15) to 10(-9) mol/kg) or substance P (10(-12) to 10(-7) mol/kg), either alone or with a continuous infusion of CGRP (10(-9) mol/kg/hr), in anesthetized guinea pigs. In in vitro studies the contractile force of guinea pig gallbladder muscle strips was examined in response to CCK-8 (10(-12) to 10(-7) mol/L) and substance P (10(-9) to 10(-6) mol/L), alone or with CGRP (10(-10) to 10(-6) mol/L). CGRP (10(-9) mol/kg/hr) inhibited in vivo gallbladder contraction that was stimulated by CCK-8, but not by substance P. CGRP alone produced a significant (p less than 0.05) dose-related decrease in the resting tension of gallbladder strips in vitro. CGRP (10(-6) mol/L) inhibited gallbladder muscle tension in vitro, stimulated by both CCK-8 and substance P. These studies show that CGRP can affect gallbladder motor activity by decreasing smooth muscle tone and that CGRP can antagonize the action of CCK and substance P. CGRP may be involved in the physiologic control of gallbladder emptying and refilling.