生长激素促分泌素受体对小鼠结肠动力的影响和机制

目的:探讨生长激素促分泌素受体及其激动剂GHRP-6对小鼠结肠动力的影响及机制。方法:小鼠随机分组后,分别注射生理盐水、GHRP-6(20、50、100、200μg/kg),用炭末推进实验的方法研究GHRP-6对小鼠结肠推进的影响。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GHRP-6(0.01、0.1、1和10μmol/L)对肌条自发收缩幅度的影响,以及神经阻断剂TTX和GHS-R阻断剂D-lys3-GHRP-6孵育肌条情况下,GHRP-6对肌条自发收缩幅度的影响。结果:GHRP-6注射剂量在50、100、200μg/kg时均能显著提高小鼠的结肠推进(P0.05)。GHRP-6浓度在0.1、1和10μmol/L时均能显著增加小鼠近端结肠环形平滑肌条的自发收缩幅度(P0.05),在TTX和D-lys3-GHRP-6孵育肌条下,Ghrelin不能增加小鼠结肠环形平滑肌条的自发收缩幅度。结论:GHRP-6可以显著增加小鼠的结肠推进,其机制可能是通过肠肌间神经丛的的GHS-R受体而起作用。     

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。     

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。     

一氧化氮与骨

一氧化氮 (nitricoxide ,NO)作为一种自由基调节着许多生理过程 ,如血管舒张、神经传递、血小板聚集和免疫调节。NO对骨细胞的功能也有调节作用[1] ,骨细胞在受到炎性细胞因子和机械应力的刺激后能促进NO的产生 ,这些NO在促进骨形成和抑制骨吸收的过程中起着重要的作用。本文就NO的生物学特性和在骨中的调节作用做以下综述。一、NO的合成和调节NO是由氧分子和L -精氨酸末端的胍基氮在NO合成酶 (nitricoxidesyn thase ,NOS)的作用下生成的 ,这个反应能被精氨酸的类似物如NG-甲基 L 精氨酸 (L NMMA)和NG-硝基 -L -精氨酸甲酯 (L…     

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.     

NANC神经递质对膀胱下尿路梗阻逼尿肌稳定性的影响

目的　观察非肾上腺素能非胆碱能 (NANC)神经递质对下尿路梗阻逼尿肌肌条自发性收缩频率及收缩幅度的作用。　方法　建立Wistar大鼠膀胱下尿路梗阻动物模型 ,6周后以充盈性膀胱测压的变化检测逼尿肌不稳定的发生率。制备离体逼尿肌肌条 ,观察NANC神经递质血管活性肠肽 (VIP)、三磷酸腺苷 (ATP)对肌条自发性收缩频率及收缩幅度的影响。　结果　大鼠膀胱下尿路梗阻 6周后逼尿肌不稳定发生率为 6 2 % ;VIP、ATP能明显抑制逼尿肌的自发性收缩 ,降低逼尿肌肌条自发性收缩频率及收缩幅度 (P <0 .0 5 ) ;梗阻后逼尿肌不稳定组、逼尿肌稳定组及对照组之间差别无显著性意义 (P >0 .0 5 )。　结论　VIP、ATP能显著抑制正常和梗阻后逼尿肌自发性收缩的频率及收缩幅度     

一氧化氮介导犬电生理诱发的阴茎勃起

应用电刺激犬盆神经诱发阴茎勃起的动物模型，观察海绵体腔内注入左旋硝基精氨酸（Ｌ－ＮＮＡ）、美蓝（ＭＢ）及阿托品对电生理性勃起的影响。结果显示，左旋硝基精氨酸及美蓝均能显著地抑制电生理的勃起效应，阿托品可部分地抑制这种效应。说明电刺激盆神经诱发的勃起由ＮＯ－ｃＧＭＰ径路介导，其中部分ＮＯ为胆碱能性来源，外源性ＮＯ（硝普钠）注入阴茎海绵体腔可诱发剂量依赖型勃起效应，提示外源性ＮＯ用于临床阳萎治疗的潜在价值。     

膀胱出口梗阻所致逼尿肌过度活动的神经电生理研究

目的 从膀胱传入神经以及盆底相关神经肌肉角度探讨神经因素及肌源性因素在膀胱出口梗阻所致的逼尿肌过度活动发生中的作用.方法 采用耻骨上膀胱颈梗阻的方法建立逼尿肌过度活动大鼠模型,测定不稳定收缩时盆神经传入电位信号,并同步测定阴部神经运动支电位、尿道外括约肌肌电及腹肌肌电的反射反应.并观察T8段脊髓截断、双侧盆神经截断、腹交感干截断以及双侧阴部神经截断后大鼠膀胱充盈测压不稳定收缩的变化.结果 成功制作了膀胱出口梗阻逼尿肌过度活动大鼠模型,成功率62.5%.充盈性膀胱测压神经肌电生理同步记录结果显示,允盈期逼尿肌过度活动可分为两种类型,一种为收缩幅度高于10 cmH2O(1 cmH2O=0.098 kPa)的逼尿肌过度活动(B-DO),伴有同步盆神经传入的信号明显增强,且能引发阴部神经、尿道外括约和腹肌肌电图出现显著变化;一种为收缩幅度低于10 cmH2O的逼尿肌过度活动(S-DO),没有上述盆神经传入及相关神经肌电变化.T8脊髓截断后,膀胱充盈-排尿收缩周期消失,膀胱基础压显著升高,B-DO消失,S-DO仍然存在,且收缩幅度较截断前略有上升,但差异无统计学意义.依次截断控制膀胱的盆神经、交感神经和阴部神经后,膀胱失去充盈-排尿收缩周期,基础压显著升高,不稳定收缩中B-DO消失,S-DO仍然存在.结论 膀胱出口梗阻所致的逼尿肌过度活动存在不依赖于中枢和周围神经的膀胱源性因素.     

粉防己碱松弛离体新西兰白兔阴茎海绵体作用的研究

目的 :探讨粉防己碱 (Tet)对离体新西兰白兔阴茎海绵体的松弛作用。　方法 :采用离体新西兰白兔阴茎海绵体肌条张力记录法 ,观察Tet对氯化钾 (KCl)和去氧肾上腺素 (PE)诱导收缩的阴茎海绵体肌条的松弛作用 ;L 硝基精氨酸 (L NNA)和亚甲蓝处理后 ,Tet对PE诱导收缩的阴茎海绵体肌条松弛的作用。　结果 :10 μmol/L及3 0 μmol/L的Tet使KCl诱导的最大收缩反应分别降低为 ( 73 .0± 3 .8) %和 ( 41.5± 3 .4) % ,降低程度与Tet的浓度呈正比 (P <0 .0 1)。Tet对 10 μmol/LPE诱导的肌条收缩具有浓度依赖性松弛作用 ,1、10、3 0、10 0 μmol/L的Tet对PE诱导的阴茎海绵体肌条收缩的松弛效应分别为 ( 6.0± 1.4) %、( 2 1.3± 2 .2 ) %、( 47.4± 3 .3 ) %和 ( 68.1±3 .6) % (P <0 .0 1) ;而L NNA及亚甲蓝对Tet的松弛作用没有影响 (P >0 .0 5 )。　结论 :Tet能浓度依耐性地松弛离体新西兰白兔阴茎海绵体 ,其作用机制可能是通过阻滞钙通道 ,而与一氧化氮 环鸟苷酸 (NO cGMP)通路无关     

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.     

Effects of GABA and homotaurine on the colonic motility of the guinea pig

The effects of GABA (gamma-aminobutyric acid) and homotaurine (3-aminopropane sulfonic acid) on propulsive activity of the isolated segment, and on longitudinal and circular muscle strips were investigated in the guinea-pig distal colon. GABA (0.1 and 1 mM) inhibited spontaneous propulsive activity with a reduction of longitudinal tension of the segment. Homotaurine (1 mM) slightly inhibited spontaneous propulsive activity. GABA (0.01-1 mM) relaxed both longitudinal and circular muscle strips. Homotaurine (1 mM) slightly relaxed circular muscle strip. Desensitization to GABA and homotaurine was observed. The inhibitory effects of GABA on both muscle strips were abolished by tetrodotoxin or atropine, but not by bicuculline. Carbachol-induced contractions on both muscle strips were not influenced by GABA or homotaurine. These results suggest that GABA-induced inhibition of propulsive activity in the isolated colonic segment may result from activation of GABAB receptor on the cholinergic neurones in the wall, which in turn leads to reduction of release of transmitter acetylcholine.     

Effects of trimebutine and metoclopramide on colonic motility in the guinea pig

The effects of trimebutine (2-dimethylamino-2-phenylbutyl-3, 4, 5-trimethoxy benzoate hydrogen maleate) and metoclopramide (N-diethylaminoethyl-2-methoxy-4-amino-5-chlorobenzamide) on propulsive activity of the isolated segmental colon, and on longitudinal and circular muscle layers of colon in guinea-pig were investigated. Trimebutine in doses up to 10(-7) g/ml slightly stimulated propulsive activity, but in doses as high as 10(-7) g/ml inhibited it. However, metoclopramide (10(-7)-10(-5) g/ml) stimulated propulsive activity in a dose dependent manner. Neostigmine-stimulated propulsive activity was inhibited by trimebutine (10(-6) g/ml) but potentiated by metoclopramide (10(-5) g/ml). Trimebutine (10(-8)-10(-5) g/ml) contracted circular muscle layer in a dose dependent manner, and contracted longitudinal muscle layer in doses up to 10(-7) g/ml, but in doses as high as 10(-7) g/ml relaxed it. While, metoclopramide (10(-8)-10(-5) g/ml) contracted both muscle layers. These results indicate that, at high doses, trimebutine-induced inhibition of propulsive activity may depend on a relaxation of longitudinal muscle, and at low doses, trimebutine-induced stimulation of propulsive activity may depend on a contraction of longitudinal muscle which was partly inhibited by atropine (10(-6) g/ml), though metoclopramide at low doses had little effect on propulsive activity.     

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.     

Electrical and mechanical interaction between circular and longitudinal muscle layers of the guinea-pig stomach

The effects of prostaglandin E1 and F2 alpha on the mechanical and electrical responses of circular strips dissected from various parts of the guinea-pig stomach were examined. Prostaglandin E1 induced the tonic contraction without an inhibition of the phasic contraction in lower parts of stomach. The amplitude of tonic contraction decayed along with greater curvature of the stomach, that is, it was largest in pylorus region and smallest in upper corpus. Furthermore, the tonic contraction increased depending on concentrations of prostaglandin E1. When a longitudinal muscle layer was removed from the circular strips, the tonic contraction disappeared. On the other hand, prostaglandin E1 or F2 alpha consistently induced an increase in the resting tone and the phasic contraction in longitudinal strips of all parts of stomach. Simultaneous recordings of the electrical and mechanical activities showed a correlation between membrane depolarization and tonic contraction induced by prostaglandin E1. Above results were not affected by nerve-blocking agent, atropine or tetrodotoxin. Thus it is suggested that the tonic contraction in circular strips induced by prostaglandin E1 is closely related to the longitudinal tonic contractions.     

Effects of bacterial endotoxin on the contraction and relaxation responses of the rabbit cavernous smooth muscles

PURPOSE: We evaluated effects of bacterial endotoxin during septicemia on contraction and relaxation responses of cavernous smooth muscles in rabbits. MATERIALS AND METHODS: We performed isometric tension studies with norepinephrine (NE), endothelium-dependent and endothelium-independent vasodilators, and nonadrenergic noncholinergic (NANC)-selective electrical field stimulation on the muscle strips of control and endotoxin (lipopolysaccharide; LPS)-treated rabbits. To determine reversibility of the LPS effects on the cavernous smooth muscle, the contraction and relaxation studies were repeated after resting the strips for 1 day at 4C. We also investigated the effect of the nonspecific nitric oxide synthase (NOS) inhibitor (NW-nitro-L-arginine methyl ester; L-NAME) and the selective immunologic NOS inhibitor (aminoguanidine) on reactivity of the strips to NE and acetylcholine. RESULTS: Contractile response to NE was significantly (p <0.01) reduced in the cavernous smooth muscles from the systemically and locally LPS-treated rabbits, compared with control group. Both aminoguanidine and L-NAME markedly improved the diminished contraction of the strips. Relaxation response to endothelium-dependent agonists (acetylcholine and bradykinin) was significantly (p <0.05) decreased in the LPS-treated groups, compared with the control group but not to endothelium-independent vasodilators (papaverine and verapamil) and NANC-selective electrical field stimulation. L-NAME completely inhibited the relaxation response to acetylcholine in the control and LPS-treated groups but aminoguanidine did not. The impaired contraction and relaxation of the strips was completely restored after resting for 1 day. CONCLUSIONS: Bacterial endotoxin may cause non-endothelial overproduction of NO and inhibition of endothelium-derived NO production, which may contribute to impairment of contraction and relaxation of rabbit cavernous smooth muscles.     

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。