Involvement of endothelin and nitric oxide in cyclosporine A-induced contractions in guinea pig isolated gallbladder strips.

The involvement of endothelin (ET), ET(A) receptors and nitric oxide (NO) in the contractions induced by cyclosporine A (CyA) were investigated in guinea pig isolated gallbladder strips. Both BQ-123, a selective ET(A) receptor antagonist, and phosphoramidon, an ET converting enzyme inhibitor, inhibited the contractile responses to the parenteral and oral CyA preparations, whereas l-NOARG, a NO synthase inhibitor, potentiated these contractions. Additionally, the pattern of the concentration-dependent contractions in response to ET-1 was similar to that of CyA preparations in gallbladder strips. Both bosentan, a non-selective ET receptor antagonist, and BQ-123 inhibited the ET-1-induced contractions. These findings suggest that an ET-1-mediated mechanism contributes to the contractile response to CyA preparations in guinea pig isolated gallbladder strips. ET(A) receptor activation is likely to be involved in this process. We also speculate that CyA-induced stimulation of NO production might act as a counter-regulatory mechanism in the effect of CyA preparations in this tissue.     

The role of nitric oxide in the electrical field stimulation-induced contractions of sphincter of oddi and gallbladder strips in Guinea pigs

The aim of this study was to investigate the modulatory role of nitric oxide (NO) in the electrical field stimulation (EFS)-induced contractions of isolated sphincter of Oddi (SO) and gallbladder strips from guinea pigs. EFS was used to activate the intrinsic nerves in SO and gallbladder strips. EFS produced frequency-dependent biphasic contractile responses in the SO strips. A smaller contraction, "on response", occurred during EFS, which was followed by a bigger contraction, "off response". Both responses were completely and irreversibly abolished by tetrodotoxin (TTX) (10(-6) M). Atropine (10(-6) M) inhibited the "on response", but not the "off response". EFS produced frequency-dependent monophasic contractile responses in gallbladder strips, which were completely and irreversibly abolished by TTX (10(-6) M) and atropine (10(-6) M). A nitric oxide synthase (NOS) inhibitor, NG-nitro-L-arginine (10(-4) M and 3 x 10(-4) M, in SO and gallbladder strips, respectively), significantly increased all EFS-induced contractions of SO and gallbladder strips. L-Arginine, but not D-arginine reversed the effect induced by the NOS inhibitor, at all frequencies, in both strips. These results suggested that NO released from nitrergic nerve endings might play a regulatory role in the cholinergic neurotransmission of guinea pig SO and gallbladder strips. The "off response" in he SO preparations might be a rebound increase that was modulated by the nonadrenergic, noncholinergic inhibitory mediator NO.     

盐酸丙哌维林对膀胱平滑肌收缩的影响(英文)

观察了盐酸丙哌维林 ( Pro)对离体豚鼠膀胱平滑肌自动节律性收缩和 KCl诱导离体豚鼠膀胱平滑肌收缩的影响 ;同时观察了 Pro对家犬在体膀胱自动节律性收缩的影响 .Pro在 1 ,1 0 μmol· L-1浓度时 ,对离体豚鼠膀胱平滑肌自动节律性活动具有兴奋作用 ,可使自动节律性收缩频率增加 ,幅度加大 ;在 1 0 0μmol· L-1浓度时则表现为抑制作用 ,可完全抑制豚鼠膀胱平滑肌的自动节律性收缩 ,同时可使平滑肌松弛 ,基础张力降低 .Pro对 KCl引起的豚鼠离体膀胱平滑肌的收缩具有明显的抑制作用 ,在 1 ,1 0 ,1 0 0 μmol· L-1浓度时对 KCl诱导豚鼠离体膀胱平滑肌收缩的抑制率分别为 ( 7.4±6.5) % ,( 31 .3± 1 2 .8) % ,( 68.4± 7.1 ) % ,其 IC50 为( 2 5.2± 4.7) μmol·L-1.十二指肠给 Pro对在体家犬膀胱自动节律性收缩具有明显的抑制作用 ,60 ,30mg· kg-1可明显降低膀胱自动节律性收缩频率和幅度且具有剂量依赖性 ,与药前比有显著性差异 ,60 mg· kg-1药后 1 0 min即可起效 ,药效可持续 90min,Pro在上述剂量下对血压 ,心率无明显影响 .本实验结果提示 Pro在低剂量时对离体膀胱自动节律性收缩具有一定的兴奋作用 ,在高剂量时则表现为明显的抑制作用 ;Pro对 KCl诱导的豚鼠离体膀胱平滑肌收缩和膀胱扩张诱导的家?     

海群生对豚鼠离体气管条平滑肌收缩的影响

目的研究海群生（枸橼酸乙胺嗪,ＤＥＣ）对豚鼠离体气管条平滑肌收缩反应的影响及其作用机制。方法取气管条放入３７℃浴管的Ｋｒｅｂｓ溶液中,分别在浴液中加入药物,测定ＫＣＩ和５－羟色胺（５－ＨＴ）收缩气管条的作用和量效反应以及ＤＥＣ和维拉帕米对ＫＣｌ和５－ＨＴ作用的影响。结果ＤＥＣ能使ＫＣＩ或５－ＨＴ引起的气管条平滑肌收缩显著抑制,其ＩＣ５０值分别为５．０３ｍｍｏｌ·Ｌ－１和９．５４ｍｍｏｌ·Ｌ－１,与维拉帕米的作用相似。ＤＥＣ使ＫＣｌ和５－ＨＴ的量效曲线右移,最大反应降低,呈非竞争性拮抗,其ｐＤ２值分别为１．５５４和１．８５１,并对细胞内Ｃａ２＋释放和细胞外Ｃａ２＋内流引起的收缩有抑制作用。结论ＤＥＣ可抑制ＫＣｌ和５－ＨＴ引起的气管条平滑肌收缩,其机制可能是通过其钙拮抗作用所致。     

硫酸锌对离体血管平滑肌的作用

硫酸锌是体内一种重要的微量元素,它使离体动物心脏动作电位振幅降低,有效不应期延长,并能显著降低家兔窦房结自律性。本文采用离体豚鼠胸主动脉条和犬门静脉环标本,观察硫酸锌对KCl,CaCl_2和去甲肾上腺素(NE)诱发血管平滑肌收缩的影响。进一步探讨硫酸锌与Ca~(2 )的作用关系。     

盐酸戊乙奎醚对豚鼠离体回肠/结肠的解痉作用

目的　研究盐酸戊乙奎醚 (PHC)对豚鼠离体回肠 /结肠肌条的抑制收缩作用。方法　将豚鼠离体回肠 /结肠条悬吊于麦氏浴槽中 ,测量给药PHC后豚鼠离体肌条自主收缩及乙酰胆碱 (Ach)所致痉挛收缩的最大张力 ,计算抑制 5.0 %收缩的PHC的浓度。结果　PHC对豚鼠离体回肠 /结肠肌条的自主收缩有明显抑制作用 ,对乙酰胆碱 (Ach)所致的痉挛性收缩有明显的松弛作用。结论　PHC能有效地缓解离体回肠 /结肠的痉挛状态。     

Mechanism of inhibitory effects of ethanol on gallbladder contraction: differences in cases of histamine- and acetylcholine-induced contraction]

We investigated the effects of different concentrations of ethanol on contraction of gallbladder isolated from guinea pig. Ethanol at 25 mM significantly inhibited the contraction induced by histamine, but not those by KCl and acetylcholine. A higher concentration (100 mM) of ethanol inhibited both histamine-, acetylcholine- and KCl- induced contractions. The inhibitory effect of the lower concentration (25 mM) of ethanol was not observed in the presence of verapamil, an antagonist of L-type Ca2+ channel or staurosporine, a selective inhibitor of protein kinase C. Verapamil and staurosporine significantly inhibited both histamine- and acetylcholine-induced contractile responses: the inhibitory effect was more potent for the histamine contraction. Our recent study has demonstrated that contraction caused by protein kinase C activation is completely dependent on Ca2+ influx through the L-type Ca2+ channel in gallbladder smooth muscle of guinea pig. Therefore, the difference in 25 mM ethanol effect on histamine- and acetylcholine-induced contractions may be due to different degree of involvement of protein kinase C activation in the agonist-induced contraction. On the other hands, the higher concentration (100 mM) of ethanol inhibits the common pathway of contraction in gallbladder smooth muscle cells.     

Diminished inibitory action of ethanol on the contraction of gallbladder isolated from chronically ethanol-fed Guinea pigs

Ethanol is known to decrease the gallbladder contractility. The purpose of this study was to clarify the mechanism of tolerance to the inhibitory action of ethanol on the gallbladder contractility. Male guinea pigs were fed ethanol (3%) or calorie-matched sucrose in the drinking water for 4 weeks. Then, the gallbladder was isolated, and its isometric tension was measured. The contractile responses to KCl, BAY K8644, histamine, and phorbol 12,13-dibutyrate in the normal medium were not different between the gallbladder strips from ethanol-fed and control guinea pigs. Ethanol at 25 mmol/l in vitro did not affect the contractile responses to KCl and BAY K8644 in the gallbladder strips from both ethanol-fed and control guinea pigs. On the other hand, ethanol at 25 mmol/l in vitro significantly inhibited the contractile responses to histamine and phorbol 12,13-dibutyrate in the gallbladder strips from the control guinea pigs, but it did not affect the contractile response to histamine and significantly augmented that to phorbol 12,13-dibutyrate in the strips from the ethanol-fed guinea pigs. Diphenhydramine, a selective H(1) receptor antagonist, abolished the histamine contraction in gallbladder strips from both control and ethanol-fed guinea pigs, while cimetidine, a selective H(2) receptor antagonist, did not affect histamine contraction, implying that histamine-induced contraction of guinea pig gallbladders is mediated only by H(1) receptors. Verapamil (1 micromol/l) completely inhibited the phorbol 12,13-dibutyrate-induced contraction of the strips from both ethanol-fed and control guinea pigs. The histamine-induced contraction was partly inhibited in the absence of Ca(2+) in the medium. In the gallbladder strips from both ethanol-fed and control guinea pigs, ethanol at 25 mmol/ in vitro did not affect the histamine-induced contraction in the absence of extracellular Ca(2+). Tolerance to the inhibitory action of ethanol developed selectively on contractile responses to histamine and phorbol 12,13-dibutyrate. Chronic ethanol administration produces tolerance to in vitro gallbladder contractility mediated by the Ca(2+) entry through L-type Ca(2+) channels linked with protein kinase C activation.     

Further evidence for the heterogeneity of functional muscarinic receptors in guinea pig gallbladder

Previous studies have suggested the presence of multiple muscarinic receptor subtypes in guinea pig gallbladder smooth muscle, although the relative abundance and functional role of these subtypes remains an area of significant research efforts. The present study utilized both radioligand kinetic and functional experiments to further probe the nature of the muscarinic receptors in gallbladder smooth muscle and their mode of coupling to intra- and extra-cellular Ca(2+) sources. Dissociation kinetic studies using [3H]N-methylscopolamine ([3H]NMS) indicated that the binding profile in guinea pig gallbladder smooth muscle could not be reconciled with that expected for a single muscarinic receptor subtype, the latter determined in parallel experiments conducted on the cloned muscarinic M(1)-M(5) subtypes in Chinese hamster ovary (CHO) cells. Furthermore, comparison of the gallbladder data with the dissociation characteristics of [3H]NMS in guinea pig urinary bladder revealed a significantly different kinetic profile, with the urinary bladder, but not the gallbladder, demonstrating biphasic radioligand dissociation kinetics. In functional experiments, carbachol caused a concentration-dependent contraction of guinea pig gallbladder smooth muscle strips in Ca(2+)-free or 5 mM Sr(2+)-substituted physiological salt solutions (PSS) with amplitudes of the maximal contractions corresponding to 45.8+/-8.0% and 33.2+/-6.6% of control responses in normal PSS, respectively. Furthermore, the stimulus-response characteristics of carbachol-mediated contraction appeared significantly altered in Ca(2+)-free PSS relative to normal or Sr(2+)-substituted PSS. The antagonist, methoctramine (1x10(-7)-3x10(-5) M), exerted only a slight inhibition of carbachol (10(-5) M)-induced contractions in 5 mM Sr(2+)-substituted medium, whereas it was significantly more potent in antagonizing gallbladder contractions in response to 10(-5) M carbachol in the absence of extracellular Ca(2+). Both atropine and tripitramine were equipotent in antagonizing carbachol-induced contractions in Ca(2+)-free (pIC(50): 6.85+/-0.11 for atropine and 5.75+/-0.32 for tripitramine) and Sr(2+)-substituted media (pIC(50): 6.88+/-0.25 for atropine and 5.70+/-0.16 for tripitramine), and pirenzepine was only slightly more potent in Ca(2+)-free PSS (pIC(50): 5.66+/-0.23) than in Sr(2+)-substituted PSS (pIC(50): 5.33+/-0.21). Taken together, our data indicate that carbachol contracts guinea pig gallbladder by stimulating two distinct muscarinic receptor subtypes linked to extracellular Ca(2+) influx and intracellular Ca(2+) release. These two subtypes may represent the muscarinic M(3) and M(4) receptors, although the presence of the muscarinic M(2) receptor subtype is also suggested from the binding data.     

Acidosis inhibits gallbladder contraction mediated by protein kinase C activation.

The effects of extracellular acidosis on gallbladder contraction were investigated using gallbladder strips isolated from guinea pigs. In an acidic medium (pH 6.9), gallbladder contraction induced by histamine and prostaglandin E2 was significantly lower than that in a normal medium (pH 7.4). Acidosis affected neither gallbladder contraction induced by histamine in the absence of extracellular Ca2+ nor that induced by KCl. Acidosis significantly inhibited Ca2+-induced contraction in the presence of sodium fluoride and phorbol 12,13-dibutyrate but not that in the presence of KCl. Staurosporine (30 nM) significantly inhibited gallbladder contraction induced by histamine and prostaglandin E2, but not that by KCl. Histamine-induced contraction in the presence of staurosporine was not affected by acidosis. Acidosis significantly inhibited Ca2+-induced contraction in the presence of histamine but not that in the presence of both histamine and staurosporine. These results suggest that extracellular acidosis selectively inhibits gallbladder contraction mediated by protein kinase C activation.     

Further studies on the effects of disodium cromoglycate on guinea pig ileum

Transmural electrical stimulation was carried out on innervated strips of the longitudinal muscle of guinea pig ileum. Disodium cromoglycate (DSCG) inhibited the electrically induced contractions. Five minutes later, prostaglandin E2 (2.5 ng/ml) was added to the bath and it reversed the action of DSCG. Furthermore, DSCG inhibits significantly the guinea pig ileum contractions induced by nicotine and also those induced by histamine and acetylcholine on ileum denervated by cooling. These results suggest that DSCG effects on guinea pig ileum contraction are mediated by membrane-stabilizing properties of this drug on smooth muscle fibres as well as on myenteric plexus.     

Involvement of cholinergic neurons in orexin-induced contraction of guinea pig ileum

The mechanism underlying orexin-induced contraction was examined in isolated preparations of guinea pig ileum, in relation to cholinergic transmission. Orexin-A caused contraction of ileal strips in a concentration-dependent manner. 1-(2-Methylbenzoxazol-6-yl)-3-[1,5]napthyridin-4-yl-urea hydrochloride (SB-334867-A) antagonized the orexin-A-induced contraction, with no effects on the acetylcholine-induced contraction and twitch contractions. The orexin-A-induced contraction was inhibited by tetrodotoxin and atropine, but not by hexamethonium, an antagonist of vasoactive intestinal peptide and a mixture of 5-hydroxytryptamine receptor antagonists. Orexin-A evoked an outflow of [3H]acetylcholine from the ileal strips preincubated with [3H]choline, in a concentration-dependent manner, and the orexin-A-evoked outflow was inhibited by tetrodotoxin, indicating that the outflow of [3H]acetylcholine originates from the nerve terminals. The orexin-A-evoked outflow of [3H]acetylcholine was antagonized by SB-334867-A. Thus, orexin-A evokes the release of acetylcholine from the enteric cholinergic neurons due to stimulation of the orexin-1 receptors and then causes contractions of guinea pig ileum.     

Different responses to drugs against overactive bladder in detrusor muscle of pig,guinea pig and mouse

Direct comparison of experimental data for drugs commonly used in the treatment of overactive bladder is difficult because of possible species differences. In this study, we compare the effects of atropine, propiverine, oxybutynin and tolterodine in strips of pig, guinea pig and mouse detrusor muscle. In the three species, we observed slight differences in potency of carbachol-induced biphasic contractile responses between the species (guinea pig>pig>mouse). Cumulative concentration-response curves for carbachol were shifted to the right by atropine, propiverine, oxybutynin and tolterodine. However, at higher concentrations of the latter three antagonists, the maximum response to carbachol was also reduced. Therefore, propiverine, oxybutynin and tolterodine must have additional pharmacological actions beyond competitive antagonism at muscarinic receptors. Electric field stimulation (30 Hz) of detrusor strips led to contraction amplitudes, which remained constant over time (210 min) in pig, decreased by 17+/-5% in guinea pig, and increased by 28+/-9% in mouse detrusor muscle. Electric field stimulation-evoked contractions were suppressed to 18% of pre-drug control by high concentrations of atropine (10 microM) in pig, but to a much lesser extent in guinea pig and mouse (to 46% and 70%, respectively). In all three species, a myogenic component of contraction was observed in the presence of tetrodotoxin (1 microM). Compared to atropine, the bladder spasmolytic agents propiverine, oxybutynin and tolterodine also reduced electrically evoked contractions in the three species, though higher concentrations were required. The differences in the reported effects of the spasmolytic agents commonly used for treating overactive bladder suggest that drug action is strongly dependent on the species. Thus, a comparison of drug effects is only feasible in the same animal model and the results cannot easily be transferred to humans.     

Investigations on calmodulin antagonistic effects of bepridil in intact and skinned fibres of smooth muscle

Potassium-induced contractions of rat aortic strips are completely inhibited by N-benzyl-beta-(isobutoxymethyl)-N-phenyl-1-pyrrolidine-ethylamine (bepridil, Cordium) 10(-5) mol/l. In contrast, contractions induced by norepinephrine are only partially inhibited (by 40%) by identical doses of bepridil. Since the latter effect could be due to an inhibition of calcium release from intracellular compartments it was investigated how bepridil influences the effect of calcium on functionally isolated contractile structures. Smooth muscle preparations (guinea pig taenia coli and pig coronary artery) were skinned with octoxinol and suspended in adenosine triphosphate salt solution. During long-term incubation (greater than 40 min) of skinned fibres in low-calcium solution (pCa greater than 8) the calmodulin (CaM) is extracted. A calcium-induced contraction occurs only by adding CaM, showing the necessity of CaM for contraction. In the presence of bepridil 10(-4) mol/l the following effects were observed: submaximal contractions induced by calcium (1.1-1.6 mumol/l) were inhibited completely, the effects of calcium (4 mumol/l and 30 mumol/l) were inhibited by 83 +/- 4.5% and 53 +/- 10.5% respectively (mean +/- S.E.M.; n = 5). These effects could be completely antagonized by addition of calmodulin, final concentration 5 mumol/l. Verapamil did not show any inhibitory effects even in high concentrations (up to 10(-3) mol/l). Thus the effects of bepridil on the contractile mechanism in vascular smooth muscle are at least partly mediated through an intracellular mechanism - most probably inhibition of calmodulin.     

Significant role of peptide leukotrienes (p-LTs) in the antigen-induced contractions of human and guinea pig lung parenchymas and bronchi or tracheas in vitro.

Chemical mediators responsible for the antigen-induced contractions of isolated, passively sensitized human and guinea pig lung parenchymas and bronchi or tracheas were evaluated by several antagonists and enzyme inhibitors, with emphasis on the effects of the potent and selective peptide leukotriene (p-LT) antagonist MCI-826. All of these preparations showed long-lasting contractions in response to an antigen challenge which lasted for more than 60 min. In either the human lung parenchyma and brochus or guinea pig lung parenchyma, pretreatment with 10(6) g/ml (2.4 x 10)-6) M) MCI-826 significantly inhibited the late phase at 10 to 60 min after the challenge of the contraction following slight suppression of the early phase. The early phase contractions of these preparations were moderately antagonized by 10(-6) g/ml mepyramine, but the late phases were not influenced or even rather enhanced. The combination treatment of MCI-826 with mepyramine additionally and markedly inhibited both phases of these preparations. On the other hand, although mepyramine apparently inhibited the early phase of the guinea pig tracheal contraction but not the late phase, no synergistic inhibitions of the contraction were observed when it was combined with MCI-826. The p-LT antagonist FPL 55712, atropine and indomethacin at 10(-6) g/ml either slightly inhibited or enhanced the contractions of human lung parenchymas, guinea pig tracheas and lung parenchymas, but the effects were not significant. From these results, it should be emphasized that p-LTs largely contribute to induction of the anaphylactic contractions of human lung parenchymas as well as human bronchi and guinea pig lung parenchymas but not guinea pig tracheas.     

葛缕酮的气道扩张作用和呼吸道抗过敏作用

目的观察留兰香油中葛缕酮的气道扩张作用和对呼吸道介质的影响。方法用豚鼠药物引喘法、豚鼠离体气管片法、致敏豚鼠肺组织ＳＲＳ Ａ释放和拮抗ＳＲＳ Ａ、致敏豚鼠离体气管Ｓｃｈｕｌｔｚ Ｄａｌｅ反应法检测。结果葛缕酮对豚鼠药物性哮喘具有保护作用,灌胃给药延长５０％剂量为７６ｍｇ·ｋｇ－１,气雾给药为６３ｇ·Ｌ－１;对豚鼠离体气管有直接松弛作用,ｐＤ２值为４２７±００８,并有抗氨甲酰胆碱作用;能抑制致敏豚鼠肺组织ＳＲＳ Ａ的释放,ＩＣ５０为１８ｍｇ·Ｌ－１,拮抗ＳＲＳ Ａ收缩回肠的ＩＣ５０为２７ｍｇ·Ｌ－１,并能抑制致敏豚鼠离体气管的Ｓｃｈｕｌｔｚ Ｄａｌｅ反应。结论葛缕酮具有气道扩张作用和呼吸道抗过敏作用。     

Effects of S-312, a new calcium antagonist, on the mechanical and electrophysiological responses of isolated cardiovascular preparations

S-312, a new calcium antagonist with a bicyclic dihydrothienopyridine structure, potently relaxed the helical strips of various isolated rabbit arteries precontracted with high K+-depolarization, serotonin (5-HT) and U46619 (thromboxane A2 analogue), and it competitively inhibited Ca++-induced contractions in depolarized basilar and femoral arteries. These effects of S-312 were more potent than nifedipine and almost comparable to or slightly more potent than those of nicardipine. In comparison with nifedipine and nicardipine, the calcium antagonistic effect and the relaxant effect on 5-HT-induced contractions of S-312 were most prominent in the basilar artery. The potent vasodilating action of S-312 in the high K+-depolarized basilar artery was not easily reversed by washing. S-312 did not affect Ca++-induced contraction in the skinned fiber of guinea pig taenia caecum. The negative inotropic effect of S-312 in isolated guinea pig left atria was much less potent than those of nifedipine and nicardipine. S-312 above 10(-7) M preferentially increased AV nodal conduction time in Langendorff-perfused isolated rabbit hearts; and above 3 x 10(-8) M, it mainly decreased the maximum upstroke velocity of the action potential in isolated rabbit sinus node preparations. In summary, the present results indicate that S-312 is a potent new calcium antagonist possessing vasculoselectivity, especially for cerebral vessels.     

Fluoride is a contractile agent of guinea pig airway smooth muscle.

1. Guinea pig parenchymal lung strips and tracheal smooth muscle contract potently after NaF-addition. Maximal contractions of lung strips and tracheal rings induced by NaF were 208 +/- 17% (n = 6) and 151 +/- 8% (n = 4) of the maximal histamine response respectively. 2. The -log EC50-value for NaF on lung strips and tracheal rings was 2.38 +/- 0.01 (n = 6) and 2.28 +/- 0.01 (n = 4) respectively. 3. Contractions induced by NaF were augmented after Al3+ pretreatment, suggesting the involvement of a G-protein. NaF responses were not affected by blockade of H1-, muscarinic-, leukotriene C4- or leukotriene D4-receptors, indicating that mast cell degranulation or nerve activation is most probably not implicated. 4. Contractions after NaF-addition were relatively insensitive to removal of extracellular calcium and were reversed via cAMP- and cGMP-mediated pathways. 5. Relaxation studies with (-)isoprenaline and 8-bromo-cGMP on lung strips, precontracted to similar levels with either a H1-agonist, KCl or NaF, showed that the level of relaxation depends on the contractile agent that is used. 6. After precontraction with KCl (-)isoprenaline relaxes lung strips only to 58 +/- 9% (n = 5) of the initial contraction, whereas lung strips precontracted with NaF or a H1-agonist relax 114 +/- 8% (n = 4) and 120 +/- 7% (n = 5) respectively with (-)isoprenaline. 7. Similar results were obtained with relaxation induced with 8-bromo-cGMP. 8. These findings suggest that NaF-induced contractions are elicited via a mechanism, that is probably similar to that of the H1-receptor. The involvement of a G-protein in the observed NaF-responses is therefore likely.     

LY249933: a cardioselective 1,4-dihydropyridine with positive inotropic activity

Compound LY249933 and its component diastereomers, (RR) and (SR), were studied for their vascular and cardiac effects in vitro and in vivo. In guinea pig cardiac ventricular membranes, LY249933, (RR), and (SR) potently displaced bound [3H]nitrendipine (Kd values = 2-6 nM). In isolated guinea pig right ventricular strips, LY249933 produced a small but significant increase in contraction, whereas (RR) substantially increased (-log EC50 (M) = 4.6 +/- 0.8) and (SR) decreased contraction (-log EC50 (M) = 4.1 +/- 0.8). In isolated canine cephalic vein, contracted with 80 mM KCl, an increase in contraction was produced by (RR), whereas relaxation was produced by LY249933 (-log EC50 (M) = 5.9 +/- 0.9) and (SR) (-log EC50 (M) = 6.0 +/- 0.7). At 20 mM KCl, (RR) increased, (SR) decreased, but LY249933 did not alter contraction. In anesthetized dogs, LY249933 (200 micrograms/kg/min, i.v.) increased dP/dt60, decreased heart rate, but did not change vascular resistance or rate pressure product. At the same dose, (RR) and (SR) both tended to increase dP/dt60 nonsignificantly, whereas (RR) increased and (SR) decreased vascular resistance. Both (RR) and (SR) tended to decrease heart rate nonsignificantly, whereas (RR) did not change and (SR) decreased rate pressure product. Thus, LY249933 produced potentially beneficial cardiovascular changes resulting from the combined actions of its (RR) and (SR) diastereomers that are postulated to be calcium agonist and antagonist, respectively.     

佛司可林类化合物对离体豚鼠气管条舒张作用的研究

目的研究佛司可林、异佛司可林、佛司可林G、J、A、I对磷酸组胺(His)、氯化乙酰胆碱(ACh)引起的离体豚鼠气管条收缩作用的影响。方法取豚鼠气管制成螺旋状气管条,用磷酸组胺、氯化乙酰胆碱诱发气管条收缩,按累积剂量法加入系列浓度的佛司可林、异佛司可林、佛司可林G、J、A、I,观察其对气管条收缩反应的舒张作用,记录各累积浓度下的量效曲线,计算解痉百分率。结果异佛司可林、佛司可林均能明显舒张由His、ACh引起的离体豚鼠气管条的收缩(P<0.01)。佛司可林G、J、A、I均能舒张由His引起的离体豚鼠气管条的收缩(P<0.01)。且随着剂量的增加,舒张作用也有所增强。结论佛司可林、异佛司可林、佛司可林G、J、A、I对His或ACh引起的离体豚鼠气管条的收缩均具有舒张作用。