Differential sensitivities of the sphincter of Oddi and gallbladder to cholecystokinin in the guinea pig: their role in transsphincteric bile flow.

Cholecystokinin (CCK) is considered to simply contract the gallbladder and relax the sphincter of Oddi with meals. In this study, we examined this hypothesis by investigating the action of CCK on the sphincter of Oddi and gallbladder of the guinea pig. The experimental design used an in vitro preparation of the sphincter of Oddi to measure contraction of the circular muscle. CCK increased tone in both the gallbladder and the sphincter of Oddi in a concentration-dependent manner. The normalized concentration-response curves for CCK, however, revealed that the gallbladder had a greater sensitivity to CCK (ED50 7 nM) than the sphincter of Oddi (ED50 22 nM; p < 0.01). Conversely, the sphincter was more sensitive to bethanechol than was the gallbladder. When the sphincter of Oddi was stimulated maximally with CCK in the presence of atropine (10(-6) M) or tetrodotoxin (10(-6) M), the contractile response was significantly reduced (p < 0.05) although not abolished. Conversely, atropine completely abolished the responses to bethanechol (10(-3) M) and transmural field stimulation (70 V, 10 Hz, 1 ms, for 20 s). Transmural field stimulation of the sphincter that had been precontracted with CCK (26 nM) caused a transient, initial relaxation followed by contraction. Pretreatment with atropine augmented the duration of this relaxation, which could be completely abolished by tetrodotoxin. Thus, CCK contracts the sphincter of Oddi in the guinea pig by a direct (myogenic) and a neural (likely cholinergic) mechanism. Relaxation of the sphincter of Oddi also occurs in the guinea pig via noncholinergic inhibitory nerves.(ABSTRACT TRUNCATED AT 250 WORDS)     

胍丁胺对离体大鼠主动脉张力的影响及其受体机制

采用离体血管环灌流方法,观察了胍丁胺（agmatine,Agm)对大鼠胸主动脉张力的影响,并探讨其受体机制,实验结果如下：（1）在苯肾上腺素PE,10^-6mol/L)引起血管预收缩的 基础上,Agm(10^-7-10^-2mol/L)剂量依赖性地舒张大鼠胸主动脉。（2）上述舒张反应在去除内皮和应用NOS抑制剂N^-G-mnitro-L-arginine methyl ester(L-NAME,0.5mmol/L)后依然存在,提示Agm的舒血管作用为非内皮依赖性,并无NO的参与。（3）在高Ca^2 (3mmol/L)引起血管预收缩的基础上,Agm也可剂量依赖性地舒张大鼠主动脉。（4）预先应用α2－肾上腺素能受体（α2－adrenergic receptor,α2－AR）和咪唑啉受体（IR）阻断剂idazoxan(10^-4mol/L)则可完全阻断Agm的上述作用。（5）应用α2－AR拮抗剂yohimbine(10^-4mol/L)可部分阻断Agm对大鼠主动脉的舒张反应,以上结果表明,Agm对大鼠主动脉血管的舒张作用是由α2－AR和IR共同介导。     

异丙肾上腺素和氨甲酰胆碱对心肌延迟后除极的影响

用乙酰毒毛旋花子甙元2.0×10~(-7)mol/L,在绵羊心室浦肯野纤维产生延迟后除极(DAD)为实验模型,观察异丙肾上腺素与氨甲酰胆碱对DAD的影响。异丙肾上腺素1.0—3.0×10~(-8)mol/L能增加DAD幅值,为剂量依赖性,并可诱发出触发型心律失常。氨甲酰胆碱2.0×10~(-6)mol/L单独作用对DAD幅值无影响,然而在异丙肾上腺素增强DAD幅值或产生触发型心律失常后,同样浓度的氨甲酰胆碱能显著地减小DAD幅值以及消除触发型心律失常。但氨甲酰胆碱对由高钙、氨茶碱和组胺等所增加的DAD幅值却无抑制作用。以上结果表明,氨甲酰胆碱能拮抗异丙肾上腺素引起的DAD增强作用,可能与M受体的激活,并继而降低膜上β受体激活时所提高的腺苷酸环化酶活性有关。     

Investigation of the vasorelaxant effects of 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1) and diethylamine/nitric oxide (DEA/NO) on the human radial artery used as coronary bypass graft

The radial artery (RA) is used as a spastic coronary bypass graft. This study was designed to investigate the mechanism of vasorelaxant effects of YC-1 (3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole), a nitric oxide (NO)-independent soluble guanylate cyclase (sGC) activator, and DEA/NO (diethylamine/nitric oxide), a NO-nucleophile adduct, on the human RA. RA segments (n = 25) were obtained from coronary artery bypass grafting patients and were divided into 3-4 mm vascular rings.Using the isolated tissue bath technique, the endothelium-independent vasodilatation function was tested in vitro by the addition of cumulative concentrations of YC-1 (10-10 to 3 x 10-7 mol/L) and DEA/NO (10-8 to 3 x 10-5 mol/L) following vasocontraction by phenylephrine in the presence or absence of 10-5 mol/L ODQ (1H-(1,2,4)oxadiazole(4,3-a)quinoxalin-1-one), the selective sGC inhibitor, 10-7 mol/L iberiotoxin, a blocker of Ca2+-activated K+ channels, or 10-5 mol/L ODQ plus 10-7 mol/L iberiotoxin. We also evaluated the effect of YC-1 and DEA/NO on the cGMP levels in vascular rings obtained from human radial artery (n = 6 for each drug). YC-1 (10-10 to 3 x 10-7 mol/L) and DEA/NO (10-8 to 3 x 10-5 mol/L) caused the concentration-dependent vasorelaxation in RA rings precontracted with phenylephrine (10-5 mol/L) (n = 20 for each drug). Pre-incubation of RA rings with ODQ, iberiotoxin, or ODQ plus iberiotoxin significantly inhibited the vasorelaxant effect of YC-1, but the inhibitor effect of ODQ plus iberiotoxin was significantly more than that of ODQ and iberiotoxin alone (p < 0.05). The vasorelaxant effect of DEA/NO almost completely abolished in the presence of ODQ and iberiotoxin plus ODQ, but did not significantly change in the presence of iberiotoxin alone (p > 0.05). The pEC50 value of DEA/NO was significantly lower than those for YC-1 (p < 0.01), with no change Emax values in RA rings. In addition, YC-1-stimulated RA rings showed more elevation in cGMP than that of DEA/NO (p < 0.05). These findings indicate that YC-1 is a more potent relaxant than DEA/NO in the human RA. The relaxant effects of YC-1 could be due to the stimulation of the sGC and Ca2+-sensitive K+channels, whereas the relaxant effects of DEA/NO could be completely due to the stimulation of the sGC. YC-1 and DEA/NO may be effective as vasodilator for the short-term treatment of perioperative spasm of coronary bypass grafts.     

非洲爪蟾卵母细胞GABAB和GABAc受体介导的电流反应

实验应用双电极电压箝技术,在具有滤泡膜的非洲爪蟾(Xenopuslaevis)卵母细胞上记录到γ-氨基丁酸(γ-aminobutyricacid,GABA)-激活电流。此GABA-激活电流的特点及有关GABA受体类型的研究和分析如下(1)在35.5%(55/155)的受检细胞外加GABA可引起一慢的浓度依赖性的外向电流。(2)GABAA受体的选择性拮抗剂bicuculline(10     

The effects of ruthenium tetraammine compounds on vascular smooth muscle.

The time course of the relaxation effect induced by a single dose (3 x 10(-6) mol/L) of trans-[Ru(NH3)4L(NO)]3+ (L=nic, 4-pic, py, imN, P(OEt)3, SO(3)(2-), NH3, and pz) species and sodium nitroprusside (4 x 10(-9) mol/L) was studied in aortic rings without endothelium and pre-contracted with noradrenaline (1 x 10(-6) mol/L). All the compounds induced a relaxing effect in the aortic rings, but the intensity and time of relaxation were different. Only the species where L=py, 4-pic, and P(OEt)3 were able to induce 100% (99-100%) of the relaxing effect during the assay. trans-[Ru(NH3)4(L)(NO)]3+ (L=SO(3)(2-) and NH3) showed the lowest relaxing effect (36 and 37%, respectively) when compared with the other compounds. Relationship was observed between the time corresponding to half of the maximum relaxation intensity observed and, respectively, k-NO, E0'[Ru(NO)]3+/[Ru(NO)]2+ in trans-[Ru(NH3)4(L)(NO)]3+ species and E0'Ru(III)/Ru(II) in trans-[Ru(NH3)4(L)(H2O)]3+ ions. These relationships strongly suggested that the NO liberation from the reduced nitrosyl complexes was responsible for the observed relaxation.     

Chemiluminescence determination of fluoroquinolone antibiotics using a soluble manganese (IV)-sulphite system.

The reaction of soluble manganese (IV) with sulphite in acidic condition was found to elicit weak chemiluminescence (CL). The CL signal was remarkably enhanced in the presence of three fluoroquinolones, viz. norfloxacin, ofloxacin and ciprofloxacin. Based on these observations, a new flow-injection CL method was developed for the determination of these fluoroquinolones. The method allows determination in the range 5.0 x 10(-8)-1.0 x 10(-6) mol/L for norfloxacin, 1.0 x 10(-7)-8.0 x 10(-6) mol/L for ofloxacin and 1.0 x 10(-7)-3.0 x 10(-5) mol/L for ciprofloxacin, with detection limits of 3 x 10(-8) mol/L, 5 x 10(-8) mol/L and 3 x 10(-8) mol/L, respectively. The method was applied to the determination of fluoroquinolones in pharmaceutical preparations.     

慢性缺氧对大鼠肺动胍内皮依赖性舒张反应及CGMP含量的影响

This experiment was designed to investigate whether chronic hypoxia affect rat pulmonary artery (PA) endothelium-dependent relaxation and the content of cGMP in PA. Both ACh and ATP could induce endothelium-dependent relaxation of PA, not prevented by indomethacin, but completely abolished by methylene blue. These results indicated that vasodilatation of PA induced by both ACh and ATP is mediated by EDRF (endothelium-derived relaxing factor). Chronic hypoxia significantly depressed PA endothelium-dependent relaxation. The percent relaxation of IPPA and EPPA by 10(-6) mol/L ACh was 61.3% and 59.2% of those in control, and the percent relaxation of IPPA and EPPA by 1.8 x 10(-5) mol/L ATP was 64.9% and 55.3% respectively of the control. Chronic hypoxia also depressed SNP-induced endothelium-independent relaxation. Chronic hypoxia significantly decreased the content of cGMP in PA. The basic level of cGMP was 51.9 +/- 5.7 (n = 14) in hypoxia group and 84.9 +/- 9.7 (n = 14) pmol/g wet wt. in control group (P less than 0.01). After treatment of PA with ACh (10(-7) mol/L), the content of cGMP was 91.4 +/- 7.3 (n = 5) pmol/g wet wt. in hypoxic group and 240.8 +/- 30.6 (n = 5) pmol/g wet wt. in control group (P less than 0.01). Our data suggest that chronic hypoxia might depress rat pulmonary artery endothelium-dependent relaxation through the inhibition of soluble guanylate cyclase in vascular smooth muscle cells.     

Calcium-independent tacrine-induced relaxation of rat gastric corpus smooth muscles

Tacrine, a non-competitive reversible acetylcholinesterase and butyrylcholineserase inhibitor, caused a concentration-dependent tonic contraction of gastric smooth muscle preparations in the concentration range 1 x 10(-7) mol/L - 1 x 10(-5) mol/L, whereas concentrations higher than 2 x 10(-5) mol/L induced a biphasic effect; a short-time contraction was followed by a prolonged relaxation. To shed some light on the mechanism underlying this untypical relaxation, the amplitude of mechanical reactions caused by tacrine were compared with those of tacrine in the presence of atropine, ipratropium, metrifonate, TTX, nifedipine, D-600, caffeine, apamin, and charybdotoxin. The results obtained revealed that the relaxation was neither cholinergic in nature, nor mediated by the influence of the drug on intramural neuronal structures. It was not influenced by processes inducing changes in cytosolic Ca2+ levels. This assumption was confirmed by experiments with permeabilized muscle preparations that were pre-contracted in a solution with pCa 5.5. Tacrine relaxed the smooth muscles in spite of the constant intracellular Ca2+ concentration resulting from the permeabilization. These findings argue that tacrine at concentrations higher than 2 x 10(-5) mol/L has a desensitizing effect on the contractile apparatus of gastric corpus smooth muscle preparations towards Ca2+.     

Study of the catalytic effect of PAR on the luminol-potassium ferricyanide reaction using a flow-injection chemiluminescence method.

We discovered that 4-(2-pyridylazo) resorcinol (PAR) has a strong catalytic effect on luminol-potassium ferricyanide chemiluminescence (CL). Results indicated that the chemiluminescence intensities at maximum light emission were linearly corrected with the concentration of PAR over the range 1.0 x 10(-5)-1.0 x 10(-7) mol/L. A detection limit of 5.7 x 10(-8) mol/L for PAR was achieved. It was found that some metal ions strongly affected this catalytic reaction. Based on this finding, the luminol-potassium ferricyanide-PAR reaction was developed for the determination of metal ions. The detection limits (S/N = 3) for Ni2+, Cr3+, Zn2+, Co2+ and Mn2+ were determined to be 1.0 x 10(-9) mol/L, 5.0 x 10(-9) mol/L, 5.0 x 10(-8) mol/L, 1.0 x 10(-9) mol/L and 1.0 x 10(-8) mol/L, respectively. In addition, the relative standard deviation values for these metal ion assays were in the range 0.82-2.72% (n = 6).     

The effect of zinc on endothelium-dependent relaxation of blood-vessels and on the ultrastructure of endothelial cells under immobilization stress

We investigated the effects of zinc on the function and ultrastructure of endothelial cells in the case of a 48-day immobilization stress provoked in Chinchilla male rabbits (n=18) by placing them in metal hutches. Half of those rabbits (n=9) received an daily oral supplement of zinc at a dose of 0.3 mg/kg body weight (in the form of zinc acetate). The control rabbits had no intervention and received no supplement of zinc. The relaxation of smooth muscles from thoracic aorta as mediated by acetylcholine at concentrations from 10(-8) mol/L to 10(-4) mol/L was determined in isometric regime. Responses were expressed as the percentage of relaxation to prostaglandin F2alpha (2.10(-5) mol/L)-induced precontraction. The ultrastructure of endothelial cells was evaluated by electron microscopy. The level of total cholesterol and zinc in the blood serum was determined by an enzymatic method and by atomic absorption spectrometry, respectively. In rabbits receiving no zinc supplement, the relaxation of smooth muscles under the influence of acetylcholine concentrations from 10(-8) mol/L to 10(-4) mol/L was significantly (P < 0.05-0.01) lower than in rabbits receiving a supplement of zinc and lower than in control rabbits. Also, in the rabbits not receiving the zinc supplement, the level of total blood serum cholesterol was increased, but the concentration of zinc decreased. In rabbits receiving the zinc supplement, the contractility of the smooth muscles effected by acetylcholine did not change as compared with control rabbits, and we found a normal structure of endothelial cells and a normal level of total cholesterol and zinc in their blood serum. Thus, zinc played an important role in the maintenance of the normal ultrastructure and function of the endothelial cells in the rabbits receiving zinc under immobilization stress.     

Voltage-dependent Vmax blockade in Na+-dependent action potentials after beta 1- and H2-receptor stimulation in mammalian ventricular myocardium

In isolated papillary muscles of guinea pigs, the influence of isoproterenol, histamine, theophylline, and phenylephrine on the maximal rate of rise (Vmax) of Na+-dependent action potentials and on isometric contractile force was studied under rested state conditions. Isoproterenol (1 x 10(-7) mol/L), histamine (2 x 10(-5) mol/L), and theophylline (2 x 10(-3) mol/L) shifted the voltage dependence of Vmax into the hyperpolarizing direction and, consequently, led to a voltage-dependent Vmax blockade. The alpha-adrenoceptor agonist phenylephrine, on the other hand, proved to be ineffective in depressing Vmax. The beta-receptor blocker pindolol (4 x 10(-6) mol/L) or the H2-receptor blocker cimetidine (4 x 10(-5) mol/L) abolished the inhibitory effects of isoproterenol and histamine, respectively, and caused Vmax to return to the initial control value. A concentration-response relationship analysis at -65 mV revealed that isoproterenol exerted only a weak inhibitory effect on Vmax compared with its positive inotropic action. The IC50 value of the former effect amounted to approximately 5 x 10(-6) mol/L, but the EC50 value of the latter effect was 4 x 10(-8) mol/L. It is, therefore, concluded that, in physiologically relevant concentrations, beta-adrenergic agonists are unlikely to significantly modulate Na+-dependent excitability even in partially depolarized myocardium.     

Involvement of nitric oxide in endothelium-dependent arterial relaxation by leptin

Leptin is a polypeptide, mainly produced in white adipose tissue, and increases sympathetic nerve activity. A few studies investigated leptin's effect on peripheral vessels. We examined the vasorelaxant effects of human leptin on rat arteries. Arterial rings were precontracted with 1 x 10(-6) mol/l of phenylephrine, and leptin was superfused. Leptin relaxed phenylephrine-precontracted arterial rings in a dose-dependent manner. ED50 was calculated to 8.4 microg/ml. Removal of endothelium abolished the effects of leptin. Indomethacin (1 x 10(-5) mol/l) did not affect the vasorelaxation by leptin, whereas 1 x 10(-4) mol/l of N(omega)-nitro-L-arginine methyl ester (L-NAME) completely suppressed it. The inhibition was antagonized by 1 x 10(-4) mol/l of L-arginine. Leptin normally relaxed arterial rings during superfusion of K channel blockers, including 3 x 10(-5) mol/l of glibenclamide, 1 x 10(-6) of mol/l apamin, and 5 x 10(-7) mol/l of charybdotoxin. Low Cl(-) solution (8. 3 mmol/l) inhibited leptin-induced relaxation, but endothelium-independent vasodilatation by nitroprusside was not impaired at low Cl(-) solution. These results suggest that arterial relaxation by leptin is mediated by nitric oxide released from endothelium, and Cl(-) plays an important role in leptin-induced nitric oxide release.     

Influence of curcumin, capsaicin, and piperine on the rat liver drug-metabolizing enzyme system in vivo and in vitro

The effect of dietary supplementation of spice-active principles, curcumin (0.2%), capsaicin (0.015%), and piperine (0.02%) on the activities of the liver drug-metabolizing enzyme system was examined. All the 3 dietary spice principles significantly stimulated the activity of aryl hydroxylase. A synergistic action of dietary curcumin and capsaicin with respect to stimulating the activity of aryl hydroxylase was also evidenced when fed in combination. The activity of N-demethylase essentially remained unaffected by dietary curcumin, capsaicin, or their combination, but was significantly lowered as a result of piperine feeding. Uridine dinucleotide phosphate (UDP)-glucuronyl transferase activity was decreased by dietary piperine and the combination of curcumin and capsaicin. NADPH-cytochrome c reductase activity was significantly decreased by dietary piperine. The levels of hepatic microsomal cytochrome P450 and cytochrome b5 were not influenced by any of the dietary spice-active principles. These spice-active principles were also examined for their possible in vitro influence on the components of the hepatic drug-metabolizing enzyme system in rat liver microsomal preparation. Piperine significantly decreased the activity of liver microsomal aryl hydroxylase activity when included in the assay medium at 1 x 10(-6) mol/L, 1 x 10(-5) mol/L, and 1x 10(-4) mol/L level. Lowered activity of N-demethylase was observed in presence of capsaicin or piperine at 1 x 10(-6) mol/L in the assay medium. Hepatic microsomal glucuronyl transferase activity was significantly decreased in vitro by addition of capsaicin or piperine. Capsaicin and piperine brought about significant decrease in liver microsomal cytochrome P450 when included at 1 x 10(-6) mol/L and 1 x 10(-5) mol/L, the effect being much higher in the case of piperine. The results suggested that whereas the 3 spice principles have considerable similarity in structure, piperine is exceptional in its influence on the liver drug-metabolizing enzyme system. The study also indicated that a combination of curcumin and capsaicin does not produce any significant additive effect on the liver drug-metabolizing enzyme system.     

心肌α1—肾上腺素受体激动对豚鼠心室乳头肌的影响

The alpha-adrenoceptor agonist phenylephrine (5.0 x 10(-6) mol/L) was used to stimulate myocardial alpha-adrenoceptors of the guinea-pig ventricular papillary muscle, and changes of transmembrane action potential and contractile force of the muscle were observed. The alpha 1-adrenoceptor blocker prazosin (5.0 x 10(-7) mol/L) and the alpha 2-adrenoceptor blocker yohimbine (5.0 x 10(-7) mol/L) were used to determine which subtype of alpha-adrenoceptor is responsible for the effects. The beta-adrenoceptor blocker propranolol (1.0 x 10(-6) mol/L) was used throughout the experiment. The results show that the myocardial alpha 1-adrenoceptor stimulation (1) increases the contractile force of the guinea-pig ventricular papillary muscle, (2) prolongs the time to peak contractile force while the duration of relaxation is not altered, (3) prolongs the fast response action potential duration, and (4) increases the maximal rate of depolarization during the phase 0 of the slow response action potential. It is suggested that the electrophysiological and positive inotropic effects of myocardial alpha 1-adrenoceptor stimulation might be due to the activation of the slow inward current and an increase in Ca2+ influx.     

Endothelium-dependent relaxation by tetraoctylammonium ions in rat isolated aortic rings

Quaternary ammonium ions are common pharmacological blockers of K+ channels. This study examined the vasorelaxant effect of tetraoctylammonium ions (TOA+) in rat isolated aortic rings. TOA+ caused a concentration-dependent transient relaxation of endothelium-intact tissues. Pretreatment with NG-nitro-L-arginine methyl ester (L-NAME, 3x10(-5) M) or methylene blue (3 x 10(-6) M) or removal of the endothelium abolished the TOA+-induced relaxation. L-arginine (10(-3) M ) partially antagonized the effect of L-NAME. Glibenclamide (3x10(-6) M), charybdotoxin (CTX, 10(-7) M), indomethacin (10(-5) M), or atropine (3x10(-6) M) had no effect. Both TOA+ (10(-5) M)- and acetylcholine (ACh, 10(-5) M)-induced increase in tissue content of cyclic GMP was significantly attenuated by NG-nitro-L-arginine (L-NNA, 10(-4) M) and abolished in endothelium-denuded arteries. These results indicate that TOA+ induced endothelium-dependent relaxation which is likely mediated through nitric oxide but not other endothelium-derived factors. This relaxant action seems unique for TOA+ since other quaternary ammonium ions did not cause nitric oxide-dependent relaxation.     

Tetrodotoxin-resistant relaxation to transmural nerve stimulation in canine saphenous veins: a possible neural origin

Transmural nerve stimulation following sympathetic (guanethidine 10(-4) mol/L, phenoxybenzamine 2 X 10(-5) mol/L, propanolol 2 X 10(-6) mol/L) and muscarinic blockade (atropine 5 X 10(-5) mol/L) produces a relaxatory response in canine saphenous veins contracted with prostaglandin F2 alpha. This relaxatory response was shown previously to be resistant to tetrodotoxin. Transmural nerve stimulation (10 V, 1.0 ms) was applied as intermittent trains of stimuli of 30 s duration at frequencies of 1-32 Hz. The veins showed a frequency dependent relaxation (maximum 2.65 +/- 0.20 g). The stimulations were repeated in the presence of lignocaine (10(-3) mol/L), apamin (10(-8) mol/L), ascorbic acid (10(-4) mol/L), or catalase (50 micrograms/mL). The relaxatory response was unaffected by apamin, scorpion toxin, superoxide dismutase, ascorbic acid, and catalase (p greater than 0.05). However, lignocaine (10(-3) mol/L) reduced significantly the relaxatory response to transmural nerve stimulation in this preparation (p less than 0.05). In a separate group of veins, lignocaine (10(-3) mol/L)l abolished the contractile response to transmural nerve stimulation with little effect upon the contractile response to exogenous noradrenaline and the relaxatory responses to isoprenaline and sodium nitrite. These findings support the proposition that the nonadrenergic, noncholinergic tetrodotoxin-resistant relaxatory response observed with transmural nerve stimulation in the canine saphenous vein is mediated by a neural mechanism.     

Kappa- but not delta-opioid receptors mediate effects of ischemic preconditioning on both infarct and arrhythmia in rats

Two series of experiments were performed in the isolated perfused rat heart to determine the role of kappa- and delta-opioid receptors (OR) in cardioprotection of ischemic preconditioning (IP). In the first series of experiments, it was found that IP with two cycles of 5-min regional ischemia followed by 5-min reperfusion each reduced infarct size induced by 30-min ischemia, and the ameliorating effect of IP on infarct was attenuated with blockade of either 5 x 10(-6) mol/l nor-binaltorphimine (nor-BNI), a selective kappa-OR antagonist, or 5 x 10(-6) mol/l naltrindole (NTD), a selective delta-OR antagonist. The second series showed that U50,488H, a selective kappa-OR agonist, or D-Ala(2)-D-leu(5)-enkephalin (DADLE), a selective delta-OR agonist, dose dependently reduced the infarct size induced by ischemia, which mimicked the effects of IP. The effect of 10(-5) mol/l U50,488H on infarct was significantly attenuated by blockade of protein kinase C (PKC) with specific PKC inhibitors, 5 x 10(-6) mol/l chelerythrine or 8 x 10(-7) mol/l calphostin C, as well as by blockade of ATP-sensitive K(+) (K(ATP)) channels with blockers of the channel, 10(-5) mol/l glibenclamide or 10(-4) mol/l 5-hydroxydecanoate. IP also reduced arrhythmia induced by ischemia. Nor-BNI, but not NTD, attenuated, while U50,488H, but not DADLE, mimicked the antiarrhythmic action of IP. In conclusion, the present study has provided first evidence that kappa-OR mediates the ameliorating effects of IP on infarct and arrhythmia induced by ischemia, whereas delta-OR mediates the effects only on infarct. Both PKC and K(ATP) channels mediate the effect of activation of kappa-OR on infarct.     

Endothelium-dependent contraction induced by nicotine in isolated canine basilar artery--possible involvement of a thromboxane A2 (TXA2) like substance

The present experiments were undertaken to determine whether the response to nicotine in the isolated canine cerebral artery is endothelium-dependent. Changes in the tension of arterial strips were recorded isometrically. Removal of the endothelium was carried out by gentle rubbing, and confirmed by scanning electron microscopy. Rubbing procedure did not affect the contractile response of the strips to serotonin. Treatment of unrubbed strips with nicotine (10(-4)M) caused a transient contraction. This response was abolished by removal of endothelium and attenuated by hexamethonium (5 x 10(-6)M) and atropine (10(-6)M). The nicotine-induced contraction was attenuated also by aspirin (5 x 10(-5)M), a cyclooxygenase inhibitor, OKY-046 (5 x 10(-5)M), a thromboxane A2 (TXA2) synthetase inhibitor and ONO-3708 (5 x 10(-9)M), a TXA2 antagonist. These results indicate that the nicotine-induced contraction in canine cerebral artery is endothelium-dependent, and suggest that the endothelium-derived contracting factor (EDCF) in the nicotine-induced response is a TXA2-like substance.