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Concentration-response Curves (concentration-response + curve)
Selected AbstractsAbstract no.: 2 The influence of clozapine on tone of isolated bovine retinal arteriesFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 3 2005Koen Boussery Aims:, It has been suggested that the atypical antipsychotic drug clozapine might be helpful in the development of new antiglaucoma agents, since it combines lowering of the intra-ocular pressure after topical instillation with vasodilation. However, the vasoactive influence of clozapine on ocular blood vessels has never been analysed. Therefore, this study aimed to evaluate whether clozapine has direct vasodilatory effects in isolated bovine retinal arteries (BRA) and to characterise pharmacologically the mechanisms involved. Methods:, Retinal arteries were isolated from bovine eyes and mounted in a wire-myograph for isometric tension recording. Concentration-response curves were generated by cumulative addition of clozapine (1 nM to 10 ,M) to the organ bath. Results:, Clozapine elicited a concentration-dependent relaxation of the BRA. Removal of the endothelium of the BRA, inhibition of nitric oxide synthase with N, -nitro-L-arginine and inhibition of soluble guanylyl cyclase with ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one) significantly attenuated the clozapine-response, whereas cyclo-oxygenase inhibition with indomethacin had no influence. The Ca2+ channel activator Bay k8644, the nonselective 5-hydroxytryptamine receptor antagonist methiothepin and the adenosine receptor antagonist 8-(p-sulfophenyl) theophylline also failed in affecting the clozapine-induced relaxations. Conclusion:, Clozapine clearly relaxes bovine retinal arteries in a direct way. Endothelium-derived NO is involved in this response. However, prostanoids, calcium entry blockade, 5-HT7 receptor stimulation and adenosine receptor stimulation all seem to be not involved. [source] Vascular reactivity to angiotensin II alone or combined with a thromboxane A2 mimetic in the isolated perfused kidney of Lyon hypertensive ratsFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 1 2002Valérie Oréa The aim of this study was to evaluate whether thromboxane A2 -prostaglandin H2 (TP) receptor activation potentiates the renal vasoconstrictor effect of Angiotensin II (Ang II) in genetically hypertensive rats of the Lyon strain (LH). Concentration-response curves (CRCs) to Ang II (5 pM to 10 nM), to the specific TP receptor agonist U46619 (7.5,960 nM) and to a mixture of Ang II + U46619 (fixed molar ratio of 1 : 9) were obtained in single-pass perfused kidneys isolated from 8 week-old LH and low blood pressure (LL) control rats. Baseline vascular resistance was significantly increased in LH compared to LL kidneys. Comparison of the CRCs obtained for Ang II and U46619 showed that, in both strains, Ang II was about 100 times more potent than U46619. For both drugs, the pD2 or slope values did not differ among the two strains. Co-activation of TP receptors, analyzed with the method of Pöch and Holzmann, tended to potentiate the effects of Ang II in LH but not in LL kidneys. In conclusion, isolated perfused kidneys of LH rat did not exhibit an increased vascular sensitivity to acute infusion of Ang II or U46619 compared to control LL ones. In addition, the results suggest that the interactions between Ang II and TP receptor agonist may differ among the two strains. [source] Effect of human chorionic gonadotrophin on in vitro contractions of stimulated detrusor muscle strips of female ratsJOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 5 2009Diaa E. E. Rizk Abstract Aims:, We studied the effect of human chorionic gonadotrophin (hCG) on the in vitro detrusor muscle contractions in female rats. Methods:, Two adjacent detrusor muscle strips from the bladder dome of 18 female Wistar rats (230,250 gm) were mounted in an organ bath for the recording of isometric tension. Carbachol (10,9,10,3 M), ,,, methylene adenosine 5,-triphosphate (ATP) (10,9,10,3 M) and potassium chloride (KCl) (10,4,10,3 M) were applied (n = 6 × 3 groups). Concentration-response curves, before and after the addition of hCG (100 iu/mL) or oxybutynin (10,5 M) to either muscle strip, were compared. Results:, All curves were displaced to the right by hCG in a concentration-dependent manner with significant inhibition of contractions induced by carbachol (P < 0.001) and KCl (P = 0.016) but not those induced by ,,,-methylene ATP (P = 0.4). Estimated order of potency of inhibition was carbachol>KCl>,,,-methylene ATP. The overall inhibitory effect of hCG was significantly less than oxybutynin (P < 0.001). Conclusions:, hCG significantly inhibited in vitro detrusor contractions induced by depolarization (KCl) and cholinergic (carbachol) but not purinergic (,,,-methylene ATP) stimulation in a dose-dependent manner in female rats. [source] Parameters of drug antagonism: re-examination of two modes of functional competitive drug antagonism on intraocular musclesJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 8 2004Popat N. Patil There are two distinct kinetic functional pharmacological procedures by which the equilibrium affinity constant, KB, of a competitive reversible blocker is obtained. The classical method on an organ system requires the study of the parallel displacement of the agonist concentration-response curve in the presence of the blocker. In the second method, the agonist-evoked functional mechanical response is reduced to half by the blocker IC50 (the concentration required for 50% inhibition). In relation to these parameters the role of the ionization constant pKa and liposolubility log Pc or log D of blockers was examined. On the ciliary muscle from human eye, IC50/KB ratios for (±)-atropine, its quaternary analogue (±)-methylatropine, (-)-scopolamine, (±)-cyclopentolate, (-)-tropicamide, (±)-oxybutynin and pirenzepine were 15, 23, 4.4, 2.6, 1.66, 1.46 and 1.71, respectively. The ratios on the iris sphincter were comparable with those of ciliary muscle. When compared with large proportions of ionized molecules with water soluble properties of (±)-atropine and (±)-methylatropine, relatively high amounts of un-ionized and/or with greater partitioning of all other blockers in the lipoid barrier co-related well to low IC50/KB ratios, as predicted by the classical theory of competitive drug antagonism. It was hypothesized that due to receptor biophase access, the reduction of the mechanical response of the agonist by the highly ionized water-soluble antagonist at IC50 represented time-distorted "pseudo-equilibrium" estimation, where a higher concentration of the blocker was needed. On the other cholinergic effectors, like that of rat anococcygeus muscle or frog rectus abdominus muscle, IC50/KB ratios of respective blockers atropine or (+)-tubocurarine and hexamethonium were close to 1. Thus physicochemical properties, which affect the distribution coefficient log D and the tissue morphology (where asymmetric distribution of receptors may occur), appeared to be a critical factor in the analysis of the affinity parameters of the competitive reversible blocker. On the intraocular muscles, two functional pharmacological procedures for obtaining KB and IC50 values were not kinetically equivalent. [source] Mechanisms involved in the relaxant action of the ethanolic extract of propolis in the guinea-pig trachea in-vitroJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2002Niraldo Paulino This study examines the mechanisms by which the standardised ethanolic extract of propolis induces relaxation of the guinea-pig trachea in-vitro. In guinea-pig trachea with or without epithelium and contracted by histamine, the propolis extract caused reproducible and graded relaxation, with a mean EC50 value of 3.8 or 10.5 ,g mL,1 and Emax of 100%, respectively. The propolis extract-induced relaxation was markedly reduced (26 ± 9 and 96 ± 3%) when guinea-pig tracheas were exposed to Krebs solution containing elevated K+ in the medium (40 or 80 mM). Pre-incubation of guinea-pig tracheas with tetraethylamonium (100 mM) or with 4-aminopyridine (10 mM) reduced the propolis extract-induced relaxation by 31±10% and 28 ± 2%. Likewise, apamin (0.1 ,M), charybdotoxin (0.1 ,M) or iberiotoxin (0.1 ,M) caused marked inhibition of propolis extract-mediated relaxation in guinea-pig trachea (percentage of inhibition: 65 ± 3%, 60 ± 5% and 65 ± 9%, respectively). Also, glibenclamide (1 ,M) inhibited the relaxant response caused by the propolis extract by 57 ± 4%. ,-Conotoxin GIVA (0.1 ,M) or capsaicin (1 ,M) produced small but significant inhibition (30 ± 5% or 47 ± 7%, respectively) of the propolis extract-induced relaxation. The vasoactive intestinal peptide (VIP) antagonist D- P -CI-Phe6, Leu17[VIP] porcine (0.1 ,M) inhibited relaxation by 55 ± 5%, while propranolol (1 ,M) induced a parallel rightward displacement (about 20 fold) of the propolis extract concentration-response curve. Finally, the propolis extract-induced relaxation was inhibited by the nitric oxide synthase inhibitor L-NG -nitroarginine (L-NOArg, 100 ,M) (48 ± 6%), and by the soluble guanylate cyclase inhibitor methylene blue (10 ,M) (37 ± 6%), while the more selective soluble guanylate cyclase inhibitor 1H -[1,2,4]oxadiazolol[4,3-a]quinoxalin-1-one (ODQ, 1 ,M) produced only a parallel (about 3 fold) rightward displacement of the propolis extract concentration-response curve. Collectively, these results support the notion that the propolis extract-mediated relaxation in the guinea-pig trachea involves the release of nitric oxide, probably from sensory neurons, besides the activation of soluble guanylate cyclase and activation of Ca2+ - and ATP-sensitive K+channels. Furthermore, the stimulation of ,2 -adrenergic and VIP receptors also seems to account for its relaxant action. [source] Synthesis and pharmacological evaluation of 5-dialkylaminomethyl-2-amino-2-oxazolines as H1 -antagonistsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 7 2001J. J. Bosc New 5-dialkylaminomethyl-2-amino-2-oxazolines have been synthezised in two steps from the corresponding dialkylamines. They were evaluated in-vitro as H1 -antagonists. Compounds 1c, 1d and 1j significantly antagonized histamine-induced contraction of guinea-pig trachea with a rightward shift of the concentration-response curve to histamine. Compound 1f, 5-[(4-benzyl-1-piperidinyl)methyl]-2-amino-2-oxazoline, induced an increase in acetylcholine Emax (the maximal response to acetylcholine 10,3 M) and a shift to the left of the concentration-response curve. The lack of effect of this compound on histamine-induced contraction rules out a non-selective potentiation of the contraction mechanisms. Preliminary structure-activity results were reported partly based on physicochemical results. [source] A Polymorphism in the ,4 Nicotinic Receptor Gene (Chrna4) Modulates Enhancement of Nicotinic Receptor Function by EthanolALCOHOLISM, Issue 5 2003Christopher M. Butt Background: Several studies indicate that ethanol enhances the activity of ,4,2 nicotinic acetylcholine receptors (nAChR). Our laboratory has identified a polymorphism in the ,4 gene that results in the substitution of an alanine (A) for threonine (T) at amino acid position 529 in the second intracellular loop of the ,4 protein. Mouse strains expressing the A variant have, in general, greater nAChR-mediated 86Rb+ efflux in response to nicotine than strains with the T variant. However, the possibility of the polymorphism modulating the effects of ethanol on the 86Rb+ efflux response has not been investigated. Methods: We have used the 86Rb+ efflux method to study the acute effects of ethanol on the function of the ,4,2 nAChR in the thalamus in six different mouse strains. Experiments were also performed on tissue samples taken from F2 intercross animals. The F2 animals were derived from A/J mice crossed with a substrain of C57BL/6J mice that carried a null mutation for the gene encoding the ,2 nAChR subunit. Results: In strains carrying the A polymorphism (A/J, AKR/J, C3H/Ibg), coapplication of ethanol (10,100 mM) with nicotine (0.03,300 ,M) increased maximal ion flux when compared with nicotine alone with no effect on agonist potency. In contrast, ethanol had little effect on the nicotine concentration-response curve in tissue prepared from strains carrying the T polymorphism (Balb/Ibg, C57BL/6J, C58/J). Experiments with the F2 hybrids demonstrated that one copy of the A polymorphism was sufficient to produce a significant enhancement of nAChR function by ethanol (50 mM) in animals that were also ,2 +/+. Ethanol had no effect on nicotine concentration-response curves in T/T ,2 +/+ animals. Conclusions: The results suggest that the A/T polymorphism influences the initial sensitivity of the ,4,2 nAChR to ethanol. [source] Pharmacological characterization of a novel investigational antimuscarinic drug, fesoterodine, in vitro and in vivoBJU INTERNATIONAL, Issue 8 2008Peter Ney OBJECTIVE To investigate the primary pharmacology of fesoterodine (a novel antimuscarinic drug developed for treating overactive bladder) and SPM 7605 (its active metabolite, considered to be the main pharmacologically active principle of fesoterodine in man) against human muscarinic receptor subtypes, and to investigate in vitro and in vivo functional activity of these agents on the rat bladder compared with existing standard agents. MATERIALS AND METHODS The displacement of radioligand binding by fesoterodine, SPM 7605 and standard agents in membrane preparations of Chinese hamster ovary (CHO) cells expressing the different human muscarinic receptors (M1,M5) was characterized. Agonistic and antagonistic activities were studied using different CHO cell lines stably expressing the human recombinant muscarinic receptor subtypes. The effects of fesoterodine and SPM 7605 on isolated bladder strips contracted by carbachol or electrical field stimulation (EFS) were investigated. In vivo the effects of fesoterodine and SPM 7605 on micturition variables were assessed using continuous cystometry in conscious female Sprague-Dawley rats, and compared to those of oxybutynin and atropine. RESULTS In vitro SPM 7605 potently inhibited radioligand binding at all five human muscarinic receptor subtypes with equal affinity across all five. Fesoterodine had a similar balanced selectivity profile but was less potent than SPM 7605. Both substances were competitive antagonists of cholinergic agonist-stimulated responses in human M1-M5 cell lines and had a similar potency and selectivity profile to the radioligand-binding studies. In rat bladder strips, fesoterodine and SPM 7605 caused a rightward shift of the concentration-response curve for carbachol with no depression of the maximum, and concentration-dependently reduced contractions induced by EFS. The potency of both drugs was similar to that of atropine and oxybutynin. In the presence of the esterase inhibitor neostigmine, the concentration-response curve of fesoterodine was shifted to the right, suggesting that part of the activity was caused by metabolism to SPM 7605 by tissue enzymes. In vivo, low doses (0.01 mg/kg) of fesoterodine and SPM 7605 reduced micturition pressure and increased intercontraction intervals and bladder capacity, but did not affect residual volume. CONCLUSIONS Fesoterodine and its active metabolite, SPM 7605, are nonsubtype selective, competitive antagonists of human muscarinic receptors, but SPM 7605 has greater potency than the parent compound. Pharmacodynamic studies in the rat bladder in vitro confirm the competitive muscarinic antagonist profile of these agents in a native tissue preparation, and in vivo studies in the rat showed effects on bladder function consistent with a muscarinic antagonist profile. [source] Smooth muscle 5-HT2A receptors mediating contraction of porcine isolated proximal stomach stripsBRITISH JOURNAL OF PHARMACOLOGY, Issue 8 2002P Janssen The aim of this study was to characterize the 5-HT receptors involved in the 5-HT-induced contraction of longitudinal muscle (LM) strips of porcine proximal stomach. This was done in a classical organ bath set-up for isotonic measurement. The concentration-contraction curve to 5-HT was not modified by 5-HT3 and 5-HT4 receptor antagonism. Methysergide, ketanserin and mesulergine antagonized the curve to 5-HT. Concomitantly, increasing concentrations of ketanserin and mesulergine progressively revealed a biphasic nature of the 5-HT curve. Ketanserin antagonized the low-affinity receptor while it did not modify the high-affinity receptor. Tetrodotoxin did not influence the concentration-contraction curve to 5-HT neither in the absence nor presence of ketanserin, indicating that nerves are not involved. Ketanserin competitively antagonized the monophasic concentration-response curve to ,-Methyl-5-HT, yielding a Schild slope that was not significantly different from unity. After constraining the Schild slope to unity, a pKB estimate of 8.23±0.90 was obtained. This affinity estimate of ketanserin closely approximates previously reported affinities at 5-HT2A receptors. In the presence of ketanserin (0.1 ,M; exposing the high-affinity receptor), a wide range of 5-HT receptor antagonists covering all 5-HT receptors known, was tested. Only methysergide and ritanserin inhibited the response to 5-HT, thus expressing affinity for the high-affinity receptor. This did not reveal the identity of the receptor involved. It can be concluded that 5-HT induces pig proximal stomach (LM) contraction via 5-HT2A receptors located on smooth muscle. A ketanserin-insensitive phase of contractions could not be characterized between the actually known classes of 5-HT receptors with the pharmacological tools that were used. British Journal of Pharmacology (2002) 137, 1217,1224. doi:10.1038/sj.bjp.0704992 [source] Lack of critical involvement of endothelial nitric oxide synthase in vascular nitrate tolerance in miceBRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2002Ellen Q Wang We examined the direct involvement of endothelial nitric oxide (eNOS) in nitrate tolerance using eNOS knockout (eNOS (,/,)) and wild-type (eNOS (+/+)) mice. Animals were treated with either nitroglycerin (NTG, 20 mg kg,1s.c. 3×daily for 3 days) or vehicle (5% dextrose, D5W), and nitrate tolerance was assessed ex vivo in isolated aorta by vascular relaxation studies and cyclic GMP accumulation. Western blot was performed to determine NOS expression after NTG treatment. In both the eNOS (,/,) and (+/+) mice, the EC50 from NTG concentration-response curve was increased by ,3 fold, and vascular cyclic GMP accumulation was similarly decreased after NTG pretreatment. Vascular tolerance did not lead to changes in eNOS protein expression in eNOS (+/+) mice. These results indicate that vascular nitrate tolerance was similarly induced in eNOS (,/,) and (+/+) mice, suggesting that eNOS may not be critically involved in nitrate tolerance development in mice. British Journal of Pharmacology (2002) 135, 299,302; doi:10.1038/sj.bjp.0704532 [source] Anandamide-induced relaxation of sheep coronary arteries: the role of the vascular endothelium, arachidonic acid metabolites and potassium channelsBRITISH JOURNAL OF PHARMACOLOGY, Issue 5 2001J Grainger The effects of the endocannabinoid, anandamide, and its metabolically stable analogue, methanandamide, on induced tone were examined in sheep coronary artery rings in vitro. In endothelium-intact rings precontracted to the thromboxane A2 mimetic, U46619, anandamide (0.01 , 30 ,M) induced slowly developing concentration-dependent relaxations (pEC50 [negative log of EC50]=6.1±0.1; Rmax [maximum response]=81±4%). Endothelium denudation caused a 10 fold rightward shift of the anandamide concentration-relaxation curve without modifying Rmax. Methanandamide was without effect on U46619-induced tone. The anandamide-induced relaxation was unaffected by the cannabinoid receptor antagonist, SR 141716A (3 ,M), the vanilloid receptor antagonist, capsazepine (3 and 10 ,M) or the nitric oxide synthase inhibitor, L -NAME (100 ,M). The cyclo-oxygenase inhibitor, indomethacin (3 and 10 ,M) and the anandamide amidohydrolase inhibitor, PMSF (70 and 200 ,M), markedly attenuated the anandamide response. The anandamide transport inhibitor, AM 404 (10 and 30 ,M), shifted the anandamide concentration-response curve to the right. Precontraction of endothelium-intact rings with 25 mM KCl attenuated the anandamide-induced relaxations (Rmax=7±7%), as did K+ channel blockade with tetraethylammonium (TEA; 3 ,M) or iberiotoxin (100 nM). Blockade of small conductance, Ca2+ -activated K+ channels, delayed rectifier K+ channels, KATP channels or inward rectifier K+ channels was without effect. These data suggest that the relaxant effects of anandamide in sheep coronary arteries are mediated in part via the endothelium and result from the cellular uptake and conversion of anandamide to a vasodilatory prostanoid. This, in turn, causes vasorelaxation, in part, by opening potassium channels. British Journal of Pharmacology (2001) 134, 1003,1012; doi:10.1038/sj.bjp.0704340 [source] Abstract no.: 6 Endothelium-dependent relaxation by purinergic receptors in the aorta of apolipoprotein E-deficient miceFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 3 2005A. Korda Previously we reported that the acetylcholine-induced relaxation in the isolated aorta of apolipoprotein E-deficient (apoE -/- ) mice deteriorates after the development of atherosclerotic plaques, but remains normal in adjacent, plaque-free segments. The present study investigated the presence of functional purinergic receptors in the murine aorta, and whether their function changes before or after the development of atherosclerosis. Endothelium-dependent relaxation was measured in aorta segments of apoE -/- , C57BL6 (WT) and human apoAI-overexpressing apoE -/- mice (apoAI/apoE -/- ) on regular chow. Rings were isometrically contracted with phenylephrine to 50% of their maximum force before performing cumulative concentration-response curves to different nucleotides or their stable analogues. After the functional study, the cross-sectional area of the plaque was determined in every segment. The nucleotides induced complete (UTP, UDP, ATP) or partial (ADP) relaxation that was abolished by endothelial cell removal or nitric oxide (NO) synthase inhibition. The responses pointed to the presence of functional P2y1, P2y2 or P2y4 receptors on endothelial cells. RT-PCR confirmed the presence of P2y1 and P2y4 mRNA in the aorta of WT mice. Nucleotide responses were unaltered in lesion-free apoE -/- mice (5 months). However, in atherosclerotic segments of apoE -/- mice (18 months), the relaxation to ATP was impaired compared to age-matched WT controls (maximum amplitude (Emax) 25 ± 14%, n = 6 vs. 90 ± 3%, n = 5, P < 0.01). A similar defect was seen for the stable analogue ATP-gamma-S (Emax 36 ± 12% vs. 86 ± 3%, P < 0.01). Atherosclerotic apoE -/- segments were less sensitive to the NO donor spermineNONOate (pD2 6.74 ± 0.18) than WT segments (7.25 ± 0.20), but maximum relaxation was unaltered. In non-atherosclerotic aorta segments of the same apoE -/- mice all relaxation responses remained normal and were not different from WT. Strong negative correlations (P < 0.001) existed between lesion size and the Emax for ATP (rs = ,0.82) and ATP-gamma-S (rs = ,0.73) in apoE -/- mice. ApoAI overexpression improved the purinergic responses (Emax ATP 64 ± 9%, ATP-gamma-S 64 ± 10%, n = 5) and these were not different from WT (P > 0.05). An analysis of covariance with plaque size as covariate suggested that this benefit was secondary to the strongly reduced plaque formation in apoAI/apoE -/- mice. It is concluded that functional P2 y receptors are present on murine aortic endothelium. Furthermore, endothelium-dependent purinergic relaxation declines after plaque development. This deterioration involves decreased bioavailability of NO rather than enhanced ATP degradation. The defect is, however, not systemic since the responses remain unaltered in plaque-free segments of atherosclerosis-prone apoE -/- mice. [source] Evidence for an endothelium-derived hyperpolarizing factor in the superior mesenteric artery from rats with cirrhosisHEPATOLOGY, Issue 5 2000Eric Barriere In cirrhosis, in splanchnic arteries, endothelium-dependent relaxation may persist even if overactive nitric oxide synthase (NOS) and cyclooxygenase (COX) are inhibited. In normal arteries, a significant endothelium-dependent relaxation to acetylcholine persists after NOS/COX inhibition. This relaxation is caused by smooth muscle cell (SMC) membrane hyperpolarization, which is sensitive to a combination of the potassium channel blockers apamin and charybdotoxin, and is mediated by an endothelium-derived hyperpolarizing factor (EDHF). The aim of this study was to detect EDHF and evaluate its pathophysiologic role in isolated superior mesenteric arteries from cirrhotic rats. Arterial rings were obtained and exposed to Nw -nitro-L-arginine (L-NNA, a NOS inhibitor) and indomethacin (a COX inhibitor). Acetylcholine-induced membrane potential responses and concentration-response curves to the relaxant of acetylcholine were obtained with and without apamin plus charybdotoxin. Acetylcholine-induced responses were measured in certain rings from endothelium-denuded arteries. Contractions caused by the ,1 -adrenoceptor agonist phenylephrine were obtained in cirrhotic and normal rings with and without apamin and charybdotoxin. Significant acetylcholine-induced, endothelium-dependent, apamin- and charybdotoxin-sensitive, SMC membrane hyperpolarization and relaxation were found. An apamin- and charybdotoxin-sensitive hyporesponsiveness to the contractile action of phenylephrine was found in cirrhotic rings. In conclusion, in cirrhotic rats, in the superior mesenteric artery exposed to NOS/COX-inhibitors, an EDHF exists that may replace NOS/COX products to induce endothelium-dependent arterial relaxation. [source] Quantitative comparison of the cytocidal effect of seven macrolide antibiotics on human periodontal ligament fibroblastsJOURNAL OF PERIODONTAL RESEARCH, Issue 4 2002Noriko Maizumi The cytocidal effect of seven macrolide antibiotics on human periodontal ligament fibroblasts (Pel cells) was studied. Pel cells were exposed for 48 h to erythromycin (EM), clarithromycin (CAM), roxithromycin (RXM), azithromycin (AZM), josamycin (JM), midecamycin (MDM), and rokitamycin (RKM), and allowed to form colonies. The cytocidal effect of the macrolides was measured as a decrease in colony-forming efficiency and was found to increase with the concentration. To obtain a quantitative measure of the cytocidal effect, the LD50, i.e. the concentration that decreases colony-forming efficiency 50% relative to control cells, was extrapolated from the concentration-response curves. The rank of the macrolides according to their cytocidal effect (LD50) was RKM > RXM > CAM > AZM > JM > MDM , EM. RKM, RXM, CAM, AZM, and JM were at least 1.7,12.2 times more cytocidal than MDM or EM. When extrapolated from the concentration-response curves, the relative survival of the Pel cells exposed to each of the macrolides at the MIC90 concentrations for periodontopathic bacteria was estimated to be: ,,53.8% for RKM, , 92.7% for RXM, , 94.6% for CAM, , 97.1% for AZM, and , 86.2% for EM. The effect of the antibiotics on the mRNA expression of alkaline phosphatase (ALP) and type I procollagen (COL) was examined in Pel cells exposed for 48 h to RXM, CAM, AZM, and EM, which exhibited strong, moderate, and weak cytocidal activity. The constitutive levels of both ALP and COL mRNA were retained in cells exposed to RXM at ,3 ,M, CAM at ,10 ,M, and AZM or EM at ,3 ,M. The MIC90 against periodontopathic bacteria is ,4.8 ,M for RXM, 5.3 ,M for CAM, 2.7 ,M for AZM, and 21.8 ,M for EM. These results suggest that topical administration of CAM or AZM to the gingival crevice at their MIC90 concentration for periodontopathic bacteria would have little adverse effect on the growth and differentiation of the periodontal ligament. It is important to note, however, that these findings have yet to be extrapolated to in vivo conditions. [source] Antagonistic effects of selective ,1 -adrenoceptor antagonists MDL73005EF and tamsulosin and partial agonists clonidine and tizanidine in rat thoracic aorta and rabbit iliac arteryJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 1 2001Mitsutoshi Satoh The antagonistic effects of MDL73005EF and tamsulosin and partial agonists clonidine and tizanidineat rat thoracic aorta and rabbit iliac artery ,1 -adrenoceptors were investigated in this study. Selective ,1 -adrenoceptor antagonists MDL73005EF and tamsulosin dose-dependently shifted the concentration-response curves for noradrenaline to the right. Schild plots of the results obtained from the inhibition by MDL73005EF (pA2 8.30 ± 0.04) and tamsulosin (pA2 10.51 ± 0.06) of noradrenaline yielded a straight line with a slope of unity in rat thoracic aorta. The slopes of Schild plots obtained from the inhibition by MDL73005EF and tamsulosin of noradrenaline were significantly different from unity in rabbit iliac artery. Schild plots of the results obtained from the inhibition by clonidine and tizanidine of noradrenaline yielded a straight line with a slope of unity in rat thoracic aorta (pA2 7.08 ± 0.04 and 7.32 ± 0.04, respectively). These results suggest that ,1D -adrenoceptors play a significant role in the ,1 -adrenoceptor-agonist-induced contraction of rat thoracic aorta and rabbit iliac artery, and that clonidine and tizanidine interact with the ,1D -adrenoceptor subtype as competitive antagonists in rat thoracic aorta. [source] A Polymorphism in the ,4 Nicotinic Receptor Gene (Chrna4) Modulates Enhancement of Nicotinic Receptor Function by EthanolALCOHOLISM, Issue 5 2003Christopher M. Butt Background: Several studies indicate that ethanol enhances the activity of ,4,2 nicotinic acetylcholine receptors (nAChR). Our laboratory has identified a polymorphism in the ,4 gene that results in the substitution of an alanine (A) for threonine (T) at amino acid position 529 in the second intracellular loop of the ,4 protein. Mouse strains expressing the A variant have, in general, greater nAChR-mediated 86Rb+ efflux in response to nicotine than strains with the T variant. However, the possibility of the polymorphism modulating the effects of ethanol on the 86Rb+ efflux response has not been investigated. Methods: We have used the 86Rb+ efflux method to study the acute effects of ethanol on the function of the ,4,2 nAChR in the thalamus in six different mouse strains. Experiments were also performed on tissue samples taken from F2 intercross animals. The F2 animals were derived from A/J mice crossed with a substrain of C57BL/6J mice that carried a null mutation for the gene encoding the ,2 nAChR subunit. Results: In strains carrying the A polymorphism (A/J, AKR/J, C3H/Ibg), coapplication of ethanol (10,100 mM) with nicotine (0.03,300 ,M) increased maximal ion flux when compared with nicotine alone with no effect on agonist potency. In contrast, ethanol had little effect on the nicotine concentration-response curve in tissue prepared from strains carrying the T polymorphism (Balb/Ibg, C57BL/6J, C58/J). Experiments with the F2 hybrids demonstrated that one copy of the A polymorphism was sufficient to produce a significant enhancement of nAChR function by ethanol (50 mM) in animals that were also ,2 +/+. Ethanol had no effect on nicotine concentration-response curves in T/T ,2 +/+ animals. Conclusions: The results suggest that the A/T polymorphism influences the initial sensitivity of the ,4,2 nAChR to ethanol. [source] KATP -mediated Vasodilation is Impaired in Obese Zucker RatsMICROCIRCULATION, Issue 6 2008BENJAMIN L. HODNETT ABSTRACT Objective: Skeletal muscle blood flow during exercise is impaired in obesity. We tested the hypothesis that the attenuated vasodilation in skeletal muscle arterioles of obese Zucker rats (OZR) is due to altered KATP channel-mediated vasodilation. Materials and Methods: KATP channel function was determined in isolated skeletal muscle arterioles in response to the KATP opener cromakalim (0.1,10 , M) during normal myogenic tone and , -adrenergic-mediated tone (0.1 , M phenylephrine). The spinotrapezius muscle was prepared and the vasodilatory responses to muscle stimulation or iloprost (0.028,2.8 , M) were observed before and after the application of the KATP inhibitor, glibenclamide (10 , M). Channel subunit expression was determined by using western blot analyses. Results: Cromakalim concentration-response curves were shifted in OZR as compared to lean controls. OZR exhibited impaired functional and iloprost-induced vasodilation as compared to the lean controls. Glibenclamide inhibited the functional and iloprost-induced dilation in the lean rats with no effects in the obese animals. Channel subunit expression was similar in femoral arteries. Conclusion:The impaired functional vasodilation in the OZR is associated with altered KATP channel sensitivity. [source] ,1D -Adrenoceptors mediate nerve and agonist-evoked contractions in mouse vas deferens: evidence obtained from knockout technologyAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 2-3 2008S. Bexis Summary 1 It has been demonstrated that nerve-evoked contractions of the rat vas deferens involve ,1D -adrenoceptors. Definitive evidence for a similar ,1D -adrenoceptor-mediated response in mouse vas deferens has been more difficult to obtain. In this study, we have used ,1D -adrenoceptor knockout (,1D -KO) mice to aid in the pharmacological characterization. 2 Mouse whole vas deferens was stimulated with a single pulse every 5 min. Once a stable response had been obtained, vehicle or antagonist was administered cumulatively at 5-min intervals and a response to stimulation obtained 5 min later. Cumulative concentration-response curves were also obtained for noradrenaline. 3 In vas deferens from ,1D -KO mice, the contractile response to low concentrations of noradrenaline and the contractile response to a single stimulus were significantly reduced as compared to wild type (WT). 4 The ,1D -adrenoceptor selective antagonist, BMY 7378, produced a concentration-dependent inhibition of single pulse-evoked contractions of vas deferens from WT and ,1D -KO mice. BMY 7378 was significantly less potent in inhibiting stimulation-evoked contractions in vas deferens from ,1D -KO mice. 5 It is concluded that ,1D -adrenoceptors mediate a component of nerve- and agonist-evoked contractions of the vas deferens of WT mice. [source] Characterization of the 5-hydroxytryptamine receptors mediating contraction in the pig isolated intravesical ureterBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2003Medardo Hernández This study was designed to investigate the effect of 5-hydroxytryptamine (5-HT) and to characterize the 5-HT receptors involved in 5-HT responses in the pig intravesical ureter. 5-HT (0.01,10 ,M) concentration-dependently increased the tone of intravesical ureteral strips, whereas the increases in phasic contractions were concentration-independent. The 5-HT2 receptor agonist ,-methyl 5-HT, mimicked the effect on tone whereas weak or no response was obtained with 5-CT, 8-OH-DPAT, m -chlorophenylbiguanide and RS 67333, 5-HT1, 5-HT1A, 5-HT3 and 5-HT4 receptor agonists, respectively. 5-HT did not induce relaxation of U46619-contracted ureteral preparations. Pargyline (100 ,M), a monoaminooxidase A/B activity inhibitor, produced leftward displacements of the concentration-response curves for 5-HT. 5-HT-induced tone was reduced by the 5-HT2 and 5-HT2A receptor antagonists ritanserine (0.1 ,M) and spiperone (0.2 ,M), respectively. However, 5-HT contraction was not antagonized by cyanopindolol (2 ,M), SDZ,SER 082 (1 ,M), Y-25130 (1 ,M) and GR 113808 (0.1 ,M), which are respectively, 5-HT1A/1B, 5-HT2B/2C, 5-HT3, and 5-HT4 selective receptor antagonists. Removal of the urothelium did not modify 5-HT-induced contractions. Blockade of neuronal voltage-activated sodium channels, ,-adrenergic receptors and adrenergic neurotransmission with tetrodotoxin (1 ,M), phentolamine (0.3 ,M) and guanethidine (10 ,M), respectively, reduced the contractions to 5-HT. However, physostigmine (1 ,M), atropine (0.1 ,M) and suramin (30 ,M), inhibitors of cholinesterase activity, muscarinic- and purinergic P2 -receptors, respectively, failed to modify the contractions to 5-HT. These results suggest that 5-HT increases the tone of the pig intravesical ureter through 5-HT2A receptors located at the smooth muscle. Part of the 5-HT contraction is indirectly mediated via noradrenaline release from sympathetic nerves. British Journal of Pharmacology (2003) 138, 137,144. doi:10.1038/sj.bjp.0705019 [source] Combined blockade of endothelin-1 and thromboxane A2 receptors against postischaemic contractile dysfunction in rat heartsBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2001Pius S Hornstein Endothelin-1 (ET-1) may play a role in myocardial ischaemia/reperfusion injury because both the release and vasoconstrictor effect of ET-1 are increased after ischaemia. Since the increased vasoconstrictor effect of ET-1 can be mediated by ET-1-induced release of thromboxane A2 (TXA2), the aim of this study was to test whether combined blockade of ET and TXA2 receptors protects the coronary flow, contractile performance, and cardiac energy metabolism during ischaemia and reperfusion. Bosentan (antagonist for ETA and ETB receptors, 1 ,M based on concentration-response curves of ET-1), SQ 30,741 (antagonist of TXA2 receptors, 0.1 ,M), or the combination thereof was administered to isolated perfused rat hearts undergoing 15 min of global ischaemia and 60 min of reperfusion. Neither bosentan or SQ 30,741 alone, nor the combination thereof, improved the incomplete postischaemic recovery of coronary flow, left ventricular developed pressure, phosphocreatine, or ATP. However, they attenuated ischaemia-induced acidosis but this did not translate into a measurable effect on haemodynamic or metabolic variables. Thus, combined blockade of ET and TXA2 receptors does not protect the coronary flow, contractile performance, and cardiac energy metabolism during ischaemia and reperfusion in isolated perfused rat hearts. This finding suggests that neither ET-1 nor ET-1-induced release of TXA2 play a major role in the postischaemic recovery of the cardiac contractile function and energy metabolism. British Journal of Pharmacology (2001) 132, 234,240; doi:10.1038/sj.bjp.0703773 [source] Collar-induced elevation of mRNA and functional activity of 5-HT1B receptor in the rabbit carotid arteryBRITISH JOURNAL OF PHARMACOLOGY, Issue 8 2000Inge S Geerts Hypersensitivity to serotonin (5-HT) develops in rabbit collared carotid arteries. Previous data demonstrated the involvement of 5-HT1 -like receptors which are not active in normal carotid arteries. This study investigated the interaction in the rabbit carotid artery between 5-HT and a moderate tone as this can uncover functional 5-HT1 -like receptors. Furthermore, the expression of messenger RNA (mRNA) and protein of 5-HT1B, 5-HT1D and 5-HT2A receptors was addressed. Silicone collars were placed around the carotid arteries of male New Zealand White rabbits for 1 week. Rings from inside (=collar) and outside (=sham) the collar were either mounted in isolated organ baths for isometric force measurements or frozen in liquid nitrogen to isolate total RNA or proteins which were subsequently analysed by respectively reverse transcriptase-polymerase chain reaction and Western blot analysis. In sham and collared rings concentration-response curves (CRC's) to 5-HT were monophasic. Only in collared segments the presence of a 5-HT2A antagonist (spiperone or ketanserin, 0.1 ,M) revealed a biphasic CRC which was even more pronounced when a moderate tone was induced by KCl pointing to functional 5-HT1 -like receptors. The rabbit carotid artery constitutively expressed 5-HT1B and 5-HT2A mRNA, not 5-HT1D mRNA. Manipulation of the carotid artery increased the 5-HT1B mRNA level. Collar placement raised it even further. The 5-HT2A mRNA level remained unchanged. All the anti-5-HT receptor antibodies tested resulted in variable, non specific patterns with multiple bands. In conclusion, collar placement elevates mRNA expression and activity of the 5-HT1B receptor in the rabbit carotid artery. British Journal of Pharmacology (2000) 131, 1723,1731; doi:10.1038/sj.bjp.0703732 [source] Effects of vitamin K1 supplementation on vascular responsiveness and oxidative stress in a rat femoral osteotomy modelCELL BIOCHEMISTRY AND FUNCTION, Issue 5 2007Arda Tasatargil Abstract The main function of vitamin K1 is to act a co-factor for gamma-glutamyl carboxylase. However, it has also been shown to lessen oxidative stress. This study was aimed to evaluate the effect of vitamin K1 supplementation on vascular responsiveness and oxidative status in rats that underwent femoral osteotomy. Twenty-four male rats were divided into three groups to serve as sham, osteotomy and vitamin K1 groups. Indices of oxidative stress (catalase), and oxidative damage (malondialdehyde) were analysed in erythrocytes. In order to evaluate vascular reactivity, concentration-response curves to phenylephrine, angiotensin II, 5-hydroxytryptamine, bradykinin and histamine were constructed. The findings of this study clearly show that oxidative stress clearly increases after femoral osteotomy in rats. Also, this operation causes a significant depression in vascular responsiveness to contracting agents and endothelium-dependent vasodilators. However, vitamin K1 supplementation prevents vascular hyporeactivity by reducing oxidative stress and may represent a novel approach during osteotomy healing. Copyright © 2006 John Wiley & Sons, Ltd. [source] EFFECT OF THE PHOSPHODIESTERASE 5 INHIBITORS SILDENAFIL, TADALAFIL AND VARDENAFIL ON RAT ANOCOCCYGEUS MUSCLE: FUNCTIONAL AND BIOCHEMICAL ASPECTSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 4 2009Haroldo A Toque SUMMARY 1The anococcygeus muscle is part of the erectile machinery in male rodents. Phosphodiesterase (PDE) 5 inhibitors enhance and prolong the effects of cGMP, which has a key role in penile erection. The aim of the present study was to provide a functional and biochemical comparison of the three PDE5 inhibitors, namely sildenafil, tadalafil and vardenafil, in the rat anococcygeus muscle. 2Muscle strips were mounted in 4 mL organ baths and isometric force recorded. Levels of cGMP were measured using an enzyme immunoassay kit. Western blots were used to determine PDE5 protein expression. 3The PDE5 inhibitors concentration-dependently relaxed carbachol-precontracted anococcygeus muscle; however, vardenafil was more potent (pEC50 = 8.11 ± 0.05) than sildenafil (7.72 ± 0.06) or tadalafil (7.69 ± 0.05). Addition of NG -nitro- l -arginine methyl ester (100 µmol/L) or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (10 µmol/L) to the organ baths caused significant rightward shifts in concentration,response curves for all PDE5 inhibitors. 4Sildenafil, tadalafil and vardenafil (all at 0.1 µmol/L) caused leftward shifts in the glyceryl trinitrate (GTN) concentration-response curves (by 4.0-, 3.7- and 5.5-fold, respectively). In addition, all three PDE5 inhibitors significantly potentiated relaxation responses to both GTN (0.01,10 µmol/L) and electrical field stimulation (EFS; 1,32 Hz), with vardenafil having more pronounced effects. 5All three PDE5 inhibitors reduced EFS-evoked contractions in a concentration-dependent manner over the concentration range 0.001,1 µmol/L. There were no significant differences between the effects of the three PDE5 inhibitors. 6Vardenafil (0.01,0.1 µmol/L) was more potent in preventing cGMP degradation in vitro than sildenafil (0.01,0.1 µmol/L) and tadalafil (0.01,0.1 µmol/L). 7Under control conditions, the expression of PDE5 was higher in the anococcygeus muscle than in the corpus cavernosum. 8In conclusion, PDE5 inhibitors enhance exogenous and endogenous nitric oxide-mediated relaxation in the rat anococcygeus muscle. The potency of vardenafil was greater than that of either sildenafil or tadalafil. [source] | ||||||||||