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Burnstock G, Ralevic V. Purinergic signaling and blood vessels in health and disease. Pharmacol Rev 2013; 66:102-92. [PMID: 24335194 DOI: 10.1124/pr.113.008029] [Citation(s) in RCA: 227] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Purinergic signaling plays important roles in control of vascular tone and remodeling. There is dual control of vascular tone by ATP released as a cotransmitter with noradrenaline from perivascular sympathetic nerves to cause vasoconstriction via P2X1 receptors, whereas ATP released from endothelial cells in response to changes in blood flow (producing shear stress) or hypoxia acts on P2X and P2Y receptors on endothelial cells to produce nitric oxide and endothelium-derived hyperpolarizing factor, which dilates vessels. ATP is also released from sensory-motor nerves during antidromic reflex activity to produce relaxation of some blood vessels. In this review, we stress the differences in neural and endothelial factors in purinergic control of different blood vessels. The long-term (trophic) actions of purine and pyrimidine nucleosides and nucleotides in promoting migration and proliferation of both vascular smooth muscle and endothelial cells via P1 and P2Y receptors during angiogenesis and vessel remodeling during restenosis after angioplasty are described. The pathophysiology of blood vessels and therapeutic potential of purinergic agents in diseases, including hypertension, atherosclerosis, ischemia, thrombosis and stroke, diabetes, and migraine, is discussed.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London NW3 2PF, UK; and Department of Pharmacology, The University of Melbourne, Australia.
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2
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ANDO T, KUME H, URATA Y, TAKAGI K. Effects of JTV-506, a new K+
channel activator, on airway smooth muscle contraction and systemic blood pressure. Clin Exp Allergy 2006. [DOI: 10.1111/j.1365-2222.1997.tb01200.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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3
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Goldschmidt M, Landzberg BR, Frishman WH. Nicorandil: a potassium channel opening drug for treatment of ischemic heart disease. J Clin Pharmacol 1996; 36:559-72. [PMID: 8844437 DOI: 10.1002/j.1552-4604.1996.tb04219.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Nicorandil is the first oral potassium channel activating drug to be used for the treatment of symptomatic coronary artery disease. It appears to relax vascular smooth muscle through membrane hyperpolarization via increased transmembrane potassium conductance and, like nitrates, through an increase in intracellular cyclic GMP. In addition, nicorandil, in a nitrate-like manner, dilates normal and stenotic coronary arteries and reduces both ventricular preload and afterload. In contrast to nitrates, however, nicorandil does not appear to cause tolerance with long-term administration. In placebo and comparison clinical trials, nicorandil has demonstrated some efficacy and safety in patients with both stable and vasospastic angina pectoris, and it was found to be a myocardial protective agent in animal studies. The antianginal activity of nicorandil, however, is relatively short lived after dosing, which will necessitate the development of extended-release formulations of the drug.
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Affiliation(s)
- M Goldschmidt
- Department of Medicine, University of Washington School of Medicine, Seattle, USA
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4
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Yamashita T, Masuda Y, Shikada KI, Tanaka S. Cardiovascular Pharmacology of NIP-121, A Potassium Channel Opener. ACTA ACUST UNITED AC 1995. [DOI: 10.1111/j.1527-3466.1995.tb00215.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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5
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Longman SD, Hamilton TC. Potassium channel activator drugs: mechanism of action, pharmacological properties, and therapeutic potential. Med Res Rev 1992; 12:73-148. [PMID: 1535674 DOI: 10.1002/med.2610120202] [Citation(s) in RCA: 111] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- S D Longman
- SmithKline Beecham Pharmaceuticals, Medicinal Research Centre, Harlow, Essex, United Kingdom
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6
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Ishibashi T, Hamaguchi M, Imai S. 2-Nicotinamidoethyl acetate (SG-209) is a potassium channel opener: structure activity relationship among nicorandil derivatives. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1991; 344:235-9. [PMID: 1658666 DOI: 10.1007/bf00167224] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The mechanism of the vasodilating action of 2-nicotinamidoethyl acetate (SG-209), a derivative of nicorandil, was examined in the isolated rabbit aorta. Comparison was made using 2-nicotinamidoethyl alcohol (SG-86) and 2-nicotinamidoethyl nitrate (nicorandil; SG-75) to reveal any structure-activity relationships. SG-209 and nicorandil caused concentration-dependent relaxation in preparations precontracted with phenylephrine (10(-7) mol/l), while SG-86 produced a relaxation only at very high concentrations. The pD2 values (-log[EC50]) of SG-209 and nicorandil were 3.59 +/- 0.07 and 5.95 +/- 0.10, respectively. The vasorelaxant activity of nicorandil was associated with significant increases in cyclic GMP content, while that of SG-209 was not. Methylene blue (10(-5) mol/l) attenuated the relaxant effect of nicorandil, but had no effect on that of SG-209. Furthermore, the relaxant effect of nicorandil was not affected by glibenclamide (10(-5) mol/l), whilst the relaxant effect of SG-209 was abolished by this compound. In the presence of methylene blue (10(-5) mol/l), however, glibenclamide (10(-5) mol/l) attenuated the relaxant effect of higher concentrations of nicorandil (greater than or equal to 10(-5) mol/l). These results indicate that the relaxant effect of SG-209 is mostly if not exclusively due to the activation of potassium channels, while this action contributes to the vasodilating action of nicorandil only at higher concentrations.
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Affiliation(s)
- T Ishibashi
- Department of Pharmacology, Niigata University School of Medicine, Japan
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7
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Masuda Y, Arakawa C, Yamashita T, Miyajima M, Shigenobu K, Kasuya Y, Tanaka S. Potassium channel opening properties of a novel compound, NIP-121, cromakalim and nicorandil in rat aorta and portal vein. Eur J Pharmacol 1991; 195:323-31. [PMID: 1831135 DOI: 10.1016/0014-2999(91)90472-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A novel compound, NIP-121, cromakalim and nicorandil caused concentration-dependent relaxation of rat aortas precontracted with 30 mM KCl, with pEC50 (M) values of 8.2, 7.1 and 5.5, respectively. At 60 mM KCl, the vasorelaxation induced by NIP-121 or cromakalim was almost abolished whereas that induced by nicorandil remained. In preparations precontracted with prostaglandin F2 alpha(PGF2 alpha) (10(-5) M), glibenclamide (10(-7) M) and phentolamine (3 x 10(-6), 3 x 10(-5) M) antagonized the relaxation induced by NIP-121 and cromakalim but not that induced by nicorandil. Methylene blue (10(-5) M) showed antagonistic effects against the vasorelaxation induced by nicorandil but not that induced by NIP-121. NIP-121 (10(-7), 10(-6) M) and cromakalim (10(-6), 10(-5) M) significantly increased the 86Rb+ efflux rate in rat aorta. The three compounds inhibited the frequency of spontaneous contractions of the rat portal vein (pIC30; NIP-121 = 8.0, cromakalim = 7.1 and nicorandil = 4.9); glibenclamide and phentolamine antagonized the effects of these compounds. In conclusion, NIP-121 is a more potent K+ channel opener than cromakalim in these tissues. Nicorandil apparently behaves as a K+ channel opener in the rat portal vein, but the vasorelaxation may involve some other mechanisms, such as generation of cyclic GMP.
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Affiliation(s)
- Y Masuda
- Shiraoka Research Station of Biological Science, Nissan Chemical Industries, Ltd., Saitama, Japan
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8
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Kamata K, Miyata N, Kasuya Y. Functional changes in potassium channels in aortas from rats with streptozotocin-induced diabetes. Eur J Pharmacol 1989; 166:319-23. [PMID: 2529128 DOI: 10.1016/0014-2999(89)90076-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The effects of K+ activators on aortas from control and diabetic rats were examined. The concentration-response curves for the relaxant effects of cromakalim were shifted to the right in diabetic rats. The relaxation responses of diabetic aortas to nicorandil did not differ from those of the controls. Treatment with oxyhemoglobin significantly reduced the relaxation responses to nicorandil in aortas from diabetic rats. It appears that the activity of aortic potassium channels is reduced in diabetic rats.
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Affiliation(s)
- K Kamata
- Department of Pharmacology, School of Pharmacy, Hoshi University, Tokyo, Japan
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9
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Obianime AW, Dale MM. The effect of relaxants working through different transduction mechanisms on the tonic contraction produced in rat aorta by 4 beta-phorbol dibutyrate. Br J Pharmacol 1989; 97:647-56. [PMID: 2758236 PMCID: PMC1854588 DOI: 10.1111/j.1476-5381.1989.tb12000.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
1. We have examined the effects of a range of smooth muscle relaxants on the maintained contractions produced in rat aortic rings by the protein kinase C activator, 4 beta-phorbol dibutyrate; these effects were compared with those on the contraction induced by the selective alpha 1-adrenoceptor agonist, methoxamine. The phorbol ester, at 0.3 microM, gave a sustained contraction which was, on average, of approximately the same magnitude as the maximum contraction produced by methoxamine, 10 microM. 2. The beta-adrenoceptor agonist, isoprenaline (0.01-1 microM) caused a dose-related relaxation of the methoxamine-induced contraction but had no effect on the contraction induced by the phorbol ester. 3. An activator of adenylate cyclase, forskolin (0.01-1 microM) produced a dose-related relaxation of the methoxamine-induced contraction and at 0.01-10 microM caused relaxation of the contraction induced by the phorbol ester. Similar results were obtained with the potassium channel activator, cromakalim (0.001-10 microM). 4. An activator of guanylate cyclase, sodium nitroprusside (0.001-100 microM) caused a dose-related relaxation of both the methoxamine-induced and the phorbol ester-induced contraction, being more effective on the former than on the latter. Similar results were obtained with enprofylline (1-1000 microM). 5. Methoxamine (10 nM-100 microM), given cumulatively, caused a dose-related contractile response. Pretreatment with isoprenaline (1 microM), enprofylline (10 microM) and nicorandil (1 microM) resulted in partial decrease of the subsequent response to methoxamine, while nicorandil (10 microM), forskolin (1 microM), sodium nitroprusside (10 microM) and cromakalim (1 microM) totally abolished it. 6. The phorbol ester, given cumulatively, caused increasing contraction in the concentration range 30 nM-10 microM. Pretreatment with forskolin (1 microM), sodium nitroprusside (10 microM), isoprenaline (1 microM), enprofylline (10 microM), nicorandil (1 microM or 10 microM), or cromakalin (1 microM or 10 microM), resulted in partial decrease of the subsequent response to 4 beta-phorbol dibutyrate. 7. These results are discussed in the light of the suggestion that protein kinase C may have a role in the 'latch-bridge' phase of smooth muscle contraction, and that inappropriate activation of protein kinase C may contribute to the pathogenesis of hypertension and other conditions involving vasospasm.
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Affiliation(s)
- A W Obianime
- Department of Pharmacology, University College, London
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10
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Eltze M. Glibenclamide is a competitive antagonist of cromakalim, pinacidil and RP 49356 in guinea-pig pulmonary artery. Eur J Pharmacol 1989; 165:231-9. [PMID: 2528466 DOI: 10.1016/0014-2999(89)90717-6] [Citation(s) in RCA: 88] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The relaxant effect of cromakalim (BRL 34915), pinacidil and RP 49356 (N-methyl-2-(3-pyridyl)-tetrahydro-thiopyran-2-carbothioamide-1-ox ide) on the sustained contractions induced by 20 mM KCl were compared with the effects of nicorandil. The preparation used was vascular smooth muscle of phenoxybenzamine-treated pulmonary artery rings from reserpinized guinea-pigs. Cromakalim, pinacidil, RP 49356 and nicorandil relaxed the tissues with -log EC50 values of 6.78, 6.12, 6.02 and 5.46, respectively. The inhibitory effect of cromakalim, pinacidil and RP 49356, but not of nicorandil, was competitively antagonized by glibenclamide (10(-7)-3 X 10(-6) M), yielding uniform pA2 values of 7.17-7.22 against all three relaxant drugs. The order of potency of other K+ channel blocking agents for the inhibition of vasorelaxation by cromakalim, pinacidil and RP 49356 was procaine greater than 4-aminopyridine greater than tetraethylammonium. The mainly competitive type of inhibition of the RP 49356-induced response was more comparable to that with pinacidil than with cromakalim. The relaxation caused by nicorandil was only attenuated by a high concentration of 4-aminopyridine or tetraethylammonium but was markedly antagonized by methylene blue (3 X 10(-6)-10(-5) M) and potentiated by M & B 22948 (3 X 10(-6)-10(-5) M). These results suggest that the vascular relaxation caused in guinea-pig pulmonary artery by cromakalim, pinacidil and RP 49356 is mediated through the same glibenclamide-sensitive K+ channel whereas the major mechanism for the effect of nicorandil seems to involve stimulation of guanylate cyclase.
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Affiliation(s)
- M Eltze
- Department of Pharmacology, Byk Gulden Pharmaceuticals, Konstanz, F.R.G
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11
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Hamilton TC, Weston AH. Cromakalim, nicorandil and pinacidil: novel drugs which open potassium channels in smooth muscle. GENERAL PHARMACOLOGY 1989; 20:1-9. [PMID: 2523328 DOI: 10.1016/0306-3623(89)90052-9] [Citation(s) in RCA: 208] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- T C Hamilton
- Beecham Pharmaceuticals Research Division, Medicinal Research Centre, Harlow, Essex, U.K
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12
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Nakao K, Okabe K, Kitamura K, Kuriyama H, Weston AH. Characteristics of cromakalim-induced relaxations in the smooth muscle cells of guinea-pig mesenteric artery and vein. Br J Pharmacol 1988; 95:795-804. [PMID: 2974740 PMCID: PMC1854238 DOI: 10.1111/j.1476-5381.1988.tb11707.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
1. The effects of cromakalim (BRL 34915) on the smooth muscle cells of guinea-pig mesenteric artery and vein were investigated with microelectrode and tension recording methods. 2. Cromakalim (greater than 10 microM) produced membrane hyperpolarization with an increase in ionic conductance. The hyperpolarization occurred to a greater extent and lasted longer in the vein than in the artery. 3. The hyperpolarization induced by cromakalim in mesenteric vein comprised two components, one of which was Mn sensitive. In mesenteric artery, the hyperpolarization was relatively insensitive to Mn. 4. From the current-voltage relationship measured from arterial smooth muscle membranes, the reversal potential of cromakalim was estimated to be -80 mV. The cromakalim-induced hyperpolarization was not modified in Na- or Cl-deficient solution. 5. In both mesenteric artery and vein, cromakalim relaxed tissues precontracted with high K with (below 40 mM) or without (above 40 mM) hyperpolarization of the membrane. 6. In the mesenteric artery, action potentials evoked by electrical stimulation ceased before the generation of hyperpolarization. 7. Cromakalim produced a cross-desensitization with nicorandil on the evoked membrane hyperpolarization in mesenteric artery. 8. It is concluded that the relaxing actions of cromakalim result from the hyperpolarization which follows the opening of Ca-dependent K channels. The inhibition of a voltage-dependent Ca current may also be involved in this inhibitory effect.
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Affiliation(s)
- K Nakao
- Department of Pharmacology, Faculty of Medicine, Kyushu University, Fukuoka, Japan
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13
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Wilson C, Coldwell MC, Howlett DR, Cooper SM, Hamilton TC. Comparative effects of K+ channel blockade on the vasorelaxant activity of cromakalim, pinacidil and nicorandil. Eur J Pharmacol 1988; 152:331-9. [PMID: 2851450 DOI: 10.1016/0014-2999(88)90728-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Three agents with K+ channel blocking activity, procaine, 4-aminopyridine (4-AP) and tetraethylammonium (TEA), were tested for inhibition of vasorelaxation and 86Rb+ efflux induced by cromakalim (BRL 34915), pinacidil and nicorandil in rabbit isolated mesenteric artery. The potency order for inhibition of vasorelaxation was procaine greater than 4-AP greater than TEA and for inhibition of efflux was procaine = 4-AP greater than TEA. The K+ channel blockers did not discriminate between cromakalim, pinacidil or nicorandil on efflux but demonstrated preferential inhibition of vasorelaxation to cromakalim greater than pinacidil greater than nicorandil. In addition, the maximum response to cromakalim was depressed but that to pinacidil and nicorandil was not. The results confirm the role of K+ channel activation in vasorelaxation to cromakalim, pinacidil and nicorandil, but suggest that additional mechanisms may be involved for pinacidil and, in particular, for nicorandil.
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Affiliation(s)
- C Wilson
- Beecham Pharmaceuticals Research Division, Medicinal Research Centre, Essex, U.K
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14
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Boyle JP, Davies JM, Foster RW, Good DM, Kennedy I, Small RC. Spasmogen action in guinea-pig isolated trachealis: involvement of membrane K+-channels and the consequences of K+-channel blockade. Br J Pharmacol 1988; 93:319-30. [PMID: 2451965 PMCID: PMC1853808 DOI: 10.1111/j.1476-5381.1988.tb11437.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
1. Acetylcholine (ACh), histamine, prostaglandin E2 and potassium chloride (KCl) each evoked concentration-dependent spasm of guinea-pig isolated trachealis treated with indomethacin (2.8 microM). 2. Neither tetraethylammonium (TEA; 0.1-10 mM) nor procaine (0.1-10 mM) potentiated these spasmogens. Indeed, procaine (10 mM) depressed the log concentration-effect curves of all the spasmogens while TEA (1-10 mM) caused some depression of the log concentration-effect curve of prostaglandin E2. 3. Intracellular electrophysiological recording was performed in trachealis bathed by normal Krebs solution or by Krebs solution containing 2.8 microM indomethacin. In either medium the majority of trachealis cells exhibited spontaneous electrical slow waves while some cells were electrically quiescent. In either medium the spasmogenic effects of ACh (1 mM) and histamine (0.2 mM) were accompanied by depolarization and abolition of slow wave discharge. In many cases the record of membrane potential subsequently exhibited noise which incorporated fast, hyperpolarizing transients. 4. In the absence and presence of indomethacin, TEA (10 mM) and procaine (5 mM) markedly reduced the membrane noise and hyperpolarizing transients evoked by ACh or histamine without augmenting the evoked tension. 5. It is concluded that slow wave discharge does not depend on prostaglandin synthesis. The membrane noise and hyperpolarizing transients evoked by ACh and histamine represent the opening of membrane K+-channels. While such K+-channel opening may offset spasmogen-induced depolarization it does not moderate the evoked tension.
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Affiliation(s)
- J P Boyle
- Department of Physiological Sciences, Medical School, University of Manchester
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15
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Ito Y, Obara K. Effects of nicorandil on isolated smooth muscle cells from guinea-pig taenia caeci. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. C, COMPARATIVE PHARMACOLOGY AND TOXICOLOGY 1988; 89:45-52. [PMID: 2894272 DOI: 10.1016/0742-8413(88)90143-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
1. The effects of nicorandil on guinea-pig taenia caeci were investigated with the use of isolated smooth muscle cells and glycerin-treated muscle fiber bundles. 2. Nicorandil inhibited high K-, Ca2+- and carbachol-induced contractions in a dose-dependent manner without affecting 45Ca fluxes in isolated cells. 3. Nicorandil had no effect on ATP-induced contraction of glycerin-treated muscle fiber bundles. 4. The present results suggest that nicorandil may inhibit the contraction by action on the contractile proteins in an indirect manner in guinea-pig taenia caeci.
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Affiliation(s)
- Y Ito
- Department of Physiology, Sapporo Medical College, Hokkaido, Japan
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16
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Osterrieder W. Modification of K+ conductance of heart cell membrane by BRL 34915. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1988; 337:93-7. [PMID: 3368016 DOI: 10.1007/bf00169483] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
1. The effect of the K+ channel agonist BRL 34915 on membrane conductance was investigated in isolated guinea-pig cardiac myocytes. 2. BRL 34915 reduced the duration of the transmembrane action potential and slightly increased the membrane resting potential in a concentration-dependent manner. 3. BRL 34915 removed the rectification in the steady-state current-voltage relationship. At membrane potentials more negative than the K+ equilibrium potential, membrane conductance was reduced. In the presence of 10(-4) mol/l BRL 34915, the current-voltage relationship was linear, i.e. of an ohmic type. 4. The BRL 34915-mediated change in membrane conductance was susceptible to the K+ channel blockers BaCl2 and tetrahydroaminoacridine. 5. In conclusion, BRL 34915 modifies K+ conductance in the cardiac cell membrane. The precise nature of the K+ conductance change remains to be elucidated.
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Affiliation(s)
- W Osterrieder
- Pharmaceutical Research Department, F. Hoffmann-La Roche & Co., Ltd., Basel, Switzerland
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17
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Coldwell MC, Howlett DR. Specificity of action of the novel antihypertensive agent, BRL 34915, as a potassium channel activator. Comparison with nicorandil. Biochem Pharmacol 1987; 36:3663-9. [PMID: 2445348 DOI: 10.1016/0006-2952(87)90017-7] [Citation(s) in RCA: 65] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Experiments have been performed to investigate the specificity of the mechanism of action of the novel antihypertensive agent, BRL 34915. BRL 34915 (0.5-100 microM) and nicorandil (10-500 microM) stimulated the efflux of rubidium from preloaded rabbit isolated mesenteric arteries. BRL 34915 also caused an increase in the rubidium efflux rate constant in other vascular smooth muscles. Tetraethylammonium (0.1-30 mM) inhibited BRL 34915 (10 microM), nicorandil (100 microM) and potassium (30 mM) induced stimulations of rubidium efflux, but had no effect on noradrenaline (30 microM) induced efflux. Only noradrenaline induced efflux was inhibited by apamin (3-100 nM). Examination of other second messenger systems demonstrated that BRL 34915 (at concentrations up to 100 microM) did not have any appreciable effect on cGMP accumulation in rabbit mesenteric artery, cAMP or cGMP phosphodiesterase in rat heart, or cAMP and inositol phosphate accumulation in rat brain slices. Nicorandil (100 microM) caused a small increase in cGMP accumulation in rabbit mesenteric artery. Radioligand binding studies showed that BRL 34915 did not interact with dihydropyridine, 5-hydroxytryptamine, dopamine, alpha 1, alpha 2 or beta adrenoceptor binding sites. [3H]-BRL 34915 did not bind specifically to any site in any tissue studied, either in vitro or ex vivo. Thus we have been unable to demonstrate an effect of BRL 34915 other than of increasing potassium efflux in rabbit vascular smooth muscle. This lends support to other evidence suggesting that BRL 34915 relaxes vascular smooth muscle (and hence lowers blood pressure) by a novel, and specific, mechanism involving hyperpolarisation of the smooth muscle cell membrane.
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Affiliation(s)
- M C Coldwell
- Beecham Pharmaceuticals, Medicinal Research Centre, Harlow, Essex, U.K
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18
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Clapham JC, Wilson C. Anti-spasmogenic and spasmolytic effects of BRL 34915: a comparison with nifedipine and nicorandil. JOURNAL OF AUTONOMIC PHARMACOLOGY 1987; 7:233-42. [PMID: 2963005 DOI: 10.1111/j.1474-8673.1987.tb00152.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
1 BRL 34915, nifedipine and nicorandil were compared for anti-spasmogenic activity against field stimulation (frequency-response curves), noradrenaline and KCl (concentration-response curves), and for spasmolytic activity against tissues pre-contacted with 3 X 10(-2) and 9 X 10(-2) M KCl, in rabbit isolated mesenteric artery. 2 BRL 34915 was an effective anti-spasmogenic agent (threshold concentration 10(-8) M) against endogenous noradrenaline released by field stimulation, and slightly less effective (threshold concentration 10(-7) M) against exogenous noradrenaline. Anti-spasmogenic activity of BRL 34915 against KCl was limited. BRL 34915 demonstrated spasmolytic activity against contractions to KCl 3 X 10(-2) M (IC50 = 3.7 X 10(-7) M) but not KCl 9 X 10(-2) M. 3 Nicorandil demonstrated anti-spasmogenic activity against all three contractile stimuli although relatively high concentrations (10(-6)-10(-4) M) of the drug were required. Spasmolytic activity was greater against 3 X 10(-2) M KCl contractions (IC50 = 1.0 X 10(-5) M) than against 9 X 10(-2) M KCl contractions (maximum relaxation of 18% at 10(-4) M). 4 Nifedipine (10(-9)-10(-7) M) was a potent inhibitor of contractions over the entire KCl concentration range (1 X 10(-2)-9 X 10(-2) M). Nifedipine was, however, much less effective against contractions to exogenous or endogenous noradrenaline. 5 The results are consistent with the hypotheses that (a) the inhibitory activity of BRL 34915 may involve K+ channel activation, (b) the inhibition by nicorandil involves an additional mechanism(s) and (c) nifedipine is a Ca2+ channel blocker with selectivity for voltage-operated rather than receptor-operated Ca2+ channels.
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Affiliation(s)
- J C Clapham
- Beecham Pharmaceuticals Research Division, Harlow, Essex, UK
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Allen SL, Boyle JP, Cortijo J, Foster RW, Morgan GP, Small RC. Electrical and mechanical effects of BRL34915 in guinea-pig isolated trachealis. Br J Pharmacol 1986; 89:395-405. [PMID: 2430658 PMCID: PMC1917004 DOI: 10.1111/j.1476-5381.1986.tb10273.x] [Citation(s) in RCA: 192] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
BRL34915 (0.1-10 microM) suppressed the spontaneous tone of guinea-pig isolated trachealis in a concentration-dependent manner. BRL34915 was not antagonized by propranolol (1 microM). In trachea where spontaneous tone was suppressed by indomethacin (2.8 microM) but subsequently restored to the same level with acetylcholine or histamine, the relaxant potency of BRL34915 was reduced. In Krebs solution containing K+ (120 mM), isolated trachealis muscle developed near-maximal tension. The relaxant effects of BRL34915 were virtually abolished in this medium. Concentration-effect curves for KCl, acetylcholine and histamine were constructed in tissues treated with indomethacin (2.8 microM). BRL34915 (10 microM) depressed the foot of the concentration-effect curve for KCl and caused minor rightward shifts in the concentration-effect curves of acetylcholine and histamine. Four K+-channel inhibitors were tested. Apamin (0.1 microM) did not modify the action of BRL34915. Tetraethylammonium (8 mM) had little effect but procaine (5 mM) and 4-aminopyridine (5 mM) each significantly inhibited the relaxant action of BRL34915. Intracellular electrophysiological recording showed that BRL34915 (0.1 microM) caused very minor relaxation and little, if any, electrical change. Higher concentrations (1-10 microM) evoked relaxation, suppression of spontaneous electrical slow waves and marked hyperpolarization of the trachealis cells. In the presence of TEA (8 mM) or procaine (5 mM) the hyperpolarization induced by BRL34915 was significantly reduced. In trachealis skinned of its plasma membranes, tension development induced by Ca2+ (20 microM) was unaffected either by BRL34915 (10 microM) or by nicorandil (1 mM). In studies of the efflux of 86Rb+ from muscle-rich strips of trachea, BRL34915 (1 and 10 microM) increased the efflux rate constant. It is concluded that BRL34915 evokes relaxation of the trachealis by a mechanism that involves neither beta-adrenoceptor activation nor direct reduction of the sensitivity of the intracellular contractile machinery to cytosolic free Ca2+. The action of BRL34915 may depend on the opening of K+ channels in the plasma membrane which are permeable to 86Rb+. The opening of these channels, or the effects of their opening, may be reduced by K+-channel inhibitors such as 4-aminopyridine, procaine and TEA but not by apamin.
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Weir SW, Weston AH. The effects of BRL 34915 and nicorandil on electrical and mechanical activity and on 86Rb efflux in rat blood vessels. Br J Pharmacol 1986; 88:121-8. [PMID: 2423172 PMCID: PMC1917103 DOI: 10.1111/j.1476-5381.1986.tb09478.x] [Citation(s) in RCA: 234] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The effects of the antihypertensive agent BRL 34915 on a variety of responses of the aorta and portal vein of the rat have been compared with those of nicorandil. On portal vein, BRL 34915 (0.01-50 X 10(-6) M) and nicorandil (0.1-500 X 10(-6) M) abolished spontaneous mechanical activity and reduced mechanical responses to noradrenaline (0.1-100 X 10(-6) M) and K+ (5-20 X 10(-3) M) but had little inhibitory effect on responses to K+ (40-80 X 10(-3) M). The onset of the reduced responses to noradrenaline was delayed by both agents. On portal vein, BRL 34915 (0.1-50 X 10(-6) M) and nicorandil (0.5-500 X 10(-6) M) abolished spontaneous electrical and mechanical activity, hyperpolarized the smooth muscle cells to a value close to their calculated potassium equilibrium potential and increased the 86Rb efflux rate coefficient. On aorta, BRL 34915 (0.2-0.8 X 10(-6) M) and nicorandil (8-32 X 10(-6) M) reduced mechanical responses to noradrenaline (0.001-1 X 10(-6) M) and K+ (5-20 X 10(-3) M) but had little inhibitory effect on responses to K+ (40-80 X 10(-3) M). On aorta, BRL 34915 (0.2-0.8 X 10(-6) M) increased the 86Rb efflux rate coefficient whereas nicorandil (8-32 X 10(-6) M) was without effect. It is concluded that the inhibitory actions of BRL 34915 on both aorta and portal vein result from the opening of membrane potassium channels. The resulting membrane shunt inhibits the effects of excitatory agents. The inhibitory effects of nicorandil result from a combination of the opening of potassium channels together with an additional, undefined action.
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Weir SW, Weston AH. Effect of apamin on responses to BRL 34915, nicorandil and other relaxants in the guinea-pig taenia caeci. Br J Pharmacol 1986; 88:113-20. [PMID: 2423171 PMCID: PMC1917124 DOI: 10.1111/j.1476-5381.1986.tb09477.x] [Citation(s) in RCA: 114] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
BRL 34915 (4-64 X 10(-7) M), isoprenaline (0.5-32 X 10(-8) M) and nicorandil (4-64 X 10(-6) M) produced a slowly-developing relaxation of spontaneous tone of the guinea-pig taenia caeci; with no after-contraction on washout. These inhibitory responses were unaffected by apamin (10(-7) M). Adenosine triphosphate (0.06-2 X 10(-3) M) and noradrenaline (1-16 X 10(-7) M) produced a rapid inhibition of spontaneous tone with a prominent after-contraction, especially on washout. Both the inhibitory effect and the rebound contraction were abolished by apamin (10(-7) M). Exposure to both BRL 34915 (64 X 10(-7) M) and to nicorandil (64 X 10(-6) M) produced an increase in the 86Rb efflux rate coefficient which was unaffected by apamin (10(-7) M). Exposure to isoprenaline (32 X 10(-8) M) had no effect on the 86Rb efflux rate coefficient. Exposure to noradrenaline (16 X 10(-7) M) produced an increase in the 86Rb efflux rate coefficient which was abolished by apamin (10(-7) M). The results confirm that both BRL 34915 and nicorandil are capable of opening potassium channels in smooth muscle but show that the channel is not apamin-sensitive.
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POSTER COMMUNICATIONS. Br J Pharmacol 1986. [DOI: 10.1111/j.1476-5381.1986.tb14741.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Allen SL, Foster RW, Morgan GP, Small RC. The relaxant action of nicorandil in guinea-pig isolated trachealis. Br J Pharmacol 1986; 87:117-27. [PMID: 2420397 PMCID: PMC1916910 DOI: 10.1111/j.1476-5381.1986.tb10163.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Nicorandil (1-1000 mumol l-1) caused concentration-dependent relaxation of guinea-pig isolated trachealis. Propranolol (1 mumol l-1) did not modify the relaxant action of nicorandil but antagonized isoprenaline. Among K+-channel inhibitors tested, apamin (0.1 mumol l-1) and procaine (5 mmol l-1) did not modify the relaxant action of nicorandil. In contrast, tetraethylammonium (TEA, 8 mmol l-1) caused five fold antagonism. Trachealis exposed to K+-rich (120 mmol l-1) Krebs solution developed near-maximal tension. Nicorandil relaxed the K+-depolarized tissue though its concentration-effect curve was shifted markedly to the right. In tissues in which tone was induced by histamine, methylene blue (100 mumol l-1) antagonized nicorandil and sodium nitroprusside but did not modify the relaxant action of aminophylline. Intracellular electrophysiological recording showed that nicorandil (1 mumol l-1) could evoke some relaxation in the absence of electrical changes. Higher concentrations (10-1000 mumol l-1) reduced the amplitude and frequency of spontaneous electrical slow waves. Nicorandil also caused concentration-dependent hyperpolarization and relaxation. When the hyperpolarization was sufficiently pronounced slow wave activity was abolished. TEA (8 mmol l-1) induced slow waves which were surmounted by a spike potential. TEA slightly reduced the maximal hyperpolarization induced by nicorandil and increased the time required for nicorandil to abolish slow wave discharge. Procaine (5 mmol l-1) induced slow waves of relatively low frequency. Sometimes these were surmounted by a spike potential Procaine markedly reduced the hyperpolarization induced by nicorandil and increased the time required for abolition of slow waves. In studies of the efflux of 86Rb+ from muscle-rich strips of trachea, nicorandil (1000 mumol l-1) increased the efflux rate constant, whereas isoprenaline (1 mumol l-1) was without effect. It is concluded that nicorandil-induced relaxation does not involve the activation of beta-adrenoceptors but is partly attributable to the formation of nitric oxide from the nitrate moiety in its molecular structure. Nicorandil can evoke relaxation in the absence of membrane potential change but towards the upper end of its effective concentration range, nicorandil increases membrane K+ conductance and thereby evokes hyperpolarization of trachealis cells. The K+ channels opened by nicorandil are permeable to 86Rb, insensitive to apamin and TEA but may be inhibited by procaine.
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Allen SL, Beech DJ, Foster RW, Morgan GP, Small RC. Electrophysiological and other aspects of the relaxant action of isoprenaline in guinea-pig isolated trachealis. Br J Pharmacol 1985; 86:843-54. [PMID: 2416377 PMCID: PMC1916636 DOI: 10.1111/j.1476-5381.1985.tb11106.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In guinea-pig isolated trachealis isoprenaline (0.001-0.1 mumol l-1) caused concentration-dependent relaxation. Propranolol (1 mumol l-1) antagonized the effects of isoprenaline by more than 100 fold but did not modify the relaxant action of sodium nitrite. The tracheal relaxant actions of isoprenaline and ATP were unaffected by apamin (0.1 mumol l-1) but apamin profoundly antagonized the effects of noradrenaline and ATP on guinea-pig isolated taenia caeci. Tetraethylammonium (TEA; 8 mmol l-1) and procaine (5 mmol l-1) each evoked tracheal spasm but neither agent antagonized the isoprenaline-evoked relaxation of the trachealis. Trachealis exposed to K+-rich (120 mmol l-1) Krebs solution developed near-maximal tension. Both isoprenaline and sodium nitrite relaxed the K+-depolarized tissue though concentration-effect curves for both relaxants were moved to the right compared to those obtained in non-depolarized tissues. The maximal effect of sodium nitrite was markedly reduced. Intracellular electrophysiological recording showed that isoprenaline (0.01-1 mumol l-1) caused hyperpolarization and reduced or abolished slow wave discharge in trachealis muscle. These effects were accompanied by relaxation. Propranolol (1 mumol l-1) virtually abolished both the electrical and mechanical responses to isoprenaline (0.1 mumol l-1). Apamin (0.1 mumol l-1) did not alter the spontaneous electrical activity of trachealis cells or their electrical and mechanical responses to isoprenaline (0.1 mumol l-1). TEA (8 mmol l-1) caused depolarization and often increased slow wave amplitude and induced spike discharge. Isoprenaline (0.01 mumol l-1) failed to hyperpolarize TEA-treated trachealis cells. Higher concentrations of isoprenaline suppressed TEA-induced spasm, caused hyperpolarization and thereby increased slow wave or spike amplitude. Slow wave or spike frequency decreased as the hyperpolarization progressed but abolition of slow waves or spikes sometimes required more than 4 min exposure to isoprenaline. Procaine (5 mmol l-1) increased the amplitude of slow waves and induced spike discharge. Procaine markedly reduced the hyperpolarization induced by isoprenaline (0.1 and 1 mumol l-1) but had little effect on isoprenaline-induced relaxation. It is concluded that isoprenaline activates beta-adrenoceptors in guinea-pig trachealis and thereby evokes relaxation and hyperpolarization of the smooth muscle. The hyperpolarization does not involve the opening of apamin-sensitive K+-channels and it probably plays a supportive rather than a crucial role in the process by which isoprenaline-induced relaxation is achieved.
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The different mechanisms of action of nicorandil and adenosine triphosphate on potassium channels of circular smooth muscle of the guinea-pig small intestine. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1985; 331:96-103. [PMID: 2415831 DOI: 10.1007/bf00498857] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Nicorandil (10 mumol/l-0.3 mmol/l) and ATP (1 mumol/l - 0.1 mmol/l) hyperpolarized the membrane of circular smooth muscle of the guinea-pig small intestine and increased conductance of the membrane probably to K ions as estimated by the effect on the current-voltage relationship. In the presence of a maximally hyperpolarizing concentration of nicorandil (0.1 mmol/l), ATP produced a further hyperpolarization of 5 mV. The ATP-induced but not the nicorandil-induced hyperpolarization required the presence of Ca in the medium, and the ATP-induced hyperpolarization was blocked by apamin treatment (1 nmol/l) or by MnCl2 (1.3 mmol/l). On the other hand, both hyperpolarization responses were blocked by the local anaesthetics procaine (0.1 - 1 mmol/l), lidocaine (0.1 - 1 mmol/l) or cocaine (0.3 - 1 mmol/l), with different potencies. Field stimulation of smooth muscle of the small intestine produced inhibitory junction potentials (i.j.p.s) and these were inhibited by apamin (10 nmol/l - 100 nmol/l). In the presence of ATP, the amplitude of the i.j.p.s was markedly reduced, but in the presence of nicorandil the amplitude was only slightly reduced, consistent with the same increase in ionic conductance and hyperpolarization of the membrane. These results indicate that ATP and nicorandil hyperpolarize the membrane by activating different K-channels, i.e. Ca dependent and Ca insensitive K channels, respectively. As assessed from the effects of local anaesthetics and the membrane properties, the circular muscle may also possess other K channels different from the ATP and nicorandil sensitive K channels.
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