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dc.contributor.authorSantos, W. C.
dc.contributor.authorHernandez-Guijo, J. M.
dc.contributor.authorRuiz-Nuno, A.
dc.contributor.authorOlivares, R.
dc.contributor.authorJurkiewicz, A.
dc.contributor.authorGandia, L.
dc.contributor.authorGarcia, A. G.
dc.identifier.citationEuropean Journal of Pharmacology. Amsterdam: Elsevier B.V., v. 417, n. 1-2, p. 99-109, 2001.
dc.description.abstractThe blockade of exocytosis induced by the putative endogenous ligand for imidazoline receptors, agmatine, was studied by using on-line measurement of catecholamine release in bovine adrenal medullary chromaffin cells. Agmatine inhibited the acetylcholine-evoked release of catecholamines in a concentration-dependent manner (IC50 = 366 muM); the K+-evoked release of catecholamines was unaffected. Clonidine (100 muM) and moxonidine (100 muM) also inhibited by 75% and 50%, respectively, the acetylcholine-evoked response. in cells voltage-clamped at -80 mV, the intermittent application of acetylcholine pulses elicited whole-cell inward currents (I-ACh) that were blocked 63% by 1 mM agmatine. the onset of blockade was very fast (tau (on) = 31 ms); the recovery of the current after washout of agmatine also occurred very rapidly (tau (off) = 39 ms). Efaroxan (10 muM) did not affect the inhibition of I-ACh elicited by 1 mM agmatine. I-ACh was blocked 90% by 100 muM clonidine and 50% by 100 muM moxonidine. the concentration-response curve for acetylcholine to elicit inward currents was shifted to the right in a non-parallel manner by 300 muM agmatine. the blockade of I-ACh caused by agmatine (100 muM) was similar at various holding potentials, around 50%. When intracellularly applied, agmatine did not block I-ACh. At 1 mM, agmatine blocked I-Na by 23%, I-Ba by 14%, I-K(Ca) by 16%, and I-K(VD) by 18%. in conclusion, agmatine blocks exocytosis in chromaffin cells by blocking nicotinic acetylcholine receptor currents. in contrast to previous views, these effects seem to be unrelated to imidazoline receptors. (C) 2001 Elsevier Science B.V. All rights reserved.en
dc.publisherElsevier B.V.
dc.relation.ispartofEuropean Journal of Pharmacology
dc.rightsAcesso restrito
dc.subjectnicotinic receptoren
dc.subjectCa2+ channelen
dc.subjectchromaffin cellen
dc.titleBlockade by agmatine of catecholamine release from chromaffin cells is unrelated to imidazoline receptorsen
dc.contributor.institutionUniv Autonoma Madrid
dc.contributor.institutionUniversidade Federal de São Paulo (UNIFESP)
dc.contributor.institutionUniv Amazonas
dc.contributor.institutionHosp Princesa
dc.description.affiliationUniv Autonoma Madrid, Fac Med, Inst Teofilo Hernando, Dept Farmacol, E-28029 Madrid, Spain
dc.description.affiliationUNIFESP, Escola Paulista Med, Dept Farmacol, BR-04034970 São Paulo, Brazil
dc.description.affiliationUniv Amazonas, Inst Ciencias Biol, Dept Ciencias Fisiol, BR-69077000 Manaus, Amazonas, Brazil
dc.description.affiliationHosp Princesa, Serv Farmacol Clin, Madrid 28006, Spain
dc.description.affiliationHosp Princesa, Inst Gerontol, Madrid 28006, Spain
dc.description.affiliationUnifespUNIFESP, Escola Paulista Med, Dept Farmacol, BR-04034970 São Paulo, Brazil
dc.description.sourceWeb of Science

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