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Predicate | Object |
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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
2
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pubmed:dateCreated |
1988-3-29
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pubmed:abstractText |
Pharmacological and electrophysiological properties of postsynaptic alpha-adrenoceptor subtypes in rat tail artery were compared using selective alpha 1- and alpha 2-adrenoceptor agonists. Five alpha-adrenoceptor agonists contracted the tail artery with the following order of maximal effects: norepinephrine (alpha 1 and alpha 2) greater than methoxamine (alpha 1) = phenylephrine (alpha 1) much greater than clonidine (alpha 2) greater than UK-14,304 (alpha 2). Phenoxybenzamine greatly diminished contractions induced by methoxamine and phenylephrine, but had little effect on responses to UK-14,304. Idazoxan antagonized more potently against UK-14,304 than against methoxamine. These results suggest the heterogeneity of postsynaptic alpha-adrenoceptors in the rat tail artery. Furthermore, responses to methoxamine and phenylephrine 1) had faster onsets and 2) were more resistant to Ca2+ entry blockers, nicardipine and diltiazem, and a promotor, Bay K 8644, or decreasing of extracellular Ca2+ and 3) were more sensitive to a calmodulin antagonist, W-7, than the responses to UK-14,304 and clonidine. Both methoxamine and UK-14,304 depolarized the membrane but methoxamine produced stronger depolarization than UK-14,304. Therefore, the high sensitivity of alpha 2-adrenoceptor agonists-induced responses to Ca2+ entry blockers and promotors cannot be accounted for solely by membrane depolarization. These results may indicate the differences in the Ca2+ movement for the contractions produced by alpha 1- and alpha 2-adrenoceptor agonists.
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pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical | |
pubmed:status |
MEDLINE
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pubmed:month |
Oct
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pubmed:issn |
0021-5198
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:volume |
45
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
249-61
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pubmed:dateRevised |
2006-11-15
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pubmed:meshHeading |
pubmed-meshheading:2893852-Adrenergic alpha-Agonists,
pubmed-meshheading:2893852-Animals,
pubmed-meshheading:2893852-Arteries,
pubmed-meshheading:2893852-Calcium,
pubmed-meshheading:2893852-Male,
pubmed-meshheading:2893852-Membrane Potentials,
pubmed-meshheading:2893852-Rats,
pubmed-meshheading:2893852-Rats, Inbred Strains,
pubmed-meshheading:2893852-Tail,
pubmed-meshheading:2893852-Vasoconstriction
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pubmed:year |
1987
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pubmed:articleTitle |
Pharmacological and electrophysiological discrimination of contractile responses to selective alpha 1- and alpha 2-adrenoceptor agonists in rat tail artery.
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pubmed:affiliation |
Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
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pubmed:publicationType |
Journal Article,
In Vitro
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