Mechanisms of the reversal of blood pressure by ephedrine (Report 1)
Mechanisms of the reversal of blood pressure by d-ephedrine (d-EPH) after the administration of l-ephedrine (l-EPH) in rats anesthetized with urethane were investigated. The dose which elicited the reversal was more than 2 mg/kg of l-EPH and more than 1 mg/kg of d-EPH to each injection of d and 1:EP...
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Veröffentlicht in: | Folia Pharmacologica Japonica 1977, Vol.73(1), pp.73-82 |
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Format: | Artikel |
Sprache: | eng ; jpn |
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Zusammenfassung: | Mechanisms of the reversal of blood pressure by d-ephedrine (d-EPH) after the administration of l-ephedrine (l-EPH) in rats anesthetized with urethane were investigated. The dose which elicited the reversal was more than 2 mg/kg of l-EPH and more than 1 mg/kg of d-EPH to each injection of d and 1:EPH (10mg/kg i.v.). The reversal was observed up to 60 min after the injection of l-EPH in both male and female cats and dogs anesthetized with pentobarbital-Na. This reversal was not blocked by atropine (1 mg/kg i.v.), hexamethonium (10mg/kg i.v.), diphenhydramine (2mg/kg i.v.), vagotomy and hypotension by blood letting but was blocked by phenoxybenzamine (2.5 mg/kg i.v.). l-EPH inhibited more remarkably a-action of tyramine and epinephrine than d-EPH. In isolated blood vessels of guinea pig and dog, contraction was produced by both l- and dl-EPH at a dose of 1.3 × 10-4 ?? 5 × 10-3 M but d-EPH did not produce contraction. In the isolated dog femoral arterial strips, d-EPH (5 × 10-3 M) inhibited more remarkably the contraction produced by Adr (1.3 × 10-5 M) than l-EPH. Femoral blood flow in dog was increased by the injection of d-EPH (1mg/kg i.v.) after the injection of 1-EPH (1 mg/kg i.v.) rather than before the injection of l-EPH. The reversal is considered to be an indirect action of d-EPH since it disappeared in reserpinized rats, and, also to be an action of a liberating substance other than β-action of CA since it was not blocked by β-blocker. It is suggested that this liberating substance may be 5-HT and that the vasodilating action of d-EPH may to some extent participate in the fall of blood pressure. |
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ISSN: | 0015-5691 1347-8397 |
DOI: | 10.1254/fpj.73.73 |