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标题：Chronotropic Effects of Optical Isomers of Ephedrine and Methylephedrine in the Isolated Rat Right Atria and in Vitro Assessment of Direct and Indirect Actions on β1-Arenoceptors
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作者：Toru KAWASUJI ; Katsuo KOIKE ; Haruo SAITO 等
期刊名称：Biological and Pharmaceutical Bulletin
印刷版ISSN：0918-6158
电子版ISSN：1347-5215
出版年度：1996
卷号：19
期号：11
页码：1423-1428
DOI：10.1248/bpb.19.1423
出版社：The Pharmaceutical Society of Japan
摘要：Effects of optical isomers of ephedrine (EPH) and methylephedrine (MEP) on the spontaneous beating rate of isolated right atrium of normal and reserpinized rat were investigated to assess direct and indirect actions on β₁-adrenoceptors. l-EPH (3×10^-7-3×10^-5M) and d-EPH (10^-6-10^-4M) markedly increased beating rate of rat right atrium. l-MEP (10^-5-3×10^-4M) showed slight increase in heart rate. The potency of positive chronotropic effect is l-EPH>d-EPH»l-MEP. l-EPH was about 3 times as potent as d-EPH. In addition, d-MEP (3×10^-5-3×10^-4M) caused a decrease in heart rate. Positive chronotropic effects of EPH isomers and l-MEP were attenuated by pretreatment with atenolol (a selective β₁-adrenoceptor antagonist) or reserpine treatment (8 mg/kg, s.c.). In reserpinized atria, the maximal increase by d-EPH was quite small, and l-MEP decreased heart rate. On the other hand, d-MEP, at 3×10^-4M, did not show antagonist activity against the positive chronotropic effect of isoprenaline (10^-10-10^-5M). These results suggest that l-EPH, d-EPH and l-MEP have β₁-adrenoceptor agonist activity, while d-MEP is suggested to have only low or no affinity for β₁-adrenoceptors. The relatively weak activity of l-MEP is believed to be mainly mediated by released noradrenaline. It is also suggested that d-EPH has very potent noradrenaline-releasing activity.
关键词：ephedrine;methylephedrine;optical isomer;β1-adrenoceptor;chronotropic effect;atrium