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峨眉唐松草碱(MAF)30μM抑制离体大鼠在心房肌的收缩性,给药后40 min使收缩力降至给药前的50±9％。MAF作用15min后心肌的功能性不应期从61±2ms延长到90±3ms,并能抑制由肾上腺素诱发出的心肌自律性收缩,使肾上腺素的阈浓度由给药前的14±7μM增加到42±19μM。MAF50μM还能降低心肌的兴奋性。MAF 30μM亦能使右心房肌的收缩力降低50±7％,使收缩频率降低60±5％。
Ethambutol (30 mg MAF) inhibited contractile activity of isolated rat atrium in 40 min after administration, and contractility was reduced to 50 ± 9% before administration. The functional refractory period of myocardium prolonged from 61 ± 2 ms to 90 ± 3 ms after MAF for 15 min, and inhibited the adrenaline-induced myocardial contractile contractions so that the threshold concentration of epinephrine increased from 14 ± 7 μM before administration To 42 ± 19 μM. MAF50μM can also reduce the excitability of myocardium. MAF 30μM also reduced contractility in the right atrial muscle by 50 ± 7% and reduced systolic frequency by 60 ± 5%.