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Dopamine이 토끼 유두근의 수축력과 활동전압에미치는 영향

Effects of Dopamine on the Contractility and Action Potential of the Rabbit Papillary Muscle

약학회지 1988년 32권 6호 p.402 ~ 414
허인회, 박종완,
소속 상세정보
허인회 (  ) - 중앙대학교 약학대학
박종완 (  ) - 중앙대학교 약학대학

Abstract


In order to clarify the receptor types and mechanisms underlying the positive inotropic effect of dopamine on the mammalian ventricular myocardium, the action potential, its first derivatives and isometric contraction of the rabbit papillary muscle were recorded using a force transducer and glass capillary microelectrodes filled with 3M KC1. The results were as follows; (1) In normal Tyrode solution, the contractile force was increased and duration of action potential was shortened with increments of dopamine concentration (10-6?10-4M). (2) The dose-response curve was markedly shifted to the right by pretreatment with reserpine (5mg/ kg i.p., 24hrs prior to the experiment). (3) In 19mM K+-Tyrode solution, the duration of action potential, maximum rate of rise (Vma:) of action potential and overshoot were significantly increased with increments of dopamine concentration (10-6?10-4M). (4) The inotropic effect of dopamine on the rabbit papillary muscle pretreated with reserpine was antagonized by atenolol (10-6M), but not by phentolamine (3 x 10-6M). (5) In rabbit papillary muscle partially depolarized by 19mM K+-Tyrode solution, slow electrical response (calcium mediated action potential) as well as contraction were restored by dopamine (10-6M); this restoration was blocked by calcium antagonists (3 x 10-5M LaC13.6H2O, 3 x 10-6M diltiazem) or p-adrenoceptor antagonist (3 x 10-6M atenolol), but not affected by a-adrenoceptor antagonist (10-6M phentolamine, 3x10-6M yohimbine) or vascular dopaminergic receptor antagonist (10-5M haloperidol). The above results may be interpreted as that the positive inotropic effect of dopamine through both direct and indirect action are caused by increase in slow inward current (Ca2+ influx. into themyocardial cell), and the direct action is mainly due to the stimulation of 13-adrenoceptors in the rabbit papillary muscle.

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