Antiarrhythmic effects of alpha-adrenoceptor antagonists in guinea pig ventricular myocardium.
J Am Coll Cardiol
; 12(6): 1590-8, 1988 Dec.
Article
em En
| MEDLINE
| ID: mdl-2903873
ABSTRACT
Antiarrhythmic effects of alpha-adrenoceptor antagonists were assessed in the reserpinized guinea pig ventricular myocardium. Both bunazosin (1 to 3 x 10(-7) M), a new alpha 1-adrenoceptor antagonist, and yohimbine (1 to 3 x 10(-7) M), another adrenoceptor antagonist, suppressed the transient depolarization and triggered activity induced by a train of rapid stimuli in the solution containing low potassium ion (K+), high calcium ion (Ca2+) and strophanthidin (1 to 5 x 10(-7) M). Bunazosin (3 x 10(-6) M) abolished the facilitatory effect of hypoxia on beta-adrenoceptor mediated abnormal automaticity. To clarify the mechanisms underlying the antiarrhythmic properties of alpha-adrenoceptor antagonists, their electrophysiologic effects on the fast and slow action potentials were investigated. Alpha-adrenoceptor antagonists (bunazosin, yohimbine and phentolamine) suppressed the slow response in a dose-related manner. The voltage-dependent block and use-dependent block of the maximal rate of rise (Vmax) of action potentials by bunazosin (10(-5) to 10(-4) M) and yohimbine (10(-6) to 10(-5) M) were studied. The analysis of the onset and recovery kinetics from the use-dependent block of drugs showed that both bunazosin and yohimbine act as slow kinetic drugs. It is concluded that alpha-adrenoceptor antagonists seem to have an antiarrhythmic effect through the inhibition of fast sodium ion (Na+) and slow Ca2+ currents of the cell membrane independently of blockade of myocardial alpha-adrenoceptors.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Antagonistas Adrenérgicos alfa
/
Coração
/
Antiarrítmicos
Tipo de estudo:
Etiology_studies
Limite:
Animals
Idioma:
En
Revista:
J Am Coll Cardiol
Ano de publicação:
1988
Tipo de documento:
Article
País de afiliação:
Japão