[Comparative activity of ethaverine and papaverine on the effective refractory period of the isolated guinea pig atrium].

From lower concentrations (from 10(-7) to 10(-5) M) ethaverine reduces the maximal following frequency (MFF) of isolated guinea-pig's right atrium during its electrical driving at increasing frequencies. On the other hand, papaverine assumes a variable effect according to its concentration: increase (10(-7) M) or decrease (10(-6) M) of MFF. Modifications of MFF are related with those of atrial effective refractory period (ERP). These results show that ethaverine induces a lengthening of ERP whereas papaverine reduces or increases ERP. These observations are discussed comparatively with previous personal data on anesthetized dogs (Lacroix et al.) and with local anesthetic properties of ethaverine.