Lack of calcium-antagonizing activity of dehydroevodiamine on the chronotropic and inotropic activities of mouse isolated atria.

Dehydroevodiamine (DeHE) was reported to induce bradycardia and to have calcium-antagonizing activity besides other actions. The purpose of the present study was to investigate if DeHE could act as a calcium antagonist on the chronotropic and inotropic activities of mouse isolated atria. The data showed that DeHE induced bradycardia but did not decrease the contraction amplitude of the right atrium. Moreover, DeHE did not attenuate the contraction amplitude of the electrically driven left atrium and, in the presence of 1 x 10(-4) M DeHE, the contraction amplitude of left atrium was increased when the calcium concentration in Krebs solution was further increased. Since calcium antagonists are known to inhibit chronotropic and inotropic activities, it seems unlikely that DeHE acts as a calcium antagonist on the chronotropic and inotropic activities of mouse isolated atria.