Further studies of alinidine induced bradycardia in the presence of caesium.

Alinidine, the N-allyl derivative of clonidine, reduces heart rate in animals and man by a selective action on the sinoatrial node. In this study, in the presence of caesium, which blocks the time dependent inward current activated by hyperpolarisation (ih or if), alinidine still caused a concentration related bradycardia in the rabbit sinoatrial node. Within the clinical range of concentrations of alinidine the curve relating heart rate to alinidine concentration in the presence of caesium was parallel to that observed in its absence. It is concluded that the alinidine induced bradycardia cannot be attributed to blockade of ih.