Role of the oscillatory afterpotentials in the arrhythmogenic action of histamine.

We used intracellular microelectrodes to study the effect of histamine on oscillatory afterpotentials (OAPs). OAPs were induced by exposing cardiac Purkinje fibers to barium (10(-5) M) and to strophanthidin (3 X 10(-7) M). Histamine consistently increased the amplitude of the barium-induced OAPs. Similar results were obtained in strophanthidin-treated preparations: histamine, in fact, was able to increase the OAPs amplitude and eventually to induce triggered activity. The effect of histamine was antagonized by cimetidine (10(-5) M). The possible role of the OAPs in the arrhythmogenic action of histamine is discussed.