A concentration-dependent effect of Ba2+ on voltage-independent opening of K+ channels in Eremosphaera was examined. Low concentrations of external Ba2+ (10−2mM) cause the release of repetitive transient potentials. Higher concentrations of Ba2+, however, inhibit these Ba2+-induced repetitive and also light-off triggered transient potentials. Experiments with different Ca2+ concentrations in the medium and the treatment with La3+ suggest the interaction of Ba2+ with Ca2+ channels and the participation of internal Ca2+ in the activation of K+ channels.
