Palytoxin induces a nonselective cation channel in single ventricular cells of rat

Palytoxin (PTX) causes a depolarization in every excitable tissue tested. We examined whether PTX induces a channel current, which might be responsible for the depolarizing action, in single ventricular cells from rat hearts using a patch-clamp technique. In cell-attached configuration, when PTX (30 pmol/l) was present in a patch pipette, a single channel current appeared, which was different from currents through known channels. When the major cation in the pipette was Na+, the amplitude of the unitary current at the resting potential level was 0.74 +/- 0.05 pA, the slope conductance was 9 pS and the reversal potential was 79 mV positive to the resting potential. The channel was little selective between cations because it was permeable not only to Na+ but also to K+, Cs+ and Li+ although it practically did not permit the passage of choline+, TEA+, Ba2+ and Ca2+. Thus PTX induces a novel, nonselective cation channel in cardiac cells, which may result in a depolarization.