Modification of Na channels by synthetic dihydrobatrachotoxinin A-20 alpha-benzoate.

Sodium channels in nodal membrane modified by a synthetic analog of batrachotoxin, 7,8-dihydrobatrachotoxinin A-20 alpha-benzoate, were studied under voltage clamp conditions. The voltage dependence of channel activation was shifted by 70-80 mV towards more negative potentials. Selectivity sequence determined from peak current reversal potential was as follows: Na:NH4:K = 1:0.46:0.23. Our data suggest that 7,8-dihydrobatrachotoxinin A-20 alpha-benzoate has qualitatively similar effects on the properties of sodium channels as does natural batrachotoxin.