Effects of barium on delayed rectifier potassium current in bullfrog sympathetic neurons pretreated with wortmannin.

The effect of barium (1 mM) on a delayed rectifier-type potassium current was examined in bullfrog sympathetic neurons. An M-type potassium current was eliminated by pretreatment of the cells with a microbial product, wortmannin (10 microM). An A-type potassium current was continuously inactivated by setting a holding potential at -65 mV. In treated cells (n = 10), the delayed rectifier at 0 mV averaged 2200 +/- 107 pA in the presence of barium (1 mM) as compared to 2308 +/- 110 pA in the controls, and 2085 +/- 103 pA after washing out the barium. It is concluded that the delayed rectifier is insensitive to barium blockage in amphibian autonomic neurons.