Hyperpolarizing shift by quinine in the steady-state inactivation curve ofdelayed rectifier-type potassium current in bullfrog sympathetic neurons

Whole-cell recordings were made from dissociated bullfrog sympathetic neuro ns to examine the actions of quinine (1-100 muM) on the steady-state activa tion and inactivation curves of a delayed rectifier-type potassium current (I-k). Quinine (EC50 approximate to 8 muM) caused a hyperpolarizing shift ( approximate to 31 mV with 30 muM) in the inactivation curve of I-k without significantly affecting its activation curve. Quinine (20 muM) was without effects on the voltage-dependence of a rapidly-inactivating A-type potassiu m current (I-A). it is concluded that quinine can selectively modulate the voltage-dependence of I-k in amphibian autonomic neurons. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.