Administration of propranolol increased voltage-gated potassium current.

<p>Currents were measured at different holding potentials. For recording total voltage-gated potassium current (<i>I</i>_Total), the membrane potential was held at −100 mV and voltage steps were from −50 to +90 mV with10-mV increments and 400 ms duration. For recording the sustained K_V current (<i>I</i>_K), the membrane potential was held at −50 mV and the voltage steps were the same as above. Currents generated by these two protocols were subtracted to produce <i>I</i>_A. Bar graphs showed the mean peak <i>I</i>_Total (A), <i>I</i>_K (C), and <i>I</i>_A (E) densities from control (CON), HIS, NS- and Prop-treated HIS (Prop) rats. The current density (pA/pF) was calculated by dividing the current amplitude by cell membrane capacitance. (A) HIS produced a significant reduction in <i>I</i>_Total while Prop treatment caused a significant increase in <i>I</i>_Total (*p<0.05, compared with CON, two sample t-Test; ##p<0.01, compared with NS). (B) HIS led to a significant decrease in <i>I</i>_K while administration of Prop resulted in a marked potentiation in <i>I</i>_K density (*p<0.05, compared with CON, two sample <i>t</i>-Test; ##p<0.01, compared with NS). (E) The <i>I</i>_A density was not significantly altered after HIS and Prop treatment. (B, D, F) Current (<i>I</i>)-Voltage (V) curves for <i>I</i>_Total (B), <i>I</i>_K (D), and <i>I</i>_A (F) recorded from control, HIS, NS- and Prop-treated HIS rats. HIS treatment did not significantly change the reversal potentials of these currents.