Fully activated current–voltage relationships for hyperpolarization-activated cation current (I_f). (A) The cell membrane was hyperpolarized from a holding potential of −40 mV to −130 mV for 2,000 ms and was then stepped back to various test potentials of +5 to −45 mV in 10-mV steps. Current records were obtained before and after 5-min exposure to 12% desflurane (DES) from the same cell. Voltage-clamp protocol is indicated above the control traces. (B) Current–voltage relationships for I_f tail currents in the absence (black) and presence (blue) of 12% desflurane, obtained from the data shown in A. Note that the reversal potential for I_f was not appreciably changed by the presence of desflurane.