Figure 1.

IK_SO in rat cultured CGNs is active at all potentials and is inhibited by muscarine. (a) In perforated patch recordings, IK_SO is seen as a noninactivating current at −20 mV and is instantaneously reduced in amplitude when cells are stepped to −60 mV for 800 ms once every 6 s. The current is inhibited by muscarine (10 μM). (b) Block and washout of block by muscarine is illustrated by measuring the standing-outward current at −20 mV. (c) Cells were held at −20 mV and then hyperpolarized to −100 mV by means of a ramp waveform at 0.1 mV/ms over 800 ms once every 6 s in the presence and absence of 10 μM muscarine. (d) Cells were treated as described in c, except in raised external [K⁺] (25 mM). (e) The muscarine-sensitive current during ramps is obtained by subtraction and shown in control and 25 mM [K⁺]. (f) Cells were treated as described in e, except in control and 100 mM external [K⁺].