Figure 1. Properties of acute desensitization of atrial GIRK current activated by Ach.

A, instantaneous reversibility of acute desensitization. Superfusion with ACh-containing (20 μmol l⁻¹) solution was performed as indicated. The response marked by the arrow indicates a full-sized response at 94% deactivation. The dotted line was drawn to indicate baseline current. The rapid deflections in this and subsequent figures represent changes in membrane current caused by voltage ramps from −120 to +60 mV (500 ms) that were applied once every 10 s to determine current–voltage relations. B, inward currents activated by rapid superfusion of a cell with solutions containing 0.5, 1.0 and 20 μmol l⁻¹ ACh. The dotted line in this panel indicates the quasi-steady-state current level. Zero current level in this and subsequent figures is indicated by a bar on the right labelled ‘0’.