Figure 2. Desensitization of the muscarinic K⁺ channel in CHO cells and rat atrial cells.

Data were recorded from either CHO cells transfected with wild-type receptor and wild-type receptor kinase (A-C) or rat atrial cells (D-F). Cell-attached configuration. A and D, slow time base recording of single channel currents during the first 3 min after the attachment of an ACh-containing pipette onto a cell. At least 5 active channels were present in the patches. B and E, fast time base records of the single channel currents from the times shown during the first 3 min after the attachment of the pipette. C and F, mean NP_o from 11 (C) and 7 (F) patches during the first 3 min after the attachment of the pipette. The data are fitted with single exponential functions with the time constants shown. In A, B, D and E, inward currents are shown in the upwards direction to facilitate comparison with the plots of NP_o in C and F. Transfection: the CHO cells were stably transfected with DNA for hm2 and GRK2 and transiently transfected with DNA for Kir3.1, Kir3.4 and GFP (see Methods for details).