Fig. 5: Different patterns of deactivation of GIRK2 and GIRK1/2 after patch excision and the role of G1-dCT.
Channels were expressed at low densities, with a high dose of Gβγ or SpV-Gβγ (5 ng Gβ and 1 ng Gγ). a representative recording of GIRK1/2. Top, the complete original recording that lasted 13.5 min. After ~4 min in cell-attached mode, the patch was excised into bath solution containing 2 mM ATP and 6 mM NaCl, causing a gradual decay of activity. Bottom, zoom on 20 s segments of the record during the indicated times before and after excision. b, c similar stretches from recordings of representative GIRK1ΔdCT/2 and GIRK2 recordings. d time course of deactivation after excision summarized as NPo within consecutive 60 s segments of record, normalized to NPo during the last minute before excision. (NPo is a measure of total activity in the patch, i.e., number of channels times Po). Each point is mean ± SEM, with number of patches shown near each symbol. Lines show single-exponential fits; fitting with two exponents did not produce better results (exemplified for GIRK1/2 with ATP, black line). e similar results were obtained when the patches were excised into an ATP-free solution. Data presentation as in (d). f comparison of exponential fit parameters for the three channel types, with and without ATP. τ is the time constant of the exponential decay and C is the extrapolated non-deactivating fraction.
