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ATP‐dependent desensitization of the muscarinic K + channel in rat atrial cells
Author(s) -
Shui Z.,
Boyett M. R.,
Zang W.J.
Publication year - 1997
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1997.077bc.x
Subject(s) - muscarinic acetylcholine receptor , desensitization (medicine) , gtp' , biophysics , chemistry , acetylcholine , carbachol , homologous desensitization , pipette , receptor , endocrinology , medicine , biology , biochemistry , enzyme
1 Fast desensitization of the muscarinic K + channel has been studied in excised patches from rat atrial cells. 2 In inside‐out patches, ACh was present in the pipette and GTP was applied via the bath to activate the channel. In outside‐out patches, GTP was present in the pipette and ACh was applied via the bath to activate the channel. In both cases, during a 30 s exposure to GTP or ACh there was a decline in channel activity as a result of fast desensitization if ATP was present. 3 In inside‐out patches, fast desensitization was still observed if the muscarinic ACh receptor was bypassed and the channel was activated by GTP γ S. This suggests that fast desensitization is a result of a modification of the channel (or the connecting G protein) and not the receptor. 4 In both inside‐out and outside‐out patches, channel activity was depressed and fast desensitization was reduced or absent, if ATP was not present. 5 The non‐hydrolysable analogue of ATP, AMP‐PNP, did not substitute for ATP in its effects on the channel. 6 The results are consistent with the hypothesis that fast desensitization of the muscarinic K + channel is the result of a dephosphorylation of the channel.