1. Fast desensitization of the muscarinic K+ channel has been studied in excised patches from @entity35 atrial cells. 2. In inside-out patches, @entity1617 was present in the pipette and @entity3007 was applied via the bath to activate the channel. In outside-out patches, @entity3007 was present in the pipette and @entity1617 was applied via the bath to activate the channel. In both cases, during a 30 s exposure to @entity3007 or @entity1617 there was a decline in channel activity as a result of fast desensitization if @entity855 was present. 3. In inside-out patches, fast desensitization was still observed if the muscarinic @entity1617 receptor was bypassed and the channel was activated by @entity3007 gamma 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 @entity308 and fast desensitization was reduced or absent, if @entity855 was not present. 5. The non-hydrolysable analogue of @entity855 , @entity860 -PNP, did not substitute for @entity855 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.

@entity855 -dependent desensitization of the muscarinic K+ channel in XXXX atrial cells.

@entity3007 :: ('MESH:D006160', 'Chemical') :: ['GTP'] @entity308 :: ('MESH:D003866', 'Disease') :: ['depressed'] @entity1617 :: ('CHEBI:22614', 'Chemical') :: ['ACh'] @entity35 :: ('10116', 'Species') :: ['rat'] @entity860 :: ('MESH:D000249', 'Chemical') :: ['AMP'] @entity855 :: ('MESH:D000255', 'Chemical') :: ['ATP']
@entity35 :: (10116,Species) :: ['rat']
