Acetylcholine activation of K+ channels in cell-free membrane of atrial cells.
The activation mechanisms of K+ channels by muscarinic acetylcholine (m-ACh) receptors were examined in isolated atrial cells by use of patch-recording technique. In "cell-attached" patch recordings, ACh, present in the pipette, activated an inwardly rectifying K+ channel. In "inside-out" patches, activation of the K+ channel by ACh diminished with time following excision of the patch, but it resumed when GTP was present in the solution bathing the intracellular side of the membrane. The A protomer of pertussis toxin, together with NAD, inhibited the channel activation in the presence of GTP. Since pertussis toxin specifically ADP-ribosylates GTP-binding proteins Ni and No, which can interact with m-ACh receptors, and inhibits their functions, it was concluded that m-ACh receptors communicate with the K+ channel via GTP-binding proteins, probably Ni and/or No, in atrial cell membrane.
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002474:Cell-Free System / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000494:pharmacology; D006168:Guinea Pigs; D006325:Heart Atria; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism*; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure; D037342:Pertussis Toxin; D011188:Potassium / Q000378:metabolism*; D011950:Receptors, Cholinergic / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D007473:Ion Channels; D011950:Receptors, Cholinergic; D010566:Virulence Factors, Bordetella; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000109:Acetylcholine; D011188:Potassium