Acetylcholine blocks Ca++-induced closure of outward K+ currents in isolated patches of canine atrial myocyte sarcolemma.
The patch clamp technique applied to canine atrial myocyte sarcolemma, showed that 2 types of K+ channels were differentially affected by Ach. The 2 channel types differed in conductance, responses to [Ca++], and sensitivity to membrane potential. Addition of Ach (10(-9) M to 10(-6) M) to pipette solutions increased outward K+ current through each channel type by a different mechanism. Atropine (10(-5) M) blocked all effects of Ach (10(-7) M). These results suggest that muscarinic receptors were linked to potassium channels without cytoplasmic intermediaries, since membrane patches were cell-free. These responses matched the time course and direction of the intact cell's response to Ach.
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D016275:Atrial Function; D002118:Calcium / Q000494:pharmacology*; D004285:Dogs; D004553:Electric Conductivity; D005260:Female; D006321:Heart / Q000502:physiology*; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials; D011188:Potassium / Q000378:metabolism*; D012508:Sarcolemma / Q000502:physiology*
D007473:Ion Channels; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium