A quantitative analysis of the acetylcholine-activated potassium current in single cells from frog atrium.
The K+ current activated by acetylcholine (ACh) in single cells from the frog atrium was analyzed using the whole-cell patch clamp technique. The ACh current was analyzed quantitatively by subtracting the currents elicited in response to voltage steps in the presence and absence of a steady bath-application of 1 microM ACh. The net ACh currents were voltage- and time-dependent. With depolarizing jumps, the ACh-activated current declined from an instantaneous peak to a new steady level. With hyperpolarizations, the instantaneous current change was followed by a time-dependent increase in current. The current relaxations were well fitted by the sum of two exponentials with time constants of approximately 20 ms and approximately 300 ms at -120 mV. Both time constants decreased with depolarization. The current-voltage relationship inwardly-rectified. This inward rectification was due both to a decrease in the single channel conductance and a decrease in the number of open channels with depolarization. The ACh-activated K+ current differs from the background K+ current in several respects. The kinetics of the background K+ current are much more rapid and the background K+ channel passes much less current in the outward direction than the ACh channel.
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D016275:Atrial Function; D004553:Electric Conductivity; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D006321:Heart / Q000502:physiology*; D006325:Heart Atria / Q000187:drug effects; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects; D011188:Potassium / Q000378:metabolism*; D011894:Rana pipiens
D007473:Ion Channels; D006165:Guanylyl Imidodiphosphate; D000109:Acetylcholine; D011188:Potassium