A quantitative analysis of the acetylcholine-activated potassium current in single cells from frog atrium

Pflugers Arch. 1987 Aug;409(4-5):454-61. doi: 10.1007/BF00583801.

Abstract

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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetylcholine / pharmacology*
  • Animals
  • Atrial Function
  • Electric Conductivity
  • Guanylyl Imidodiphosphate / pharmacology
  • Heart / physiology*
  • Heart Atria / drug effects
  • In Vitro Techniques
  • Ion Channels / drug effects
  • Ion Channels / physiology*
  • Kinetics
  • Membrane Potentials / drug effects
  • Myocardial Contraction / drug effects
  • Potassium / metabolism*
  • Rana pipiens

Substances

  • Ion Channels
  • Guanylyl Imidodiphosphate
  • Acetylcholine
  • Potassium