A Quantitative Analysis of the Acetylcholine-activated Potassium Current in Single Cells from Frog Atrium

Overview

Journal Pflugers Arch

Specialty Physiology

Date 1987 Aug 1

PMID 2442711

Citations 16

Authors

M A Simmons

H C Hartzell

Affiliations

Soon will be listed here.

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.

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