Acetylcholine activation of single muscarinic K|[plus]| channels in isolated pacemaker cells of the mammalian heart

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摘要：

Acetylcholine (ACh) released on vagal stimulation 1 reduces the heart rate by increasing K + conductance of pacemaker cells in the sinoatrial (S-A) node 2,3 . Fluctuation analysis of ACh-activated currents in pacemaker tissue showed this to be due to opening of a separate class of K + channels gated by muscarinic ACh receptors (m-AChRs) 4 . On the other hand, it has been suggested that m-AChRs may simply regulate the current flow through inward rectifying resting K + channels ( g K1 ) 5,6 . We report here the measurement of ACh-activated single channel K + currents and of resting K + channel currents in isolated cells of the atrioventricular (A-V) and S-A node of rabbit heart. The results show that the ACh-dependent K + conductance increase in nodal cells is mediated by K + channels which are different in their gating and conductance properties from the inward rectifying resting K + channels in atrial and ventricular cells. The resting K + channels in nodal cells are, however, similar to those activated by ACh.

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DOI：

10.1038/303250a0

被引量：

1021