ISSN:
1432-2013
Keywords:
Key words Cardiac pacemaker cell
;
Sinoatrial node cell
;
Spontaneous action potential
;
Sustained inward current
;
Guinea-pig
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Single myocytes were dissociated from the sino-atrial (SA) node of guinea-pig hearts. Only a quite small fraction of the cell population showed spontaneous action potentials and these cells were characterized by the presence of the hyperpolarization-activated cation current I f , the delayed rectifier K+ current I K and the L-type Ca2+ current I Ca,L as well as by the absence of both the transient outward current I to and the inward rectifier K+ current I K,1. After blocking I f and I K, depolarizing pulses from –80 mV revealed a large nicardipine-sensitive late current (NSLC). The NSLC was scarcely affected by decreasing extracellular [Ca2+] ([Ca2+]o) from 1.8 to 0.1 mM, while it was decreased significantly by depleting [Na+]o, differently from I Ca,L. NSLC was blocked by nicardipine and was increased by Bay K 8644. NSLC was increased by isoprenaline and the additional application of acetylcholine reversed the increase of this current. We conclude that NSLC is largely composed of I st described in the rabbit SA node pacemaker cells, and that I st is unique for the pacemaker cells in mammalian SA node cells. Most of the quiescent cells showed neither I f nor I st.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004240050293
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