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Properties of the current if in the sino‐atrial node of the rabbit compared with those of the current iK, in Purkinje fibres.
Author(s) -
DiFrancesco D,
Ojeda C
Publication year - 1980
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1980.sp013475
Subject(s) - conductance , current (fluid) , purkinje fibers , voltage clamp , biophysics , chemistry , hyperpolarization (physics) , electrophysiology , time constant , physics , membrane potential , condensed matter physics , neuroscience , biology , thermodynamics , stereochemistry , electrical engineering , nuclear magnetic resonance spectroscopy , engineering
1. Properties of the ‘pace‐maker’ current if in rabbit sino‐atrial node have been investigated by voltage clamp of small preparations and compared with those of the iK2 current in the Purkinje fibre. Besides having a similar voltage range of activation and responding in a similar way to adrenaline, if resembles iK2 in other respects. 2. When external Na is reduced, if decreases proportionally. In 25% Na the time‐dependent current change due to if disappears. 3. 20 mM‐Cs completely abolishes it. 4. The time constant of if during a hyperpolarizing voltage‐clamp pulse displays a relatively high temperature dependence. 5. In spite of the similarities between the two current systems, experiments in high K solutions (48 mM) rule out the possibility that the current change seen on a hyperpolarization reflects the decay of a pure K current. 6. From conductance measurements during onset of if it is deduced that if behaves as an inward current activated by hyperpolarizations.