Premium
Comparison of Step and Ramp Voltage Clamp on Background Currents in Guinea‐Pig Ventricular Cells
Author(s) -
Spindler A. J.,
Noble S. J.,
Noble D.
Publication year - 1999
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1111/j.1469-445x.1999.01790.x
Subject(s) - guinea pig , voltage clamp , clamp , biophysics , patch clamp , electrophysiology , current (fluid) , chemistry , steady state (chemistry) , physics , membrane potential , medicine , biology , thermodynamics , mechanical engineering , clamping , engineering
SUMMARY Isolated cardiac ventricular myocytes from guinea‐pig were used to investigate the effect of voltage clamp protocols on background Na + current ( i b.Na ) and inward rectifier current ( i K1 ). Using long (4 s) clamp pulses and very long step clamps, the i‐V relations showed that removal of Na + reduces the amplitude and shifts the voltage dependence of i K1 (Spindler et al. 1998). Ramp clamps, however, gave more complicated results, with slower ramps more often giving the same results as steps and pulses. Both i K1 itself and, during faster ramps, other currents show hysteresis, so masking the steady‐state changes. Using pulses, TTX had no effect on steady‐state current. Small differences occurred in the ramps, but even at fast ramp speeds the effects are very much smaller than in Purkinje tissue. Only part of i b,Na is TTX sensitive and the effect does not occur in all cells.