Open AccessElectrophysiological Effects of Procaine in Rabbit Sino-Atrial Node Cells
Author(s) -
Hiroyuki Satoh,
Keitaro Hashimoto
Publication year - 1986
Publication title -
japanese journal of pharmacology/japanese journal of pharmacology
Language(s) - English
Resource type - Journals
eISSN - 1347-3506
pISSN - 0021-5198
DOI - 10.1254/jjp.40.83
Subject(s) - procaine , electrophysiology , chemistry , depolarization , hyperpolarization (physics) , voltage clamp , membrane potential , biophysics , resting potential , anesthesia , medicine , biochemistry , biology , stereochemistry , nuclear magnetic resonance spectroscopy
Effects of procaine (50-500 micrograms/ml) on membrane potential and currents were investigated using a two microelectrode-voltage clamp technique. Procaine reduced the action potential amplitude (APA), the maximum diastolic potential and the maximum rate of depolarization (Vmax) in a dose-dependent manner. At the same time, the action potential duration and the cycle length were prolonged. In voltage clamp experiments, procaine (50 micrograms/ml) did not affect the slow inward current (Isi), but reduced the time-dependent outward current (Ik). At concentrations higher than 100 micrograms/ml, procaine reduced both currents and the inward current activated by hyperpolarization in a dose-dependent manner. In 7 of 20 specimens, a low concentration of procaine (50 or 100 micrograms/ml) increased Isi which enhanced the Vmax and APA, but did not increase Ik. Procaine did not affect the steady-state inactivation of Isi (f infinity) and the activation of Ik (p infinity). The results suggest that the depressions of currents induced by procaine are due to a reduction in conductances of the current systems.