Hideaki Sada

Effects of tocainide and lidocaine on the transmembrane action potentials as related to external potassium and calcium concentrations in guinea-pig papillary muscles

SummaryEffects of lidocaine and tocainide on transmembrane potentials were studied in isolated guineapig papillary muscles, superfused with modified Tyrodes solution containing either 5.4, 2.7, 10.0 or 8.1 mmol/l potassium concentration, [K]0. The last solution applied contained either 1.8 (normal [Ca]0) or 7.2 mmol/l [Ca]0) (high [Ca]0). The concentrations of lidocaine and tocainide used were 18.5, 36.9 and 73.9 μmol/l and 43.7, 87.5 and 174.9 μmol/l in 5.4 mmol/l [K]0 solution and 36.9 and 87.5 μmol/l in the other solutions, respectively. At the driving rate of 1 Hz in 5.4 mmol/l [K]0 solution, both drugs produced dosedependently a reduction of maximum rate of rise of action potential (

Effects of various structurally related beta-adrenoceptor blocking agents on maximum upstroke velocity of action potential in guinea-pig papillary muscles

\dot V_{\max }

Developmental changes in β‐adrenergic and cholinergic interactions on calcium‐dependent slow action potentials in rat ventricular muscles

), together with a prolongation of the relative refractory period.

Effects of para-substituted beta-adrenoceptor blocking agents and methyl-substituted phenoxypropanolamine derivatives on maximum upstroke velocity of action potential in guinea-pig papillary muscles.

\dot V_{\max }

Effects of beta-adrenoceptor blocking agents of N-tertiary butyl derivatives on maximum upstroke velocity of action potential in guinea-pig papillary muscles

decreased progressively as the driving rate was increased from 1 Hz (for lidocaine) and from 0.25 Hz (for tocainide) to 5 Hz. This action was accentuated dose-depently. A slow component (time constant τ=195–232 ms for lidocaine, 281–303 ms for tocainide) and slower component (τ=2.1–3.8 s for tocainide) of the recovery (reactivation) of