U. Borchard

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In rat ventricular myocytes we found two components of transient outward current, which could be discriminated time- and voltage- dependently. Besides the well known fastly inactivating transient outward current (ito,f, tau = 35 +/- 8 ms, n = 4) we investigated properties of a slowly inactivating transient outward current (ito,s, tau = 1.7 +/- 0.4 s, n =(More)
The inhibition of the pacemaker current (if) in sheep cardiac Purkinje fibers by ZD 7288 [4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino)pyrimidinium++ + chloride] is lost use-dependently. This disinhibition of if was investigated by using the two-microelectrode voltage-clamp technique. The pulse protocol consisted of a rest period (holding(More)
The bradycardic mechanism of ZD 7288 (4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino)pyrimidinium++ + chloride) was investigated in sheep cardiac Purkinje fibres. The pacemaker i(f)-current measured with the two-microelectrode voltage-clamp technique, as well as the diastolic depolarization rate and the frequency of spontaneously active fibres were(More)
In sheep cardiac Purkinje fibers concentration-dependent inhibition of transient outward current (ito) by 4-aminopyridine (4-AP, 3-1000 mumol/l) was recorded with the two-microelectrode voltage-clamp technique, and correlated effects on action potential duration measured at -70 mV (APD-70) were investigated. Half-maximal inhibition of ito-amplitude occurred(More)
The electrophysiologic mode of action and potency of the verapamil derivative YS 035 (N,N-bis-(3,4-dimethoxyphenethyl)-N-methyl amine) were investigated in sheep cardiac Purkinje fibres. Action potential duration measured at a repolarization level of -60 mV (APD-60) and membrane currents recorded with the two-microelectrode voltage-clamp technique were(More)
Unlike other clinically used local anesthetics, carticaine contains a thiophene ring. Current voltage relations of peak sodium current INa and steady state potassium current IK were measured in voltage clamp experiments on the node of Ranvier of Rana esculenta. The dependence of the maximum sodium conductance on external concnetration of carticaine is(More)
The influence of monomeric methylmethacrylate (MMA) on resting and compound action potential of the isolated desheathed sciatic nerve of the frog (sucrose gap method) was determined. Above 10 mM there was a dose-dependent decrease of the compound action potential and a hyperpolarization of the membrane which was augmented with increasing MMA concentrations(More)
The action of the antituberculous agent ethambutol on the myelinated nerve was studied in two ways: (1) Resting and compound action potentials of the desheathed sciatic nerve were measured; (2) Na+ and K+ currents through the node of Ranvier were investigated by means of the voltage clamp. Reversible dose-dependent decreases of the compound action potential(More)