1. Archive
2. Vol.51, No.3

A Voltage-Dependent Transient K⁺ Current in Rat Dental Pulp Cells

Abstract: We characterized a voltage-dependent transient K⁺ current in dental pulp fibroblasts on dental pulp slice preparations by using a nystatin perforated-patch recording configuration. The mean resting membrane potential of dental pulp fibroblasts was −53 mV. Depolarizing voltage steps to +60 mV from a holding potential of −80 mV evoked transient outward currents that are activated rapidly and subsequently inactivated during pulses. The activation threshold of the transient outward current was −40 mV. The reversal potential of the current closely followed the K⁺ equilibrium potential, indicating that the current was selective for K⁺. The steady-state inactivation of the peak outward K⁺ currents described by a Boltzmann function with half-inactivation occurred at −47 mV. The K⁺ current exhibited rapid activation, and the time to peak amplitude of the current was dependent on the membrane potentials. The inactivation process of the current was well fitted with a single exponential function, and the current exhibited slow inactivating kinetics (the time constants of decay ranged from 353 ms at −20 mV to 217 ms at +60 mV). The K⁺ current was sensitive to intracellular Cs⁺ and to extracellular 4-aminopyridine in a concentration-dependent manner, but it was not sensitive to tetraethylammonium, mast cell degranulating peptide, and dendrotoxin-I. The blood depressing substance-I failed to block the K⁺ current. These results indicated that dental pulp fibroblasts expressed a slow-inactivating transient K⁺ current.

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