Resting membrane potential and potassium currents in cultured parasympathetic neurones from rat intracardiac ganglia.

1. Whole-cell K+ currents contributing to the resting membrane potential and repolarization of the action potential were studied in voltage-clamped parasympathetic neurones dissociated from neonatal rat intracardiac ganglia and maintained in tissue culture. 2. Rat intracardiac neurones had a mean resting membrane potential of -52 mV and mean input resistance of 850 M omega. The current-voltage relationship recorded during slow voltage ramps indicated the presence of both leakage and voltage-dependent currents. The contribution of Na+, K+ and Cl- to the resting membrane potential was examined and relative ionic permeabilities PNa/PK = 0.12 and PCl/PK 5 s. The instantaneous current-voltage relationship, examined under varying external K+ concentrations, was linear, and the reversal (zero current) potential shifted in accordance with that predicted by the Nernst equation for a K(+)-selective electrode. The shift in reversal potential of the tail currents as a function of the extracellular K+ concentration gave a relative permeability, PNa/PK = 0.02 for the delayed outward K+ channel(s).(ABSTRACT TRUNCATED AT 400 WORDS)