[Deactivation of calcium currents in the soma of spinal ganglion neurons after elimination of the depolarizing shift in the membrane potential].

Kinetic and voltage-dependent characteristics of deactivation of calcium inward currents with the removal of membrane depolarization were studied in the somatic membrane of rat dorsal root ganglion neurons by intracellular dialysis technique. The "tail" of low-threshold calcium current could be described reliably by one exponent with time constant tau 1-1.2-1.8 ms at repolarization to --90 mV. The "tail" of the high-threshold calcium current represented a sum of several exponents; the time constant of the main component tau h was in the range of 250-380 microseconds. tau 1 and tau h remained practically unchanged for repolarization potentials in the subthreshold region; however, they increased if it was in the range of potentials at which the corresponding component of the calcium current started to activate. A dependence of tau 1 and tau h on the duration of depolarizing shift was observed. The results obtained are discussed in the framework of a three-level kinetic model of calcium channels.