| Abstract: | Potential dependence of calcium inward current deactivation kinetics was studied in the somatic membrane of mouse dorsal root ganglion neurons by intracellular dialysis technique. The decay of the high-threshold calcium current upon repolarization was reasonably described by single-exponential process with the time constant tau less than or equal to 130 microseconds (V = = -80 mV), when the intracellular solution contained tris-PO4, and by two-exponential process (tau congruent to 0.1 and tau = 0.8 divided by ms, V = -80 mV), when the intracellular solution contained Cs-aspartate and EGTA. Both time constants were strongly voltage dependent. The amplitude of the fast component of the tail current had sigmoidal voltage dependence, and the slow component had V-shaped voltage dependence. The low-threshold calcium current deactivation occurs more slowly with high voltage dependent kinetics (tau = 1.1 divided by 1.2 ms, V = -160 mV). A dependence of low-threshold current deactivation time constant on the type of penetrating cation was observed. A kinetic model of calcium current deactivation was proposed considering three types of calcium channels presented in the somatic membrane of the neurons studied. |
