Separation of current- and voltage-dependent inactivation of calcium current in frog sensory neuron.
The inactivation process of the calcium current was studied in frog dorsal root ganglion cells using a newly developed 'concentration clamp' technique, and an inactivation component independent of Ca influx was separated from the Ca-dependent component. The neuron was first placed in Ca-free solution, and pre-pulses of various amplitude were applied, thereby inducing depolarization without the Ca influx. Successive test pulses were applied immediately after a rapid exchange to a solution containing normal Ca. The amount of inactivation under this condition was much smaller than that measured when both pre- and test pulses were applied in the normal solution, and reached a steady level on pre-pulses over +50 mV. We suggest that the inactivation process of the Ca current consists of two components, i.e. a dominant component which is dependent on Ca influx, and a smaller one which is presumably voltage-dependent.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004594:Electrophysiology / Q000379:methods; D005727:Ganglia, Spinal / Q000166:cytology / Q000502:physiology; D007473:Ion Channels / Q000502:physiology*; D009475:Neurons, Afferent / Q000378:metabolism*; D011892:Rana catesbeiana
D007473:Ion Channels; D002118:Calcium