[Single channels of low and high-threshold calcium channels of the membrane of sensory neurons in the mouse].

Single calcium channels of cultured dorsal root ganglion cells from mouse embryos were studied using patch clamp method in its cell-attached configuration. Two types of activity of unitary calcium channels were found. The first one which arose at membrane potentials near--50-40 mV was characterized by unitary current amplitude of 0.37 +/- 0.04 pA with 40 mmol/l Ca2+ in the pipette solution, mean open time of 0.6 ms and intraburst mean shut time of 1.2 ms. It displayed voltage- and time-dependent inactivation. The corresponding values for the second one which required much more positive depolarization to be activated (approximately 0 mV) and did not express noticeable inactivation were: 0.53 +/- 0.04 pA, 0.8 ms and 0.8 ms. It is concluded that the recorded types of unitary activity are associated respectively with low- and high-threshold calcium currents which have been found earlier while studying whole cell currents.