PT  - JOURNAL ARTICLE
AU  - M Umemiya
AU  - AJ Berger
TI  - Single-channel properties of four calcium channel types in rat motoneurons
AID  - 10.1523/JNEUROSCI.15-03-02218.1995
DP  - 1995 Mar 01
TA  - The Journal of Neuroscience
PG  - 2218--2224
VI  - 15
IP  - 3
4099  - http://www.jneurosci.org/content/15/3/2218.short
4100  - http://www.jneurosci.org/content/15/3/2218.full
SO  - J. Neurosci.1995 Mar 01; 15
AB  - Previous studies have demonstrated multiple components of whole-cell calcium currents in hypoglossal motoneurons (HMs); HMs possess a low- voltage-activated (LVA) current and three types of high-voltage- activated (HVA) calcium currents based on sensitivity to omega-Aga IVA, omega-Conotoxin GVIA (omega-CgTx) and dihydropyridine analogs (DHPs). In the present study, we recorded single-calcium channel activities from HMs using a cell-attached patch-clamp method and found four types of channels that could be discriminated based on kinetics, voltage dependency, DHP sensitivity, and single-channel conductances. The average single-channel conductances with 110 mM barium as a charge carrier were 7, 14, 20, and 28 pS. T-type channels had a single-channel conductance of 7 pS, activated at the most negative potentials for the calcium channels and inactivated during depolarization. L-type channels (DHP-sensitive channels) did not inactivate during depolarization and had a 28-pS single-channel conductance. Based on kinetics and sensitivity to holding potential, it is likely that the channels with conductances of 14 pS and 20 pS represent N-type and P-type channels, respectively. The N-type channel (14 pS) was sensitive to holding potential, showed modal gating, and inactivated during maintained depolarizations, whereas the P-type channel (20 pS) was rather insensitive to holding potential and did not inactivate during depolarization.