When studied in vitro, type I hair cells in amniote vestibular organs have a large, negatively activating K+ conductance. In type II hair cells, as in nonvestibular hair cells, outwardly rectifying K+ conductances are smaller and more positively activating. As a result, type I cells have more negative resting potentials and smaller input resistances than do type II cells; large inward currents fail to depolarize type I cells above -60 mV. In nonvestibular hair cells, afferent transmission is mediated by voltage-gated @entity141 channels that activate positive to -60 mV. We investigated whether @entity141 channels in type I cells activate more negatively so that quantal transmission can occur near the reported resting potentials. We used the perforated patch method to record @entity141 channel currents from type I and type II hair cells isolated from the @entity35 anterior crista (postnatal days 4-20). The activation range of the @entity141 currents of type I hair cells differed only slightly from that of type II cells or nonvestibular hair cells. In 5 mM external @entity141 , currents in type I and type II cells were half-maximal at -41.1 +/- 0.5 (SE) mV (n = 10) and -37.2 +/- 0.2 mV (n = 10), respectively. In physiological external @entity141 (1.3 mM), currents in type I cells were half-maximal at -46 +/- 1 mV (n = 8) and just 1% of maximal at -72 mV. These results lend credence to suggestions that type I cells have more positive resting potentials in vivo, possibly through K+ accumulation in the synaptic cleft or inhibition of the large K+ conductance. @entity141 channel kinetics were also unremarkable; in both type I and type II cells, the currents activated and deactivated rapidly and inactivated only slowly and modestly even at large depolarizations. The @entity141 current included an L-type component with relatively low sensitivity to @entity7236 antagonists, consistent with the alpha subunit being CaV1.3 (alpha1D). @entity35 vestibular epithelia and @entity21 were probed for L-type alpha-subunit expression with the reverse transcription-polymerase chain reaction. The epithelia expressed CaV1.3 and the @entity21 expressed CaV1.2 (alpha1C).

Voltage-gated calcium channel currents in type I and type II hair cells isolated from the XXXX crista.

@entity141 :: ('CHEBI:29108', 'Chemical') :: ['Ca2+'] @entity21 :: ('MESH:D001480', 'Disease') :: ['ganglia'] @entity7236 :: ('MESH:C038806', 'Chemical') :: ['dihydropyridine'] @entity35 :: ('10116', 'Species') :: ['rat', 'Rat']
@entity35 :: (10116,Species) :: ['rat']
