RT Journal Article SR Electronic T1 Contribution of the Plasmalemma to Ca2+ Homeostasis in Hair Cells JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 2640 OP 2650 DO 10.1523/JNEUROSCI.21-08-02640.2001 VO 21 IS 8 A1 Catherine Boyer A1 Jonathan J. Art A1 Claude J. Dechesne A1 Jacques Lehouelleur A1 Jean Vautrin A1 Alain Sans YR 2001 UL http://www.jneurosci.org/content/21/8/2640.abstract AB Calcium influx through transduction channels and efflux via plasmalemmal Ca2+-ATPases (PMCAs) are known to contribute to calcium homeostasis and modulate sensory transduction in vertebrate hair cells. To examine the relative contributions of apical and basolateral pathways, we analyzed the calcium dynamics in solitary ciliated and deciliated guinea pig type I and type II vestibular hair cells. Whole-cell patch-clamp recordings demonstrated that these cells had resting potentials near −70 mV and could be depolarized by 10–20 mV by superfusion with high potassium. Fura-2 measurements indicated that ciliated type II cells and deciliated cells of either type had low basal [Ca2+]i, near ∼90 nm, and superfusion with high potassium led to transient calcium increases that were diminished in the presence of Ca2+ channel blockers. In contrast, measurements of type I ciliated cells, hair cells with large calyceal afferents, were associated with a higher basal [Ca2+]iof ∼170 nm. High-potassium superfusion of these cells induced a paradoxical decrease in [Ca2+]i that was augmented in the presence of Ca2+ channel blockers. Optical localization of dihydropyridine binding to the kinocilium suggests that they contain L-type calcium channels, and as a result apical calcium influx includes a contribution from voltage-dependent ion channels in addition to entry via transduction channels localized to the stereocilia. Eosin block of PMCA significantly altered both [Ca2+]i baseline and transient responses only in ciliated cells suggesting that, in agreement with immunohistochemical studies, PMCA is primarily localized to the bundles.