Abstract
Ca2+ currents in hair cells of the frog crista ampullaris were studied using the whole-cell patch-clamp technique. Currents were recorded in situ from hair cells in peripheral, intermediate and central regions of the sensory epithelium. Two types of Ca2+ currents were found: a partially inactivating current that was expressed by nearly all central cells and by about 65% of intermediate and peripheral cells, and a sustained current expressed by the remaining cell population. The mean Ca2+ current amplitude was larger in intermediate cells than in central or peripheral cells. The two types of Ca2+ currents were composed of two components: a large, nifedipine-sensitive (NS) current and a small, nifedipine-insensitive (NI) current. The latter was resistant to SNX-482, ω-conotoxin MVIIC and ω-agatoxin IVA and to ω-conotoxin GVIA, antagonists of R, P/Q and N-type Ca2+ channels. The amplitude of NS and NI currents varied among peripheral cells, where the current density gradually increased from the beginning of the region toward its end. No significant variation of Ca2+ current density was detected in hair cells of either intermediate or central regions. These results demonstrate the presence of regional and intraregional variations in the expression of L and non-L Ca2+ channels in the frog crista ampullaris. Finally, immunocytochemical investigations revealed the presence of Ca2+ channel subunits of the α1D type and the unexpected expression of α1B-subunits.
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References
Bezprozvanny N, Scheller RH, Tsien R W (1995) Functional impact of syntaxin on the gating of N-type and L-type calcium channels. Nature 378:623–626
Crawford AC, Fettiplace R (1981) An electrical tuning mechanism in turtle cochlear hair cells. J Physiol (Lond) 312:377–412
Fuchs PA, Nagai T, Evans MG (1988) Electrical tuning in hair cells isolated from the chick cochlea. J Neurosci 12:800–809
Fuchs PA, Evans MG, Murrow BW (1990) Calcium currents in hair cells isolated from the cochlea of the chick. J Physiol (Lond) 429:553–568
Green GE, Khan KM, Beisel DW, Drescher MJ, Hartfield JS, Drescher DJ (1996) Calcium channel subunits in mouse cochlea. J Neurochem 67:37–45
Goldberg JM (1991) The vestibular end organs: morphological and physiological diversity of afferents. Curr Opin Neurobiol 1:229–235
Goldberg JM, Brichta AM (1998) Evolutionary trends in the organization of the vertebrate crista ampullaris. Otolaryngol Head Neck Surg 119:165–171
Guth PS, Perin P, Norris CH, Valli P (1998) The vestibular hair cells: post-transductional signal processing. Prog Neurobiol 54:193–247
Honrubia V, Hoffman LF, Sitko S, Schwartz IR (1989) Anatomic and physiological correlates in bullfrog vestibular nerve. J Neurophysiol 61:688–701
Hudspeth AJ, Lewis RS (1988a) Kinetic analysis of voltage- and ion-dependent conductances in saccular hair cells of the bullfrog, Rana catesbeiana. J Physiol (Lond) 400:237–274
Kollmar R, Fak J, Montgomery LG, Hudspeth AJ (1977) Predominance of α1D subunit in L-type voltage-gated Ca2+ channels of hair cells in the chicken's cochlea. Proc Nat Acad Sci USA 94:14883–14888
Lang DG, Correia MJ (1989) Studies of solitary semicircular canal hair cells in adult pigeon: voltage-dependent ionic conductances. J Neurophysiol 62:935–945
Lopez I, Ishiyama G, Ishiyama A, Jen JC, Liu F, Baloh RW (1999) Differential subcellular immunolocalization of voltage-gated calcium channel α1 subunits in the chinchilla cristae ampullaris. Neuroscience 92:773–782
Lysakowsky A (1996) Synaptic organization of the crista ampullaris in vertebrates. Ann NY Acad Sci 781:164–182
Marcotti W, Russo G, Prigioni I (1999) Position-dependent expression of inwardly rectifying K+ currents by hair cells of frog semicircular canals. Neuroreport 10:601–606
Martinez-Dunst C, Michaels RL, Fuchs PA (1997) Release sites and calcium channels in hair cells of chick's cochlea. J Neurosci 17:9133–9144
Martini M, Rossi ML, Rubbini G, Rispoli G (2000) Calcium currents in hair cells isolated from semicircular canals of the frog. Biophys J 78:1240–1254
Masetto S, Correia MJ (1997) Electrophysiological properties of vestibular sensory and supporting cells in the labyrinth slices: before and during regeneration. J Neurophysiol 78:1913–1927
Masetto S, Russo G, Prigioni I (1994) Differential expression of potassium currents by hair cells in thin slices of frog crista ampullaris. J Neurophysiol 72:443–455
Moser T, Beutner D (2000) Kinetics of exocytosis and endocytosis at the cochlear inner hair cell afferent synapse of the mouse. Proc Natl Acad Sci USA 97:883–888
Parsons TD, Lenzi D, Almers W, Roberts WM (1994) Calcium-triggered exocytosis and endocytosis in an isolated presynaptic cell: capacitance measurements in saccular hair cells. Neuron 13:875–883
Perez-Reyes E, Schmeider T (1995) Molecular biology of calcium channels. Kidney Int 48:1111–1124
Perin P, Soto E, Vega R, Botta L, Masetto S, Zucca G, Valli P (2000) Calcium channels functional roles in the frog semicircular canal. Neuroreport 11:417–420
Perin P, Masetto S, Martini M, Rossi ML, Rubbini G, Rispoli G, Guth P, Valli P (2001) Regional distribution of calcium currents in frog semicircular canal hair cells. Hear Res 152:67–76
Peterson EH (1998) Are there parallel channels in vestibular nerve? News Physiol Sci 13:194–201
Platzer J, Engel J, Schrott-Fischer A, Stephan K, Bova S, Chen H, Zheng H, Striessing J (2000) Congenital deafness and sinoatrial node dysfunction in mice lacking class D L-type Ca2+ channels. Cell 102:89–97
Prigioni I, Masetto S, Russo G, Taglietti V (1992) Calcium currents in solitary hair cells isolated from frog crista ampullaris. J Vestib Res 2:31–39
Prigioni I, Russo G, Marcotti W (1996) Potassium currents of pear-shaped hair cells in relation to their location in frog crista ampullaris. Neuroreport 7:1841–1845
Rennie KJ, Ashmore JF (1991) Ionic currents in isolated vestibular hair cells from the guinea-pig crista ampullaris. Hear Res 51:279–291
Rennie KJ, Correia MJ (1994) Potassium currents in mammalian and avian isolated type I semicircular canal hair cells. J Neurophysiol 71:317–329
Ricci AJ, Gray-Keller M, Fettiplace R (2000) Tonotopic variations of calcium signalling in turtle auditory hair cells. J Physiol (Lond) 524:423–436
Roberts WM, Jacobs RA, Hudspeth AJ (1990) Colocalization of ion channels involved in frequency selectivity and synaptic transmission at presynaptic active zones of hair cells. J Neurosci 10:3664–3684
Robertson D, Paki B (2002) Role of L-Type Ca2+ channels in transmitter release from mammalian inner hair cells. Single-neuron activity. J Neurophysiol 87:2734–2740
Rodriguez-Contreras A, Yamoah EN (2001) Direct measurement of single-channel Ca2+ currents in bullfrog hair cells reveals two distinct channel subtypes. J Physiol (Lond) 534:669–689
Rüsch A, Eatock RA (1996) A delayed rectifier conductance in Type I hair cells of the mouse utricle. J Neurophysiol 76:995–1004
Russo G, Lelli A, Marcotti W, Prigioni I (2001) Gradients of expression of calcium and potassium currents in frog crista ampullaris. Pflugers Arch 442:814–820
Singer D, Biel M, Lotan I, Flockerzi V, Hofmann F, Dascal N (1991) The roles of the subunits in the function of the calcium channel. Science 253:1553–1557
Spassova M, Eisen MD, Saunders JC, Parsons TD (2001) Chick cochlear hair cell exocytosis mediated by dihydropyridine-sensitive calcium channels. J Physiol (Lond) 535:689–696
Striessing J (1999) Pharmacology, structure and function of cardiac L-type Ca2+ channels. Cell Physiol Biochem 9:242–269
Su ZL, Jiang SC, Gu R, Yang WP (1995) Two types of calcium channels in bullfrog saccular hair cells. Hear Res 87:62–68
Wang G, Dayanithi G, Newcomb R, Lemos JR (1999) An R-type Ca2+ current in neurohypophysial terminals preferentially regulates oxytocin secretion. J Neurosci 19:9235–9241
Weng T, Correia MJ (1999) Regional distribution of ionic currents and membrane voltage responses of type II hair cells in the vestibular neuroepithelium. J Neurophysiol 82:2451–2461
Wersall J, Bagger-Sjoback D (1974) Morphology of the vestibular sense organ. In: Kornhuber HH (ed) Handbook of sensory physiology Vol. VI. Springer, Berlin Heidelberg New York, pp 123–170
Westenbroek RE, Hell JW, Warner C, Dudel SJ, Snutch TP, Catteral WA (1992) Biochemical properties and subcellular distribution of an N-type calcium channel α1 antibody. Neuron 9:1099–1115
Yokoyama CT, Westenbroek RE, Hell JW, Soong TW, Snutch TP, Catterall WA (1995) Biochemical properties and subcellular distribution of the neuronal class E calcium channel alpha 1 subunit. J Neurosci 15:6419–6432
Zidanic M, Fuchs PA (1995) Kinetic analysis of barium currents in chick cochlear hair cells. Biophys J 68:1323–1336
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This work was supported by the Ministero Italiano dell' Università e della Ricerca (MIUR), grant-Cofin-MURST-2000 and 2002, Rome, Italy. The authors wish to thank Dr. W. Marcotti for his critical reading of an early version of the manuscript.
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Russo, G., Lelli, A., Gioglio, L. et al. Nature and expression of dihydropyridine-sensitive and -insensitive calcium currents in hair cells of frog semicircular canals. Pflugers Arch - Eur J Physiol 446, 189–197 (2003). https://doi.org/10.1007/s00424-003-1050-y
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DOI: https://doi.org/10.1007/s00424-003-1050-y