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Calcium signalling mediated by the α9 acetylcholine receptor in a cochlear cell line from the Immortomouse
Author(s) -
Jagger D. J.,
Griesinger C. B.,
Rivolta M. N.,
Holley M. C.,
Ashmore J. F.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.t01-1-00049.x
Subject(s) - calcium , calcium in biology , organ of corti , extracellular , intracellular , chemistry , calcium signaling , voltage dependent calcium channel , acetylcholine , caffeine , hair cell , fura 2 , cell culture , receptor potential , calcium channel , receptor , ryanodine receptor , biophysics , microbiology and biotechnology , endocrinology , biochemistry , cochlea , biology , anatomy , genetics , enzyme , organic chemistry , cytosol
1 We have investigated the characteristics of the α9 acetylcholine receptor (α9AChR) expressed in hair cell precursors in an immortalized cell line UB/OC‐2 developed from the organ of Corti of the transgenic H‐2Kb‐ ts A58 mouse (the Immortomouse) using both calcium imaging and whole‐cell recording. 2 Ratiometric measurements of fura‐2 fluorescence revealed an increase of intracellular calcium concentration in cells when challenged with 10 μM ACh. The calcium increase was seen in 66 % of the cells grown at 39 °C in differentiated conditions. A smaller fraction (34 %) of cells grown at 33 °C in proliferative conditions responded. 3 Caffeine (10 mM) elevated cell calcium. In the absence of caffeine, the majority of imaged cells responded only once to ACh. A small proportion (< 2 % of the total) responded with an increase in intracellular calcium to multiple ACh presentations. Pretreatment with caffeine inhibited all calcium responses to ACh. 4 In whole‐cell tight‐seal recordings 10 μM ACh activated an inward, non‐selective cation current. The reversal potential of the ACh‐activated inward current was dependent on the extracellular calcium concentration with an estimated P Ca / P Na of 80 for the α9 receptor at physiological calcium levels. 5 The data indicate that ACh activates a calcium‐permeable channel α9AChR in UB/OC‐2 cells and that the channel has a significantly higher calcium permeability than other AChRs. The results indicate that the α9AChR may be able to elevate intracellular calcium levels in hair cells both directly and via store release.