TY - JOUR
T1 - Constitutive expression of the α10 nicotinic acetylcholine receptor subunit fails to maintain cholinergic responses in inner hair cells after the onset of hearing
AU - Taranda, Julián
AU - Ballestero, Jimena A.
AU - Hiel, Hakim
AU - De Souza, Flavio S.J.
AU - Wedemeyer, Carolina
AU - Gómez-Casati, M. Eugenia
AU - Lipovsek, Marcela
AU - Vetter, Douglas E.
AU - Fuchs, Paul A.
AU - Katz, Eleonora
AU - Elgoyhen, A. Belén
N1 - Funding Information:
The authors want to thank the laboratory of Marcelo Rubinstein at INGEBI for generating the transgenic mouse line. This work was supported by the National Institutes of Deafness and other Communication Disorders (NIDCD) grant R01DC001508 to P.A.F. and A.B.E, an International Research Scholar Grant from the Howard Hughes Medical Institute, The National Organization for Hearing Research, a Research Grant from ANPCyT (Argentina), and a Grant from the University of Buenos Aires (Argentina) to A.B.E., NIDCD R01DC006258 to D.E.V, and a CONICET grant to EK.
PY - 2009/9
Y1 - 2009/9
N2 - Efferent inhibition of cochlear hair cells is mediated by α9α10 nicotinic cholinergic receptors (nAChRs) functionally coupled to calcium-activated, small conductance (SK2) potassium channels. Before the onset of hearing, efferent fibers transiently make functional cholinergic synapses with inner hair cells (IHCs). The retraction of these fibers after the onset of hearing correlates with the cessation of transcription of the Chrna10 (but not the Chrna9) gene in IHCs. To further analyze this developmental change, we generated a transgenic mice whose IHCs constitutively express α10 into adulthood by expressing the α10 cDNA under the control of the Pou4f3 gene promoter. In situ hybridization showed that the α10 mRNA is expressed in IHCs of 8-week-old transgenic mice, but not in wild-type mice. Moreover, this mRNA is translated into a functional protein, since IHCs from P8-P10 α10 transgenic mice backcrossed to a Chrna10 -/- background (whose IHCs have no cholinergic function) displayed normal synaptic and acetylcholine (ACh)-evoked currents in patch-clamp recordings. Thus, the α10 transgene restored nAChR function. However, in the α10 transgenic mice, no synaptic or ACh-evoked currents were observed in P16-18 IHCs, indicating developmental down-regulation of functional nAChRs after the onset of hearing, as normally observed in wild-type mice. The lack of functional ACh currents correlated with the lack of SK2 currents. These results indicate that multiple features of the efferent postsynaptic complex to IHCs, in addition to the nAChR subunits, are down-regulated in synchrony after the onset of hearing, leading to lack of responses to ACh.
AB - Efferent inhibition of cochlear hair cells is mediated by α9α10 nicotinic cholinergic receptors (nAChRs) functionally coupled to calcium-activated, small conductance (SK2) potassium channels. Before the onset of hearing, efferent fibers transiently make functional cholinergic synapses with inner hair cells (IHCs). The retraction of these fibers after the onset of hearing correlates with the cessation of transcription of the Chrna10 (but not the Chrna9) gene in IHCs. To further analyze this developmental change, we generated a transgenic mice whose IHCs constitutively express α10 into adulthood by expressing the α10 cDNA under the control of the Pou4f3 gene promoter. In situ hybridization showed that the α10 mRNA is expressed in IHCs of 8-week-old transgenic mice, but not in wild-type mice. Moreover, this mRNA is translated into a functional protein, since IHCs from P8-P10 α10 transgenic mice backcrossed to a Chrna10 -/- background (whose IHCs have no cholinergic function) displayed normal synaptic and acetylcholine (ACh)-evoked currents in patch-clamp recordings. Thus, the α10 transgene restored nAChR function. However, in the α10 transgenic mice, no synaptic or ACh-evoked currents were observed in P16-18 IHCs, indicating developmental down-regulation of functional nAChRs after the onset of hearing, as normally observed in wild-type mice. The lack of functional ACh currents correlated with the lack of SK2 currents. These results indicate that multiple features of the efferent postsynaptic complex to IHCs, in addition to the nAChR subunits, are down-regulated in synchrony after the onset of hearing, leading to lack of responses to ACh.
KW - Acetylcholine
KW - Efferent medial olivocochlear
KW - Nicotinic cholinergic receptors
KW - SK2 channel
KW - Transgenic mice
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U2 - 10.1007/s10162-009-0173-z
DO - 10.1007/s10162-009-0173-z
M3 - Article
C2 - 19452222
AN - SCOPUS:68549133283
SN - 1525-3961
VL - 10
SP - 397
EP - 406
JO - JARO - Journal of the Association for Research in Otolaryngology
JF - JARO - Journal of the Association for Research in Otolaryngology
IS - 3
ER -