Analysis of nicotinic acetylcholine receptor subunits in the cochlea of the mouse

The present study was designed to catalogue and compare nicotinic receptor subunit messages in the mammalian cochlea. Fourteen nicotinic acetylcholine receptor subunit messages were examined by polymerase chain reaction (PCR) analysis and nucleotide sequencing. Total RNA was extracted from the auditory organs of 14- to 18-day-old CBA_J mice, and mRNA was purified using oligo-dT cellulose. After reverse transcription, resulting cDNA was amplified by PCR with the use of primers specific for the nucleotide sequences representing the following nicotinic receptor subunits: muscle types α1, β1, γ, δ and ε{lunate} and neuronal types α2,3,4,5,6,7 and β2,3,4. cDNA from cochlear tissue corresponding to the muscle-type receptor subunit β1 and to neuronal-type receptor subunits α2,4,5,6 and β2,3 was amplified, whereas cDNA for muscle types α1, γ, δ and ε{lunate} and neuronal types α3,7 and β4 was not. All PCR products were homologous in nucleotide sequence to the corresponding reference cDNAs from which the primers were designed. The current results indicate that nicotinic acetylcholine receptor (nAChR) subunits that are similar or identical to the stated muscle and neuronal types are expressed in the murine cochlea. The presence of messages corresponding to the muscle-type β1 and neuronal-type nAChR subunits may be correlated with the atypical cholinergic response of cochlear hair cells to agonists and antagonists.