Comparison of Nicotinic Acetylcholine Receptor Subunit Alpha 9 between Rat and Guinea Pig

Abstract

Based on its high level of expression in hair cells, the recently-cloned nicotinic receptor subunit, α9, is likely to be the postsynaptic receptor for acetylcholine in hair cells either as a homomeric complex or with other subunits yet to be identified. To study this receptor further, we cloned and sequenced α9 cDNA from the guinea pig organ of Corti library. The sequence of the guinea pig a9 cDNA is similar to that of the rat, with homologies of 85% and 89% at the nudeotide and amino add levels, respectively. Most differences are in the cytoplasmic loop domain between the transmembrane segments 3 and 4. We also observed minor differences in the putative ligand binding regions. These changes could account for the different responses to the agonist 1, 1-dimethyl-4-phenylpiperazinium (DMPP) reported for rat and guinea pig outer hair cells.