Analysis of gamma-aminobutyric acidA receptor subunits in the mouse cochlea by means of the polymerase chain reaction

Abstract

Thirteen GABAA receptor subunits were examined in the cochlea of the CBAJ mouse by PCR analysis. Total RNA was extracted from the auditory organs of 14-18-day-old animals, and mRNA was isolated using oligo-dT cellulose. After reverse transcription, resulting cDNA was amplified by PCR with primers specific for nucleotide sequences representing GABAA subunits. PCR products corresponding to subunits alpha 1-alpha 6, beta 1-beta 3, and gamma 2 were amplified, whereas those representing gamma 1, gamma 3, and delta were not amplified above background. These results provide the most direct evidence to date that GABAA receptors composed of the detected subunits are expressed in the mammalian cochlea, lending new support to previous studies implicating GABA as a cochlear transmitter. The pronounced expression of alpha 2 and alpha 6 subunits suggests type II and "cerebellar-type" benzodiazepine pharmacology in the cochlea.