Potassium channel ether à go-go mRNA expression in the spiral ligament of the rat

Identification of the K+ transporters located in the lateral wall of the cochlea is essential for a better understanding of the mechanisms by which a positive endocochlear potential and a high K+ concentration are achieved in endolymph. In this study, we have determined the distribution of the K+ channel rat ether à go-go (eag) mRNA in the cochlea. After reverse transcription of adult rat cochlear tissues, cDNA was amplified with primers specific to eag channel. The eag mRNA was localized in cochlear tissues by in situ hybridization using specific oligonucleotide probes tailed with digoxigenin conjugated UTP. Eag mRNA was detected in the organ of Corti but mainly in the fibrocytes of the spiral ligament but not in spiral prominence or in stria vascularis. The expression pattern of rat eag transcript in spiral ligament is complementary to the Na+,K+-ATPase distribution in the cochlear lateral wall. The localization of eag mRNA suggests that eag potassium channel may be produced in the corresponding cells. Considering the importance of the K+ gradient in the cochlea, the result reported here suggests that eag channel may play a role in the control of K+ fluxes in the spiral ligament.