EXPRESSION OF ADENYLYL-CYCLASE TYPE-I IN COCHLEAR INNER HAIR-CELLS

Expression of calcium/calmodulin-activated adenylyl cyclase type I (AC I) mRNA has been determined in the cochlea and in an organ-of-Corti su bdissected tissue fraction by reverse transcriptase-polymerase chain r eaction (RT-PCR) analysis, Amplification products of predicted size we re obtained from the mouse cochlea and rat organ of Corti with nucleot ide sequences corresponding to respective ACI brain transcripts. In ad dition, ACI template was detected in a rat inner hair cell cDNA librar y by PCR. Immunoreactivity to ACI has been localized within the organ of Corti to the inner hair cell, with diaminobenzidine staining found in both the cell body and in the stereocilia. Evidence, thus, has been obtained that both ACI transcript and protein are expressed in the in ner hair cell, the primary mechanosensory receptor cell of the cochlea . We hypothesize that ACI is activated by calcium influx through a cal cium/calmodulin interaction and that this adenylyl cyclase isoform may have a role in modulation of receptoneural afferent transmission and/ or mechanosensory transduction in the cochlea. (C) 1997 Elsevier Scien ce B.V.