LOCALIZATION OF CALRETININ MESSENGER-RNA IN RAT AND GUINEA-PIG INNER-EAR BY IN-SITU HYBRIDIZATION USING RADIOACTIVE AND NONRADIOACTIVE PROBES

The localization of calretinin mRNA was studied in the rat and guinea pig inner ear by in situ hybridization, and compared to the distributi on of the protein previously examined by immunocytochemistry. Radioact ive and non-radioactive in situ hybridizations (ISH) were performed us ing oligonucleotide probes labelled with S-35 or digoxigenin. Radioact ive ISH was more sensitive than non-radioactive ISH. In cochlear and v estibular ganglia, calretinin mRNA was localized in subpopulations of neurons with patterns of distribution similar to those shown by immuno cytochemistry. By contrast, the observations in the sensory epithelia differed with the two techniques, ISH revealing less positive structur es than immunocytochemistry. Rat inner hair cells and guinea pig inner hair cells, Hensen's cells and Deiters cells, which had been describe d strongly immunoreactive, appeared positive with radioactive but not with non-radioactive ISH. On the other hand, rat vestibular type II ha ir cells and guinea pig interdental cells of the spiral limbus which w ere faintly immunoreactive were not positive with both ISH techniques.