Expression of mRNA encoding the H1, H2, and H3 histamine receptors in the rat cochlea

Histamine may have physiological functions in the inner ear. Histamine receptors, however, have not yet been identified in the mammalian cochlea. We determined, using reverse transcription polymerase chain reaction (RT-PCR), that H1, H2, and H3 histamine receptor mRNA is expressed in the rat cochlea. To investigate the distribution of each receptor, the cochlea was divided into three parts: the lateral portion, the medial portion, and the modiolus. The mRNA for each receptor subtype was detected in the modiolus but not in the lateral and medial portions of the cochlea. This is the first evidence of H1, H2, and H3 histamine receptor mRNA in the rat cochlea. These findings support the suggestion that histamine may play a physiological role in the cochlea.