In order to evaluate the cytological homology of intermediate cells an
d melanocytes, and to investigate the function of melanocytes in the i
nner ear, hearing acuity and cochlear pathology were studied in three
strains of mice, namely, wild type mice (+/+), albino mice without mel
anin (c(2J)/c(2J)) and microphthalmia mice with no melanocytes (mi(bw)
/mi(bw)). Our histochemical data indicated that intermediate cells sho
wed cytological characteristics almost identical to those of melanocyt
es and that disorders of melanin and/or melanocytes were reflected in
the stria vascularis of each mouse. While c(2J)/c(2J) presented the sa
me normal hearing acuity and normal structure of the stria vascularis
as +/+, the hearing acuity of mi(bw)/mi(bw) mutants was severely impai
red. Their stria vascularis was abnormally thin, lacking intermediate
cells. According to these results, lack of melanin has little influenc
e on hearing acuity; however, the absence of intermediate cells or mel
anocytes causes severe hearing loss, presumably due to a strial dysfun
ction.